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Comparative persistence of marine fish larvae from pelagic versus demersal eggs off southwestern Nova Scotia, Canada
Abstract
Two groupings of larval fish were repeatedly identified by principal component analyses of larval densities from four broad-scale surveys during the spring and summer of 1985–1987 off southwestern Nova Scotia, Canada. Larvae originating from pelagic eggs (four species within Gadidae and Pleuronectidae) constituted one group, which were uniformly distributed over the sampling area with densities not correlated with bathymetry, although nearly all spawning occurs on the shallow western cap of Browns Bank, 100 km offshore. Larvae from demersal eggs (five species within Pholidae, Stichaeidae, Cottidae, Agonidae) constituted the second group, which dominated the shallow-water environments both inshore and on Browns Bank. Lower patchiness indices were evident amongst larvae from pelagic eggs in small and large sampling-gear collections (average 3.4 and 3.1, respectively) compared to fish hatching from demersal eggs (average 5.1 and 4.6). Fine-scale nearshore surveys over a 5 wk period in 1987 also showed that larvae of demersal eggs had a less variable distribution along an inshoreoffshore transect. Larvae from demersal eggs appear spatially persistent through the release of well-developed larvae from non-drifting eggs. These conclusions are consistent with other studies over a range of spatial scales in temperate and tropical environments, demonstrating that single-species models of larval dispersal are inadequate to account for the distributional patterns of larval fish in general.
... The deep (ap proximately 150 m) channel ('The Scotian Gulf') be tween Emerald and LaHave Banks is the main conduit of the onshore flow of continental slope waters. The NSC is generally stronger in the inner shelf (our Fig. 2; Brickman & Drozdowski 2012) and, along with diffusive processes and retentive gyres (Loder et al. 1988, Cong et al. 1996, drives particle transport, including pelagic larvae (Suthers & Frank 1991, Frank 1992, Reiss et al. 2000, within the mixed layer (0−25 m), potentially connecting and/or isolating bank communities. Recirculation features (Loder et al. 1988, Cong et al. 1996 act to retain larval fish on these banks and thus contribute to population structuring at this scale (Frank 1992). ...
... The importance of distance along shelf as a predictor of crustacean assemblage structure (Fig. 11a) indicated that while most crustacean species were observed shelf-wide, the along-shelf decline in species' biomasses likely resulted from NE−SW shifts in temperature and other collinear habitat properties (Fig. 12). These findings agree with many species-specific studies, indicating that most SS larvae are transported NE to SW (Roff et al. 1986, Suthers & Frank 1991, Frank 1992, Tremblay 1997, Reiss et al. 2000 and that temperature plays an important role in determining species distributions and therefore the species compositions of geographically defined assemblages (Pörtner 2002, Pinsky et al. 2013, Pörtner & Gutt 2016. ...
Modern extensions of the theory of island biogeography (TIB) posit that the slope of the species-area relationship (SAR) reflects the insularity of ecological communities and is strongly influenced by species’ motility. We explore the relative insularity of crustacean, echinoderm and mollusk/Cirripedia assemblages in terms of both alpha diversity (species richness) and assemblage structure (relative biomass of species). These taxa/groups differ in adult motility and larval dispersal capacity. The habitats of interest were 10 offshore banks on the Scotian Shelf, northwest Atlantic Ocean, a region dominated by the NE- to SW-flowing Nova Scotia Current (NSC). Banks in the NE tended to be larger, more heterogeneous, cooler, less saline, more retentive and more productive (higher chlorophyll a ) than those in the SW. Only mollusks/Cirripedia, the least motile and dispersive group, had a significant SAR slope, supporting TIB. For crustaceans and echinoderms, temperature/salinity properties and habitat heterogeneity, respectively, were important predictors of alpha diversity. Inter-bank variation in crustacean assemblage structure was accounted for largely by bank location relative to the NSC; the leading variables accounting for echinoderm and mollusk/Cirripedia assemblage structure were retention time and mean annual chlorophyll concentration, respectively. Along the NE to SW axis of the NSC, there was a substantial loss of species (7 crustacean, 9 echinoderm and 13 mollusk/Cirripedia species) and decreases in the biomass of common cold-water species. A complex interplay of species motility/dispersal capacity, local oceanography and habitat properties determine the extent to which (1) TIB applies to submarine macroinvertebrate assemblages and (2) upstream and downstream assemblages are interconnected.
... In general, eggs and newly hatched larvae from pelagic marine fish are small and their distribution is largely dependent on ocean currents, while demersal eggs are generally larger and the emerging larvae have functional fins, eyes, and digestive tract (Suthers and Frank 1991). In spite of being demersal, damselfish eggs and larvae are rather small, imposing greater difficulties in their larval rearing. ...
Fishes belonging to the family Pomacentridae (clownfishes and damselfishes) dominate the marine ornamental fish trade. However, only 1.0–4.2% of marine ornamental species traded in the US are reproduced in captivity, while the vast majority are wild-caught, an environmentally damaging practice. Reproduction in captivity undoubtedly is an adequate strategy for moving in the direction of sustainability. Among ornamental marine fish species, the most spectacular advances in captive breeding have been made for clownfishes. Twenty-five species of clownfishes have been captive-bred for commercial purposes. Furthermore, numerous clownfish varieties or color morphs have been developed through selective breeding and hybridization between species has been achieved. Of at least thirty-nine damselfish species that have been reproduced in captivity, only nine are currently commercially available. This is related to the small size of eggs and to the underdeveloped state of altricial damselfish larvae. In addition, long larval periods (up to 50 dph) and low survival rates (typically less than 10%) create barriers to the success in commercial aquaculture of damselfishes. Improvements in the low survival of damselfish larvae can be expected as zootechnical aspects for larviculture are perfected (especially improved nutrition).
... Larvae of coastal species hatching from either benthic (COB) or pelagic (COP) eggs were found to occur predominantly either in the onshore zone or at the front. The abundance of Blenniidae (COB) and Gobiesocidae (COB) larvae has been suggested to decrease with increasing distance from shore, due to the absence of passive drift during the demersal egg phase (Leis and Miller, 1976;Marliave, 1986;Kingsford and Choat, 1989;Suthers and Frank, 1991;Brogan, 1994). Gobiesocidae and Blenniidae larvae do, however, hatch with functional eyes, developed fins and some positive active swimming toward light (Villegas-Ríos et al., 2009). ...
Within the coastal zone, oceanographic features, such as fronts, can have major effects on the abundance and distribution of larval fish. We investigated the effects of fronts on larval fish assemblages by jointly collecting physical (ADCP and CTD) and biological (larvae) data in the nearshore waters of the south coast of South Africa, on four separate neap-tide occasions. Accumulation of fish larvae at predominantly internal wave-associated fronts was observed, with higher larval densities inshore of and within the front than farther offshore. On each occasion, larvae of coastal species with pelagic eggs (Mugillidae and Sparidae) were numerically dominant at the front itself, while inshore of the front, larvae of coastal species with benthic eggs (Gobiesocidae and Gobiidae) were more abundant. Offshore catches mainly comprised Engraulidae (pelagic species with pelagic eggs) larvae, which were generally restricted to the bottom, where current velocities were onshore on each occasion. On the occasion when fast (>100 cm/s) currents prevailed, however, accumulation of the larvae of coastal species occurred offshore of the front, and larvae were mixed throughout the water column. Thus, larval occurrence at these coastal frontal systems was strongly affected by the degree of mixing by currents, which on most occasions resulted in onshore retention. The results underline the importance of frontal systems in determining the nearshore distributions of fish larvae, particularly by retaining coastal fish species in the inshore region. The environmental variability observed at these frontal systems has potential implications for larval connectivity of fish populations.
... Distributional studies of larval fishes frequently show that larvae of different species originating from the same sort of habitat (often, a coral reef) have differing distributions (Boehlert, 1996;Cowen and Sponaugle, 1997). Some authors speculated that behaviour might be responsible for such distribution (Leis and Miller, 1976;Leis, 1982;Suthers and Frank, 1991), but there was little or no hard information on behaviors of the larvae, other than vertical distribution (Leis, 2006;Steffe, 1991;Steffe and Westoby, 1991). ...
... Somero ( (Nybakken, 1988), en las cuales la alta producción primaria generada por las descargas de aguas continentales o eventos de surgencia, forman frentes costeros ricos en nutrientes que constituyen áreas propicias para la alimentación y crianza de larvas de peces (Cowan y Shaw, 1991;Chen et al., 1997, Rodriguez y Paramo, 2012. Adicionalmente, la heterogeneidad de la comunidad ictioplanctónica está relacionada con las áreas y épocas de desove, los hábitos de las larvas y diversos procesos físicos como las corrientes que las dispersan o concentran (Sabatés, 1990;Southers y Frank, 1991) o biológicos como la depredación que pueden reducir fuertemente su abundancia (Pepin, 2004) (Figura 8.36). Por ejemplo, los quetognatos son un grupo de depredadores importante y abundante dentro del zooplancton marino (Pearre, 1982) IT IT IT ITF F F F ----Programa de investigación pesquera en aguas marinas jurisdiccionales Programa de investigación pesquera en aguas marinas jurisdiccionales Programa de investigación pesquera en aguas marinas jurisdiccionales Programa de investigación pesquera en aguas marinas jurisdiccionales de Colombia 201 de Colombia 201 de Colombia 201 de Colombia 2016 6 6 6 190 que aprovecha para alimentarse en gran medida de las larvas de los peces y los copépodos (Alvariño, 1985;Saito y Kiorboe, 2001). ...
... Futheromre, the inside assemblage was composed mainly of larvae of demersal spawners while the outside assemblage was composed mainly of larvae of pelagic spawners. This result is in a full agreement with the findings of Leis (1982); Smith et al. (1987), Clarck (1991, Suthers & Frank (1991), Leis & McCormic (2002) and Paris and Cowen (2004). Brogan (1994) stated that larvae from demersal spawners can be used to measure the larval retention. ...
... The inshore assemblage was composed mainly of larvae of demersal spawners while the offshore assemblage composed mainly of larvae of pelagic spawners. This result is in a full agreement with findings of Leis (1982); Smith et al. (1987); Clarck, (1991); Suthers & Frank (1991); Leis & McCormic (2002); Paris and Cowen (2004). Brogan (1994) noted that larvae from demersal spawners are used to measure the larval retention. ...
... Most collected larvae from the offshore exposed sites hatched from pelagic spawners, whereas the majority of fish larvae in the offshore sheltered sites hatched from demersal eggs. This is consistent with results of other studies, where larval fish assemblages inshore were dominated by larvae from demersal spawners (Leis 1982;Smith et al., 1987;Suthers & Frank, 1991;Leis & McCormic, 2002;Paris and Cowen, 2004). ...
... Many studies have shown that the abundance of ichthyoplankton varies with distance from shore (Suthers and Frank 1991, MacGregor and Houde 1996, Grioche and Koubbi 1997. In this study, the greatest abundances of fish eggs and larvae were found in shallow nearshore areas. ...
The survival of fishes in the early life stages is the primary determinant of future cohort strength, and the probability of survival is directly related to environmental conditions that change in time and space. The distribution of pelagic drifting fish eggs and larvae and the factors that drive them are largely unknown in Green Bay, Lake Michigan. In this study, two sampling methods were used to assess the influences of space, time, and environmental conditions on ichthyoplankton assemblages in Lower Green Bay and the Fox River during summers 2014 and 2015. Ichthyoplankton samples were collected biweekly at the same 35 sites, and environmental data including dissolved oxygen, water temperature, pH, turbidity, and chlorophyll a were simultaneously collected at each site to characterize environmental conditions. A total of 36,935 larval fish and 65,531 eggs were collected in this study. Statistical analyses revealed that environmental factors influence variation in the abundance and distribution of fish eggs and larvae, specifically water temperature, pH, chlorophyll a, dissolved oxygen, and depth. However, space combined with environmental factors also contributed substantially to ichthyoplankton variability. Preferred spawning and nursery habitats combined with the effects of environmental forces were considered to be the major causes of spatial variation. Although best-fitting models did not include the effect of time, abundance of fish eggs and larvae showed temporal variation that was determined to be due to the reproductive strategy of adult fishes in Lower Green Bay and the Fox River.
... The inshore assemblage was composed mainly of larvae that hatched from demersal spawners and that of offshore had most larvae hatched from pelagic eggs. There is evidence of reef fish being retained nearshore and that the fish larval assemblages inshore are dominated by larvae from demersal spawners (Leis 1982;Leis, 1987;Suthers and Frank, 1991;Leis and McCormic, 2002;Paris and Cowen, 2004). Leis (1982) showed that dominance by larvae of demersal spawners in inshore waters was due to a few speciesprimarily tripterygiid, schindleriid and gobiid larvae. ...
The larval community of coral reef fishes in the Red Sea was studied in coastal and offshore sites to determine the effects of the exposure to waves and currents and the distance from the shore in structuring the larval fish community. Plankton sampling from inshore and offshore sites and the exposed and sheltered sides of the reefs resulted in the collection of 2048 larvae representing 49 different fish taxa belonging to 11 orders and 36 families of fish. The overall density of fish larvae at all sites was calculated as the larvae numbers in 1000m-3 and there was a significant difference in larval density between sites and between months. Most larvae were collected in the warmer months of the year from May to August. The inshore sheltered site (H3) is significantly different from all other sites in having the highest density with 2824 larvae 1000 m-3, whereas the inshore exposed site had the lowest density of all sites (621 larvae 1000 m-3). Number of species varies significantly among sites. Data of the seasonal and regional occurrence of fish larvae obtained from the present work could be very valuable for the fisheries management. It also gives an idea about how larval stages of reef fish distribute in regard to the reef topography and the distance from the shore.
There was a marked similarity in the spawning locations of the 2 species: primary spawning occurred on Browns Bank, although lower levels of spawning were observed on adjacent banks and in the inshore region. Cod egg abundance peaked in April in all years, while that of haddock varied between April-June. -from Authors
Observations are consistent with retention of cod in the Browns Bank gyre, coupled with episodic leakage and northerly advection in the residual current. Recent growth determined from otolith increment widths was significantly less for those cod sampled at nearshore stations than for cod offshore and on the Bank. Recent growth was significantly correlated with zooplankton biomass in a size range suitable for postlarval cod, while sea temperature was correlated in only one cruise. Nearshore areas had on average 25% of the zooplankton biomass found on the Bank. Recent growth indices of the 3rd and 4th week precapture were not significantly different between the nearshore and offshore, implying that the cod had shared a common environment, and common origin such as Browns Bank. -from Authors
Ten species of marine shore fishes with a wide range of life-history strategies were collected from four areas in southern California, U.S.A., and Baja California, Mexico, and examined for patterns of genetic differentiation. Multilocus D and FST values (based on 32-42 presumptive gene loci in each species) were both negatively correlated with estimated dispersal capability. These results were robust to variations in the number and type of loci used in the analysis and are compatible with the hypothesis that levels of genetic differentiation in these shore fishes are determined primarily by gene flow and genetic drift. There is no a priori reason to expect the observed correlation to result from natural selection or historical factors. The findings thus suggest that populations of these shore fishes are in at least a quasi-equilibrium with respect to migration, mutation, and genetic drift. Present data were also used to compare estimates of mNe obtained by three different methods. Estimates based on FST values calculated by the methods of Nei and Chesser (FST(N) ) and Weir and Cockerham (FST(W) ) were highly correlated, but FST(N) ≤ FST(W) for every species, leading to generally higher mNe estimates for Nei and Chesser's method. Estimates of mNe based on the frequency of private alleles (Slatkin, 1985a) were not as strongly correlated with dispersal capability as were FST and D values. A low incidence of private alleles in many species may be responsible for this relatively weak correlation and may limit the general usefulness of Slatkin's method. In spite of their sensitivity to natural selection, FST and D may be better indicators of relative gene flow levels for high gene flow species.
Patchy distributions matter, from the point of view of the animals involved, because the individuals tend to find more others of their own kind right around them than would be the case in a random distribution. The animals are more 'crowded', in this sense, than their mean density would lead one to believe. For data from randomly placed quadrats, the proposed parameter 'mean crowding' ($\overset \ast \to{m}$) attempts to measure this effect by defining the mean number per individual of other individuals in the same quadrat. 'Mean crowding' is algebraically identical with mean density, augmented by the amount the ratio of variance to mean exceeds unity, i.e. $\overset \ast \to{m}=m+(\sigma ^{2}/m)-1$. It can be viewed as equal to that increased mean density which a patchily distributed population could have, and be no more 'crowded' on the average than it is now, if it had a random distribution. The contention that populations with differing mean densities but the same 'mean crowding' would suffer the same density-dependent effects on mortality, natality, and dispersal implies the untested assumption that the effect of crowding on each individual varies linearly with the number of others around it, which are responsible for the crowding. Also implied is that each local situation (quadrat) is equally good habitat for the animals, has an equal rate of supply of expendable resources, and provides an equal amount of 'room', or cover, which the animals can use to avoid each other. If this assumption is perfectly fulfilled, however, then the patchy distribution itself becomes an ecological enigma: if the effects of crowding are more severe in the locally densest patches, then the local density should decrease more rapidly and increase more slowly there than elsewhere. The overall patchiness should decrease, in fact, until the distribution eventually comes to resemble a random one. Undoubtedly, a great deal of the patchines that one finds in continuous habitats can be explained in terms of local differences in habitat suitability. On the other hand, there is often a large component that appears to be utterly capricious. Since all of the capricious component should long since have been eroded away by density-dependent effects of crowding-if these are important-I must conclude that they are not important in such species, or, if they are, that other population processes (e.g. interactions with other species) regenerate patchiness as rapidly as it is destroyed. This fits in well with a general conviction that patchiness has a great deal more to do with undercrowding than with overcrowding, since 'mean crowding' often appears to be as great in rare species as it is in common ones (of comparable size). A suitable measure of patchiness is the ratio of 'mean crowding' to mean density. Where the distribution can be adequately approximated by the negative binomial, with parameters m and k, we have $\overset \ast \to{m}/m=1+k^{-1}$. The sample estimate for 'mean crowding' is $\overset \ast \to{x}=\overline{x}(1+\hat{k}^{-1})$. Standard errors are given for the cases where k̂ is estimated by maximum likelihood, by moments, by the number of empty quadrats, and also for the truncated negative binomial. The idea is briefly extended to apply to 'mean crowding' between species and to 'subjective' species diversity, without attempting in these cases to develop standard errors. Most importantly, I have tried to specify the types of habitats and distributions to which the parameter 'mean crowding' is not intended to apply.
An in situ particle counter system was developed to count measure food particles in numbers per liter within the size range 150- 600mu m, the sizes of copepod nauplii captured by 1st feeding cod larvae. Patches of particles/nauplii of 50-100 per liter were found in the spawning and larval 1st feeding area. Different sizes of copepod nauplii showed diel vertical migration, and this influenced the formation of patches. Mixing of the water column by wind forces created a homogeneous vertical distribution of particles. Gut content analysis of cod larvae during these hydrographical conditions indicated reduced accessibility of food organisms to larvae. -Authors
Walleye pollock form an intense spawning aggregation in late winter in Shelikof Strait. This produces a dense patch of planktonic eggs in early April, and later in spring a patch of larvae that can be followed as it drifts to the SW. In May 1983 larvae were concentrated vertically between 15-50 m and showed a crepuscular pattern of increased density at 14-28 m during twilight. Neither the vertical nor horizontal patterns of larval occurrences seemed closely associated with particular values of temperature or salinity. Most larvae were found in a temperature range of 7.0-5.5°C and a salinity range of 31.5-32.2‰. Guts of larvae collected during darkness contained less food that those from daytime. Copepod nauplii were largely replaced by Pseudocalanus spp. copepodids in the diet of larvae >14 mm. Zooplankton production in the area did not impact larval growth, even in the area of maximum density. -from Authors
