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Some Aspects of the Ecology of Lake Macquarie, N.S.W., with Regard to an Alleged Depletion of Fish. X. The Movements of Fish
Abstract
Of 20,128 fish of 29 species tagged, 9.4 per cent. were recovered by commercial fishermen and anglers. A further 1.5 per cent. were retaken by the tagging crew. Only 11 species were tagged in numbers greater than 100. Returns covered 17 species, showing recovery rates varying from 1 to 21 per cent.
Some exchange of fish takes place between the northern and southern parts of the lake, but this is consistent only in the case of the flat-tail mullet. Within the two parts of the lake lateral movements of some species take place; other species are sedentary. These facts suggest that the necessary condition for population estimation, that tagged fish should be randomly distributed amongst the
population, is not achieved for most species.
... Limited empirical data, however, exists on their movement patterns and indicate that movements are complex and involve uncertainties. Mark-recapture experiments conducted in NSW showed that tagged luderick moved distances up to 450 km from their point of release, travelling in a predominantly northerly direction along the coast [27,32,33]. Gray et al. [27,31] suggested that some movements may be related to pre-spawning migrations. ...
... Despite these relatively large movements luderick may also remain within the same area for long periods of time. The majority of tagged luderick recaptured during the mark-recapture experiments [27,32,33] were caught within the same estuary in which they were released, in some instances nearly two years later, indicating that luderick were probably residing within those estuaries. Little, however, is known of their movements within these estuaries. ...
... Movement patterns and behaviour of luderick observed here indicate a high level of habitat familiarity, and suggests that fish were residing on release reefs. Luderick are clearly capable of moving large distances along the coastline [27,32,33], and some fish were observed making relatively large trips between reefs in this study, however the majority of their time was spent on what we would argue are ''home'' reefs (i.e. release reefs). Fish made trips from these home reefs, but generally these were to adjacent reefs and not much further. ...
Understanding movement patterns, habitat use and behaviour of fish is critical to determining how targeted species may respond to protection provided by "no-take" sanctuary zones within marine parks. We assessed the fine and broad scale movement patterns of an exploited herbivore, luderick (Girella tricuspidata), using acoustic telemetry to evaluate how this species may respond to protection within Jervis Bay (New South Wales, Australia). We surgically implanted fourteen fish with acoustic transmitters and actively and passively tracked individuals to determine fine and broad scale movement patterns respectively. Eight fish were actively tracked for 24 h d¯(1) for 6 d (May 2011), and then intermittently over the following 30 d. Six fish were passively tracked from December 2011 to March 2012, using a fixed array of receivers deployed across rocky reefs around the perimeter of the bay. Luderick exhibited strong site fidelity on shallow subtidal reefs, tending to remain on or return consistently to the reef where they were caught and released. All eight fish actively tracked used core areas solely on their release reef, with the exception of one fish that used multiple core areas, and four of the six fish passively tracked spent between 75 to 96% of days on release reefs over the entire tracking period. Luderick did move frequently to adjacent reefs, and occasionally to more distant reefs, however consistently returned to their release reef. Luderick also exhibited predictable patterns in movement between spatially distinct daytime and night-time core use areas. Night-time core use areas were generally located in sheltered areas behind the edge of reefs. Overall, our data indicate luderick exhibit strong site fidelity on shallow subtidal reefs in Jervis Bay and suggests that this important herbivore may be likely to show a positive response to protection within the marine park.
... Existing data indicate that the species is primarily detritivorous (Pease et al., 1981), but the intra-estuarine movements of the species have not yet been resolved in detail for any estuary. Historic studies indicate that fish can mature in the estuary, before running to sea and spawning near the mouths of estuaries and the inshore habitats (Thompson, 1959). Thompson (1959) showed (using tag-recapture) that the species tends to favor the upper estuary, and had Fig. 1). ...
... Historic studies indicate that fish can mature in the estuary, before running to sea and spawning near the mouths of estuaries and the inshore habitats (Thompson, 1959). Thompson (1959) showed (using tag-recapture) that the species tends to favor the upper estuary, and had Fig. 1). Red hatching indicates main contamination plume (corresponding with the box indicated in Fig. 2). ...
Contamination in urbanised estuaries presents a risk to human health, and to the viability of populations of exploited species. Assessing animal movements in relation to contaminated areas may help to explain patterns in bioaccumulation, and assist in the effective management of health risks associated with consumption of exploited species. Using polychlorinated dibenzodioxin and polychlorinated dibenzofuran (PCDD/Fs) contamination in Sydney Harbour estuary as a case study, we present a study that links movement patterns resolved using acoustic telemetry to the accumulation of contaminants in mobile fish on a multi-species basis. Fifty-four individuals across six exploited species (Sea Mullet Mugil cephalus; Luderick Girella tricuspidata; Yellowfin Bream Acanthopagrus australis; Silver Trevally Pseudocaranx georgianus; Mulloway Argyrosomus japonicus; Yellowtail Kingfish Seriola lalandi) were tagged with acoustic transmitters, and their movements tracked for up to 3years. There was substantial inter-specific variation in fish distribution along the estuary. The proportion of distribution that overlapped with contaminated areas explained 84-98% of the inter-specific variation in lipid-standardised biota PCDD/F concentration. There was some seasonal variation in distribution along the estuary, but movement patterns indicated that Sea Mullet, Yellowfin Bream, Silver Trevally, and Mulloway were likely to be exposed to contaminated areas during the period of gonadal maturation. Acoustic telemetry allows examination of spatial and temporal patterns in exposure to contamination. When used alongside biota sampling and testing, this offers a powerful approach to assess exposure, bioaccumulation, and potential risks faced by different species, as well as human health risks associated with their consumption.
... Often studies quantifying the size and abundance of targeted species inside and outside marine reserves are done without knowledge of movement patterns in relation to marine reserve design and vice versa. Luderick G. tricuspidata is considered to be highly mobile (Kingsford, 2002;Curley et al., 2013) and mark-recapture experiments carried out in NSW have shown that some tagged fish can move distances up to 450 km from their point of release (Thomson, 1959;Gray et al., 2012). It is for this reason that G. tricuspidata is considered unlikely to benefit from marine reserves (Kearney, 2007). ...
... It is for this reason that G. tricuspidata is considered unlikely to benefit from marine reserves (Kearney, 2007). Despite these relatively large movements, markrecapture experiments have shown that the majority of tagged G. tricuspidata recaptured were caught within the same estuary in which they were released (Thomson, 1959;West, 1993;Gray et al., 2012), in some instances nearly two years later, indicating residency within those estuaries. Initial acoustic tracking data has also demonstrated G. tricuspidata exhibit strong site fidelity on shallow subtidal reefs over a three month period (Ferguson et al., 2013). ...
A key objective of marine reserves is to maintain ecological processes important to the functioning of marine ecosystems. Grazing by tropical herbivores contributes to maintaining resilient coral reefs and marine reserves are critical in conserving herbivores and the functional role they provide. Less is known, however, about the effects of marine reserves on herbivorous fish and their role on temperate reefs. This study evaluated the potential for marine reserves to enhance grazing by herbivores on temperate reefs in Jervis Bay Marine Park, Australia. First, the movement patterns of a dominant grazer, luderick Girella tricuspidata, were determined using acoustic telemetry to assess the potential effects of marine reserves on G. tricuspidata. Second, the size and abundance of G. tricuspidata and other grazers (rock blackfish Girella elevata and silver drummer Kyphosus sydneyanus) was quantified on shallow subtidal reefs inside and outside marine reserves using a diver operated stereo-video system. Finally, grazing rates were quantified inside and outside marine reserves using video cameras. Luderick G. tricuspidata exhibited strong site fidelity on shallow subtidal reefs and was significantly larger and more abundant within marine reserves. Rock blackfish G. elevata was significantly more abundant in one of four marine reserves, although showed no difference in size between zones. Silver drummer K. sydneyanus was significantly larger in marine reserves, although not significantly more abundant. On shallow subtidal reefs, G. tricuspidata was the dominant grazer compared to other girellids and kyphosids, accounting for > 97% of total algal bites (predominantly on algal turfs). Grazing rates were higher on average within marine reserves (although not significantly higher) and there was a positive correlation between the relative abundance of G. tricuspidata and number of algal bites, indicating grazing intensity increased with abundance. The findings in this study demonstrate the clear potential for greater grazing by herbivores within temperate marine reserves. This study also suggests that exploitation of targeted herbivores on temperate reefs is significant and marine reserves can reduce this impact and allow it to be measured via reference areas.
... The tag-recapture data presented here and by Thomson (1959) show that Girella tricuspidata are capable of moving between distant estuaries (up to 450 km) and that these movements are predominantly in a northerly direction. These movements, along with the potential relocation of eggs and larvae southwards via the East Australian Current, suggest that there is considerable population mixing of G. tricuspidata along eastern Australia. ...
... Heupel & Simpfendorfer 2008, Danylchuk et al. 2011). Nevertheless, we hypothesise that the predominant northerly movement displayed by G. tri cus pidata, along with several other estuarine and coastal teleosts (Mugil cephalus, Acanthopagrus australis, Pagrus auratus and Pomatomus saltatrix) (Thomson 1959) and crustaceans (Penaeus plebejus) (Montgomery 1990) along the east Australian coast, is a life-history tactic to facilitate the wide dispersal of eggs and larvae by the southward-flowing East Australian Current to coastal and estuarine nursery areas. Essentially, fish move upstream into the prevailing current to spawn, after which eggs and larvae are transported and dispersed by longshore currents to nursery habitats, a tactic displayed by coastal fishes inhabiting other coastal boundary current systems (Hare & Cowen 1993). ...
Girella tricuspidata is widely distributed and harvested by recreational and commercial fishers along the coastline of eastern Australia. The present study examined variability in the reproductive biology and growth of individuals within populations of G. tricuspidata across 3 estuaries (Clarence, Tuggerah and Tuross) and assessed population connectivity via a large-scale tag-recapture study in which fish were tagged across 9 estuaries. Spawning occurred predominantly between June and September in the Clarence River and between October and January in the Tuross River, suggesting that spawning occurs later in the year at higher latitudes. The recruitment of young to nursery grounds was spatially and temporally variable. G. tricuspidata are group-synchronous spawners, and the estimated batch fecundity was positively correlated with fish length. The estimated length and age at which 50% of G. tricuspidata attained reproductive maturity was similar for both sexes: ~286 mm fork length (FL) and 4.1 yr for males and 295 mm FL and 4.5 yr for females. G. tricuspidata were aged using otoliths to >26 yr, whereas the reading of scales consistently underestimated the age of fish older than 5 yr. Growth was flexible but varied significantly between sexes and among estuaries; females grew faster than males and attained a larger asymptotic length in the Clarence and Tuross Rivers but not in Tuggerah Lake. Growth was rapid for both sexes until 4 to 5 yr of age, after which it slowed. Of the 6871 G. tricuspidata tagged, 15% were recaptured, with 96% of these fish recaptured in the estuary in which they were initially tagged. The recaptured individuals that migrated between estuaries predominantly displayed a northward movement into the prevailing coastal current, which is probably a life-history tactic to facilitate wide dispersal of eggs and larvae along eastern Australia.
... It has been shown that juvenile M. cephalus actively avoid polyhaline and euhaline waters, preferring freshwater and oligohaline waters in a stratified study carried out in several inland estuaries of the Island of Menorca (Western Mediterranean ) (Cardona 2000). However, occupation of freshwater is not obligatory for newly recruited M. cephalus and abundant evidence is available from around the world of this species remaining in estuaries until mature and then returning to the sea (Thomson 1959; Wallace and van der Elst 1975). The cruising speed of subadult M. cephalus approximately 15 cm TL was 7 body lengths per second whilst they were migrating along the mid- Atlantic coast of North America, which is considerably higher than typical cruising speeds for other fishes at 2–3 body lengths per second (Peterson 1976). ...
... Although a quantification of these transfers has yet to be undertaken M. cephalus, by virtue of its abundance and biomass, is likely to be one of the more important fish species providing connectivity within the coastal zone. An indication of this importance is provided by Thomson (1959) who estimated that 1? and older M. cephalus in the 44 km 2 Lake Macquarie, New South Wales, had a population of 2.693 9 10 6 (806 9 10 3 kg) or 61 individuals ha -1 (18 g m -2 ). The flathead mullet is situated at the base of the food pyramid and, by virtue of its consumption of particulate organic matter, detritus and benthic microalgae , this species is able to 'telescope' the food chain and make high quality fish protein available to top predators. ...
This study reviews published information on Mugil cephalus from around the world, with recent genetic studies indicating that the flathead mullet may indeed be a species complex. Disciplines that are covered range from the taxonomy, genetics and systematics, through a variety of biological and ecological attributes, to biomarker and fisheries studies. The eurytopic nature of M. cephalus is emphasized, with the migratory life history covering a succession of very different aquatic environments (e.g. rivers, estuaries, coastal lakes/lagoons, marine littoral, open ocean), each of which is occupied for varying lengths of time, depending on the population characteristics within a region and the life-history stage of the species. Interpretation of these movements over time has been greatly enhanced by the use of otolith micro-chemistry which has enabled scientists to map out the different habitats occupied by individual fish at the different life stages. The range of physico-chemical attributes within these environments necessitates a wide tolerance to differing conditions, especially with regard to salinity, turbidity, dissolved oxygen and temperature, all of which are discussed in this review. The importance of M. cephalus to the ecological functioning of coastal systems is emphasized, as well as the pivotal role that this species fulfills in fisheries in some parts of the world. The parasites range from internal trematode and cestode infestations, to external branchyuran and copepod parasites, which use M. cephalus as either an intermediate or final host. The value of the flathead mullet as a biomarker for the monitoring of the health of coastal habitats is discussed, as well as its potential as an indicator or sentinel species for certain ecosystems.
... In New Zealand fish settle on very shallow reefs within estuaries, move to reefs just inside estuaries at 50 mm and to open coastal reefs at 90-100 mm and *1 year of age (Morrison 1990), and remain on reefs adjacent to estuaries for 1-2 years before moving to more distant sites. Luderick also undertake pre-spawning migrations along the coast of NSW, with tagged estuarine fish moving distances of[150 km between estuaries (Thomson 1959;Morrison 1990;West 1993a;Gray et al. 2000). Such movements may be the cause of the significant temporal variation in densities of luderick on coastal reefs (Curley 2007). ...
... Morrison (1990) proposed that luderick exhibits intraspecific variation in movement, with some fish displaying high site fidelity and others being migratory. This is supported by tagging data showing that many individuals were re-captured within their release estuary, while others travelled [100 km among estuaries (Thomson 1959;West 1993a;Gray et al. 2000). Preliminary data showing a positive response of luderick to protection within a small coastal MPA B 0.2 km 2 in NSW also indicates that some individuals may be relatively sedentary (Curley 2007). ...
Knowledge of the population biology, life-history ecology and scales of pre and post-settlement movement of marine species are needed to inform effective conservation management strategies, particularly when spatial information is required for management purposes such as zoning in Marine Protected Areas. This review provides the most current summary from primary and grey literature on the biology and ecology of several coastal fishes of economic and ecological significance in south-east Australia; identifies key knowledge gaps which may impede the development of effective spatial management; and recommends future research directions and methods. Reviewed species are luderick (Girella tricuspidata), eastern rock blackfish (Girella elevata), yellowfin bream (Acanthopagrus australis), tarwhine (Rhabdosargus sarba), snapper (Pagrus auratus), red morwong (Cheilodactylus fuscus) and eastern blue grouper (Achoerodus viridis). The species have a diverse range of life-histories and population traits, and selected parameters were well studied in several species, such as growth (blue groper, luderick, yellowfin bream, tarwhine, snapper), post-settlement movement (red morwong), and larval ecology (yellowfin bream). However, empirical data on levels of pre- and post-settlement connectivity and real-time movements are not available for most species, and this represents a significant gap for improved spatial management. A multidisciplinary approach incorporating a range of methods including acoustic tracking and telemetry, otolith chemistry, intergenerational markers, and biophysical modelling will provide a more comprehensive understanding of life history parameters, movement and connectivity at scales relevant to MPA planning and monitoring.
... Sciaenids form the basis of commercial and recreational fisheries in tropical and temperate regions throughout the world (Lenanton and Potter 1987; Rutherford et al. 1989), are used widely in aquaculture (Arnold et al. 1988) and are commonly caught as by-catch in trawl fisheries (Pauly 1979; Sheridan et al. 1984; Gray et al. 1990). Despite this, there is little published information on the biology and ecology of sciaenids in Australia, even for the large economically important species Argyrosomus hololepidotus LacCpkde; there is only limited information available for this species in Western Australia (Penn 1977; Potter et al. 1983; Loneragan et al. 1987), southern Australia (Hall 1986) and south-eastern Australia (Thomson 1959; Anon. 1981). ...
... Many facets of its biology and ecology have been studied in southern Africa (Wallace 1975; Wallace and Schleyer 1979; Smale 1984 Smale , 1985 Smale and Bruton 1985; Beckley 1986 Beckley , 1990). Juveniles occur in estuaries, embayments and nearshore coastal environments (Thomson 1959; Wallace 1975; Anon. 1981; Potter et al. 1983; Smale 1985 ), but little is known of their spatial distribution in estuaries. ...
The distribution, recruitment, relative abundance and growth of juvenile mulloway,
Argyrosomus hololepidotus Lacepede, was investigated in the Hawkesbury River.
Otter trawling was used monthly between July 1986 and March 1988 at 12 sites
along a salinity gradient over 85 km of the estuary. The greatest numbers of juveniles
were caught at sites in the mid section of the estuary (20-40 km from the mouth) where
salinities were greatly reduced. No A. hololepidotus were caught at sites that were
permanently fresh water and few were caught at the marine-dominated sites closest
to the mouth of the estuary. The greatest numbers of juveniles were caught between
March and September (autumn-winter) and the fewest between October and January
(spring-summer). Juveniles with an estimated age of 2-6 months were caught between
February and July (late summer-winter) each year at a size of 30-150 mm total length.
Juveniles increased in length by 80-100 mm between March and October.
... Further, M. cephalus, Acanthopagrus spp. and G. tricuspidata are migratory, with some individuals not only moving between estuaries, but also inhabiting and spawning in coastal waters (Thomson 1959;Gray et al. 2012;Fowler et al. 2016). Thus, the broader population connectivity and mixing of individuals among estuaries (both ROF and non-ROF) and coastal waters needs consideration in determining broad-scale protective synergies of estuarine ROF Vol:. ...
Management of fisheries by preventing commercial, whilst allowing recreational-only fishing in some areas, is intended to increase stocks so that sustainable recreational fishing is conserved or enhanced. This study examined whether the relative abundances and length and age characteristics of five harvested species of fish differed between recreational-only fished (ROF) estuaries, and those open to both recreational and commercial fishing (non-ROF) in southeastern Australia. Specific predictions based on absolute and ranked values of a range of parameters were made so that conclusions could be reached about the effects of management. Fish were sampled using multimesh gillnets in a standard and stratified manner across two ROF and two non-ROF estuaries over three years, six to eight years post ROF implementation. Abundances of each species fluctuated among individual estuaries and sampling times with no indication of greater abundances in ROF estuaries. For four species (Sillago ciliata, Mugil cephalus, Acanthopagrus spp. and Girella tricuspidata), the mean lengths and the proportions of individuals of legal length, were mostly greater in the ROF compared to the non-ROF estuaries. However, for Platycephalus fuscus there were no discernible patterns. Three species (P. fuscus, S. ciliata and Acanthopagrus spp.) had a significantly greater proportion of older fish in the ROF estuaries, but for M. cephalus and G. tricuspidata this was only evident in one ROF estuary. It is hypothesised that the cessation of commercial fishing and subsequent reduction in fishing pressure in the ROF estuaries allowed a greater proportion of individuals of each species to survive to become larger and older. This study provides correlative evidence that ROF estuaries can protect some harvested species at the local scale of estuary. Examination of lengths and ages of fish, rather than simply their abundances, was necessary to identify the effects of removing commercial fishing. Further research is required to determine the potential broader-scale and long-term sustainability benefits on species as well as any spill-over effects on other organisms and estuarine ecosystems.
... Nevertheless, based on some preliminary genetic sampling , it is likely that the northern RR and CR contained mostly pure A. australis and few (if any) hybrids, whereas hybrid complexes most likely dominated populations in SB and WG. The other study estuaries may have contained variable and potentially temporally dynamic mixes of all three Acanthopagrus types as a result of variable recruitment and movements of individuals among estuaries (Thomson, 1959). Thus, the genetic composition of each estuary population could potentially be variable across years. ...
Knowledge of spatial variation in growth and demographic characteristics of exploited teleost populations is informative for understanding levels of resilience and susceptibility to environmental and anthropogenic perturbations and for resource management. This study investigated variation in length-and age-compositions, length-at-age and growth, longevity and mortality of Acanthopagrus (A. australis, A. butcheri and their hybrids) population complexes across seven estuaries spanning seven degrees of latitude in eastern Australia. Populations were sampled using two gears according to standardised fishery-independent survey protocols. Populations within each estuary displayed considerable variation in length-at-age, with sex-specific growth attributes evident in some estuaries but not others. Nevertheless, females dominated populations, and on average, the mean lengths and ages of females were greater than males within each estuary population. Estuary type and location appeared to influence the estuary-specific growth characteristics of both sexes, with populations in the southern coastal lakes having, on average, greater mean lengths at age and faster growth than those in the northern riverine estuaries. Length and age compositions of populations did not vary accordingly, with observed longevities and estimated natural mortalities varying among estuaries, most likely reflecting estuary-specific environmental conditions and anthropogenic activities. In general, populations across all estuaries primarily comprised fish <25 cm fork length (FL) and 10 years of age. Given their potential to reach FLs up to 50 cm and ages >20 years, populations across most estuaries appeared length and age truncated. Ecological relationships and resource management implications are discussed.
... The species also undertakes pre-spawning migrations along the coast of NSW. Despite potential for large scale movements tagging information also supports intraspecific variation in movement with some fish displaying site fidelity to estuaries or reefs and others being migratory (Curley, 2007;Gray et al., 2000;Kingsford, 2002;McNeill et al., 1992;Morrison, 1990;Thomson, 1959;West, 1993) There are no published tagging data on the movements of silver drummer. Temporal changes in densities, however, suggest they move at scales >1 km on coastal reefs. ...
... Since the Fisheries Inquiry of 1880, the recreational sector has continued to grow and this has led to increased conflict with the commercial sector as both groups strive to maximise their share of limited fisheries resources. An extensive investigation into the hydrology, geology and ecology of Lake Macquarie was initiated in 1955 as a result of emphatic allegations that the fish stocks in Lake Macquarie had been depleted by commercial over-exploitation (see Baas Becking 1959;Baas Becking et al. 1959;Davis 1959;MacIntyre 1959;Spencer 1959;Thomson 1959aThomson , 1959bThomson , 1959cThomson , 1959dWood 1959aWood & 1959b. Similar allocation disputes within NSW have been concentrated in other estuarine fisheries near large metropolitan areas such as Botany Bay and Sydney Harbour (Ruello and Henry 1977, State Pollution Control Commission (SPCC) 1981, Henry 1984. ...
... Since the Fisheries Inquiry of 1880, the recreational sector has continued to grow and this has led to increased conflict with the commercial sector as both groups strive to maximise their share of limited fisheries resources. An extensive investigation into the hydrology, geology and ecology of Lake Macquarie was initiated in 1955 as a result of emphatic allegations that the fish stocks in Lake Macquarie had been depleted by commercial over-exploitation (see Baas Becking 1959;Baas Becking et al. 1959;Davis 1959;MacIntyre 1959;Spencer 1959;Thomson 1959aThomson , 1959bThomson , 1959cThomson , 1959dWood 1959aWood & 1959b. Similar allocation disputes within NSW have been concentrated in other estuarine fisheries, usually near large metropolitan areas such as Botany Bay and Sydney Harbour (Ruello and Henry 1977, State Pollution Control Commission (SPCC) 1981, Henry 1984. ...
... They showed that siphon predation appeared to inhibit successful reproduction as siphon regeneration took place at the expense of energy, which might otherwise have been channelled into growth and reproduction. This inhibition of successful reproduction by the Tellina population was probably related to conditions prevailing at the study site, as tank experiments suggested that once the availability of siphons fell below a certain threshold, the plaice no longer fed as intensely on Thompson (1959) (1 ...
The food and feeding ecology of five species of Genes in the estuaries of Natal, were investigated from 1978 to 1980. The Kosi system, consisting of an estuary and three main lakes was selected as the main study area due to an abundance of Genes. Four other estuarine systems were sampled.
At Kosi polychaetes were important at the estuary, siphon tips (distal ±5 mm) of the bivalve Hiatula lunulata were most commonly taken in Lakes Makhawulani and Mpungwini, while chironomid larvae were important in Lake Nhlange. Ivlev's electivity test showed that Genes positively selected bivalve siphon tips when searching for food. The food taken by Genes from other estuaries was similar to that at Kosi, although the proportions of the different prey varied. At Kosi between three and five species occurred sympatri-cally. Resource segregation was through differences in diet and feeding periodicity and a superabundance of food (H. lunulata siphon tips) during summer and autumn. During winter and spring when food may be limiting, most Genes leave shelf areas of the Kosi system, only G. acinaces remains in large numbers. Little is known of the diet of other fish which feed on benthic invertebrates in Kosi but there is probably little direct competition with Gerreidae, although Acanthopagrus berda and Pomadasys commersonni have been recorded feeding on the siphons of the bivalve Solen corneus, the former in Durban Bay and the latter at Kosi. In areas where the bivalve H. lunulata occurs it is suggested that Gerreidae have developed optimal foraging techniques which enhance resource partitioning.
... Several tag-recapture studies have been done on A. japonicus, although the objectives and scales of the studies, and the data published, have been variable and in some cases, unclear. In Australia, separate tag-recapture studies have been done on A. japonicus in NSW (Thomson, 1959; West, 1993; NSW Fisheries unpublished data), South Australia (Hall, 1984) and Western Australia (Anon, 1993), while in southern Africa there have been two published studies (Griffiths, 1996; Griffiths and Attwood, 2005). ...
Argyrosomus japonicus is a member of the family Sciaenidae, which are commonly known as drums and croakers. A. japonicus occurs in estuarine and nearshore Pacific Ocean and Indian Ocean waters surrounding Australia, Africa, India, Pakistan, China, Korea and Japan. The biology of A. japonicus is relatively well studied in South Africa, and more recently studied in Australia, but no information is readily available from other areas of its distributional range. The early life history distribution of A. japonicus may differ among regions, with their distribution in estuaries linked to salinity, turbidity, freshwater flows and depth of water. Studies in South Africa and Australia found that juvenile fish grow rapidly, attaining 35 cm TL in 1 year and 87–90 cm TL in 5 years. Sexual maturity also differs among regions and is attained at 2–3 years of age and >50 cm in eastern Australia, 5–6 years of age and >80 cm TL in western Australia and southern Africa. The maximum reported length and age of A. japonicus is 175 cm and 42 years, respectively. Spawning most likely occurs in nearshore coastal waters although there is evidence to suggest that it may also occur in the lower reaches of estuaries. Time of spawning varies among geographic localities and is probably linked to water temperature and oceanography. Juvenile fish (<2 years) appear to be relatively sedentary, but sub-adults and adults can move relatively long distances (>200 km) and such movements may be linked to pre-spawning migrations. A. japonicus is important in many recreational and commercial fisheries, but like other sciaenids, is prone to overfishing. It is classified as recruitment overfished in South Africa and overfished in eastern Australia. Although much research has been done to minimize the capture of juveniles in Australian prawn-trawl fisheries, greater protection of spawners and improved fishing practices to enhance survival of discarded juveniles, particularly from prawn trawling, may be required. An aquaculture industry is developing for A. japonicus in Australia and preliminary research on the impacts and success of re-stocking wild populations has begun in an attempt to arrest the apparent decline in populations.
... Lake Macquarie had been at the centre of conflict between the commercial and recreational sectors for many years. In the 1950s a large number of scientific studies were undertaken in the estuary to investigate claims, from the recreational sector, that fish stocks were being reduced by over-exploitation by the commercial fishing sector (Thomson, 1959). Claims of overexploitation by either sector were confounded by a general deterioration of the Lake's environmental quality following 100 years of development in the Lake and its catchment that included power stations, heavy industry, tourism, coal mining, agriculture, and urban development (Lake Macquarie Task Force, 1999; WBM Oceanics Australia, 1997). ...
In its effort to resolve the conflict between commercial and recreational fishers the New South Wales (NSW) government (NSW Fisheries) banned commercial fishing in the estuarine waters. The NSW Fisheries conducted a number of studies and held meetings with the affected communities including commercial fishers prior to the implementation of the ban. To investigate how community consultation played a role in the decision-making process especially as perceived by the commercial fishers and to determine actual social impacts of the ban on commercial fishers, in-depth interviews were conducted with the commercial fishers. This research reveals that despite the NSW Fisheries' consultations with commercial fishers prior to the closure, the latter were confused about various vital aspects of the decision. It further reveals that, the commercial fishers faced a number of significant changes as a result of this decision. We argue that a better decision-making process and outcome would have been possible through a meaningful consultation with the commercial fishers and a social impact assessment.
This synthesis highlights Mugil cephalus research conducted in the fields of population genetics, life
history traits, migrations and biomarkers. The economic importance of this species to global fisheries is also stressed and future perspectives given.
Previous studies have shown that accumulation of perfluoroalkyl acids (PFAAs) in the tissues of aquatic species is highly variable. Movement and migration patterns in these species represent an important consideration when evaluating contaminant accumulation in exposed biota, and may have a large influence on the risk profiles for migratory seafood species. In this study, relationships between PFAA concentrations in muscle and liver tissue, and recent fish migration history (inferred from metals profiles in fish otoliths, otherwise known as otolith chemistry) were evaluated in Sea Mullet (Mugil cephalus). A greater number of PFAAs, and higher concentrations, were found in liver compared to muscle tissue. Perfluorooctane sulfonate (PFOS) was present in highest concentrations in both muscle and liver tissues, and there was strong correlation in concentrations between these two tissues. PFOS was found to decrease and increase alongside recent strontium and barium concentrations (respectively) in the otolith, suggesting higher concentrations of PFAAs in fish recently exposed to comparatively lower salinity environments. This study highlights how otolith chemistry can be employed to examine links between contaminant concentrations in fish, and their recent migration history. This approach shows promise for studying contaminant residues in mobile seafood species within the natural environment.
The national reporting framework used in the Status of key Australian fish stocks reports 2014 was developed collaboratively by fisheries scientists from around Australia. This framework uses standardised terminology and reference points for stock status classifications. Following release of the Status of key Australian fish stocks reports 2012, a review was undertaken to document the lessons learned. Feedback from stakeholders suggested that national reporting on the status of key Australian fish stocks should continue, and that effort should be made to incorporate reporting on fishery-level environmental, economic, governance and social aspects.
The national framework for these reports considers both the abundance (number or biomass [weight]) of fish in a stock and the level of fishing pressure (rate of fishing) applied to a stock. The status classifications assess whether the current abundance of fish in a stock is adequate—that is, whether there is a large enough proportion of the original adult stock remaining that the production of juveniles is not significantly reduced. They also assess whether the amount of fish currently being removed through fishing is adequately controlled to ensure that stock abundance is not reduced to a point at which production of juveniles is significantly reduced. The framework makes these assessments against the biomass reference point of 'recruitment overfished', which is the point at which the spawning stock biomass has been reduced by fishing so that average recruitment (that is, the production of juveniles) is significantly reduced. There are five classification categories (refer to Introduction for full descriptions):
Sustainable stock —indicates that biomass (or biomass proxy) is at a level sufficient to ensure that, on average, future levels of recruitment are adequate (that is, the stock is not recruitment overfished) and that fishing pressure is adequately controlled to avoid the stock becoming recruitment overfished.
Transitional –recovering stock—indicates that biomass is recruitment overfished, but management measures are in place to promote stock recovery, and recovery is occurring.
Transitional–depleting stock —indicates that biomass is not yet recruitment overfished, but fishing pressure is too high and moving the stock in the direction of becoming recruitment overfished.
Overfished stock —indicates that spawning stock biomass has been reduced through catch, so that average recruitment levels are significantly reduced (that is, the stock is recruitment overfished). Current management is not adequate to recover the stock; or adequate management measures have been put in place but have not yet resulted in measurable improvements.
Environmentally limited —indicates that spawning stock biomass has been reduced to the point where average recruitment levels are significantly reduced, primarily as a result of substantial environmental changes or disease outbreaks (that is, the stock is not recruitment overfished). Fisheries management has responded appropriately to the environmental change in productivity.
Undefined stock —indicates that insufficient information exists to determine stock status.
Rocky reef habitat is common in many estuaries, yet its role as a habitat for fishes is poorly understood. There is also limited understanding of how access of coastal species into estuaries and habitat quality can affect the distribution of rocky reef fishes within estuaries. This study used baited remote underwater video stations to determine spatial patterns in fish assemblages associated with rocky reef habitat throughout a barrier estuary with a permanently open but restricted inlet. Estuarine rocky reefs provided habitat for a diverse assemblage of fishes, many of which were large juveniles and subadults. In the absence of a pronounced salinity or temperature gradient, a clear transition in fish assemblages occurred from coastal waters, through the inlet channel, to the central estuary, and into the inner estuary. The inlet channel, notably its narrowness and length, limits tidal input into this estuary, which acts as a significant impediment to the dispersal of many coastal fishes, and insufficient habitat excludes many coastal rocky reef species from the inner estuary. This study highlights the need to recognise estuarine rocky reefs as providing habitat for diverse fish assemblages and the role inlets play in restricting access of coastal species.
Age and growth patterns of luderick, Girella tricuspidata (Quoy and Gaimard), taken in the Moreton Bay net fishery are described. Scales have prominent annuli which are formed during the period May-July. The mean body length is similar for males and females, except for age class III where female fish are significantly larger. This probably results from the early movement of faster growing females onto the fishing ground. The scale method and length-frequency analysis both indicate that the variation in body lengths in each age class is large. The length-weight relationship was obtained and relative condition factor was found to be highest in July which corresponded with the peak in gonosomatic index.
Monthly changes in the gonosomatic index indicate that yellowfin bream, Acanthopagrus australis, in Moreton Bay have a short spawning season with a peak during the period July to August each year. The growth rate of A. australis was estimated from tag-recapture data and by length-frequency analysis. Modes representing age classes 0, I and II often appeared in length-frequency distributions, however modes for older age classes were difficult to identify. The von Bertalanffy growth curve parameters calculated from release–recapture data are: L∞= 29.5 cm; K= 0.51; t0=– 0.32 years.
Yellowfin bream, Acanthopagrus australis, support an important angling fishery in Moreton Bay, a large estuarine system on the east coast of Australia. An analysis of the records of catches by anglers indicates that abundance and mean size of yellowfin bream have changed little in Moreton Bay during the period 1945 to 1980. Over the past 5 years substantial increases have occurred in the total angling effort for yellowfin bream at surf bar spawning areas in Moreton Bay. This has resulted in a decrease in mean catch per unit effort but no apparent decrease in total yield. Reclamation and development projects which cause degradation of the surf bar spawning areas have the greatest potential to cause reduction in abundance of yellowfin bream in Moreton Bay.
Yellowfin bream were tagged and released in three non-spawning areas and two spawning areas in Moreton Bay, a large estuarine system on the east coast of Australia. A total of 194 fish were recaptured. Juvenile fish made only small-scale movements (less than 6 km) from the release site. Small-scale movements were also recorded for adult fish, although large-scale movements from 10 to 90 km were also recorded. The large-scale movements appear to be associated with the migration of adult fish to or from surf bar spawning areas. Some adult fish remained in feeding areas during the spawning season (May-August). There was no indication from tag recoveries of any movements of yellowfin bream outside Moreton Bay and the results indicate that adult yellowfin bream in Moreton Bay may be regarded as a unit stock for the purpose of fisheries management.
We investigated the relationship between distance from the ocean and the recruitment of ocean-spawned juvenile fish to seagrass
shallows within marine dominated Lake Macquarie, a coastal barrier lagoon in Southeast Australia. Samples were taken by seine
net every 6 wk between June 1986 and June 1987, at 20 sites established at various distances from the entrance channel. The
fish fauna was diverse: 80 species from 39 families were caught, with the Gobiidae, Monacanthidae, Syngnathidae, Tetraodontidae,
Mugilidae, Atherinidae, Clupeidae, Mullidae, Sparidae, and Blenniidae being well represented. Ambassis jacksoniensis, Atherinomorus ogilbyi, and Gerres subfasciatus accounted for 46% of all individuals. Thirty-two species were classified as ocean spawners, 38 as lagoon spawners, and 10
as unknown in terms of spawning area. Newly settled juveniles of ocean spawners were concentrated near the lagoon's entrance,
where most recruited in spring. This pattern occurred in the absence of a salinity gradient: distance from the ocean coupled
with weak internal water circulation appears to limit larval distribution and hence juvenile recruitment. Small juveniles
of Rhabdosargus sarba were sufficiently abundant for their subsequent dispersal to be directly traced. On the basis of results for this species,
and indirect evidence of dispersal for several others, it is suggested that ocean-spawned juveniles, after settling near the
entrance, gradually disperse as they grow and change their habitat. Thus, further from the entrance, their recruitment to
seagrass shallows is later, at larger sizes, and in smaller numbers. Newly settled juveniles of lagoon spawners, however,
were widely distributed within the lagoon. The optimal recruitment of ocean-spawned juveniles to similar coastal lagoons may
depend on suitable habitat being available near the entrance. *** DIRECT SUPPORT *** A01BY081 00003
Epiphytic diatoms were collected from both the leaves and internodes of Ruppia maritima in a New Jersey salt marsh during the growing season of the host plant. Community diversity (H and the number of diatom taxa) values were initially high as Ruppia began its growth, but quickly dropped to sustained low levels as vegetative growth of the host ceased and new attachment sites were no longer available. A critical examination of all structural characteristics indicated that the leaves and internodes of Ruppia support a single, nearly homogeneous epiphytic diatom community. An analysis of variance indicated that differences between leaves and internodes were minimal, as did a comparison of the assemblages present on these two sites by a selected similarity index. A total of 57 taxa were encountered and the single dominant taxon was Navicula pavillardi, which accounted for one out of every three individuals counted. A comparison of the epiphytic diatom community with those inhabiting the sediments on the marsh proper revealed that the marsh sediments were the major source of individuals for Ruppia colonization.
The fishes occurring in a subtropical mangrove (Avicennia marina) area in Moreton Bay, Australia, were studied for one year (November 1987 to November 1988, inclusive). Fishes within the mangroves were sampled using a block net, whilst those in adjacent waters were sampled using seine and gill nets. Forty six percent of the species, 75% of the number of fishes and 94% of the biomass taken during the study (all methods combined) were of direct importance to regional fisheries. The fish community utilising the habitat within the mangrove forest differed from that occurring in adjacent waters in terms of density, standing crop, species composition and diversity-index values. Standing-crop estimates for the fishes occurring within the mangroves (study period mean SD = 25.3 20.4 g m–2) were amongst the highest recorded values for estuarine areas whilst those for adjacent waters (2.92.3 g m–2) were comparable to those of other estuarine studies.
The fish assemblages inhabiting two intermittently open coastal lagoons and one permanently open coastal lagoon on the mid
south coast of New South Wales were studied over several years during the mid to late 1980s. Fish were sampled either monthly
or bimonthly using rotenone ichthyocide and beam trawls (in shallow vegetated habitats), beach seines (in shallow inshore
sand habitats), and multiple-panel gill nets (in deep lagoon habitats with mud or sand floors). These fish assemblages were
compared and contrasted spatially according to habitat both within lagoons and between the two lagoon types using a multivariate
ordination technique. In the permanently open lagoon, Lake Conjola, dominant faunal elements of commercial or recreational
fisheries importance included Girellidae, Clupeidae, Monacanthidae, Pomatomidae, Mugilidae, Sparidae, Sillaginidae, Gerreidae,
Terapontidae, and Platycephalidae. Dominant faunal elements of no commercial or recreational fisheries importance here included
Ambassidae, Scorpaenidae, Gobiidae, Atherinidae, and Eleotridae. In the intermittently open lagoons, Swan Lake and Lake Wollumboola,
the dominant faunal elements included Sparidae, Mugilidae, Girellidae, Hemiramphidae, Pomatomidae, and Arripidae amongst the
commercial group; and Atherinidae, Syngnathidae, Gobiidae, Eleotridae, and Scorpaenidae amongst the noncommercial group. The
overall species richness of the permanently open lagoon (≈100 species, including 52 commercial species) was found to be approximately
2.5 times that of each of the two intermittently open lagoons (39 species, including 22 commercial species for Swan Lake;
and 41 species, including 26 commercial species for Lake Wollumboola). The dominant faunal elements of the latter two south-eastern
Australian intermittently open lagoons were also compared with those of similar lagoons in south-western Australia, southern
Africa, and western Mexico, and the faunal similarities at the species, genus, and family levels are discussed. Available
commercial and recreational fisheries catch data for the three south-eastern Australian coastal lagoons were also analyzed
and compared. The two intermittently open lagoons were found to support number of species in the latter and also its greater
water surface area.
The research conducted for this thesis has produced quantitative data on the biology and population genetic structure of the Mulloway Argyrosomus japonicus in Western Australia, where this sciaenid is recreationally and commercially fished. These data were used 1) to test various hypotheses regarding the relationship between key biological characteristics of A. japonicus and both latitude and environmental variables, 2) to investigate the population structure and genetic characteristics of populations of A. japonicus on the west and south coasts of Western Australia and to assess the relationships between these populations and those of A. japonicus in eastern Australia and South Africa, and 3) to consider the implications of the biological and genetic results for management.
Mulloway are a large native inshore marine fish that are currently being evaluated by NSW Fisheries for their potential in aquaculture. The current study developed and applied molecular genetic markers to assess the geographical scale at which future hatcheries should be developed for the species. In addition, it evaluated the impact that current breeding practices in NSW have had on genetic diversity in culture cohorts. The study showed that wild Australian populations of this species constitute a single management unit (genetic stock), but that current hatchery practices employed in NSW are eroding natural genetic diversity. Thus a single hatchery could provide cultures stock to the whole Australian industry without compromising wild populations but that hatchery management practices will need to be modified in the future, to minimise levels of inbreeding.
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