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New Zealand Demersal Fish Assemblages
Abstract
Demersal fish assemblages in the New Zealand Exclusive Economic Zone were identified using presence–absence data from 19 215 bottom trawl tows made over a 37-year period. The dataset spanned latitudes 34–54°S and depths of 4–1500 m. A total of 123 taxa occurred in more than 1% of the tows (121 fish and 2 squid). Multivariate ordination and classification (correspondence analysis and Ward's cluster analysis) identified four primary species assemblages that were associated with the inner continental shelf, mid–outer continental shelf and shelf edge, upper continental slope and mid continental slope. The most frequently occurring species (> 40% of tows) in each assemblage were (in descending order): inshore – Chelidonichthys kumu, Pagrus auratus and Zeus faber; shelf – Nototodarus spp., Squalus acanthias and Thyrsites atun; upper slope – Macruronus novaezelandiae, Lepidorhynchus denticulatus, Genypterus blacodes and Hydrolagus sp.; mid slope – Hoplostethus atlanticus, Etmopterus baxteri, Halargyreus johnsonii, Coryphaenoides subserrulatus, Deania calcea, Coryphaenoides serrulatus, Pseudocyttus maculatus, Mora moro, Diastobranchus capensis and Centroscymnus crepidater. Further species associations were also identified within each primary assemblage. Canonical correspondence analysis revealed that most of the explainable variation in species composition was associated with depth and latitude; longitude and season explained little extra variance. The usefulness of our results is limited by the use of presence–absence rather than abundance data, and by the uneven spatial distribution of trawl tows. However, the present study provides a large-scale framework within which to interpret the results of studies using abundance data over smaller spatial and temporal scales.
... Fish are the most abundant and diverse group of vertebrate animals on earth and play a key role in structuring marine ecosystems; interactions within and between fish species and their physical environment are important in defining community structure, diversity and stability in marine ecosystems (Francis, Hurst, McArdle, Bagley, & Anderson, 2002 ...
... In some areas, difficult terrain resulted in a paucity of tows, for example, the narrow and topographically complex continental shelf off Fiordland (on the West coast at 45-46°S) and the Kermadec and Colville Ridges ( Figure 1a; Francis et al., 2002). This sampling bias was not specifically addressed here as it was assumed that the substantial number of observations across a broad range of environmental gradients provided adequate coverage for species distribution modelling. ...
... Zealand, eighteen high-resolution gridded environmental predictors, mostly at a native resolution of 250 m, were collated and imported into ArcGIS (version 10.4). These variables were selected based on their known influence on demersal fish settlement, growth, survival and distribution (Beentjes, Bull, Hurst, & Bagley, 2002;Bull, Livingston, Hurst, & Bagley, 2001;Francis et al., 2002;Kendrick & Francis, 2002;Leathwick et al., 2006Leathwick et al., , 2012 and consequent likely influence on fish species assemblage composition and turnover (Table 1). For example, several physicochemical variables are likely to be critical physical determinants of habitat suitability for most fish species, including annual averages of seafloor temperature (BotTemp), salinity (BotSal), nitrate (BotNi), oxygen (BotOxy) and silicate (BotSil); benthic sediment disturbance (Beddist), which is an important feature in shallower depths (<200 m); ocean productivity, as described by vertically generalized production model (VGPM), with complementary information on surface water productivity provided by a spatial summary of gradients in sea surface temperature (SstGrad); other variables that act as surrogates for a range of correlated biophysical variables, for example, Depth (Bathy), seafloor roughness (Roughness) and sediment type (Sed). ...
Aim
Producing quantitative descriptions of large‐scale biodiversity patterns is challenging, particularly where biological sampling is sparse or inadequate. This issue is particularly problematic in marine environments, where sampling is both difficult and expensive, often resulting in patchy and/or uneven coverage. Here, we evaluate the ability of Gradient Forest (GF) modelling to describe broad‐scale marine biodiversity patterns, using a large dataset that also provided opportunity to investigate the effects of sample size on model stability.
Location
New Zealand's Extended Continental Shelf to depths of 2,000 m.
Methods
GF models were used to analyse and predict spatial patterns of demersal fish species turnover (beta diversity) using an extensive demersal fish dataset (>27,000 research trawls) and high‐resolution environmental data layers (1 km² grid resolution). GF models were fitted using various sized, mutually exclusive subsets of the demersal fish data to explore the effect of variation in numbers of training observations on model performance and stability. A final GF model using 13,917 samples was used to transform the environmental layers, which were then classified to produce 30 spatial groups; the ability of these groups to identify fish samples with similar composition was evaluated using independent sample data.
Results
Model fitting using varying sized subsets of the data indicated only minimal changes in model outcomes when using >7,000 observations. A multiscale spatial classification of marine environments created using results from a final GF model fitted using ~14,000 samples was highly effective at summarizing spatial variation in both fish assemblage composition and species turnover.
Main conclusions
The hierarchical nature of the classification supports its use at varying levels of classification detail, which is advantageous for conservation planning at differing spatial scales. This approach also facilitates the incorporation of information on intergroup similarities into conservation planning, allowing greater protection of distinctive groups likely to support unusual assemblages of species.
... According to this 'water mass hypothesis', the southeast Australian mid-slope community has affinities with assemblages in the northwest and northeast Atlantic due to the intrusion of intermediate and deep Antarctic water masses at similar depths in each region (Koslow et al. 1994). It is increasingly apparent that some species of the upper and mid-slope have a global distribution at similar latitudes in the northern and southern hemispheres (Francis et al., 2002). ...
... Haedrich and Merrett (1990) stated that communities of demersal fishes do not exist in the deep sea, and are no more than random assemblages. There was no evidence that members of demersal assemblages identified by Francis et al. (2002) formed interacting communities, yet the authors suggested that their spatial coherence between Australia and New Zealand precluded these assemblages from being random. In contrast, the assemblage described by Koslow et al. (1994) is considered to be a coherent biological community, with evidence of predation, competition and co-adaptation between species (Bulman and Koslow, 1992;Williams et al., 2001). ...
... sp. B. Paulin et al. (1989) described this species as a mid-water fish found at depths of 100-500 m., whilst Francis et al. (2002) calculated its preferred depth off New Zealand as 210 m. It is possible that E. sp. ...
The sustainability of deep-sea fisheries requires an understanding of trophic interactions between target and bycatch species. The study aimed to examine and compare the diets of two shark species that are important in the bycatch of orange roughy (Hoplostethus atlanticus) fisheries off Tasmania. Following dissection, the diets of Etmopterus baxteri and E. sp. B from three sites (St. Patrick's Head, Cascade Plateau, Southern Hills) were described in terms of a range of indices (%O, %N, %W, %IRI), based on broad prey categories, narrow prey taxa and functional prey groupings. Etmopterus sp. B was identified as an opportunistic teuthivore, with a diet dominated by benthic cephalopods (74 %O, 96 %IRI), including Histioteuthis macrohista. However, squid remains were over-represented by number and under-represented by weight in the diet of Etmopterus spp., due to rapid digestion of soft tissues and accumulation of hard parts. Thus future dietary studies should employ a similarly broad range of dietary measures, to enable identification of bias and interpretation of the effects of differential rates of digestion. Benthic teleost prey, notably Hoplostethus atlanticus, dominated the stomach contents of the opportunistic benthopelagic piscivore E. baxteri (67.1 %O, 72.9 %IRI). The importance of teleost prey in the diet of E. baxteri increased with shark length (25-54 cm length class, 56.46 %IRI; 75-84 cm length class, 86 %), while crustaceans became less important. Etmopterus baxteri is a potential competitor and predator of orange roughy in waters off Tasmania, although it was unclear to what extent the consumption of H. atlanticus represented net feeding or natural predation behaviour. Similar trophic mechanisms support aggregations of Hoplostethus atlanticus and Etmopterus spp. on the mid-slope off Tasmania, namely predation upon demersal prey species and upon mesopelagic or vertically migrating nekton advected laterally onto the mid-slope due to the intrusion of Antarctic Intermediate Water.
... Besides protection, the PMNM also has great variability in oceanographic characteristics (Polovina et al., 1995;Firing and Brainard, 2006) that can influence the distribution of some benthic deep-sea fish assemblages facilitating horizontal larval dispersal (Koslow et al., 1994;Francis et al., 2002), or acting as a vertical barrier (Koslow et al., 1994) when interacting with the physiography of the area (Mundy, 2005). Among these factors, surface currents can be used to split the Hawaiian Archipelago into three sections. ...
... After accounting for time of day and latitude, another variable that came up as significant was surface current vector u (east-west flow) at 300 and 450 m. Surface currents have been observed to influence the differences in assemblage structure on seamounts (Genin, 2004) On one hand, surface currents may influence the larval dispersal of some benthic fish species (Koslow et al., 1994;Francis et al., 2002). On the other hand, currents can interact with the slope to determine the amount of organic material moving vertically or horizontally on seamounts (Genin and Boehlert, 1985). ...
Deep-sea fishes on seamounts have recently been shown to have strong changes in assemblage patterns with
depth. However, horizontal variability patterns within a single seamount and among seamounts remain drastically
understudied. The Papah¯anaumoku¯akea Marine National Monument (PMNM) is part of an extensive
seamount chain that is relatively unimpacted by human activity as well as highly variable in physiographic and
oceanographic characteristics. Three PMNM seamounts, Necker Island, French Frigate Shoals (FFS), and Pioneer
Bank, were explored using Autonomous Underwater Vehicle surveys to document the deep-sea fish assemblages
and their horizontal patterns of distribution at three different depths. Quantitative comparisons were made
among the sides of the seamount and among the three seamounts while controlling for depth. The Gadiformes
were the most abundant order with the highest number of individuals at 300 and 450 m on Pioneer and FFS. At
600 m the Myctophiformes showed the highest number of individuals overall and were the most abundant on
FFS. Significant differences in abundance by seamount, side, and their interaction were observed at 300 and 600
m. Significant differences in some diversity metrics occurred in one, both, or the interaction of the factors of
seamount and side at each depth. At all depths, the structure of the fish assemblage showed significant variation
among seamounts and sides, which was explained mostly by the interaction term. After accounting for the
variability explained by the confounding factor of time of day, the most common environmental factors related to
assemblage structure for at least two depths were the east-west component of currents (u), latitude, chlorophyll a
(chl a), and particulate organic carbon (POC). At 300 m, oxygen and salinity were also important, at 450 m mean
direction of the substrate was an additional factor that was correlated with assemblage structure. At 600 m the
factor that explained the most variation in community structure was percent rugosity. The results obtained in this
study show significant horizontal variability in seamount fish assemblages within a given depth range; this
variability should be taken into consideration in the management and conservation of the Monument and other
seamounts.
... Here, catch data from the Fisheries New Zealand research trawl database trawl that is managed by NIWA were used to model the distribution of seven shark species in the 200 nm Economic Exclusive Zone (EEZ). A number of previous studies have used subsets of the trawl database to assess species richness, and identify and classify fish assemblages and their relationships with a range of environmental variables, in part or all of the EEZ (Anderson et al. 1998, Beentjes et al. 2002, Bull et al. 2001, Francis et al. 2002, Leathwick et al. 2006, Stephenson et al. 2018, Stephenson et al. 2020, and further details of the database can be found in those reports. ...
... As part of a large project assessing marine species distributions across New Zealand (Anderson et al. 1998, Francis et al. 2002, Leathwick et al. 2006, research trawl data were extensively groomed to assess the accuracy of species identification. Identification was indexed as 1 (high confidence in species identification), 2 (identification may include two species), or 3 (confidence in identification only to the genus). ...
Vector Autoregressive Spatio-Temporal (VAST) models were applied to research trawl survey and environmental data to provide updated information on stock status for seven deepwater sharks. Deepwater sharks were found to be ubiquitous around New Zealand, with each species shown to have a unique distributional pattern. Deepwater shark “hotspots” in New Zealand waters were identified (e.g., Puysegur). There was little evidence to suggest any temporal or spatial changes in distribution or abundance.
... Peltorhamphus novaezeelandiae is found primarily on sand and mud bottoms in estuarine (Parrott 1960;Webb 1972Webb , 1973aRyan 1974;McMillan et al. 2011McMillan et al. , 2019Francis 2012;Beentjes & MacGibbon 2013) and coastal marine waters to moderate depths (ca. 65 m) on the inner continental shelf Beentjes et al. 2002;Francis et al. 2002;Stevenson 2004Stevenson , 2006Beentjes & MacGibbon 2013;. Capture depth information, available for 573 museum specimens examined in the present study (Table 5), revealed that this species has been taken from 0.5 m to 274 m. ...
... were taken in 40 m or less; another 24 specimens (4.2%) were taken between 41 and 62 m; and a single individual each was collected at 126 m and 274 m. James (1972) reported a similar depth distribution from 2.0 to 124 m, with greatest abundance between 5.0 and 40 m. Anderson et al. (1998) also noted the majority of captures of this species in less than 100 m. Francis et al. (2002), based on analysis of presence/absence data compiled from analysis of 19,232 trawls, classified this species as a member of the inshore demersal assemblage with a depth preference of ca. 20 m. ...
The flatfish genus Peltorhamphus Günther, 1862 (Pleuronectiformes: Rhombosoleidae) and its constituent species are redescribed based on examination of 1885 specimens. Four species are considered valid: three previously described (P. novaezeelandiae Günther, 1862, P. latus James, 1972, and P. tenuis James, 1972) and P. kryptostomus n. sp., described herein. Peltorhamphus novaezeelandiae, P. latus, and P. tenuis have widespread distributions on soft sediments in shallow coastal and inner continental shelf waters off both islands of New Zealand. Peltorhamphus novaezeelandiae has also been reported at the Chatham Islands. Previous reports of P. novaezeelandiae from Norfolk Island are erroneous. Peltorhamphus kryptostomus n. sp. has the most restricted geographic distribution in shallow coastal waters of the Otago-Southland region along the southeastern coast of South Island. The four species of Peltorhamphus are morphologically similar and overlap in many traditional meristic and morphometric features rendering identifications difficult, especially of juveniles and earlier life-history stages. Furthermore, throughout New Zealand waters, as many as three of the species possibly occur sympatrically, while in inshore areas of southeastern South Island, all four species may occur in sympatry. Novel morphological characters discovered in this study, combined with traditional diagnostic characters were used to identify and diagnose the species. Peltorhamphus tenuis is the most distinctive of the four, differing from congeners in the following combination of characters: greater length of second ocular-side pectoral-fin ray; its higher numbers of dorsal- and anal-fin rays and total vertebrae; having a series of small scales (best developed in specimens >70 mm SL) on blind sides of dorsal- and anal-fin rays (scales absent in congeners); its elongate body; and ocular-side pigmentation. The other three species are more similar morphologically and have frequently been misidentified both in fish collections and in some previous literature on these fishes. Of these three, P. novaezeelandiae, the largest in the genus, is distinguished from congeners by the combination of: its large size (reaching 510 mm SL vs. ≤ 200 mm SL); rounded head shape; blind-side squamation; the second ocular-side pectoral-fin ray shorter than body depth; ontogenetic variation in interorbital width; greater distance (4–8 scales wide) between ventral margin of lower eye and dorsal (upper) margin of rostral hood above the mouth; and 2–6 fleshy, finger-like filaments on the inner anteroventral margin of the fleshy skinfold on the ocular-side lower jaw. Peltorhamphus latus differs from congeners by the combination of: its short (maximum 150 mm SL), relatively deep body and bluntly pointed snout; blind-side squamation; relatively long, robust gillrakers on first gill arch, with upper limb gillrakers long, but not usually overlapping tips of dorsalmost gillrakers on the lower limb; black pigment on entire roof of mouth; relatively large eyes and narrow interorbital width (without significant ontogenetic variation); short diagonal distance (usually 2–3 scales wide) between ventral margin of lower eye and dorsal (upper) margin of rostral hood above the mouth; and absence of finger-like filaments on the inner anteroventral margin of the fleshy skinfold on the ocular-side lower jaw. Peltorhamphus kryptostomus n. sp. is distinguished from congeners by the combination of: its deep body and smoothly rounded snout; blind-side squamation; long, robust gillrakers on the first gill arch, with some posterior gillrakers on the upper limb overlapping tips of the first and second dorsalmost gillrakers on the lower limb; black pigment on the entire roof of the mouth; relatively large eyes and relatively narrow interorbital width; wide distance between ventral margin of lower eye and upper margin of rostral hood (3–6, usually 4–5, scales wide); and 1–4 finger-like filaments on the inner anteroventral margin of the fleshy skinfold on the ocular-side lower jaw. Ecological and life-history information are summarized for each species, and a key to juveniles > 40 mm SL and adults is also provided. Re-assessment of the number of valid species of Peltorhamphus provides better understanding of species diversity within this genus and within the Rhombosoleidae, as well as that for the flatfish assemblage residing in New Zealand waters.
... Received 24 January 2019; Received in revised form 16 July 2019; Accepted 30 July 2019 their specific values of temperature, dissolved oxygen, salinity, and density (Koslow et al., 1994;Clark et al., 2010a;Tracey et al., 2012;Victorero et al., 2018). Water masses play two important roles: acting as a vertical barrier for many species (Koslow et al., 1994) and facilitating horizontal larval dispersal (Norcross and Shaw, 1984;Haedrich and Merrett, 1990;Koslow, 1993;Francis et al., 2002). ...
... These results are consistent with previous studies in terms of the variation of deep-sea assemblages on seamounts (Richer de Forges et al., 2000;Tracey et al., 2004Tracey et al., , 2012McClain, 2007;Morato and Clark, 2007;Rowden et al., 2010;Bo et al., 2011;Clark et al., 2010aClark et al., , 2010b2012;Schlacher et al., 2014;Long and Baco, 2014;Morgan et al., 2015). In New Zealand, Francis et al. (2002) found that the assemblage structure of fishes in many seamounts depends on latitude and depth. Tracey et al. (2012) mentioned that the proximity of the seamounts in their study did not allow recognition of latitude as an important variable for the structure of the assemblage, but depth was correlated as it was also for other studies in the area (Donovan, 1998;Jacob et al., 1998). ...
Evidence is accumulating that within any given seamount, the abundance and diversity of fauna may vary strongly with environmental variability. Necker Island, located in the Northwestern Hawaiian Islands, has not been subject to commercial trawl fisheries and is currently protected from fishing activities as part of the
Papahānaumokuākea Marine National Monument. The relatively pristine nature of this seamount makes it an excellent location to assess the abundance and diversity of the deep-sea fish fauna of a seamount and their variability relative to environmental parameters, with minimal confounding of natural patterns by human impacts.
Using 51,988 AUV photos that showed 18,478 fishes, 92 species were identified from three study sites on different slopes of Necker Island at depths of 200–700 m. The deep-sea fish assemblages were dominated by Stomiiformes, Gadiformes, Myctophiformes, Aulopiformes, and Perciformes. From 250 to 700 m, relative
abundance of fishes was significantly different among study sites, with the NE side having the lowest abundance. Species richness and rarefaction estimates of the expected species richness showed significant differences by study site, depth, and their interaction. The NE slope of the island had the lowest estimated richness. By depth,
species richness showed two peaks, one at 350m and the highest at 500 m, in which diversity was also very high with low dominance. The highest values of dominance were observed at 250 and 700 m. Community structure was significantly different by study site, depth, and their interaction. Variation by depth was observed in the NMDS plot, with three assemblages characterized by different dominant species. Fish assemblage structure was correlated with dissolved oxygen, salinity, percentage of sand, rugosity, slope, POC, and current vectors u and v. These results support significant variability in deep-sea fish abundance, diversity, and assemblage structure on
seamounts over relatively narrow depth ranges and among sides of a seamount at the same depth. This variability should be considered in future ecological studies of seamounts as well as in the management and conservation of seamounts.
... Graham (1938Graham ( , 1953 recorded the stomach contents of a small number of specimens from the Otago Harbour and presented some observations on the behaviour of this shark. Subsequent ecological references to C. isabellum were limited to records of occurrence (e.g., Zintzen et al., 2012), general comments about habitat and biology in books summarising elasmobranch species (e.g., Michael, 1993;Cox and Francis, 1997;Francis, 2012), their parasites (Hewitt and Hine, 1972), and investigations of demersal fish assemblages where C. isabellum was shown to be an important component of the outer shelf assemblage along the continental shelf and upper slope of the east coast of South Island (Beentjes et al., 2002) and throughout most of the New Zealand continental shelf (Francis et al., 2002). ...
... All sizes of C. isabellum, and both sexes, occur in shallow depths, but larger fish predominate in deeper waters. Francis et al. (2002) estimated the preferred depth and 90% range for C. isabellum throughout the New Zealand continental shelf to be 140 m (40-360 m). It is apparent, however, that the preferred depth distribution range deepens with northward movement. ...
The carpet shark Cephaloscyllium isabellum is abundant and widespread around the New Zealand coastal shelf from the tidal zone to about 500 m. Their overall depth distribution deepens with decreasing latitude, indicating a distribution moderated by water temperature. Cephaloscyllium isabellum is a generalist benthic carnivore and scavenger that uses both ambush and active searching hunting strategies. It has a broad diet (mainly fish, crustaceans, cephalopods, gastropods, and holothurians) and an apparent ability to manipulate prey to remove the shells of gastropods and pagurids before ingesting these animals. Length at maturity is about 60 cm for male and 76 cm for female C. isabellum. They may have an egg-laying peak around summer but probably reproduce throughout the year; the egg laying process is described. Females attain a larger size (c. 92 cm) than males (c. 80 cm). Growth and mortality rates are unknown, and constitute the main knowledge gap for C. isabellum and for Cephaloscyllium species in general.
... Species assemblages are acknowledged to be an important feature of marine ecosystems and contribute to shaping their structure, diversity, and stability (Francis et al., 2002). The term assemblage describes the set of species present at a defined location, whether or not there are interactions among them (Wootton, 1998). ...
... The term assemblage describes the set of species present at a defined location, whether or not there are interactions among them (Wootton, 1998). The description of species assemblages generates a great deal of interest because of its potential as a tool for characterizing and understanding interactions among species and relationships between species and their environment (Snelgrove and Haedrich, 1985;Mahon et al., 1998;Brown, 2000;Auster et al., 2001;Francis et al., 2002). Assemblage patterns are also a useful parameter to describe and monitor biodiversity. ...
Chouinard, P-M., and Dutil, J-D. 2011. The structure of demersal fish assemblages in a cold, highly stratified environment. – ICES Journal of Marine Science, 68: 1896–1908.
Fish are a major component of marine ecosystems, with many species co-occuring in the same habitats. Potential interactions among species and with the environment can be studied through the identification of species assemblages. Data from bottom trawl surveys (2004–2008) conducted in the estuary and northern Gulf of St Lawrence were analysed using multivariate methods (cluster, multidimensional scaling, and detrended canonical correspondence analysis) to describe the structure and composition of demersal fish assemblages, including rare and smaller non-commercial species. The spatial variability in environmental conditions that characterizes the study area has a significant impact on the composition of fish assemblages in the region. In all, 35 taxa were classified as key, and 6 main fish assemblages were described, based on catch in numbers. These assemblages had a coherent spatial distribution in the study area, associated with either depth, salinity and temperature, or dissolved oxygen. The analyses showed overall strong correlations between species abundance and prevalent environmental conditions and explained 18.4% of the variance in species abundance data and 79.2% of the variance in the species–environment relationship.
... The decreasing gradient in species richness towards higher latitudes observed in this study is consistent with the general trends described in the Atlantic Ocean for both Actinopterygii and Chondrichthyes (Floeter et al. 2004;Lucifora et al. 2012;Macpherson 2002;Sabadin et al. 2020). Site and habitatspecific (i.e., alpha) richness values matched with results from previous studies (e.g., Galván et al. 2009) and were similar to those reported for other regions at comparable latitudes in the southern hemisphere (Francis et al. 2002;Pérez-Matus et al. 2022). It is important to emphasise that sampling completeness was generally large and that variations in the number of samples per site did not affect the observed richness pattern. ...
Aim
To evaluate alpha and beta diversity of coastal marine fishes across different spatial scales—habitat, regional, and biogeographical—along a 14° latitudinal gradient (41° S–55° S).
Location
Southern Southwest Atlantic Ocean (SWA).
Taxon
Coastal marine fishes.
Methods
We sampled four benthic habitats—rocky reefs, soft bottoms, transition habitats, and kelp forests—across seven shallow coastal sites (≤ 30 m depth) spanning distances of up to 1500 km. We conducted a total of 335 hourly deployments by using Baited Remote Underwater Video Stations (BRUVS). We analysed the alpha diversity by site and habitat and assessed beta diversity along with the influence of environmental variables across different spatial scales. Furthermore, we identified key taxa contributing to compositional changes.
Results
We recorded 7045 individuals representing 32 fish taxa: 30 species, one genus— Patagonotothen— and one family—Myxinidae. Taxonomic richness decreased with latitude, and a gradual turnover in species composition was recorded along the latitudinal gradient. This turnover distinguished warm‐temperate assemblages of the Argentine Biogeographic Province from cold‐water assemblages of the Magellanic Province and disclosed a southwards displacement of the biogeographic transition zone between them. In the Argentine Province, four species were identified as recent colonisers from lower latitudes. In addition, benthic habitats showed relatively high species turnover, with 25% of the recorded taxa being exclusive to a single habitat.
Main Conclusions
This study represents the first standardised BRUVS survey conducted across such an extensive spatial scale in the SWA, and one of the broadest latitudinal assessments using this method globally. Our findings fill a knowledge gap in high‐latitude fish biogeography, reveal climate‐driven shifts in fish assemblages in the SWA, and highlight the contribution of different benthic habitats to overall fish diversity. Our study also uncovers scale‐dependent patterns in marine coastal fish assemblages and has implications for their monitoring and management.
... The results of relative importance showed that the most important factor affecting the distribution of C. lucidus in spring and autumn was water depth (Figure 3). Water depth can not only reflect changes in pressure and light intensity but also lead to changes in physical and chemical factors such as water temperature and salinity [41]. The model fitting results and the distribution map (Figures 4 and 5) showed that the tail density of C. lucidus was the highest near a water depth of 28~30 m in spring. ...
Collichthys lucidus is a small fish found in offshore waters that is economically important for China. It is imperative to understand its distribution characteristics and driving factors. Based on survey data of trawl fishery resources offshore of Zhejiang province, China, in spring (April) and autumn (November) from 2018 to 2022, the spatial and temporal distributions of C. lucidus in this area were analyzed. The random forest (RF) model was used to determine the important marine factors affecting the distribution of C. lucidus. The relationship between the distributions of the important variables was analyzed. The results showed that C. lucidus was mainly distributed in coastal waters. The tail density of the species exhibited obvious seasonal variation and was significantly greater in autumn than in spring. The most important factor affecting the distribution of this species in spring and autumn was water depth. The bottom temperature, bottom salinity and dissolved oxygen concentration were also important influencing factors. The importance of these factors differed among the different seasons, while the chlorophyll a concentration and pH had no significant effect on the species distribution. This study revealed the distribution pattern of C. lucidus in offshore waters of Zhejiang Province and the influence of important marine factors on its distribution. This study can enrich the survey data on C. lucidus and provide basic data for its scientific management and protection.
... There have been efforts across the globe to characterize demersal fish assemblage structure, and these have been mostly concentrated on continental shelves and upper slopes, with fewer studies off oceanic islands or on seamounts (Clark et al., 2010;Drazen et al., 2021). The focus has been in the southwestern and southeastern Pacific Ocean (e.g., Koslow et al., 1994;Francis et al., 2002;Tracey et al., 2004), off Japan (e.g., Fujita et al., 1995), the Nazca and Sala-y Gomez Ridges (Parin, 1991;Parin et al., 1997;Tapia-Guerra et al., 2021), across the central Pacific Ocean (Drazen et al., 2021), and in several areas of the North Atlantic (Colvocoresses and Musick, 1984;Haedrich and Merrett, 1990;Mahon et al., 1998;Menezes et al., 2006;Bergstad et al., 2008;Menezes et al., 2009;Morato et al., 2009;Amorim et al., 2017;Parra et al., 2017). These studies have found that depth is a strong driver of assemblage structure with major shifts in fauna between the continental shelf (0-200 m), upper slope (200-600 m), mid-slope (600-800 m), and deep mid-slope (800-1200 m). ...
Demersal deep-sea fish assemblages from islands and seamounts are poorly described, even in the Hawaiian archipelago. Knowledge across all depths, in similar settings, is even sparser for other archipelagos in the central and western Pacific. However, recent remotely operated vehicle (ROV) explorations and archived video from human-occupied submersible dives conducted by the Hawai`i Undersea Research Laboratory (HURL) provide an opportunity to explore the structure of these assemblages. Here we describe demersal fish assemblages across the central and western Pacific, including in four Marine National Monuments, and examine the relationship of the assemblages to depth and environmental conditions. We used data collected from 227 underwater vehicle dives resulting in the identification of 24,837 individuals belonging to 89 families and 175 genera. The most frequently occurring genera at depths of 250-500 m were Epigonus, Setarches, Polymixia, and Antigonia, between 500-1000 m were Chlorophthalmus, Aldrovandia, and Neocyttus, and between 1000-3000 m were Synaphobranchus, Kumba, Halosaurus, Ilyophis, and Ipnops. There are strong changes in the fish assemblages with depth and region, and assemblages become more similar between regions with greater depth. Depth and region explained the most variance in assemblage structure followed by seafloor particulate organic carbon flux (a food supply proxy), concentrations of dissolved oxygen, and salinity. The Line Islands and Tokelau Ridge had the highest values of seafloor particulate organic carbon flux for all depth zones investigated (250-3000 m) and the highest abundance of fishes at 250-500 m and 500-1000 m, respectively. Taxon accumulation curves indicated that diversity at the genus level within all regions and depth bins (except 1000-2000 m and 2000-3000 m) had not been reached with the existing sampling effort. However, when combining samples from all regions, diversity generally appeared to decrease with depth. Overall, this study demonstrates that there are significant regional differences in the composition of the deep-sea fish fauna as well as differences across depth. Such distribution patterns suggest that the four Marine National Monuments (Papahānaumokuākea, Marianas Trench, Pacific Remote Islands, and Rose Atoll Marine National Monuments, encompassing an area of 3,063,223 km²) are not replicates of diversity, but complementary components of the regional fauna.
... Many factors influence fish populations and consequently total catch and CPUE. Studies within New Zealand's EEZ have shown that bottom temperature and depth are good predictors of fish assemblages (Francis et al., 2002;Stephenson et al., 2018). Therefore, spatially explicit estimates of depth (m) and bottom water temperature ( o C) (1 km grid resolution, Stephenson et al., 2022) were used to calculate mean depth and bottom temperature for each trawl event. ...
the cessation of fishing. However, the effects of marine protection on fishing fleet behaviour and fish catches outside of MPAs are less well understood. Here we investigated changes in total catch and Catch per Unit Effort (CPUE) of bottom trawlers outside the borders of offshore MPAs in New Zealand. We used Regression Discontinuity in Time (before versus after protection) on both aggregate and individual trawl event data for one Marine Reserve, two Benthic Protected Areas, one Closed Seamount Area and one Marine Mammal Sanctuary. Despite the various forms of protection that reduce the total fishable area, total catch tended to increase after MPA implementation. Yet, there was little evidence that this was due to the net-movement of fish from larger populations within MPA boundaries i.e. spillover. Rather, the increases in catch in the post protection period appeared to be a consequence of changes in the behaviours of commercial fishers. This may be an unintended and previously unreported negative consequence of marine protection that could dampen some of the many benefits of MPAs.
... The inner continental shelf off eastern Australia is relatively narrow (Cresswell et al., 2017). In New Zealand such habitat is common, and C. kumu were assessed as being the most frequent species in inshore assemblages with the widest latitudinal range and the third greatest depth range (Francis et al., 2002). ...
The red gurnard (Chelidonichthys kumu) is a coastal benthic fish supporting substantial fisheries in the Indo-West Pacific. Despite this, biological knowledge of the species is limited to New Zealand, placing other fished populations at risk of overexploitation if they are less productive. We determined the age, growth, reproductive biology and commercial catch composition of C. kumu from the trawl fishery in New South Wales (NSW). We also tested the hypothesis that growth rates and body size in NSW would be smaller than New Zealand, given the less productive marine environment in NSW and relative food limitation. Similar to New Zealand, individuals from NSW ranged in length from 13 to 56 cm FL and 1 to 13 years of age, with the largest and oldest fish being predominantly female. Females grew faster and to a greater maximum size than males. Growth was broadly similar between populations in NSW and New Zealand. Spawning period in NSW was protracted (11 months) and peaked in winter, contrasting with a peak in spring/summer in New Zealand. Size-at-maturity was similar between the two regions. The current study provides fundamental biological information to inform stock assessment and management of C. kumu in NSW.
... Assemblage studies from the extent of the New Zealand Exclusive Economic Zone (EEZ) have used New Zealand research trawl data from depths of ~4 to 1500 m. Francis et al. (2002) identified four primary assemblages, with ling being a dominant species in the upper continental slope group (occurring in 43% of tows and being the third most caught species in that assemblage). Point estimate preferences for ling were a depth of 480 m and latitude of 48° S. Most of the explainable variation in species composition was associated with depth and latitude. ...
This report aims to review the available literature and data on ling (Genypterus blacodes), primarily to provide synopses on the biology and life history of the species from worldwide sources, but also to provide references should the reader wish to investigate particular aspects in more detail.
... These groups can be considered communities as they describe groups of spatially and temporally co-occurring taxa, which may interact to some extent with one another (Morin, 2009). Some species in a community will interact either directly (e.g., through predator-prey interactions) or indirectly (e.g., by feeding on the same organisms), while other taxa may not necessarily interact with each other and may only be "associated" because they inhabit the same physical space (Francis et al., 2002). There is still a paucity of information with regards to species interactions at the spatial scales of the communities identified by the New Zealand SCC. ...
To support ongoing marine spatial planning in New Zealand, a numerical environmental classification using Gradient Forest models was developed using a broad suite of biotic and high-resolution environmental predictor variables. Gradient Forest modeling uses species distribution data to control the selection, weighting and transformation of environmental predictors to maximise their correlation with species compositional turnover. A total of 630,997 records (39,766 unique locations) of 1,716 taxa living on or near the seafloor were used to inform the transformation of 20 gridded environmental variables to represent spatial patterns of compositional turnover in four biotic groups and the overall seafloor community. Compositional turnover of the overall community was classified using a hierarchical procedure to define groups at different levels of classification detail. The 75-group level classification was assessed as representing the highest number of groups that captured the majority of the variation across the New Zealand marine environment. We refer to this classification as the New Zealand “Seafloor Community Classification” (SCC). Associated uncertainty estimates of compositional turnover for each of the biotic groups and overall community were also produced, and an added measure of uncertainty – coverage of the environmental space – was developed to further highlight geographic areas where predictions may be less certain owing to low sampling effort. Environmental differences among the deep-water New Zealand SCC groups were relatively muted, but greater environmental differences were evident among groups at intermediate depths in line with well-defined oceanographic patterns observed in New Zealand’s oceans. Environmental differences became even more pronounced at shallow depths, where variation in more localised environmental conditions such as productivity, seafloor topography, seabed disturbance and tidal currents were important differentiating factors. Environmental similarities in New Zealand SCC groups were mirrored by their biological compositions. The New Zealand SCC is a significant advance on previous numerical classifications and includes a substantially wider range of biological and environmental data than has been attempted previously. The classification is critically appraised and considerations for use in spatial management are discussed.
... Estuaries are always dynamic with huge environmental variability to influence the biological community and featured by being transitional places between terrestrial and marine habitats (Kupschus and Tremain, 2001). Their structure, diversity and stability are defined by biologic interactions (intra and interspecific) (Francis et al., 2002). Fish, for example, constitute the main biological component using these ecosystems as feeding, reproduction, growth and protection grounds (Raz-Guzman and Huidobro, 2002), in terms of their tolerance limits to those hydrologic certain species, especially from the juvenile age group (Whitfield, 1999). ...
It is increasingly recognized that Estuarine Set Bag Net (ESBN) is very popular gear in the coastal fishing community of Bangladesh. In order to reveal the species composition of the ESBN catch and to study the impact of environmental parameters on the spatio-temporal variation of fish assemblages, a one-year baseline survey was conducted in coastal waters of the Moheshkhali Island, northern Bay of Bengal, Bangladesh. A total of 59 taxa were identified of which 47 were finfishes, 7 were shrimps and 5 were from other categories i.e. crab, holothruim, lobster, squid and squila. Among them, 54 species were commonly distributed in all four seasons and stations with 23 and 24 species were found dominant to the total communities in different seasons and sites, respectively. Similarity percentage analysis revealed significant variation in structure and composition of total communities in temporal and spatial scale: (1) the highest (89.33%) and lowest (70.10%) average species similarity was observed in monsoon and winter, respectively; (2) the average species similarity was found highest in Sonadia (88.30%) and lowest in Nalbila (74.83%). SIMPER analysis demonstrated that the contributory species (i.e. Crab, Squid, Pampus chinensis, Chirocentrus nudus, Ascetes sp. Penaeus monodon, Metapenaeus brevicornes, Arius sp., Tenualosa ilisha, Uranoscopus sp., Machrobrachium ruddis, Gerres filamentosus, Coillia dussumieri, Squila, Glossogobius giuris, Rastrelliger kanagurta, Rhynchorhamphus georgii, Chirocentrus nudus, Ascetes sp., Metapenaeus brevicornes, Tenualosa ilisha, Uranoscopus sp., Rhynchorhamphus georgii, Penaeus indicus) varied among different sites and seasons. One-way ANOVA and Canonical Correspondence Analysis (CCA) revealed that the total communities were significantly driven by temperature, salinity, pH, DO and water transparency. Multivariate analyses showed that the diversity of ESBN fishery is high in this Island. These findings signify that this coastal zone is one of the nursery grounds and highly diversified for many marine fishes.
... In addition, studies on the biological and ecological characteristics, such as fish interspecific relationships (e.g., predation and competition) and food availability are necessary (Hixon and Jones, 2005;Tableau et al., 2016). The definition of the structure, diversity and stability of fish assemblages is related to the interactions between species of fish and between them and the physical environment (Francisa et al., 2002). ...
The composition and structure of fish assemblages in the inner continental shelf of the Paraná State are affected by cold fronts and the rainfall regime. Data from fishing activities in this region, as well as the analysis of environmental characteristics, are the main tools available for understanding fish dynamics, under influence of increasing human activities. In order to better understand patterns and temporal variations in fish assemblages in the inner continental shelf of the Paraná State, a total of 24 double trawls were performed with an otter trawl between August 2000 and July 2001, in two sampling areas, the North area in front of the northern mouth of the Paranaguá Estuary Complex, and the South area, in front of the Leste beach. A total of 45,277 fish specimens belonging to 35 families and 97 species were caught. Sciaenidae was the most abundant family, with 37.1% of the total number of individuals caught, and with the highest richness (18 species). Statistical analyses evidenced significant differences in environmental characteristics and in fish fauna, and that both areas disturbances were observed in the fish assemblages during the dry and wet season, being more intense in the Southern area, disturbances that would be related to the shrimp fishing present in the two areas sampled in this study.
... for NE Caribbean, Quattrini et al., 2017). The differences may be partly related to the latitudinal effect of increasing species abundance and productivity from the Equator to higher latitudes(Chaudhary et al., 2017;Francis et al., 2002;Tracey et al., 2004).At NE Atlantic level, despite some similarity in species composition as before mentioned, clear variations in species richness can be found among Azorean seamounts and those in the Madeira (e.g., 41spp. recorded for Seine seamount,Menezes et al., 2009), Canaries (e.g., 55 spp. ...
Seamount fish communities are susceptible to variations due to the oceanographic conditions and level of historical fishing effort. In the NE Atlantic, the Azores is considered an "oceanic seamount ecosystem area" because seamount concentration is high relative to other regions. Scientific information on seamounts in the Azores remains scarce and demersal fishery occurs mostly without any knowledge to endorse sustainable harvest strategies. To make available an important baseline information on dynamics of demersal fish populations inhabiting commercially exploited seamounts, the present study has as specific objectives to (a) describe the taxonomic composition of demersal fish assemblages on underwater mountains, (b) examine whether assemblages vary spatial and temporally, and (c) investigate what drives distributional patterns of species in terms of abundance and size composition. For this, three Azorean seamounts (Açores, Princesa Alice and Mar da Prata) exploited by bottom fishing were selected as case study areas. Data were obtained from scientific surveys and commercial fishery over the past c. 25 years. A total of 84 species from 45 families were identified. Sebastidae, Moridae, Sparidae and Centrophoridae were the most abundant families, mainly represented by Helicolenus dactylopterus, Mora moro, Pagellus bogaraveo and Deania profundorum, respectively. Fish assemblages were more distin-guishable spatially than temporally. Depth was identified as the main factor responsible for these differences. The higher occurrence of shallow and intermediate (i.e., up to 600 m) habitats in Princesa Alice and Açores seems to favor the occurrence of a greater number of species and higher abundances in comparison to Mar da Prata. Phycis phycis, Pontinus kuhlii, H. dactylopterus, P. bogaraveo, Conger conger and M. moro were the species which primarily contributed to dissimilarities in assemblage structure among sample groups. Abundance indices and fish sizes showed a decreasing trend for many of these species, especially for those with sedentary behaviour inhabiting historically highly exploited seamount areas. These results highlighted the vulnerability of demersal fishes to the expansion of fishing effort in the offshore seamount areas. Spatial management of seamounts should be a priority being fish conservation balanced with strategies that support sustainable fisheries.
... 400 species of grenadier in four groups (bathygadids, macrourids, macrouroidids and trachyrincids) worldwide and 72 species live in the New Zealand Exclusive Economic Zone (Iwamoto, 2008;Roberts et al., 2015). Many of these species are small (<50 cm), some species are abundant and comprise a major component of demersal fish assemblages (Francis et al., 2002) and are a common bycatch of research (Bagley et al., 2013;O'Driscoll et al., 2011) and commercial demersal trawls (Anderson, 2009;Ballara et al., 2010). ...
Feeding habits of six deep‐sea demersal trawl‐caught macrourids on Chatham Rise, New Zealand, were examined from stomach contents during the austral summer. Three species were predominantly benthic foragers: smallbanded rattail Coelorinchus parvifasciatus on small epifaunal crustaceans, twosaddle rattail Coelorinchus biclinozonalis on epifaunal decapods and humpback rattail Coryphaenoides dossenus on benthic fishes and epifaunal decapods. Three species were predominantly benthopelagic foragers: banded rattail Coelorinchus fasciatus on hyperiid and gammarid amphipods and calanoid copepods, blackspot rattail Lucigadus nigromaculatus on small epifaunal crustaceans and suprabenthic mysids and Mahia rattail Coelorinchus matamua on epifaunal decapods and calanoid copepods. The most important predictors of diet variability were identified using distance‐based linear models and included areal predictors in C. parvifasciatus, L. nigromaculatus and C. dossenus, fish size in C. dossenus, C. biclinozonalis and C. matamua, sample year in C. biclinozonalis and C. fasciatus and depth in C. matamua. Results are compared with previously published data for four other macrourid species from the same study area. The 10 grenadier species comprise benthic, benthopelagic and mesopelagic foraging guilds. This study brings the number of grenadier species for which diet on Chatham Rise has been described in detail to 12.
... Given these characteristics, we expect this classification to have potentially strong value as a summary of spatial variation in fish assemblages that can provide a common currency for discussions among those with interests in marine management and conservation. In comparative terms, the broad spatial structure of this new GF-based classification is strongly consistent with results from previous studies at various spatial scales ranging from regional to national, e.g. in Bull et al. (2001); Beentjes et al. (2002); Francis et al. (2002); Kendrick and Francis (2002); Snelder et al. (2007). Using correspondence and cluster analysis, these studies identified depth, and to a lesser extent, water temperature, latitude (as a proxy for temperature and water mass) and major oceanographic features as important variables structuring variation in species composition. ...
Spatial classifications of the environment have previously been used to characterise biodiversity and to facilitate management planning at large spatial scales. Such classifications are more likely to be adopted if they can demonstrate integration of real patterns in habitats or biotic assemblages, in addition to environment. A previous classification used Gradient Forest analysis to derive 30 classes based on demersal fish assemblage patterns and environmental gradients. Here we provide a detailed description of the similarities and differences in the environment and fish assemblages of classes resulting from an updated classification using the same methodology. Environmental differences were associated with varying levels of differences in the distributions of fish species. At broad spatial scales, assemblages are differentiated primarily according to oceanographic conditions such as temperature and depth; at finer scales, patterns in species assemblages are more closely associated with more localised environmental conditions such as productivity, sea-surface temperature gradients and tidal currents. The 30-group classification allows complex biodiversity information to be summarised in ways accessible to stakeholder and environmental managers. Given the hierarchical nature of the classification, there is considerable scope to use a larger number of groups for applications at regional to local scales.
... for NE Caribbean, Quattrini et al., 2017). The differences may be partly related to the latitudinal effect of increasing species abundance and productivity from the Equator to higher latitudes(Chaudhary et al., 2017;Francis et al., 2002;Tracey et al., 2004).At NE Atlantic level, despite some similarity in species composition as before mentioned, clear variations in species richness can be found among Azorean seamounts and those in the Madeira (e.g., 41spp. recorded for Seine seamount,Menezes et al., 2009), Canaries (e.g., 55 spp. ...
Seamount fish communities are susceptible to variations due to the oceanographic conditions and level of historical fishing effort. In the NE Atlantic, the Azores is considered an "oceanic seamount ecosystem area" because seamount concentration is high relative to other regions. Scientific information on seamounts in the Azores remains scarce and demersal fishery occurs mostly without any knowledge to endorse sustainable harvest strategies. To make available an important baseline information on dynamics of demersal fish populations inhabiting commercially exploited seamounts, the present study has as specific objectives to (a) describe the taxonomic composition of demersal fish assemblages on underwater mountains, (b) examine whether assemblages vary spatial and temporally, and (c) investigate what drives distributional patterns of species in terms of abundance and size composition. For this, three Azorean seamounts (Açores, Princesa Alice and Mar da Prata) exploited by bottom fishing were selected as case study areas. Data were obtained from scientific surveys and commercial fishery over the past c. 25 years. A total of 84 species from 45 families were identified. Sebastidae, Moridae, Sparidae and Centrophoridae were the most abundant families, mainly represented by Helicolenus dactylopterus, Mora moro, Pagellus bogaraveo and Deania profundorum, respectively. Fish assemblages were more distin-guishable spatially than temporally. Depth was identified as the main factor responsible for these differences. The higher occurrence of shallow and intermediate (i.e., up to 600 m) habitats in Princesa Alice and Açores seems to favor the occurrence of a greater number of species and higher abundances in comparison to Mar da Prata. Phycis phycis, Pontinus kuhlii, H. dactylopterus, P. bogaraveo, Conger conger and M. moro were the species which primarily contributed to dissimilarities in assemblage structure among sample groups. Abundance indices and fish sizes showed a decreasing trend for many of these species, especially for those with sedentary behaviour inhabiting historically highly exploited seamount areas. These results highlighted the vulnerability of demersal fishes to the expansion of fishing effort in the offshore seamount areas. Spatial management of seamounts should be a priority being fish conservation balanced with strategies that support sustainable fisheries.
... For example, flocks of Hutton's shearwater have been reported along the Kaikōura and Canterbury coastline south to Banks Peninsula, out to the Chatham Rise in the east, and north to the Cook Strait (Harrow, 1976;Hawke, 1998;Pinkerton, 2011). These areas coincide with longline and trawl fisheries due to their high species richness (Francis, Hurst, McArdle, Bagley, & Anderson, 2002;Leathwick, Elith, Francis, Hastie, & Taylor, 2006;McClatchie et al., 1997;Richard et al., 2015). Although Hutton's shearwaters generally do not associate or follow boats (Marchant & Higgins, 1990;Wood, 1993), at least two by-catch occurrences of Hutton's shearwaters have been reported in the region (Tarburton, 1981;West & Imber, 1985). ...
The Hutton's shearwater Puffinus huttoni is an endangered seabird endemic to Kaikōura, New Zealand, but the spatial and temporal aspects of its at‐sea foraging behavior are not well known.
To identify foraging areas and estimate trip durations, we deployed Global Positioning Systems (GPS) devices and Time‐Depth Recorders (TDR) on 26 adult Hutton's shearwaters during the chick‐rearing period in 2017 and 2018.
We found Hutton's shearwaters traveled much further from their breeding grounds at Kaikōura than previously considered, with most individuals foraging in coastal and oceanic areas 125–365 km south and near Banks Peninsula. Trip durations varied from 1 to 15 days (mean = 5 days), and total track lengths varied from 264 to 2,157 km (mean = 1092.9 km).
Although some diving occurred in near‐shore waters near the breeding colony, most foraging was concentrated in four regions south of Kaikōura. Dive durations averaged 23.2 s (range 8.1 to 71.3 s) and dive depths averaged 7.1 m (range 1.5 to 30 m). Foraging locations had higher chlorophyll a levels and shallower water depths than nonforaging locations. Birds did not feed at night, but tended to raft in areas with deeper water than foraging locations.
Mapping the spatial and temporal distribution of Hutton's shearwaters at sea will be fundamental to their conservation, as it can reveal potential areas of overlap with fisheries and other industrial users of the marine environment.
... G. blacodes is a benthic-demersal species found in the oceans around southern Australia, Chilean Patagonia, Brazil, Argentina and New Zealand in depths from 22 to 1000 m (Young et al., 1984;Francis et al., 2002;Nyegaard et al., 2004). Adults exhibit a demersal behavior and they are usually found at depths between 45 and 350 m (Cousseau and Perrotta, 2000;Nyegaard et al., 2004). ...
In this research we evaluated simple aspects of the sperm biology of Genypterus blacodes, in particular assessing the effects of pH (6, 7, 8 and 9), temperature (4, 8 and 16 °C) and osmolalities 100% sea water (1010 mOsm/kg, Control), 75% sea water (774 mOsm/kg, T 1), 50% sea water (488 mOsm/kg, T 2) and distilled water (0 mOsm/ kg, T 3)) on the motility of Genypterus blacodes intratesticular spermatozoa. In addition, we determined the fertilization rate. Our results show that G. blacodes spermatozoa have a sperm density of 5.35 ± 0.16 × 10 9 spermatozoa/mL. Sperm motility is initiated on contact with a hyperosmotic swimming medium under normal conditions (1010 mOsm/kg, pH 8 and 8 °C). The longest motility duration (432.48 ± 8.89 s) was recorded at 4 °C. The maximum percentage of motile cells was recorded at 8 °C (65.66 ± 4.95) at osmolality 1010 mOsm/kg, whereas an optimum was observed at pH 8. The fertility rate was 73.9 ± 17%. This is the first report on sperm motility of G. blacodes spermatozoa. In conclusion, the results of this study permit a baseline to be established for further research and protocols for artificial reproduction of this species to be developed and optimized. In addition, the information gathered in this research will be useful for developing the biotechnology of Genypterus blacodes.
... This may improve the precision of CPUE prediction, and possibly explain more spatial variation in hoki CPUE, than stratum. Francis et al. (2002) and Fujita (2016) found that depth was a statistically significant predictor of CPUE for species on the Chatam Rise. Depth interval could be explored with further research. ...
In order to carry out assessment of marine stock levels, an accurate estimate of the current year's population abundance must be formulated. Standardized catch per unit of effort (CPUE) values are, in theory, proportional to population abundance. However, this only holds if the species catchability is constant over time. In almost all cases it is not, due to the existence of spatial and temporal variation. In this thesis, we fit various models to test different combinations and structures of spatial and temporal autocorrelation within hoki (Macruronus novaezelandiae) CPUE. A Bayesian approach was taken, and the spatial and temporal components were modelled using Gaussian Markov random fields. The data was collected from summer research trawl surveys carried out by the National Institute of Water and Atmospheric Research (NIWA) and the Ministry for Primary Industries (MPI). It allowed us to model spatial distribution using both areal and point reference approaches. To fit the models, we used the software Stan (Gelman et al., 2015) which implements Hamiltonian Monte Carlo. Model comparison was carried out using the Watanabe-Akaike information criterion (WAIC, (Watanabe, 2010)). We found that trawl year was the most important factor to explain variation in research survey hoki CPUE. Furthermore, the areal approach provided better indices of abundance than the point reference approach.
... There are several recent biogeographical accounts that applicants may find useful, including global epipelagic (Spalding et al. 2012), mesopelagic (Sutton et al. 2017) and benthic classifications. There are also a number of more regional or New Zealand accounts, including Rowden et al. (2005) for seamounts, Francis et al. (2002) for demersal fishes, and two recent generic environmental classifications of the EEZ, the Marine Environment Classification (MEC) (Snelder et al. 2006), and a Benthic Optimised MEC (Leathwick et al. 2012). ...
Interest in offshore hydrocarbon and minerals exploration is growing rapidly as investors identify the potential economic returns from New Zealand’s rich marine resources. The challenge for management agencies is how to facilitate development of these natural resources while ensuring environmental sustainability is not compromised. In 2012 the Ministry for Business, Innovation and Employment funded NIWA to lead a research project entitled “Enabling management of offshore mining through improved understanding of environmental impacts”. This research programme aimed to develop, validate and implement science-based guidelines for effective environmental management of offshore mineral and hydrocarbon extraction, as well as address some critical gaps in our understanding of the environmental impacts of mining operations on New Zealand’s marine estate.
The first research aim of the project included the development of a generic template for Environmental Impact Assessment (EIA), and guidelines for its use that could be used by any offshore mining or drilling company to guide the preparation of an assessment of the environmental impacts of the proposed operation. These were initially produced in 2014, but have been revised and updated for this guidance document that accompanies the generic EIA template for offshore mining and drilling activities. It is important to note that the template and guidance have been prepared in the joint context of New Zealand’s Exclusive Economic Zone and Continental Shelf (Environmental Effects) Act 2012 (the EEZ Act) and the broader Pacific context where activities in ‘The Area’ are managed. An international need for a consistent approach to assessment of environmental impacts has been identified and addressed by the International Seabed Authority (ISA) and the Pacific Community (SPC) in their own developing EIA templates. The template and guidance presented here draws lessons from that international best practice but provides direct reference to New Zealand’s own legislation.
The guidance is not intended to be exhaustive or prescriptive. Each resource and each location will have its own set of circumstances that are best described and assessed in a particular way. However, the document covers aspects that should be in every EIA, and provides general guidance to the content in each section of the template. It includes a background to the project and the purpose of this guidance document; outlines (and appends in full) the EIA template; provides general advice on how to prepare an EIA; and then details specific guidance on template sections. The report also contains a list of references cited in various sections to help the reader access important sources of information, a glossary of key terms and abbreviations, and a table containing useful websites for further information.
The document focusses on guidance for environmental and ecological assessment of impacts. The template includes sections and subsections on social, economic, and cultural issues, and in doing so follows the recent production of an EIA template by the ISA. These issues are often treated separately, and how that is addressed can be evaluated for each specific case. Their inclusion here attempts to progress the concept of a more integrated impacts assessment, even though provision of advice on them was beyond the scope of the existing study.
A related report covering the scientific research requirements for baseline surveys and monitoring programmes has been developed between NIWA and the SPC, and provides more specific detail than given in this higher-level document.
... PCA (P<0.01). (Francis et al., 2002;Garces et al., 2006;Tittensor et al., 2010). . , , (P<0.05), (Joo, 2006;Im, 2007). ...
The community composition and distribution of fish species in the middle of the Yellow Sea were investigated in summer from 2008 to 2014. A total of 72 demersal fish species from 46 families and 17 orders were collected. The most common species were Larimichthys polyactis, Engraulis japonicus, and Chaeturichthys hexane, which accounted for 72.0% of the total number of individuals while Liparis tanakai, Larimichthys polyactis, and Lophius litulon accounted for 67.8% of the total biomass. A cluster analysis based on the Bray-Curtis similarity revealed that the fish community fell into three groups, according to latitude. Principal Component Analysis (PCA) and correlation analysis showed that variation in bottom water temperature could act as an indicator of variation in community structure and abundance of the dominant species. Characteristics of fish communities, such as the number of species, the total number of individuals (/km^2), and biomass (/km^2), were highly correlated with bottom water temperature and depth.
... Oxynotus bruniensis has a limited distribution, inhabiting temperate waters of the outer continental and insular shelves of southern Australia and New Zealand (Garrick, 1960;Last & Stevens, 2009). In New Zealand waters, O. bruniensis have been reported most frequently off the east coast of the South Island from depths of 200-1000 m (Beentjes et al., 2002;Francis et al., 2002;Tracey et al., 2004). ...
The reproductive biology and diet of prickly dogfish Oxynotus bruniensis, a deep-sea elasmobranch, endemic to the outer continental and insular shelves of southern Australia and New Zealand, and caught as by-catch in demersal fisheries, are described from specimens caught in New Zealand waters. A total of 53 specimens were obtained from research surveys and commercial fisheries, including juveniles and adults ranging in size from 33·5 to 75·6 cm total length (L T). Estimated size-at-maturity was 54·7 cm L T in males and 64·0 cm L T in females. Three gravid females (65·0, 67·5 and 71·2 cm L T) were observed, all with eight embryos. Size-at-birth was estimated to be 25–27 cm L T. Vitellogenesis was not concurrent with embryo development. Analysis of diet from stomach contents, including DNA identification of prey using the mitochondrial genes cox1 and nadh2, revealed that O. bruniensis preys exclusively on the egg capsules of holocephalans, potentially making it the only known elasmobranch with a diet reliant solely upon other chondrichthyans. Based on spatial overlap with deep-sea fisheries , a highly specialized diet, and reproductive characteristics representative of a low productivity fish, the commercial fisheries by-catch of O. bruniensis may put this species at relatively high risk of overfishing.
... The shelf-to-upper slope transition in New Zealand fish fauna has been characterised from a remarkable 19,215 trawl samples ranging across the shelf down to about 1500 m (Francis et al. 2002). Beyond shelf assemblages, an upper slope assemblage of fish preferring 400-740 m depths was recognised. ...
Pioneering deep-sea surveys established that the fauna of the continental margins is zoned in the sense that individual species and assemblages occupy restricted depth bands. It has been speculated that the causes of this wide-spread pattern might involve cold temperatures, high pressures and limited food availability. Increased sampling over the past two decades has confirmed the global presence of depth zonation. Well-defined zonation in the cold polar oceans and the warm Mediterranean indicate that temperature per se may be of less importance on ecological timescales than originally proposed. Strong alternatives are range restriction by pressure and food availability. Understanding of pressure physiology has advanced greatly, and it is to be expected that all deep organisms possess some form of genetic adaptation for pressure tolerance. Since high pressure and low temperatures affect membrane and enzyme systems similarly, combined piezo-thermal thresholds may limit depth ranges. There is a negative, exponential gradient of food availability caused by the decrease in labile carbon influx to bottom. The TROX model linking carbon influx with interstitial oxygen levels has been successful in explaining deep distributions of benthic Foraminifera and may be more broadly applicable. Current efforts to relate metazoan ranges to food availability are, however, hindered by limited understanding of how organisms recognise and utilise the nutritious content of detritus. Thus, the exact controls of depth zonation remain conjectural. Zonation studies are gaining in importance due to the increasing availability of deep fauna databases and the need to establish regulatory boundaries. Future studies may benefit from a growing body of biogeographic theory, especially the understanding of bounded domains. It is proposed that continental slope fauna may be more effectively studied if viewed as the overlapping of three components: species extending down from the shelf, species extending up from the abyss and species truly restricted to the slope. © R. N. Gibson, R. J. A. Atkinson, and J. D. M. Gordon, Editors Taylor & Francis.
... An initial step towards understanding the ecosystem-based fisheries management (EBFM) approach is understanding the functioning of biological communities in space and time, including their correlation with the environment (Sousa et al., 2005). The identification of fish assemblages and their relation to environmental variables may be seen as one probable measure of potential interactions between species (Francis et al., 2002). Therefore, the shift towards EBFM has resulted in many studies, carried out worldwide, to determine how fish assemble in space and time. ...
... There are several recent biogeographical accounts that applicants may find useful, including global pelagic (Spalding et al. 2012) and benthic classifications. There are also a number of more regional or New Zealand accounts, including Rowden et al. (2005) for seamounts, Francis et al. (2002) for demersal fishes, and two recent generic environmental classifications of the EEZ, the Marine Environment Classification (MEC) (Snelder et al. 2006), and a Benthic Optimised MEC (Leathwick et al. 2012). ...
Executive summary
Interest in offshore hydrocarbon and minerals exploration is growing rapidly as investors identify the potential economic returns from New Zealand’s rich marine resources. The challenge for management agencies and scientists is how to facilitate development of this natural resources while ensuring environmental sustainability is not compromised. In 2012 the Ministry for Business, Innovation and Employment funded NIWA to lead a research project entitled “Enabling management of offshore mining through improved understanding of environmental impacts”. This research programme aims to develop, validate and implement science-based guidelines for effective environmental management of off-shore mineral and hydrocarbon extraction, as well as address some critical gaps in our understanding of the environmental impacts of mining operations on New Zealand’s marine estate.
The first research aim of the project included the development of a generic template for Environmental Impact Assessment (EIA), and guidelines for its use that could be used by any offshore mining or drilling company to guide the preparation of an assessment of the environmental impacts of the proposed operation.
This is the guidance document that accompanies the generic EIA template for offshore mining and drilling activities. It is not intended to be exhaustive or prescriptive. Each resource and each location will have its own set of circumstances that are best described and assessed in a particular way. However, the document covers aspects that should be in every EIA, and provides general guidance to the content in each section of the template. It includes a background to the project and the purpose of this guidance document; outlines (and appends in full) the EIA template; provides general advice on how to prepare an EIA; and then details specific guidance on template sections. The report also contains a list of references cited in various sections to help reader’s access important sources of information, a Glossary of key terms and abbreviations, and a table containing useful websites for further information.
The document focusses on guidance for environmental and ecological assessment of impacts. The template includes sections and subsections on social, economic, and cultural issues, and in doing so follows the recent production of an EIA template by the International Seabed Authority. These issues are often treated separately, and that can be evaluated for each specific case. Their inclusion here attempts to progress the concept of a more integrated impacts assessment, even though provision of advice on them was beyond the scope of the existing study.
These guidelines are provisional. Although they have been developed building on an International Seabed Authority template, and have been discussed with both government and industry contacts, it is expected there will be revisions based on wider consultation. We welcome feedback before finalising the template and guidance document. Comments can be emailed to Malcolm Clark (malcolm.clark@niwa.co.nz) by 31 December 2014.
Please note that a report covering the requirements for baseline surveys and monitoring programmes is being developed, and will provide more specific detail than given in this higher-level document.
... Depth was the single environmental factor that had the greatest effect on assemblage structure in the CCA. In many studies on groundfish assemblage structure, depth has been an important structuring environmental factor (Overholtz and Tyler 1985, Gabriel 1992, Gomes et al. 1992, Francis et al. 2002, Magnussen 2002. This may be seen simply as assemblage boundaries following depth contours or by using ordination methods such as CCA. ...
... It is fished hard down on the bottom, and so can catch and affect the abundance of a wide variety of other demersal fish species (e.g. Koslow et al. 1994;Clark et al. 2000;Francis et al. 2002), as well as cause damage to sessile invertebrate fauna. Koslow et al. (2001) and Clark and O'Driscoll (2003) have recorded a strong contrast in the bottom fauna of fished and unfished seamounts off Tasmania and New Zealand, and have attributed this largely to the impact of bottom trawling. ...
Government fisheries observers made detailed records of the catch weights of all species caught on 545 trawls between October 1997 and August 2000 in the South Tasman Rise orange roughy (Hoplostethus atlanticus) fishery. Bycatch ratios, the ratio of bycatch weight to tow duration, were derived from these data and used to make estimates of total annual bycatch for several species groups. Bycatch ratios based on tow duration were chosen over ratios based on orange roughy catch weights after comparing the coefficients of variation (c.v.) of sets of trial data. Bycatch ratios and total bycatch were estimated for three species of oreos (Oreosomatidae), corals and all other bycatch species combined, for the fishing years from 1997–1998 to 2000–2001. Total oreo bycatch dropped from about 7400 t to less than 350 t during this time. These estimates agreed well with recorded oreo landings data for three of the four years. There was a considerable bycatch of corals, with both the bycatch ratio and the total bycatch reducing during the period examined, the latter from about 1750 t to 100 t per year. The coral bycatch comprised a large number of species, but was dominated by the reef-forming stony coral Solenosmilia variabilis. Annual bycatch of all other species combined, mainly rattails (Macrouridae) and dogfishes (Squalidae), was low (13–120 t). Bycatch of this group dropped sharply in each year as the result of a combination of decreasing bycatch ratio and decreasing fishing effort.
... In some oceanic regions, the depth range could warrant further subdivision where there may be marked changes in species composition or diversity (e.g., Carney, 2005). In the South Pacific, for example, demersal fish communities change with depth, and lower continental slope faunas dominated by species such as orange roughy and oreos decline below about 1200 m (Koslow et al., 1994;Francis et al., 2002). Deep-sea corals (Order Scleractinia) are abundant at depths of 600-1400 m where they can form extensive reef-type habitat on seamounts and ridge peaks (e.g., Clark et al., 2010a;Tracey et al., 2011). ...
While there are many generalized schemes representing the biogeographic
distribution of life in the deep sea, reviewed here, a comprehensive
analysis has not been undertaken since Vinogradova (1979, 1997) for the
abyssal and Belyaev (1989) for the hadal. The purpose of this paper is
to propose global biogeographic provinces for the lower bathyal and
abyssal benthos (>800 m depths) in order to aid high seas management
efforts. Biological samples from these depths are sparse so delineation
of biogeographic provinces was initially hypothesized using
oceanographic proxies, and examined with documented locations of select
benthic marine species. These biogeographic provinces were first
developed in 2009 via an expert consultation workshop to delineate
biogeographic provinces in offshore regions - the Global Open Ocean and
Deep Sea (GOODS) classification. We have refined the GOODS deep-sea
classification by incorporating additional high-resolution hydrographic
and organic-matter flux data for the seafloor. Water mass
characteristics (temperature and salinity) and particulate organic flux
to the seafloor were the strongest determinants in the final delineation
of provincial boundaries. This process resulted in the delineation of 14
lower bathyal and 14 abyssal provinces. The bathyal and abyssal
classifications presented here should be used with other management
tools and analyses (e.g., predictive habitat modeling, seamount
classifications, etc.) to help determine where marine protected areas
should be placed and to minimize the negative impacts of commercial
activities in the high seas.
... Fishes are often associated with particular features of their environment (e.g. Gust et al. 2001, Francis et al. 2002, rendering habitat-specific management viable (e.g. Peterson et al. 2000). ...
Relationships between fishes and habitat variables were assessed by transect counts and manipulative experiments on subtidal rocky reefs in 3 poorly known regions of New Zealand (eastern Bay of Plenty, western Cook Strait, and eastern Stewart Island). Canonical correspondence analysis successfully described associations between fishes and habitat features. Depth, topographic complexity, and macroalgal canopy cover were most consistently identified as influencing fish abundance. Experimental macroalgal clearances at eastern Bay of Plenty (short term) and western Cook Strait (longer term) indicated that Notolabrus celidotus used areas comprising macroalgal canopy more than cleared areas, whereas Parapercis colias and N. fucicola were more active in cleared areas. Effects of canopy clearance on fish activity were most obvious in summer at Cook Strait. Orthogonal manipulations of canopy and topographic complexity at a distant site (Tasman Bay) produced similar results for 2 species, indicating geographic generality of habitat models for N. celidotus and P. colias.
... Given that bottom depth accounts for much of the spatial variation in the species composition of demersal fish communities (e.g,. Bianchi 1992;Francis et al. 2002;Tolimieri and Levin 2006), it was used as the predictor habitat variable. Furthermore, depth is often the only habitat variable recorded during commercial fishing. ...
Reliable catch statistics are essential for assessing fishing impacts on individual stocks. However, fisheries that capture a mixture of stocks or species for which catch statistics are not disaggregated pose a challenge. Nonetheless, catch composition can be inferred given information on fishing date and location and a prevalent role of season and habitat in structuring fish assemblage composition. Here, a harmonic regression model for multinomial data, intended to predict the species composition of catches based on season and depth, is developed using bottom-trawl survey data. Model development was motivated by the need to quantify catches of individual skate (Rajidae) species in fisheries for which landing and discard data are only reliable at the family level. The model was validated by applying it to flatfishes (Pleuronectidae), whose catches are generally reliably and consistently disaggregated by species. The predicted species composition of flatfish matched the composition observed in fishery catches well. The present approach should be applicable to other well-surveyed ecosystems where assemblage composition is structured by one or more key environmental variables of known spatial distribution.
... Several guide books on fishes of New Zealand (Ayling and Cox 1982;Paulin and Stewart 1985;Paul 1986 and2000;Paulin et al. 1989 and2001) indicate that A. pinnifasciatus, the spotted flounder, is widespread in deeper waters on the continental shelf and upper continental slope around New Zealand. However, though reported as widespread in this region, Azygopus does not appear to be taken in abundance, judging from the few studies of New Zealand fish communities that even list this species among those caught in demersal trawls (Iwai et al. 1972;Shuntov 1979;McClatchie et al. 1997;Anderson et al. 1998;Jacob et al. 1998;Francis et al. 2002). Moreover, published statements regarding the ecology and life history of New Zealand Azygopus are vouchered by relatively few specimens (Nielsen 1961;Manikiam 1969;Iwai et al. 1972;Amaoka 1990;McClatchie et al. 1997). ...
Since its description, Azyygopus Norman, 1926 was considered by subsequent authors to be a monotypic genus in the Or-der Pleuronectiformes comprised only of A. pinnifasciatus Norman, 1926, known from deep waters (90-900 m, usually 200-600 m) off the southern and southeastern coasts of Australia. In 1961, a subspecies, A. pinnifasciatus flemingi Niels-en, was described based on three specimens collected at 610 m in the Tasman Sea off the South Island, New Zealand. From its description to contemporary literature evaluating its status, recognition of A. p. flemingi as a distinct taxon has been rejected by all but two studies reporting on Azygopus from New Zealand waters. Until the late 20th century, specimens of Azygopus had been rarely collected off New Zealand and little was known about these fishes. Over the past 25 years, col-lecting by scientific expeditions and expanding deep-sea fisheries have captured over 195 specimens of Azygopus from a variety of deep-sea locations around New Zealand. Recently-captured specimens of Azygopus collected around New Zea-land and deposited in fish collections have been identified as either A. pinnifasciatus Norman or A. flemingi Nielsen, sug-gesting the possibility that two species of Azygopus occur in New Zealand waters. This study examined the holotype, a paratype, and 25 non-type specimens of A. pinnifasciatus collected off Australia, and the most comprehensive series of specimens of Azygopus collected from New Zealand waters. These specimens included the holotype and two paratypes of A. p. flemingi and 191 other specimens collected from throughout the entire depth range (153-942 m) and representing wide coverage of geographic areas around New Zealand where Azygopus have been collected. Comparisons of these spec-imens indicate that a second species, A. flemingi Nielsen, should be recognized in the genus Azygopus, and that this species is the only member of this genus occurring in New Zealand waters. Azygopus flemingi is readily distinguished from A. pinnifasciatus by conspicuous differences in ocular- and blind-side color patterns, in numbers of ocular-side pelvic-fin rays, total vertebrae, lateral-line scales, and gillrakers on the first gill arch, morphology of blind-side scales and squama-tion patterns, length of blind-side pectoral fins, presence/absence of scales between upper jaw and ventral margin of lower eye, and pigment patterns on dorsal and anal fins of adults. Adult A. flemingi and A. pinnifasciatus are sexually dimorphic in several features. Data on maximum size and size at maturity, and depth of occurrence are summarized for A. flemingi.
The oceanography of the Labrador Sea is well studied because of its globally important deep‐water convection that oxygenates the deep ocean and drives climate‐regulating ocean currents. However, little is known about the fish communities that inhabit this area, particularly beyond the depths accessible to standard research surveys and commercial fishing activities. We used baited longline surveys to characterize important components of demersal fish communities across a depth gradient of 200–3000 m and compared these data to a similar dataset collected c. 1200 km to the south in the Flemish Cap Region. We found demersal fish communities in the Labrador Sea to be similar to those of the Flemish Cap Region despite unique oceanography and lower primary productivity in the Labrador Sea. Moreover, both areas had high abundance, biomass, and species richness at intermediate depths that suggests factors beyond depth drive community structure in the deep ocean. These data are important for identifying high‐value areas for potential protective measures in the northwest Atlantic and provide necessary data with which to assess potential environmental impacts of extractive industries that are expanding north and to deeper waters.
As global oceans continue to warm and deoxygenate, it is expected that marine ectotherms will reduce in body size resulting from the interactive effects of temperature and dissolved oxygen availability. A temperature-size response describes how wild populations of ectothermic species grow faster and reach a smaller size within warmer temperatures. While temperature-size responses are well observed in marine ectotherms, the mechanisms underpinning such a reduction in body size remain debated. Here, we analyse the relative influence of temperature, dissolved oxygen concentration, and geographic location (which encompasses multiple latent variables), on the maximum body length of four fish, one crustacean, and one squid species, which inhabit shallow to deep sea (1000 m) New Zealand waters across a temperature gradient of 1.5 to 18 °C. We found that all study species displayed a temperature-size response, with the strongest response exhibited by the largest species, hoki ( Macruronus novaezelandiae ). We also found that temperature was more important than dissolved oxygen concentration in determining maximum body length, as dissolved oxygen levels were at or near saturation in the study area. Our results suggest that larger-bodied species may experience the strongest temperature-size responses, and support expectations from the gill-oxygen limitation theory (GOLT) and the oxygen and capacity limited thermal tolerance (OCLTT) concept that increases in oxygen demand may be size- and temperature-dependent, thus driving a reduction in maximum body length of marine ectotherms with warming.
Understanding how marine food webs are affected by anthropogenic stressors is an important steppingstone toward the improved management of natural resources. Stable isotope analysis of historical and modern samples spanning a century indicated that the niche width of an exploited fish community increased after the expansion of New Zealand fisheries. Since the 2000s most species increased their reliance on food webs supported by pelagic production, compared to coastal production supported by macroalgae, and shifted to a higher trophic level. Overall changes were coincident with ocean warming, climate oscillations, prey abundance and fishing intensity, but their effects were specific to each fish assemblage analyzed. Data derived from historical samples revealed how anthropogenic stressors can drive long-term shifts in the trophic structure of an exploited fish community.
El presente informe contiene la revisión de los datos e información disponible para las especies brótula Salilota australis, cojinoba moteada Seriolella punctata y cojinoba del sur Seriolella caerulea en las regiones X, XI y XII correspondientes a la pesquería de la zona austral de Chile. El objetivo fue establecer un análisis exploratorio de la información disponible para cada recurso ante una eventual evaluación de stock. Se estudiaron y analizaron las principales fuentes de información para estos tres recursos, a saber; cifras oficiales de desembarques y capturas, bases de datos del monitoreo de la pesquería, informes técnicos y publicaciones científicas.
Los desembarques, de estas tres especies han tenido una extensa historia en Chile, existiendo registros desde los 70s, sin embargo, estos recursos constituyen parte de la fauna acompañante de las especies objetivo de la pesquería demersal austral de merluza del sur Merluccius australis, congrio dorado Genypterus blacodes, merluza de cola Macruronus magellanicus y merluza de tres aletas Micromesistius australis (Chong et al., 2017) operado principalmente por la flota arrastrera industrial. A pesar de ser consideras fauna acompañante y/o pesca incidental, fue posible comprobar los distintos comportamientos y ciertas tendencias de los datos de desembarques registrados por Sernapesca (2017). De acuerdo a la información biológica de estas especies, los principales estudios encontrados fueron realizados en otras zonas de distribución de los recursos, como Argentina y Nueva Zelandia. En Chile, estudios de Aguayo & Chong (1991) y Chong & Aguayo (1994) fueron los primeros avances para conocer aspectos de su biología y reproducción, y que han sido actualizados por Chong et al. (2017).
Una de las principales piezas de información revisada en este documento, fueron las bases de datos provenientes del monitoreo de la pesquería arrastrera de la zona sur austral, proyecto de seguimiento que lleva a cabo IFOP. En este aspecto se revisaron los datos disponibles de las estructuras de tallas y las bitácoras de pesca de cada especie entre los años 1997 y 2018. Respecto a la información de las bitácoras de pesca se realizaron 2 tipos de análisis. El primero fue identificar patrones espaciales y temporales de las cantidades extraídas por la flota arrastrera para cada una de las especies. El segundo análisis que se obtuvo de esta pieza de información, fue la construcción de un índice de abundancia para cada recurso, el cual es parte fundamental para una eventual evaluación de stock.
Como resultados de este levantamiento de datos y análisis exploratorio de la información disponible para eventuales evaluaciones de stock para las tres especies en cuestión, se procedió a clasificarlas en el sistema de “tiers” propuesto por Payá et al.(2014). De acuerdo a lo explorado, fue posible clasificar cada recurso para la aplicación de metodologías de evaluación de stock. Para la brótula y cojinoba moteada se propone el uso de un modelo estructurado ya sea en talla o edad. Para cojinoba del sur, la suficiencia de datos fue escasa, sin embargo, es posible aplicar métodos de evaluación de datos pobres, ya sea en capturas o en las estructuras de tallas.
Trawls are among the most commonly used types of sampling gear for surveying deep-sea faunal communities. In this chapter we outline the main types of trawl (otter, shrimp, beam, Agassiz, midwater), and describe aspects of their use given the type of seafloor and target faunal groups. Details are given of trawl deployment and operation, on ways to modify trawls for use on rough seafloor, and advice is provided on how to evaluate performance of trawl tows. Standardization of trawl gear, and the need for full description of its construction, set-up and operation, are stressed. Information is included on sample sorting and processing, as well as interpretation of trawl-derived data.
An overview of the commercial fishery for hoki (Macruronus novaezelandiae) in New Zealand with current knowledge about the biology, and life history characteristics of the fish, is provided. Hoki form New Zealand's largest finfish fishery, and stock abundance has been closely monitored to enable catch adjustments to be made when necessary. The total allowable commercial catch (TACC) for the 2012/2013 fishing year was set at 130,000 t. In New Zealand, hoki are taken almost exclusively as a target species by large commercial trawlers. Fishing occurs throughout the year with over half of the catch taken during the spawning season in the austral winter (July/August). Most of the spawning season catches are taken with mid-water trawls, and outside the spawning season with bottom trawls. Fishers complete a comprehensive catch return system to monitor tow and catch effort, and the government implements an Observer Scheme that independently reports on the finfish by-catch and protected species by-catch in the fishery. Although a single TACC is set for hoki under New Zealand's Quota Management System, a catch split arrangement is implemented each year to reflect the stock structure and the status of the two sub-populations of hoki. Assessment models suggest that the spawning biomass of both sub-populations declined to a minimum in about 2005 but has since re-built. Current spawning biomass of both sub-populations is currently estimated to be within the target zone of 35-50% B0.
Critical amino acid replacements in opsin proteins shift the maximal absorbance of visual pigments to perceive different photic environments (spectral tuning). Here we studied the molecular basis for spectral tuning of the rhodopsin (RH1) pigment in 19 species of marine teleosts inhabiting different light environments, from shallow waters to the deep-sea. We identified replacements at the critical sites 194, 195, 292 and 299, which have been defined relative to the bovine RH1 gene and are known to be involved in shifting the λmax value of RH1 pigments towards the blue light. All the species had the substitutions P194R and H195A. However, we detected a relationship between the combination of amino acids at the critical sites 292 and 299 and the maximum depth of the species under study. The combination 292S/299A was only found in the deep-sea congeners Hoplostethus atlanticus and H. mediterraneus. This may reflects an adaptation of these species to the bathypelagic light environment. All the epipelagic species studied and the epi-mesopelgic species Parapercis colias, had the combination 292A/299S, except Chelidonichthys kumu (292A/299A) and Notolabrus celidotus (292S/299S). It is possible that the combination 292A/299S is an adaptation to longer wavelengths of light in comparison with the deeper species. This is the first study in the rhodopsin gene sequence in all the species under study, except for Macruronus novaezelandiae and H. mediterraneus.
Este artigo descreve a frequência e o número de Sphyrion
laevigatum da pele de Genypterus blacodes, o qual
é um importante recurso econômico no Chile. A análise baseada em modelos
de distribuição espacial, demonstrou que os parasitos tendem a ficar agrupados.
A variação numérica de parasitas por hospedeiro pode ser descrita por
distribuição binomial negativa. O número máximo observado de parasitas por
hospedeiro foi dois.
Owing to the paucity of data on the red muscle of deep-sea fishes, the goal of this study was to determine the proportions of red muscle in demersal fishes and its enzymatic activities to characterize how routine swimming abilities change with depths of occurrence. Cross sectional analysis of the trunk musculature was used to evaluate the proportion of red muscle in 38 species of Californian demersal fishes living at depths between 100 and 3000 m. The activity of metabolic enzymes was also assayed in a sub-set of 18 species. Benthic fishes had lower proportions of red muscle and lower metabolic enzyme activities than benthopelagic species. Mean proportion of red muscle declined significantly with depth with the greatest range of values in shallow waters and species with low proportions found at all depths. This suggested that while sedentary species occur at all depths, the most active species occur in shallow waters. Citrate synthase activity declined significantly with depth across all species, indicating that the mass-specific metabolic capacity of red muscle is lower in deep-sea species. These patterns may be explained by coupling of red and white muscle physiologies, a decrease in physical energy of the environment with depth or by the prevalence of anguilliform body forms and swimming modes in deep-living species.
To understand responses of marine ecosystems to climate changes in the
northwestern Pacific, especially responses to the 1998 regime shift, we
related month-specific variability in hydrographic conditions to
long-term changes in mesozooplankton in four regions adjacent to the
Korean peninsula: the eastern Yellow Sea (EYS), northern East China Sea
(NECS), and southwestern and northwestern Japan/East Sea (SJES and
NJES). Sea surface (10-m depth) temperature in February has increased
since the early 1990s in all four regions. Sea surface temperature in
April and June has increased since the late 1990s in the SJES and EYS.
Surface salinity has decreased, especially since the late 1990s, except
NJES. Biomass of mesozooplankton in Korean sea regions (the EYS, NECS
and SJES) began to increase after the early 1990s, with sharp increases
after the late 1990s, indicating a regime shift triggered by the
increased seawater temperatures. Unusually higher biomass was also
occasionally observed in April, June or October after the late 1990s in
the EYS and NECS. Abundances of the four major zooplankton groups
(copepods, amphipods, chaetognaths and euphausiids) have generally
increased since the late 1990s. The pattern of change in zooplankton
abundance varied depending on taxonomic group and region, but we
concluded that the four seas responded to the 1989 or 1998 regime shifts
with respect to water temperature, salinity and zooplankton. We detected
an additional sudden shift in both the zooplankton community and
fisheries catch in the Korean waters, which we speculated was associated
with the strong 1982/1983 El Niño event. The 1982-1983 shift was
characterized by increased dominance of copepods, and was pronounced in
the EYS, which is strongly influenced by river discharge. The results
highlight the need for further retrospective analyses of regional
ecosystems.
Adoption of the ecosystem approach to fisheries management relies on recognition of the link between fish and other components of the ecosystem, namely their physical and biological habitat. However, identifying the habitat requirements of marine fishes and hence determining their distribution in space and time is scientifically complex. We analysed the methodologies and findings of research on temperate, demersal fish habitat requirements to highlight the main developments in this field and to identify potential shortfalls. Many studies were undertaken over large spatial scales (≥100s km2) and these generally correlated abundances of fish to abiotic variables. Biological variables were accounted for less often. Small spatial scale (≤m2), experimental studies were comparatively sparse and commonly focused on biotic variables. Whilst the number of studies focusing on abiotic variables increased with increasing spatial scale, the proportion of studies finding significant relationships between habitat and fish distribution remained constant. This mismatch indicates there is no justification for the tendency to analyse abiotic habitat variables at large spatial scales. Innovative modelling techniques and habitat mapping technologies are developing rapidly, providing new insights at the larger spatial scales. However, there is a clear need for a reduction in study scale, or increase in resolution additional to the integration of biotic variables. We argue that development of sound predictive science in the field of demersal fish habitat determination is reliant on a change in focus along these lines. This is especially important if spatial management strategies, such as Marine Protected Areas (MPA) or No Take Zones (NTZ), are to be used in future ecosystem-based approaches to fisheries management.
Seasonal hypoxia [dissolved oxygen (DO) ≤ 2 mg l−1] occurs over large regions of the northwestern Gulf of Mexico continental shelf during the summer months (June–August) as a result of nutrient enrichment from the Mississippi–Atchafalaya River system. We characterized the community structure of mobile fishes and invertebrates (i.e., nekton) in and around the hypoxic zone using 3 years of bottom trawl and hydrographic data. Species richness and total abundance were lowest in anoxic waters (DO ≤ 1 mg l−1) and increased at intermediate DO levels (2–4 mg l−1). Species were primarily structured as a benthic assemblage dominated by Atlantic croaker (Micropogonias undulatus) and sand and silver seatrout (Cynoscion spp.), and a pelagic assemblage dominated by Atlantic bumper (Chloroscombrus chrysurus). Of the environmental variables examined, bottom DO and distance to the edge of the hypoxic zone were most strongly correlated with assemblage structure, while temperature and depth were important in some years. Hypoxia altered the spatial distribution of both assemblages, but these effects were more severe for the benthic assemblage than for the pelagic assemblage. Brown shrimp, the primary target of the commercial shrimp trawl fishery during the summer, occurred in both assemblages, but was more abundant within the benthic assemblage. Given the similarity of the demersal nekton community described here to that taken as bycatch in the shrimp fishery, our results suggest that hypoxia-induced changes in spatial dynamics have the potential to influence harvest and bycatch interactions in and around the Gulf hypoxic zone.
Deep-sea fishes are the target of directed fisheries and are considered a conservation concern. Yet, we still know little about the factors that affect deep-sea fish distributions and assemblage patterns on relatively small spatial scales. We used results from remotely operated vehicle surveys that observed 105 km (∼346 960 m2) of seafloor over a depth range of 351–2245 m in three canyons off Newfoundland to examine the occurrence, behavior, habitat specificity, and regional assemblage patterns of deep-sea fishes in this region. We found distinct assemblages based on both depth and habitat classifications. The most obvious unique assemblage was that associated with outcrops, which served as habitat for relatively rare species such as Neocyttus helgae, Hoplostethus atlanticus, and Lepidion eques. Several coral habitats hosted distinct assemblages when compared to other habitats with low or medium structural complexity. Our results illustrate that any program targeted at protecting deep-sea ecosystems must protect a wide-range of habitats and depths to conserve a variety of fish species and assemblages.
Bottom trawl data from the depth interval 300-2050 m on the slope off Norway were analysed to study distribution of fish biomass and the associated species assemblages. It is hypothesised that the pronounced hydrographic front between the warm Atlantic Watermass and the cold Norwegian Sea Deep-water, combined with a declining food supply with depth and distance from the shelf, structure the assemblages on the continental slope of the eastern Norwegian Sea. From a high level at the shelf edge and upper slope, the fish biomass declined abruptly at about 720 m when crossing the 0 °C-isotherm associated with the hydrographic front. Beneath the frontal zone, the fish biomass was only 11 % of that above it and decreased further with increasing depth. In upper slope waters, the fish biomass increased with increasing latitude. Arctic species such as Lycodes frigidus and Paraliparis bathybius were dominant in the deep cold slope waters. The high fish biomass associated with the steep temperature gradient at 600-720 m was mainly attributable to a few large and/or abundant boreo-arctic species, i.e. Greenland halibut Reinhardtius hippoglossoides, redfishes Sebasles mentella and S. marinus, roughhead grenadier Macrourus berglax, and Raja hyperborea. In the shallower and warmer upper slope waters a species assemblage occurred which resembled that associated with adjacent deep shelf areas strongly influenced by the Atlantic Watermass.
We examined the relationship between demersal fish assemblage and depth, temperature, latitude and longitude off southern New Zealand (46–54°S and 165–180°E) in water depths of 80–787m. Catch weight data were analysed by two-way indicator analysis (TWIA), groupaverage agglomerative clustering (UPGMA) and Detrended Correspondence Analysis (DCA). The spatial pattern of demersal fish off southern New Zealand conforms to the concept of species groups or fish assemblages related to environmental gradients. Shallow-water assemblages were dominated by species from the families Gempylidae, Squalidae, Triakidae and Moridae, mainly represented by Thyrsites atun, Squalus acanthias, Galeorhinus australis, and Pseudophycis bachus. Deep water assemblages were dominated by Chimaeridae, Argentinidae, Merlucciidae and Macrouridae, mainly represented by Hydrolagus novaezelandiae, Argentina elongata, Macruronus novaezelandiae, and Lepidorhynchus denticulatus. Total catch weight was often dominated by Merlucciidae, Macrouridae and Gempylidae. Fish assemblages were related to discrete ranges of depth (300m) and temperature (9.5°C), but the range of sediment types was too narrow to show any correlation.
Data collected during five winter and three summer research trawl surveys in Pegasus Bay and Canterbury Bight (10–400 m), east coast of the South Island, New Zealand, were used to identify demersal fish assemblages from hierarchical cluster analysis and non‐metric multidimensional scaling. The environmental variables—depth, latitude, season, water temperature, sediment type, sea surface condition, and sea colour—were examined to determine their relationship to fish assemblages using multivariate redundancy analysis. Patterns of species richness were examined and described. Catch rates were generally higher in summer than winter (21 of 28 species) and higher in south Canterbury Bight in the depth range 30–200 m. Preferred depth was greater in winter than summer (21 of 28 species). Species richness declined with depth in winter. Four main demersal species assemblages were identified (inner shelf, outer shelf, shelf break, and upper slope) with minor changes in membership between summer and winter mostly as a result of a change in species preferred depth. Depth was the primary variable influencing fish assemblages with secondary effects of latitude, sediment, and bottom temperature.
The demersal fish community was examined at 15 sites on the continental shelf and upper slope off Sendai Bay, Japan, from 1989 to 1991. The community structure was analyzed along the depth gradient (ca 150 to 450 m). The species compositions at the shallowest site and the deepest site were different from the other sites. The depth range covered not only an upper slope community but also the shallower shelf community and the deeper slope community. The species composition varied annually at each site, but some stable species composition was observed in intermediate-depth waters (ca 240 to 370 m). The intermediate depths were considered to be center depths of the distribution of the uppermost slope community which was characterized by the dominance of Theragra chalcogramma and Gadus macrocephalus, high biomass and low species diversity. Biomass was maximum and species diversity was minimum at the intermediate depths, and gradually changed with depth toward the other communities. The transition depths were located on both sides of the center depths of the upper slope community, where the percentage by biomass of the 2 dominant fish species was low and/or variable and the species composition was heterogeneous compared to the center depths.
Canonical Correspondence Analysis (CCA) is quickly becoming the most widely used gradient analysis technique in ecology. The CCA algorithm is based upon Correspondence Analysis (CA), an indirect gradient analysis (ordination) technique. CA and a related ordination technique, Detrended Correspondence Analysis, have been criticized for a number of reasons. To test whether CCA suffers from the same defects, I simulated data sets with properties that usually cause problems for DCA. Results indicate that CCA performs quite well with skewed species distributions, with quantitative noise in species abundance data, with samples taken from unusual sampling designs, with highly intercorrelated environmental variables, and with situations where not all of the factors determining species composition are known. CCA is immune to most of the problems of DCA.
This study describes and maps demersal fish assemblages for the east coast of North America from Cape Hatteras, North Carolina, to Cape Chidley, Labrador, evaluates evidence for interannual shifts in assemblage distribution, and examines the relationship of the assemblages to accepted biogeographical boundaries. Demersal trawl survey data collected from 1975 to 1994 were analyzed. Visual classification of distribution maps for the 108 most abundant demersal species revealed nine species groups, based on both geography and depth distribution. Eighteen assemblage groups were identified using principal components analysis (PCA) and mapped. Assemblage groups were also identified by cluster analysis. Fish assemblages identified by both methods were spatially coherent. Assemblage distribution patterns were not consistent with accepted biogeographical boundaries. The PCA explained only 56.3% of the variance in distribution of the species, indicating that the assemblages should be interpreted as indeterminate, potentially adaptable entities rather than as rigid ecological constructs. Assemblages were persistent in composition through time but appeared to shift in location. The apparent looseness of the assemblages and their persistence through time in spite of severe impacts from fishing suggest that single-species management approaches may not be entirely inappropriate for the major groundfish species in the study area.
Continental shelf and upper slope fish communities were studied along the Catalan coast based on 66 experimental bottom otter trawls. A total of 79 demersal fish species were studied by means of cluster analysis and multi-dimensional scaling (MDS) ordination for community structure. Analysis revealed the existence of five major location clusters. Similarity percentage analysis (SIMPER) was determined by comparing the dissimilarity between two groups of samples using the discriminating species. Geomorphological characteristics, bottom substratum and depth showed direct influences on species assemblages. High correlation between the biotic data samples and depth was observed. The fish species assemblages identified five main demersal fish associations which corresponded with the five location clusters and with five benthic sediments (mud of the upper slope, sand and gravel, mud of the shelf, muddy-sand and sand with rocky outcrops).
This chapter concerns data analysis techniques that assist the interpretation of community composition in terms of species' responses to environmental gradients in the broadest sense. All species occur in a characteristic, limited range of habitats; and within their range, they tend to be most abundant around their particular environmental optimum. The composition of biotic communities thus changes along environmental gradients. Direct gradient analysis is a regression problem—fitting curves or surfaces to the relation between each species' abundance, probability of occurrence, and one or more environmental variables. Ecologists have independently developed a variety of alternative techniques. Many of these techniques are essentially heuristic, and have a less secure theoretical basis. This chapter presents a theory of gradient analysis, in which the heuristic techniques are integrated with regression, calibration, ordination and constrained ordination as distinct, well-defined statistical problems. The various techniques used for each type of problem are classified in families according to their implicit response model and the method used to estimate parameters of the model. Three such families are considered. The treatment shown here unites such apparently disparate data analysis techniques as linear regression, principal components analysis, redundancy analysis, Gaussian ordination, weighted averaging, reciprocal averaging, detrended correspondence analysis, and canonical correspondence analysis in a single theoretical framework.
Ecologists are making increasing use of computer methods in analyzing ecological data on plant and animal communities. Ecological problems naturally involve numerous variables and numerous individuals or samples. Multivariate techniques permit the summary of large, complex sets of data and provide the means to tackle many problems that cannot be investigated experimentally because of practical restraints. Ecologists are thus enabled to group similar species and similar sample sites together, and to generate hypotheses about environmental and historical factors that affect the communities. This timely book presents a full critical description of three methodologies - direct gradient analysis, ordination, and classification - from both theoretical and practical viewpoints. Both traditional and new methods are presented. Using a wide range of illustrative examples, Hugh Gauch provides an up-to-date synthesis of this field, which will be of interest to advanced students and ecologists. These mathematical tools are also used in a wide variety of other areas, from natural resource management and agronomy to the social and political sciences.
Twenty-three bottom-trawl fish assemblages were identified from the relative biomass of 33 dominant species that occurred in the National Marine Fisheries Service's triennial trawl surveys over the continental shelf and upper slope off California, Oregon, and Washington from 1977 to 1992. The assemblages accounted for about 70% of the total variation in species composition among 2565 hauls. Although the assemblages persisted over the 15- year study period and occurred within broad geographic boundaries, some had substantially different spatial distributions among surveys. The ability to differentiate assemblages across five environmental variables (latitude, depth, surface and bottom water temperatures, and surficial substrate) was low. The preponderance of hake-dominated assemblages throughout the study area suggests that Pacific hake (Merluccius productus) may play a large role in the dynamics of demersal fish communities off the west coast of the United States.
Boundaries between faunal zones tended to follow isotherms and isobaths. During the late winter-early spring, the following faunal zones were found: northern inner shelf, northern mid-shelf, southern inner- and mid-shelf, and outer shelf-shelf break. Five species groups were identified: a small cryophilic group restricted to the first zone, a cold-water boreal group found in the first two zones, a ubiquitous boreal/resident group containing the major dominants, a warm-temperate group confined to the warmer southern and outer shelf waters, and a group of slope residents confined to the deepest zone. During the fall, 5 faunal zones were found: southern inner/mid-shelf, northern inner shelf, northern mid-shelf, outer shelf, and shelf break. Five species associations were largely analogous to those in the spring, with the following exceptions: the cryophilic group was absent, the ubiquitous group contained mixed boreal and warm-temperate elements, and a 2nd outer shelf group was recognized. The most notable change in the distribution of groups from the spring was a general northward shift and a sharply defined inshore moement of the temperate group. -from Authors
Comparisons were made of the structure of demersal fish communities in and near a deep-water sewage disposal site from otter trawl samples collected during dumping in 1990 and 1991 and prior to dumping from 1973 to 1978. Community structure remained relatively stable with both recent and historical data sets showing rapid faunal changes on the continental slope (200-2000 m) and slow faunal changes on the continental rise and abyssal plain (>2000 m). Species richness was similar during both periods and was maximal on the lower slope (~ 2000 m) with a rapid decline into the abyss. Dominant species with bathymetric station groups showed little difference between recent and historical data sets. The same dominant species occurred in both data sets with only minor differences in the ranks of individual species. Both numerical abundance and biomass showed a marked decline with depth and the patterns were similar for both recent and historical data sets. The slope of numerical abundance versus depth was steeper than that for biomass versus depth suggesting that average fish weight increased with depth. However, this 'bigger-deeper' phenomenon was shown to be a 'smaller-shallower' phenomenon mitigated by smaller numbers of small fishes in deeper water and lower catchability of large fishes in shallower water. Statistical comparisons of recent biomass values in and directly downstream from the dumpsite with those from other stations from similar depths (2000-3000 m) showed no significant difference. Thus, no detectable changes in demersal fish biomass, abundance, species richness or dominant were found at or near DWD-106 after sewage sludge dumping. Other studies suggest that discernible biological effects of sewage sludge are confined to a relatively small area close to the dumpsite. Even though input of organic material may be doubled in this small area, its effects have not become apparent in the abyssal fish community because most fishes there are wide-ranging and are two or three trophic levels removed. Thus, the potential increased production signal may be masked by the relatively small area affected compared to the total active feeding ranges of the fishes involved, and entropy in the food web. Changes in abundance of some coastal fishes on the continental shelf before and after dumping at DWD-106 were mostly likely due to overharvesting and natural year-class fluctuation rather than to effects of sewage disposal. The decades-long stability of bathyal and abyssal fish assemblages found in this study suggests that they should be recognized as communities and that the concept of the 'biological community' is extremely important in deep-sea ecology.
Its life table encapsulates in a quantitative form the life-history pattern of a population. Fishes have evolved a diversity of life-history patterns (Breder and Rosen, 1966). In some species, sexual maturity is reached within a few weeks of hatching, in others only after several years. Some species are semelparous, others iteroparous. Some have short life spans, others may live for many decades. Even within a species, there may be major variations in the life-history patterns shown by different populations. Intraspecific differences in migration, growth, age at first reproduction, life span and fecundity are described in earlier chapters. What are the environmental factors that favour the evolution of a particular life-history pattern? How will a life-history pattern change as environmental conditions change? This second question is relevant to the effects of fishing and pollution which constitute new causes of mortality or impose other adverse effects on a population.
Previous chapters describe the effects that environmental factors have on the survival, growth and reproduction of individual fish. This chapter explores the changes in the abundance and total weight of fish in a population that result from these effects. Fishes have high fecundities (see Chapter 7) so the potential lifetime production of offspring is high. Although fish populations vary in abundance (Fig. 10.1) (Cushing, 1982; Rothschild, 1986), increases in abundance are usually several orders of magnitude lower than the potential maximum increase. Even when a population is increasing, the fate of most zygotes is to die before growing to sexual maturity.
If a fish is to be represented genetically in the next generation, at some time in its life it must begin to allocate resources to reproduction. Its reproductive success will depend on where and when it reproduces and on the resources it allocates to reproduction. Consequently, a study of the ecology of reproduction will include analyses of these problems in relation to the effects of environmental factors: where and when does spawning take place and what resources are allocated to reproduction as opposed to maintenance and growth? The problem of timing raises two sets of questions. The first set asks at what age does a fish becomes sexually mature and what factors determine this age? The second set asks what factors determine when in the year reproduction takes place? The problem of allocation also has two basic components: what portion of available resources is allocated to each reproductive attempt; and of the material resources that are allocated to reproduction, what portion is allocated to each individual offspring? This chapter explores each of these questions, where possible in relation to the effect that environmental factors have on their resolution.
The energy in the food ingested has one of two fates. Some is dissipated in the form of waste products or heat and some is incorporated as new tissue. The heat losses are generated by the metabolic processes through which the energy in the food is released to do useful work. This includes the work done in tissue function and repair, synthesizing new tissue and swimming. The processes which result in the dissipation of energy can be grouped together as maintenance. New tissue may take two forms: growth or gametes (Fig. 1.2). The income of energy (and nutrients) will be limited by time, the availability of food and the capacity of the gut to process food. How should this limited income be allocated among maintenance, growth and reproduction? What pattern of allocation will maximize the lifetime production of offspring? This chapter starts the discussion of these questions by first introducing the concept of an energy budget and then describing the effects of abiotic environmental factors on the maintenance item in the energy budget using a classification originally developed by Fry (1971). The succeeding three chapters examine the allocation of time and energy in relation to patterns of movement (Chapter 5), growth (Chapter 6) and reproduction (Chapter 7).
Six geographic regions along the Laurentian Great Lakes in Ontario, represented by 286 lakes, were examined to identify the existence of regional similarities of fish species composition and their association to geographic location and regional patterns of lake morphology and pH. Lakes differed significantly among regions with respect to surface area, maximum depth, and pH. Species presence/absence data were summarized using correspondence analysis, and the resultant scores were used in multivariate analysis of variance and canonical variates analysis. These results indicated that the fish faunas of the six geographical areas were distinct. Interregional distances based on fish community scores, lake morphology--chemistry data, and geographical distances were contrasted using Mantel's test. Regional faunal similarities were correlated significantly with geographical proximity, but not with lake morphology. We propose that post-glacial dispersal and lake thermal regimes are important determinants in structuring regional patterns of fish assemblages, whereas environmental conditions such as lake depth and pH assume greater importance in determining species compositions of individual lakes.
The chapter introduces the idea that the relationships between natural conditions and the outcome of an observation may be deterministic, random, strategic or chaotic, and that numerical ecology addresses the second type of data; it describes the role of numerical ecology among the various phases of an ecological research. The chapter includes discussion of the following topics: spatial structure, spatial dependence, and spatial correlation (independent observations, independent descriptors, linear independence, independent variable of a model, independent samples, origin of spatial structures, tests of significance in the presence of spatial correlation, and classical sampling and spatial structure), statistical testing by permutation (classical tests of significance, permutation tests, alternative types of permutation tests), computer programs and packages, ecological descriptors (i.e. variables: mathematical types of descriptors, and intensive, extensive, additive, and non-additive descriptors), descriptor coding (linear transformation, nonlinear transformations, combining descriptors, ranging and standardization, implicit transformation in association coefficients, normalization, dummy variable coding, and treatment of missing data (delete rows or columns, accommodate algorithms to missing data, estimate missing values). The chapter ends on a description of relevant software implemented in the R language.
The winter distributions of mesopelagic fishes, crustaceans, and cephalopods across the Subtropical Convergence east of New Zealand are shown to reflect the hydrological changes associated with convergence of Subtropical and Subantarctic Surface Waters. Samples collected in the upper 400 m in each of these water masses and in mixed water over the Chatham Rise contained members of faunal associations apparently characteristic for each area. The area of strongest hydrological change was characterised, at least for fishes and crustaceans, by a considerable decrease in species richness. Use of cluster analysis confirmed the clear correpondence between geographic species associations and water masses.
The structure of demersal assemblages (fish, crustaceans and cephalopods) of the continental shelf and upper slope between the Gulf of Tehuantepec and the Gulf of Papagayo was studied from data obtained in the course of surveys carried out by the RV 'Dr. F. Nansen' in 1987, by means of an ordination technique, Detrended Correspondence Analysis (DCA) implemented by the program DECORANA, and a classification technique, Two-Way Indicator Species Analysis (TWIA) implemented by the program TWINSPAN. Three major groups of species were identified: those distributed above the thermocline, those within the range of the thermocline and a third group below the thermocline, where oxygen content is extremely low. Highest biomass densities were found below the thermocline, consisting mainly of the galatheid crustacean Pleuroncodes monodon (H. Milne Edwards, 1837). Correlation of DCA Axis 1 with depth, temperature, salinity and oxygen showed that depth is the main gradient along which faunal changes occur.
Twenty-three bottom-trawl fish assemblages were identified from the relative biomass of 33 dominant species that occurred in the National Marine Fisheries Service's triennial trawl surveys over the continental shelf and upper slope off California, Oregon, and Washington from 1977 to 1992. The assemblages accounted for about 70% of the total variation in species composition among 2565 hauls. Although the assemblages persisted over the 15-year study period and occurred within broad geographic boundaries, some had substantially different spatial distributions among surveys. The ability to differentiate assemblages across five environmental variables (latitude, depth, surface and bottom water temperatures, and surficial substrate) was low. The preponderance of bake-dominated assemblages throughout the study area suggests that Pacific bake (Merluccius productus) may play a large role in the dynamics of demersal fish communities off the west coast of the United States.
The geographic distributions of 375 reef and reef‐associated fishes are reported for 16 regions ranging from Norfolk and Kermadec Islands in the north to Macquarie Island in the south. Species diversity was greatest at Norfolk Island (228 species) and lowest at Macquarie Island (6 species). Diversity declined linearly with increasing latitude. Most species were either widespread or had very restricted distributions. Widespread species generally ranged from Three Kings Islands to Stewart Island. The most widespread species occurred in 14 of the 16 regions. Species with restricted distributions were mainly tropical or subtropical species that occurred at one or more of Norfolk Island, Kermadec Islands, and North‐East North Island. Principal Components Analysis (PCA) identified eight groups of regions with similar species compositions. These eight groups reflected the latitudinal variation in sea surface temperature. Seven species distributional groups were recognised. Tropical (167 species) and antarctic (4 species) groups were identified using distributional data from the literature. A PCA ordination was carried out on the remaining 204 species and five further species groups were identified: subtropical (77 species), warm temperate (32), widespread (81), cool temperate (10), and subantarctic (4).
Catch rate data for fish species caught in 200–800 m depths during summer trawl surveys of the Chatham Rise to the east of New Zealand in 1992–99 were explored to assess community structure and species associations and to identify changes that occurred within the time series of surveys. The community was dominated by hoki (Macruronus novaezelandiae Hector), a Southern Hemisphere merlucciid hake, which was more abundant than all other species combined and occurred at 97% of the 1048 trawl stations. Three groupings offish species were identified on the basis of descriptive and cluster analyses, associated with the 200–350, 350–550, and 550–800 m depth ranges. Redundancy analysis showed that depth, latitude, and to a lesser extent longitude explained most of the variation in abundance and composition of catches. Spatial patterns in species diversity and fish density were investigated. Trends within the time series show a significant decline in the biomass of hoki and changes in biomass of several other abundant species. However, there was little change in diversity, density, or division into groupings. The changes in abundance may be related to increased fishing activity and/or other factors such as changes in catchability because of the rising bottom temperatures observed during the surveys.
Two trawl surveys were carried out in the summer months (June–July) of 1996 and 1997 along the whole South Adriatic area (Mediterranean sea) for the first time, using the same vessel and the same sampling gear (European Community Research Project ‘MEDITS’); previous research data referred only to the south-western Adriatic side. A total list of 168 demersal species (fishes, cephalopods and crustaceans) was obtained during the surveys; species abundance data (individuals/trawling hour) were processed according to multivariate techniques in order to describe the composition and the distribution of the main species assemblages within the investigated area (10–800-m bathymetric range). Multivariate analysis of MEDITS survey catch data showed a bold relationship between fish assemblages and depth, while the influence of depth was lower with respect to cephalopod and especially crustacean assemblage distribution.
The seasonal organization patterns of demersal assemblages (fish and cephalopods) in the Gulf of Lions were investigated on the basis of a set of bottom trawl surveys. The use of Partial Triadic Analysis (PTA) provided a detailed representation of: (1) the common part of the spatial organization of demersal assemblages at seasonal scale; and (2) the seasonal variability of each species around this common structure. During the course of the study, demersal assemblages exhibited a strong seasonal stability in their organization patterns and only few species showed a strong seasonal variation in their spatial distribution. Demersal assemblages of the Gulf of Lions were structured primarily on the basis of a non depth coast–open sea gradient, which occurred from the coast to the midshelf region. The influence of depth on the structure of fish assemblages appeared to be only of limited importance and mainly restricted to the continental slope area. The PTA combined with contouring technics could be used to improve our knowledge of community structuring factors, and offers a theoretical framework to assess the reproducibility of multispecies structures.
Catches of two trawls, a semi-balloon trawl (OTSB) and a Granton trawl were very similar when towed on paired warps. Significant differences were found between the catches of the OTSB trawl towed on single and paired warps. DCA effectively provided information on the important gradients (eg depth, trawl type) and indicated which species were most abundant in the different depth zones and trawl type. Accounts of the abundance and biomass of different species by trawl type and depth zone are given. -from Authors
The theory of gradient analysis is presented in this chapter, in which the heuristic techniques are integrated with regression, calibration, ordination and constrained ordination as distinct, well-defined statistical problems. The various techniques used for each type of problem are classified into families according to their implicit response model and the method used to estimate parameters of the model. Three such families are considered. First, the family of standard statistical techniques based on the linear response model is dealt with, because they are conceptually the simplest and provide a basis for what follows, even though their ecological application is restricted. Second, a family of somewhat more complex statistical techniques are outlined which are formal extensions of the standard linear techniques and incorporate unimodal (Gaussian-like) response models explicitly. Finally, the family of heuristic techniques is considered based on weighted averaging. These are not more complex than the standard linear techniques, but implicitly fit a simple unimodal response model rather than a linear one. Ordination diagrams and their interpretation on bi plots and joint plots are also given in the chapter. This chapter has discussed which response model to choose from direct and indirect gradient analysis, and then in direct system, which one to choose from regression and constrained ordination.
Benthic and pelagic fishes were sampled east of Maria Island, Tasmania, at two-monthly intervals from April 1984 to June 1985, from the surface to the bottom (500 m depth), using commercial-sized trawls. Biomass was calculated by the area swept/volume filtered method and divided by estimated catchability coefficients so that catches from the two sampling gears could be combined. Of the 54 families caught, three (Myctophidae, Squalidae, Sternoptychidae) contributed 25% of the 115 species. Most benthic and dispersed species were caught regularly, whereas most pelagic species occurred only occasionally and in low numbers, although a core group was always present. Total fish biomass was high (range=77 to 532 g m-2; x= 390 g m-2), due almost entirely to the myctophid Lampanyctodes hectoris (over 90% of the biomass). Benthic biomass was relatively low and stable, but derived from many species. Pelagic biomass was high, fluctuated widely and was composed of a few species. Biomass was highest in summer: Maurolicus muelleri increased by a factor of 200, Diaphus danae by 50, and L. hectoris, Macruronus novaezelandiae and Lepidorhynchus denticulatus by almost 10. Peaks in biomass may correlate with the interactions of the subtropical convergence and the East Australian Current and the resultant marked seasonal cycle in water temperature, nutrients and primary productivity.
Experimental trawl surveys were performed in the Gulf of Lions. A multicompartmental approach was used to study the spatial
distribution of demersal assemblages and to estimate their associations with two other components of the ecosystem: the benthic
macrofauna and substratum type. At the Gulf scale, we found that these components explained 38 and 19% of the total variability
of the spatial organization of groundfishes, respectively. Our results showed that groundfish and benthic macrofauna species
were primarily distributed along a coast–open sea gradient and secondarily along a longitudinal axis. The longitudinal variability
of the spatial organisation of species was maximal in the shelf area, whereas the upper-slope and coastal areas were characterized
by strong homogeneity. Although no partitioning could be made based on their spatial distribution, the coastal groundfish
assemblages were split into two groups. In the first group, groundfishes were strongly associated with both benthic macrofauna
and type of substratum; in the second group, they were strongly independent of these two components. Furthermore, in the Gulf
of Lions, the presence of productive zones associated with the Rhône river plume or with shelf-break upwelling seemed to attract
some groundfishes. This study illustrates how useful such a multicompartmental approach can be for both fisheries management
and community ecology.
The mid-slope (800–1200 m) demersal fish community off southeastern Australia was sampled at 376 random, depth-stratified trawl stations. The mean density of demersal species was 4.82 g m−2. Thirty-seven families and 111 species of demersal fish were represented in the catch. The density of mid-slope fishes off southeastern Australia was comparable to that observed in the Northern Hemisphere. However, landings and acoustic and egg surveys of orange roughy (Hoplostethus atlanticus) indicate that densities of that species alone are an order of magnitude higher than the total fish density indicated by trawl surveys. Water-column productivity over the mid-slope region appears insufficient to support the higher range of density estimates, implying a significant flux of energy into the region either from offshore or downslope.The dominant mid-slope demersal fishes appear to comprise an identifiable community within a biogeographic province that extends at least from the Great Australian Bight to the Chatham Rise (New Zealand), a distance of ∼5000 km. Distinct assemblages of demersal fish were found at upper (500 m) and mid-slope (800–1200 m) depths off southeast Australia. The mid-slope community could be sub-divided into assemblages by depth (shallow, intermediate and deep) and area (east and west Tasmania), which were statistically robust although with considerable overlap of species composition. There was no overlap in species composition of the southeast Australian mid-slope demersal fish community with fish communities at similar latitudes and depths in the North Pacific, but there were affinities with those in the North Atlantic. These biogeographic patterns, which appear consistent with oceanic circulation at intermediate depths, provide strong evidence that negates the recent hypothesis that deepwater fish communities cannot be defined over broad areas and are only random assemblages (Haedrich and Merrett, 1990, Progress in Oceanography, 24, 239–250).
Traditional methods of analysis of community ordinate and/or cluster survey data. The patterns extracted are the basis for inferences about habitat preferences of species and interactions among them. Following the logic of those inferences we develop a set of hierarchical simulations to investigate what patterns are diagnostic of the biological processes of habitat selection and interspecific competition (or facilitation). The simulations also include fishing on the simulated populations. The simulations illustrate that preferences of a pair of species along a habitat gradient produce characteristic patterns when species abundances are plotted on axes of abundance of each species. Directed fishing on one of the species eliminates much of the evidence of the pattern. Adding competitive interactions to habitat preferences creates additional diagnostic patterns in the simulated data. Fishing again eliminates much of the evidence of these patterns. Data from multispecies trawl surveys which capture flatfish produce plots that are consistent with the simulation results, although frequent zero catches for one species in a pair produces patterns not included in the simulations. With regard to explaining the distribution and abundance of flatfish in survey data, any evidence of competitive interactions and much of the evidence of differential habitat selection may be removed by the effects of directed fishing. Further simulations with more complex scenarios of fishing, habitat selection, and competition are warranted. However, gains in realism are likely to be offset by losses in clarity.
Recent studies of basin-scale patterns of diversity of benthic macrofauna reported strong latitudinal gradients of diversity in the deep North Atlantic, in contrast to regionally variable patterns in the Southern Hemisphere. Here we use data from fisheries research trawl surveys to examine spatial patterns of species richness, Shannon-Wiener diversity index, and evenness of demersal fish communities in relation to latitude and depth from 80 to 898 m off south-east New Zealand. We found species richness decreased latitudinally within regions in the poleward direction, and increased with depth. Areas of high species richness were concentrated along the margins of the Chatham Rise and were associated with current intensification in regions of enhanced surface phytoplankton pigment concentration. Species richness was highest between the 500 and 1000 m contours on the Chatham Rise, where enhanced surface phytoplankton pigment is associated with a major oceanographic feature, the Subtropical convergence. A predominance of species-rich locations was found on the more steeply shelving northern margin of the Chatham Rise. The regional latitudinal pattern of diversity appears to be correlated with regional production, and to be influenced by mesoscale oceanographic features constrained by the bathymetry, although the proximal causes for high diversity remain speculative.
Demersal fish data from 9 deep-sea surveys in the North Atlantic were examined to assess (1) the coherence and continuity of zones around the ocean basin, and (2) the persistence of structured communities over more than just a local scale. The 63 cruises took 96,779 specimens and 325 species in 692 benthic trawl hauls between 204 and 5345m depth. Measures of similarity and overlap applied to this faunal data did not produce patterns other than those reflecting the occurrence of two widespread and abundant species - Synaphobranchus kaupi at slope depths and Nematonurus armatus on the rise. Communities defined within a survey area by commonly-used analytical procedures cannot be identified from place to place over broader areas, and the concept along with its implication should be abandoned.
This book can be found for open access at www.carme-n.org
Optimal Transformations in Multivariate Analysis of Trawl Data
- C Donovan
- C. Donovan
Donovan, C. 1998. Optimal Transformations in Multivariate
Analysis of Trawl Data. M.Sc. Thesis, University of Auckland,
Auckland. 91 pp.
- J M N W Fenaughty
- Bagley
Fenaughty, J.M. & N.W. Bagley. 1981. W.J. Scott New Zealand
trawl survey. South Island east coast. Min. Agric. Fish., Fish.
Tech. Rep. 157. 224 pp.
- J M N W Fenaughty
- Bagley
Fenaughty, J.M. & N.W. Bagley. 1981. W.J. Scott New Zealand
trawl survey. South Island east coast. Min. Agric. Fish., Fish.
Tech. Rep. 157. 224 pp.
Multivariate Analysis of Fish Community Structure in the Hauraki Gulf
- M P Francis
- M.P. Francis
Francis, M.P. 1976. Multivariate Analysis of Fish Community Structure in the Hauraki Gulf, Auckland. M.Sc. Thesis,
University of Auckland, Auckland. 73 pp.
- R. Mahon