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Pigfish, Orthopristis chrysoptera, is a candidate for aquaculture because it is a regionally popular marine baitfish and commercial production could increase its supply and reduce fishing pressure on wild populations. Identifying optimal conditions for pigfish growout is needed for efficient production. We investigated the effects of temperature on growth and survival from hatching to market size at five constant temperatures, ranging from 22 to 30 C. Larval survival was greatest at 22 C, but growth was slowest. Complete mortality of larvae at 30 C occurred by 6 d after hatch, suggesting an upper thermal limit between 28 and 30 C. For juveniles, growth in length and weight was greatest at 28 and 30 C, but there were no differences in survival among temperatures. The predicted upper thermal limit for juveniles is 35 C. Results indicate that maximum growth and survival would be achieved by rearing larvae at 24 C and juveniles at 28 C. Under this temperature schedule, pigfish would reach preferred market sizes of 7.6 cm (for bay fishing) and 15 cm (for offshore fishing) after 2.5 and 4 mo of culture, respectively. [ABSTRACT FROM AUTHOR]

Background. The silver therapon, Leiopotherapon plumbeus (Kner, 1864), is an endemic and economically important freshwater food fish in the Philippines. The natural populations of this species have been declining during the past years, mainly due to intense fishing pressure, habitat degradation, and introduction of invasive alien species. At present, it is considered a target species for domestication and conservation efforts. Despite several attempts of artificial reproduction and larval rearing, little is known on larval and early juvenile development of silver therapon. The presently reported study was therefore intended to fill this gap in the knowledge by determining the growth and describing body proportions, pigmentation, and fin formation of this fish. Materials and methods. Newly hatched larvae were reared in mesocosm tanks at a mean temperature of 29.5°C. Larvae up to 30 days after hatching were sampled at irregular intervals and preserved in 5% buffered formalin. Early development stages for 245 preserved specimens were described in detail with reference to changes in morphology, growth and body proportions, pigmentation, and fin formation. Results. Five developmental stages of silver therapon were identified: yolk sac larva (1.88 mm TL), preflexion (2.51 mm TL), notochord flexion (4.50-8.27 mm TL), postflexion larva (6.90-12.21 mm TL), and early juvenile (≥13.40 mm TL). Growth was isometric for eye diameter and gape size whereas positive allometry was observed for body depth, head length, and preanal length. Some body proportions showed abrupt changes from preflexion to postflexion larvae before it stabilized during the early juvenile stage. Pigmentation in the form of stellate and punctate melanophores increased with developmental stage, with larvae becoming heavily pigmented from postflexion to early juvenile stage. These morphological changes, together with the full complement of fin rays and squamation observed in specimens larger than 13.4 mm TL, suggest the attainment of the juvenile stage of this species. Conclusion. These morphological changes may explain the food and feeding habits during the early life stages of silver therapon which is critical to their survival and recruitment in the wild and in a mesocosm hatchery environment. [ABSTRACT FROM AUTHOR]

The biological benefits of copepods as live feed for marine finfish larvae have already been well established in the literature. Copepods have better biochemical compositions that improve growth, reduce malpigmentations and allow successful farming of 'new' marine finfish species. However, their current usage is quite limited. One of the reasons has been lack of economic knowledge concerning the cost-effectiveness of copepod application compared to other commonly used feed items such as the brine shrimp Artemia. In this study, a cost-effectiveness analysis is made on two alternative live feed items (copepods and Artemia) in juvenile turbot farming. Unit cost of production and profit are compared between the two feeding regimes using a unique data set from an existing turbot fry production facility in Denmark. The result reveals that copepods are not only biochemically superior but they are also economically a cost-effective alternative. Thus, a commercial use of copepods will significantly reduce the production costs for turbot. Furthermore, the unexploited economic potential can be utilized for the successful farming of other high-valued marine finfish species such as tuna, flounders, cod, sole and halibut. Generally, the biochemical superiority coupled with economic benefits can lead to the commercial utilization of copepods as complementary live feed in the short run and in some situations as a substitute in the long run. [ABSTRACT FROM AUTHOR]

This essay contrasts the inferences about the patterns of size-dependent mortality in larval fish based on the traditional catch-curve approach with that achieved through the vertical life table method in an application to data from coastal Newfoundland. Although both approaches reveal that the average mortality rates decline with increasing body size, the rate of decline estimated using the vertical life table approach is much less pronounced than estimated from the catch-curve method. More important, however, is that on a case-by-case assessment the vertical life table reveals that mortality increases with increasing body size in 70% of the cases and declines in the remainder. Instances with greater rates of loss in larger individuals are consistent with larvae becoming more susceptible to the dominant planktivore in the study region. The contrasting results indicate that the patterns of change in mortality rates need to be measured over relatively short-time and/or length intervals. Such inferences have important implications for the development of studies dealing with larval fish dynamics. To be effective and applicable, comparative analyses that aim to develop macroscopic principles for the early life stages of fish must take the local foodweb structure into consideration to gain appropriate understanding of the trophic interactions that most strongly affect losses from larval fish populations. [ABSTRACT FROM AUTHOR]

Polybrominated diphenyl ethers (PBDEs) are persistent organic pollutants that are widely detected in the environment, biota, and humans. In mammals, PBDEs can be oxidatively metabolized to form hydroxylated polybrominated diphenyl ethers (OH-BDEs). While studies have examined behavioral deficits or alterations induced by exposure to PBDEs in both rodents and fish, no study to date has explored behavioral effects from exposure to OH-BDEs, which have been shown to have greater endocrine disrupting potential compared to PBDEs. In the present study, zebrafish ( Danio rerio ) were exposed during embryonic and larval development (0–6 days post fertilization, dpf) to a PBDE metabolite, 6-hydroxy, 2,2′,4,4′ tetrabromodiphenyl ether (10–50 nM) and then examined for short and long-term behavioral effects. Exposed zebrafish tested as larvae (6 dpf) showed an altered swimming response to light–dark transitions, exhibiting hypoactivity in light periods compared to control fish. When fish exposed from 0–6 dpf were tested as juveniles (45 dpf), they showed an increased fear response and hyperactivity in response to tests of novel environment exploration and habituation learning. These results demonstrate that early life exposure to a PBDE metabolite can have immediate or later life (more than a month after exposure) effects on activity levels, habituation, and fear/anxiety. [ABSTRACT FROM AUTHOR]

Recruitment of early life stages into estuaries is an integral part of the life cycle of many marine fish species. Although estuaries are naturally environmentally dynamic, they also are subject to anthropogenic disturbances, including land use and climate change, which may affect recruitment.Rhabdosargus holubiis an endemic marine-spawning species predominantly associated with freshwater-rich estuaries which serve as nursery areas for postflexion larvae and juveniles. This study assessed the effect of environmental variables on the dynamics of recruitment ofR. holubilarvae and juveniles into the Swartkops and Sundays estuaries, South Africa. Over a period of two years, fyke nets were set at each estuary mouth to monitor movement into the estuaries at each tidal phase over a 24 h cycle during two sampling sessions per season.Rhabdosargus holubilarvae recruited into estuaries primarily in summer and autumn and during the ebb tide at night, while juvenile movements showed no pattern. Salinity, turbidity and temperature were significantly important factors affectingR. holubirecruitment, with pH having no significant effect. Turbidity and salinity are affected by rainfall and freshwater abstraction which may thus influence recruitment.Rhabdosargus holubiis dependent on estuaries, so a combination of future changes in turbidity, salinity and temperature due to predicted climate change may place populations at risk. [ABSTRACT FROM AUTHOR]

The purpose of this experiment has been to evaluate the suitability of commercially available early-weaning microdiets (MDs) for the production of sea bream early juveniles and in comparison with late-weaning protocols already in use by Hellenic marine fish hatcheries. Four sea bream experimental groups were allocated in rearing tanks of a commercial Hellenic marine fish hatchery. Each group represented a different protocol (A, B, CA, and CB) based on the combination of two different early-weaning MDs (A and B) and a late-weaning diet (C). In addition, the late-weaning protocols have received Artemia instar II only and not Artemia instar I. In protocol A, Artemia instar I first feeding and the early-weaning diet A were administered at 17 days post-hatch (17 dph). In protocol B, Artemia instar I first feeding started at 15 dph and the early-weaning diet B was administered at 18 dph. In the C protocols, Artemia instar II first feeding started at 20 dph and the early-weaning diets (A or B) were administered at 25 dph. All protocols have received the late-weaning diet C only after the 50th dph. The experiment lasted for 65 days. By the end of the experiment, early-weaning protocol A and late-weaning protocol CB had similar wet weights, but still lower to the wet weights recorded for the late-weaning protocol CA. These results cannot be explained solely by the nutritional profile of each weaning diet. The larval fatty acid profile of each protocol and at various time intervals reveals the importance that the succession of Artemia, rotifers, and MDs has for each protocol and not just the nutritional profile of the weaning diets, per se. [ABSTRACT FROM AUTHOR]

The dispersal patterns of marked larvae of the nase carp (Chondrostoma nasus L.) were observed alongside dissimilar shoreline configurations in the main channel of the free-flowing Austrian Danube and compared with those of floating particles to investigate the mode of dispersal (active–passive). Individuals of different larval stages and floats at similar densities were released at an artificial rip-rap with groynes and a rehabilitated gravel bar. In both habitats, marked individuals were recaptured during the sampling period of 4 d after release. Relevant shoreline attributes for larval dispersal, such as the accessibility of nursery habitats, connectivity between adjacent habitats, and retention potential, were more pronounced at the gravel bar than at the rip-rap. At the gravel bar, larvae moved upstream and downstream within the connected bankside nurseries and displayed longer residence times. Larvae settled in groyne fields along the rip-rap as well; however, longitudinal dispersal was disrupted by groynes, forcing larvae to enter the main channel. Rather than settling in subsequent groyne fields, we assume that these larvae are displaced downstream and potentially lost from the local population. [ABSTRACT FROM PUBLISHER]

Larval growth and development of hybrid flounder were observed and compared with those of their parent species. The reciprocal hybrids of female starry flounder Platichthys stellatus and male stone flounder Kareius bicoloratus (hybrid Sb) and of female K. bicoloratus and male P. stellatus (hybrid Bs) both survived and grew to juveniles. Development was divided into nine stages (A-I). Many of the hybrids' traits were identical and intermediate to those of their parents. The position of the eye, however, was primarily sinistral in both hybrids (80% in Sb and 76% in Bs), a trait possessed by P. stellatus (80%) in the western Pacific Ocean. The daily growth rates of the larvae were similar. In the parent species, development was more rapid in P. stellatus than in K. bicoloratus whereas rate of development was intermediate in both Sb and Bs hybrids. The size at settlement [standard length ( LS) at stage H (mean ± s.d.)] was 9·82 ± 1·47 mm for the hybrid Sb and 9·99 ± 0·90 mm for the hybrid Bs, while the minimum age at metamorphosis (initial age at stage H) was 29 days after hatching ( DAH) in both hybrids. In comparison, LS at settlement in parent species was 6·43 ± 0·25 mm for P. stellatus and 12·87 ± 1·29 mm for K. bicoloratus. Minimum age at metamorphosis for the parents was 23 DAH at stage G in P. stellatus and 34 DAH at stage H in K. bicoloratus. Thus, the timing of settlement of hybrids was different from that of their parent species. These traits may occur with high frequency in a natural habitat. [ABSTRACT FROM AUTHOR]

Feeding experiments were carried out in 15-liter glass aquaria with 10 liters of water containing 1000 larvae aged 1.5 days post-hatching (before mouth opening) in three replicates. It was found that the feeding scheme of larval giant gourami aged 5-17 days (TL 8.36-13.40 mm) consumed Moina. The larvae aged 14-17 days (TL 12.40-13.40 mm) consumed both Moina and artificial pellet. Larvae aged more than 18-days (TL 13.60 mm) consumed only artificial pellet. Daily food uptake by the larvae and juvenile were determined in a 15-liter aquaria (water volume 10 liters) containing 500 larvae. The larvae were fed with Moina at density of 10 ind/ml. Aquaria without larvae were also set for a control of natural fluctuation in food density. The amount of food intake was calculated based on changes of food density in the aquarium with and without fish larvae. It was found the average uptake of Moina in digestive tract per day of larvae aged 5, 8, 11, 14 and 17 days old were 38, 52, 182, 205 and 266 individual/larva, respectively at density of 1.27, 1.73, 6.07, 6.83, and 8.87 individual/ml, respectively. [ABSTRACT FROM AUTHOR]

Gobiidae is the most specious fish family in the world with almost 2 000 species, however only 11% of them have been described for their larval stages. The entire life cycle information is essential to understand the biology and ecology of this important fish group. Previous studies on zooplankton samples from Ensenada de La Paz, México, have shown the presence of several Gobiidae larvae and juveniles which were identified as Evermania zosterura. The main objective of this work was to describe the larval stages of this species, widely distributed in the Eastern tropical Pacific. The development of E. zosterura larvae was described based on 66 specimens. A total of 53 specimens were used to describe morphometrics and pigmentation patterns, while 13 specimens were cleared and stained, to obtain meristic characteristics. Cleared specimens had 30 to 31 total vertebrae; dorsal-fin elements: IV; I, 13-14, anal-fin elements: I, 13-14, and most had pterygiophore formula 4-111100. The combination of these characteristics confirmed these specimens as E. zosterura. The pigment pattern is similar throughout ontogeny. Larvae are characterized by having three to five dendritic melanophores along the post-anal ventral margin, four to nine smaller melanophores along the ventral margin between the isthmus and anus, and one on the midpoint of the dorsal margin of the tail. There is one small pigment spot on the angle of the jaw, and other on the tip of lower lip. There is an elongated internal pigment under the notochord, between the head and gas bladder. Notochord flexion starts near 3.5mm BL and ends at 4.6mm BL; transformation to the juvenile stage is at about 13.6mm BL. Our conclusion is that the most useful characters to distinguish this species early-larval stages from those of similar species in the area, are the number of myomeres, the large melanophores (approximately uniformly in size) on the post anal ventral margin, and the elongate internal pigment under the notochord, anterior to the gas bladder. [ABSTRACT FROM AUTHOR]

Abstract: In this study, three microdiets were tested on weaning of Florida pompano larvae: Otohime, Gemma and a reference diet LR803. The experimental system was stocked with 11-day-old larvae, which were co-fed micro-diets and live food from 11dph to 17dph then micro-diets only until 28dph. Survival from 11dph to 28dph was similar for all treatments, with an average of 33%. At the end of the trial, the Gemma larvae were significantly longer and heavier than those larvae fed the other diets. Significant differences were observed in fatty acid composition of the diets and larvae between treatments. The Gemma larvae incorporated the lowest amount of eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA) and arachidonic acid (ARA). However, they had the highest DHA/EPA and ARA/EPA ratios, which is in agreement with the concept that the proportions of polyunsaturated fatty acids could be of greater importance than their absolute amount. Results from the enzyme analysis suggest that fishmeal is suitable as the main protein source for Florida pompano larvae. This study gives new insights on Florida pompano early nutritional requirements and demonstrated the full functionality of the pancreas at 16days post hatch, opening possibilities of an earlier weaning time. [Copyright &y& Elsevier]

Acute ammonia toxicity was investigated in four developmental stages of the juvenile ide, Leuciscus idus: 1, 10, 20 and 30 days after the first feeding. Mean (±SD) total length of the larvae was 8.5 ± 0.3, 15.7 ± 0.7, 23.0 ± 2.0 and 29.7 ± 2.0 mm, and standard weight was 1.6 ± 0.3, 9.2 ± 5.5, 94.9 ± 31.0 and 196.0 ± 31.7 mg, respectively. The larvae used for toxicity tests were reared in the experimental, closed recirculating system. Groups of fishes ( n from 7 to 10; in respect of fish size) were exposed to the ammonium chloride solutions in 1-L glass units. Water temperature was 25 ± 0.1 °C for both the rearing and the toxicity tests. pH was not adjusted and ranged between 8.4 and 8.7. The ammonium chloride solutions were renewed every 12 h. At the same time, dead larvae were counted and removed, and the pH and temperature measurements were taken. Each acute toxicity test duration was 96 h, and lethal concentration LC, LC and LC values were calculated for 24, 48, 72 and 96 h. The susceptibility of the ide larvae to ammonia decreased linearly with age up to 20th day and surprisingly increased during the next 10 days. The LC (48 h) values ranged from 0.27 mg L of unionized ammonia nitrogen for 1 day after the first feeding (AFF) larvae to 1.42 mg L at day 20 after first feeding. The LC (48 h) for 30 days AFF was as high as 0.67 mg L. The critical level of the unionized ammonia nitrogen for ide larvae was suggested as 0.21 mg L. [ABSTRACT FROM AUTHOR]

Abstract: The distribution and composition of marine larval and early juvenile fish were investigated during a multidisciplinary project conducted in the nearshore Canadian Beaufort Sea in July and August, 2005. Larvae were sampled using replicate bongo net (500μm) tows within 50m water depth. A total of 458 larval fish representing seven families were captured. Multivariate statistical analyses revealed two distinct larval assemblages that were closely correlated to water mass category. The two larval fish assemblages were defined as coastal and estuarine. The coastal assemblage was dominated by Pacific Herring (Clupea pallasii) and was found in the shallow intense plume water mass. This area is greatly influenced by the Mackenzie River outflow. The estuarine assemblage was dominated by Arctic Cod (Boreogadus saida) and was typically found within the diffuse plume and oceanic water masses. Other larval fish families that were represented in the estuarine assemblage were Cottidae, Stichaeidae, Liparidae and Agonidae. Species richness and abundance was greater along the Toker transect in Kugmallit Bay than the Paktoa transect northwest of Garry Island in the Mackenzie Bay. [Copyright &y& Elsevier]

This paper proposes a hierarchical Bayesian framework for modeling the life cycle of marine exploited fish with a spatial perspective. The application was developed for a nursery-dependent fish species, the common sole (Solea solea), on the Eastern Channel population (Western Europe). The approach combined processes of different natures and various sources of observations within an integrated framework for life-cycle modeling: (1) outputs of an individual-based model for larval drift and survival that provided yearly estimates of the dispersion and mortality of eggs and larvae, from spawning grounds to settlement in several coastal nurseries; (2) a habitat suitability model, based on juvenile trawl surveys coupled with a geographic information system, to estimate juvenile densities and surface areas of suitable juvenile habitat in each nursery sector; (3) a statistical catch-at-age model for the estimation of the numbers-at-age and the fishing mortality on subadults and adults. The approach provided estimates of hidden variables and parameters of key biological significance. A simulation approach provided insight to the robustness of the approach when only weak data are available. Estimates of spawning biomass, fishing mortality, and recruitment were close to the estimations derived from stock-assessment working groups. In addition, the model quantified mortality along the life cycle, and estimated site-specific density-dependent mortalities between settled larvae and age-0 juveniles in each nursery ground. This provided a better understanding of the productivity and the specific contribution of each nursery ground toward recruitment and population renewal. Perspectives include further development of the modeling framework on the common sole and applications to other fish species to disentangle the effects of multiple interacting stress factors (e.g., estuarine and coastal nursery habitat degradation, fishing pressure) on population renewal and to develop risk analysis in the context of marine spatial planning for sustainable management of fish resources. [ABSTRACT FROM AUTHOR]

Abstract: Marine protected areas (MPAs) can benefit fisheries through export of pelagic eggs and larvae and the net emigration of adults and juveniles (spillover). Spillover was investigated for a marine protected area on the north shore of Oahu, Hawai‘i utilizing a seascape approach. This study incorporated habitat variables and underwater visual surveys of fishes and benthos measured at two distinct scales (125m2 and 1000m2) inside and outside the protected area at varying distance from the boundary. The relationship between fish biomass from fine-scale surveys and key habitat variables was found to account for a large portion of the variability for both resource (targeted) fish species (15%) and non-resource fish (28%). The remaining variation in resource fish biomass was significantly correlated with distance from the MPA boundary showing a decreasing gradient from inside to outside (r 2 =0.46, p =0.001), indicating fish spillover at a local scale (<1km). In contrast, non-resource fish biomass demonstrated no such relationship (p =0.45). The evidence of spillover based on the fine-scale surveys was corroborated by results from broad-scale surveys, which also showed a significant relationship (r 2 =0.19, p <0.01) between resource fish biomass and distance from the MPA boundary. In addition, observed spatial distribution of fishing effort was consistent with predictions that fishers respond to biomass gradients across protected area boundaries. Fish spillover can help mitigate costs associated with the establishment of marine protected areas in terms of lost fishing area and therefore have a positive effect on the attitudes of fishers toward marine reserves and marine protected areas. [Copyright &y& Elsevier]

The presence of skeletal anomalies in farmed teleost fish is currently a major problem in aquaculture, entailing economical, biological and ethical issues. The common occurrence of skeletal abnormalities in farmed fish and the absence of effective solutions for avoiding their onset or definitely culling out the affected individuals as early as possible from the productive cycle, highlight the need to improve our knowledge on the basic processes regulating fish skeletogenesis and skeletal tissues differentiation, modelling and remodelling. Severe skeletal anomalies may actually occur throughout the entire life cycle of fish, but their development often begins with slight aberrations of the internal elements. Comprehensive investigation efforts conducted on reared larvae and juveniles could provide a great contribution in filling the gap in knowledge, as skeletogenesis and skeletal tissue differentiation occur during these early life stages. The aim of this review is to provide a synthetic but comprehensive picture of the actual knowledge on the ontogeny, typologies and occurrence of skeletal anomalies, and on the proposed causative factors for their onset in larvae and juveniles of European farmed fish. The state-of-art of knowledge of these issues is analysed critically intending to individualize the main gaps of knowledge that require to be filled, in order to optimize the morphological quality of farmed juveniles. [ABSTRACT FROM AUTHOR]

Lynam, C. P., Halliday, N. C., Höffle, H., Wright, P. J., van Damme, C. J. G., Edwards, M., and Pitois, S. 2013. Spatial patterns and trends in abundance of larval sandeels in the North Sea: 1950–2005 – ICES Journal of Marine Science, 70: 540–553.Early recruitment indices based on larval fish data from the Continuous Plankton Recorder (CPR) have the potential to inform stock assessments of Ammodytes marinus in the North Sea. We evaluate whether the CPR data are reliable for sandeel larvae. Spatially, CPR larval data were comparable with catches by dedicated larval samplers (Gulf and bongo nets) during ICES coordinated surveys in 2004 and 2009. ICES data are also used to explore environmental influences on sandeel distributions. Temporally, CPR data correlate with larval data from plankton surveys off Stonehaven (1999–2005), with sandeel 0-group trawl data at the east Fair Isle ground (since 1984), and with recruitment data (since 1983) for the Dogger Banks stock assessment area. Therefore, CPR data may provide an early recruit index of relative abundance for the Dogger Banks assessment area, where the majority of the commercial catch of A. marinus is taken, and the Wee Bankie area that is particularly important for seabird foraging. While warm conditions may stimulate the production of sandeel larvae, their natural mortality is typically greater, in the Dogger Banks and Wadden Sea areas, when the larvae are hatched in warm years and/or with abundant 1-year-old sandeel that are likely to be cannibalistic. [ABSTRACT FROM PUBLISHER]

Abstract: Annual recruitment levels of age-0 juvenile Atlantic menhaden to Chesapeake Bay, which historically supported >65% of coastwide recruitment, have been consistently low since the 1980s. Diminished larval supply to the Bay is one hypothesized explanation. In a three-year ichthyoplankton survey at the Chesapeake Bay mouth, abundance of ingressing larvae varied nine-fold among years. Larvae were most abundant in 2007–2008 and less abundant in 2005–2006 and 2006–2007. High month-to-month variability in larval concentrations was attributable primarily to seasonality of occurrences. There was no defined spatial pattern in distribution of larvae across the 18-km-wide Bay mouth, but larvae at the south side were longer and older on average than larvae at the middle and north side. Environmental variables measured at the times of larval collections were not correlated consistently with temporal and spatial variability in abundance of larvae at ingress, highlighting complexity and suggesting that abundance may be controlled by processes occurring offshore during the pre-ingress phase. Moreover, the substantial differences in inter-annual abundances of larvae at the Bay mouth were not concordant with subsequent abundances of age-0 juveniles in the three survey years, indicating that important processes affecting recruitment of Atlantic menhaden operate after ingress, during the larval to juvenile transition stage. [Copyright &y& Elsevier]

For species with complex life histories such as scleractinian corals, processes occurring early in life can greatly influence the number of individuals entering the adult population. A plethora of studies have examined settlement patterns of coral larvae, mostly on artificial substrata, and the composition of adult corals across multiple spatial and temporal scales. However, relatively few studies have examined the spatial distribution of small (≤50 mm diameter) sexually immature corals on natural reef substrata. We, therefore, quantified the variation in the abundance, composition and size of juvenile corals (≤50 mm diameter) among 27 sites, nine reefs, and three latitudes spanning over 1000 km on Australia’s Great Barrier Reef. Overall, 2801 juveniles were recorded with a mean density of 6.9 (±0.3 SE) ind.m−2, with Acropora, Pocillopora, and Porites accounting for 84.1% of all juvenile corals surveyed. Size-class structure, orientation on the substrate and taxonomic composition of juvenile corals varied significantly among latitudinal sectors. The abundance of juvenile corals varied both within (6–13 ind.m−2) and among reefs (2.8–11.1 ind.m−2) but was fairly similar among latitudes (6.1–8.2 ind.m−2), despite marked latitudinal variation in larval supply and settlement rates previously found at this scale. Furthermore, the density of juvenile corals was negatively correlated with the biomass of scraping and excavating parrotfishes across all sites, revealing a potentially important role of parrotfishes in determining distribution patterns of juvenile corals on the Great Barrier Reef. While numerous studies have advocated the importance of parrotfishes for clearing space on the substrate to facilitate coral settlement, our results suggest that at high biomass they may have a detrimental effect on juvenile coral assemblages. There is, however, a clear need to directly quantify rates of mortality and growth of juvenile corals to understand the relative importance of these mechanisms in shaping juvenile, and consequently adult, coral assemblages. [ABSTRACT FROM AUTHOR]

To determine whether genetic improvement could be attained through a selective breeding programme, divergent selection for shell length was conducted in a base population of the Manila clam, Ruditapes philippinarum. The 10% largest and 10% smallest clams were selected as parents for the upward-selected and downward-selected lines, respectively. Equal numbers of clams were randomly chosen to serve as parents for the control line before the selection. The selected and control lines were reared under the same environmental conditions at larvae, juvenile, and grow-out stages. The values of standardized responses to selection (SR) and realized heritability ( at the age of 360 d were 0.268 and 0.165 for the upward-selected line and 0.341 and 0.260 for the downward-selected line, respectively. Asymmetric differences were evident between the upward-selected and downward-selected lines in both SR and . Performance in shell length is improved by 3.55% in the upward-selected line after one generation, indicating that mass selection for shell length in a base population of the Manila clam, R. philippinarum, is effective and encouraging. [ABSTRACT FROM AUTHOR]

The effect of dietary n-3 HUFA and light intensity on the ingestion rate of Artemia by 23 and 31 days post-hatch (dph) gilthead sea bream larvae was investigated. In separate experiments, 23 and 31 dph larvae were stocked into triplicate 6-l floating round mesh cages (100-200 larvae/cage), placed in 1.5 m³ conical tanks, and fed rotifers (Brachionus rotundiformis) from 3 to 18 dph and Artemia spp. nauplii from 19 to 31 dph. Both rotifers and Artemia were fed a low (control) or high n-3 HUFA emulsion that contained a DHA:EPA ratio of about 5:1. For each treatment, one 1.5 m³ tank was exposed to a light intensity of 300-365 lux, while a second 1.5 m³ tank was tent-covered with semi-opaque black plastic creating a surface light intensity of 10-20 lux. On days 23 and 31, larvae were fed one ration of unenriched nauplii at 3 and 5 nauplii/ml, respectively, and the nauplii were counted at intervals of 15 min for 2 h and 10 min for 3.5 h, respectively, to determine the decrease in nauplii and calculate feeding rates. Compared to its deposition in the body of the larvae, dietary DHA selectively accumulated in the eyes. Data suggest that dietary DHA markedly increased the ingestion rate of Artemia nauplii in 23 dph larvae kept in the tank with subdued light intensity but did not affect the prey capture rate under high light intensity or in older 31 dph larvae. [ABSTRACT FROM AUTHOR]

Ages, growth and hatch dates of ingressing Brevoortia tyrannus larvae were determined in a 3 year sampling survey at the mouth of the Chesapeake Bay, U.S.A. To determine if otolith-aged cohorts had variable relative survival, hatch dates of summer-caught young-of-the-year (YOY) juveniles collected throughout the Chesapeake Bay were compared with hatch dates of ingressing larvae. Modal total length of ingressing larvae was similar among years: 28 mm in 2005-2006 and 2007-2008, and 30 mm in 2006-2007. Ages of ingressing larvae ranged from 9 to 96 days post hatch (dph); mean ages were similar among years, but significantly older in 2006-2007 (50 dph) than in 2005-2006 (44 dph) and 2007-2008 (46 dph). Larval growth rates differed among years. Earliest growth, when larvae were offshore (0-20 dph), was faster in 2006-2007 (0·62 mm day−1), than in 2005-2006 and 2007-2008 (0·55 mm day−1 in these years). Subsequently, from 30 to 80 dph, growth was slowest in 2006-2007. Hatch dates of ingressing larvae occurred from September to March and 90% (2007-2008) to 98% (2006-2007) had hatched prior to 31 December. In contrast, most surviving YOY juvenile B. tyrannus had hatched in January to February, suggesting selective mortality of early-hatched individuals, apparently during the overwinter, larval to juvenile transition period. [ABSTRACT FROM AUTHOR]

Abstract: A high incidence of jaw malformation has hindered the production of quality striped trumpeter Latris lineata juveniles and has been correlated with walling behaviour in Artemia-fed larvae. In this study, striped trumpeter were reared from first feeding to 29days post-hatching (dph) in different coloured tanks (black or white), culture conditions (clear or greenwater) and fed different diets (enriched or non-enriched rotifers and Artemia), to examine behaviour, retinoid receptor gene expression and jaw malformation. The highest incidence and severity of jaw malformations occurred in clearwater and enriched diet treatments and were significantly more common in white (70±15%, mean±SD) than in black tanks (26±15%). In black tanks, jaw malformation was significantly more common in larvae fed enriched diets (18±14%) than in those fed non-enriched diets (8±8%) and in clearwater (19±14%) versus greenwater (7±6%). At the end of the rotifer feeding phase, larvae were significantly larger in black than white tanks, and longer in greenwater than in clearwater. In the Artemia feeding phase, larval growth was slowest and mortality was highest in non-enriched diet treatments. Larval length and survival were higher in black tanks and in enriched diet treatments, whilst survival was almost twice as high in greenwater (46±18%) than clearwater (26±13%). The average proportion of larvae walling over the duration of the experiment was higher in white than black tanks, and higher in enriched than non-enriched treatments, with lowest walling in greenwater. There was no consistent relationship between feed intake and jaw malformation. However, there was a significant positive correlation between walling and the incidence of jaw malformation at 29dph in larvae fed enriched diets. The expression pattern of three retinoid receptor genes indicated that live feed enrichment and stress could potentially perturb retinoic acid-associated pathways leading to skeletal abnormality. We found that the use of greenwater, black tanks and enriched live feeds is required for good growth, development, survival and final yield of striped trumpeter. The study emphasises the importance of reducing walling in the culture of oceanic larvae and may have direct application in the rearing of other marine fish with similar malformations. [Copyright &y& Elsevier]

An individual-based length back-calculation method was developed for juvenile Baltic sprat ( Sprattus sprattus), accounting for ontogenetic changes in the relationship between fish length and otolith length. In sprat, metamorphosis from larvae to juveniles is characterized by the coincidence of low length growth, strong growth in body height, and maximal otolith growth. Consequently, the method identifies a point of metamorphosis for an individual as the otolith radius at maximum increment widths. By incorporating this information in our back-calculation method, estimated length growth for the early larval stage was more than 60% higher compared with the result of the biological intercept model. After minimal length growth during metamorphosis, we found the highest increase in length during the early juvenile stage. We thus located the strongest growth potential in the early juvenile stage, which is supposed to be critical in determining recruitment strength in Baltic sprat. [ABSTRACT FROM AUTHOR]

Abstract: Gaining reliable estimates of how long fish early life stages can survive without feeding and how starvation rate and time until death are influenced by body size, temperature and species is critical to understanding processes controlling mortality in the sea. The present study is an across-species analysis of starvation-induced changes in biochemical condition in early life stages of nine marine and freshwater fishes. Data were compiled on changes in body size (dry weight, DW) and biochemical condition (standardized RNA–DNA ratio, sRD) throughout the course of starvation of yolk-sac and feeding larvae and juveniles in the laboratory. In all cases, the mean biochemical condition of groups decreased exponentially with starvation time, regardless of initial condition and endogenous yolk reserves. A starvation rate for individuals was estimated from discrete 75th percentiles of sampled populations versus time (degree-days, Dd). The 10th percentile of sRD successfully approximated the lowest, life-stage-specific biochemical condition (the edge of death). Temperature could explain 59% of the variability in time to death whereas DW had no effect. Species and life-stage-specific differences in starvation parameters suggest selective adaptation to food deprivation. Previously published, interspecific functions predicting the relationship between growth rate and sRD in feeding fish larvae do not apply to individuals experiencing prolonged food deprivation. Starvation rate, edge of death, and time to death are viable proxies for the physiological processes under food deprivation of individual fish pre-recruits in the laboratory and provide useful metrics for research on the role of starvation in the sea. [Copyright &y& Elsevier]

Abstract: It is difficult to estimate natural mortality for many marine fish populations, especially during the transition period from larvae to juveniles, because the appropriate data are scarce. Plaice (Pleuronectes platessa) is an exception since it has been studied extensively. The study of mortality rates in juveniles is made easier because the nursery grounds are inshore and generally less than 5m deep. This contribution considers the factors affecting mortality rates for eggs and larvae, and for settlement and nursery ground phases. There are problems associated with estimating mortality rates, especially for juveniles because immigration into nursery areas at the beginning of the season and emigration of larger individuals off nursery grounds in the latter part of the season confound losses due to mortality. The shifts in mortality schedules and the causes through the early life history are investigated in relation to concepts such as ‘nursery ground carrying capacity’ and ‘self-thinning’. Predation in the pelagic phase is probably density independent and a source of inter-annual variability in survival of early life-history stages. Predation mortality during the nursery ground phase is most likely density dependent. However, there is a need for further in-depth study, especially during the period of settlement. [Copyright &y& Elsevier]

Feeding scheme experiments were done in a 15-liter glass aquarium (water volume 10 liters) containing 500 of two-day old larvae (stage at first feeding). It was found that larval snake head fish aged 3-11 days (average total length 6.08-10.86 mm) consumed Moina. Larvae aged 12-15 days (average total length 10.79-14.61 mm) consumed both Moina and commercial pellet (40 % crude protein). Larvae aged more than 16 days consumed only commercial pellet. Determining the daily food uptake by the larvae and juveniles was done in a 15-liter glass aquarium (water volume 10 liters) containing 1,000 larvae. The larvae consumed Moina ,provide of a density of Moina 10 individual/ml. The amount of food intake was calculated based on changes of food density in the aquarium with and without fish larvae at 2-hour intervals. It was found that larvae aged 3-15 days consumed Moina. The average uptake of Moina in digestive tract per day of larvae age 3, 6, 9, 12 and 15 days old was 28.7, 115.70, 162.27, 195.30 and 227.30 individual/larva, respectively at water temperatures ranging between 25 and 28°C. A starvation experiment was carried out using a 15-liter glass aquarium (water volume 10 liters) with three replications. Two hundred newly hatched larvae were kept without feeding. Larvae started to die at 216 hr and totally died within 326 hr after hatching at water temperature ranging between 28.0 and 30.5°C. [ABSTRACT FROM AUTHOR]

Exchanges of fish larvae between the inner continental shelf and estuaries can be critical to the functional significance of these habitats as nurseries. We sampled near-surface fishes on the inner continental shelf off New Jersey and in an adjacent estuary during the summer and fall of 2005 and 2006 to evaluate the occurrence and variation in these connections. Very few of the abundant taxa ( Anchoa mitchilli, Brevoortia tyrannus, Urophycis regia, Etropus microstomus, Peprilus triacanthus, and Pomatomus saltatrix) were exclusive to either habitat but some did change in relative habitat affinity among seasons. For some species, this was indicative of a departure from the ocean for estuaries (e.g., Micropogonias undulatus) while others used both habitats during the summer and fall (e.g., Syngnathus fuscus, Scophthalmus aquosus, and A. mitchilli). Together, these observations confirm the high degree of connectivity between the near-surface larval fishes from the inner continental shelf and estuaries. [ABSTRACT FROM AUTHOR]

Abstract: Anchored and drifting Fish Aggregating Devices (FADs) are intensively used in tropical tuna fisheries. In both small-scale and industrial fisheries, skipjack (Katsuwonus pelamis) and yellowfin tuna (Thunnus albacares) are the main targets. The increasing development of this fishing practice by industrial purse seiners has raised the question of the impact of FADs on tuna communities, as they might act as an ecological trap. This study investigated the feeding habits of skipjack and yellowfin tuna associated with anchored and drifting FADs in the western Indian Ocean. The diet of 352 tunas was analysed taking into account the type of FAD, ontogenetic variations, and the resources richness of the area. Poor-food and rich-food areas were defined according to the abundance of stomatopod Natosquilla investigatoris, the main prey of tunas, on the fishing sites. Diet composition was expressed through functional groups of prey. Significant dietary differences were found between both FAD types, as well as an effect of individual size. Around anchored FADs tuna preyed on diverse assemblages of coastal fish and crustacean larvae and juveniles, whereas a low diversity of epipelagic prey dominated the tuna diet associated with drifting FAD. Compared to anchored FADs, the frequency of empty stomachs was significantly higher and the stomach content mass significantly lower among skipjack and small yellowfin tunas caught around drifting FADs. This was magnified in poor-food areas, where drifting FADs often evolved, suggesting that these FADs could negatively impact the growth of skipjack and small yellowfin tuna. Larger yellowfin tuna exhibited differences in their dietary habits between anchored and drifting FADs, and between poor-food and rich-food areas. However, drifting FADs did not impact them as strongly as juveniles of yellowfin or skipjack tunas. Our study gives new highlights on possible detrimental effects of FAD on tunas, and this has to be considered in future sustainable management strategies of tuna fisheries. [Copyright &y& Elsevier]

The morphological development, including the pigmentation, body proportions, fins, and survival rate for 30 days after hatching, of laboratory-reared larval and juvenile Hypsibarbus malcolmi is described. Body lengths (BL) of larvae and juveniles were 2.0 ± 0.2 (mean ± SD) mm at 1 h after hatching (day 0) and 9.2 ± 0.6 mm on day 16, reaching 12.1 ± 0.9 mm on day 30. Yolk volume decreased linearly, with the yolk being completely absorbed by day 3 in all preflexion larvae (all specimens >3.2 mm BL). Feeding was observed on day 2 in fish which had rapidly undergone complete yolk absorption following mouth and anus opening on day 1, and on day 3 in all remaining fish. Myomere numbers were 20-21 + 11-12 = 31-33, although they were not clearly visible in juveniles. Melanophores were few on the body during days 0-2, but increased with growth and covered the entire upper dorsal body surface during the juvenile stage. Body proportions tended to become constant in juveniles. Notochord flexion began in larvae >5.2 mm BL on day 8, and was completed in larvae >8.4 mm BL on day 14. Specimens with full fin ray complements were initially observed on day 22 (10.4 mm BL in juveniles). All specimens >11.5 mm BL had attained the juvenile stage. A high survival rate of 92.7% was estimated on day 30. [ABSTRACT FROM AUTHOR]

Larvae and juveniles of the alepocephalid fishes, Leptoderma lubricum [26.9-69.0 mm in standard length (SL)] and Leptoderma retropinnum (21.1-67.2 mm SL), collected within 1-8 m of the seafloor in Suruga Bay, southern Japan, are described. They can be easily distinguished from each other by the following adult-like characters: membrane morphology between the vertical fin rays and procurrent caudal-fin rays (separated in L. lubricum vs. continuous in L. retropinnum), numbers of dorsal-fin rays (34-40 vs. 45-52) and anal-fin rays (50-57 vs. 65-72), and caudal peduncle length (11.7-13.4% SL vs. 4.5-5.9% SL), in addition to several other body proportional differences. Unique characters in the larval stages of Leptoderma include a translucent occipital region, horizontally elongated eye, and head below the upper margin of the orbit and abdominal cavity densely covered by melanophores, ontogeny being characterized by the acquisition of general adult characters to the postflexion stage, indistinct transformation, and the retention of few larval characters until almost the end of the juvenile stage, as in other known alepocephalids. In addition to the near-bottom larval and juvenile collections of both species, the occurrences of benthic or near-bottom taxa, including Harpacticoida, in their gut contents confirmed the early life history dependence of the former on the near-bottom. [ABSTRACT FROM AUTHOR]

1. Elevated allochthonous inputs of nutrients and sediments to aquatic ecosystems are associated with eutrophication and sedimentation. Reservoirs receive substantial subsidies of nutrients and sediments from catchments due to their large catchment : lake area ratios. We examined the effect of elevated subsidies of sediments and/or dissolved nutrients on the success (survival, growth, biomass and condition factor) of larval gizzard shad ( Dorosoma cepedianum), a widespread and dominant omnivorous fish in reservoir ecosystems. 2. We simulated allochthonous agricultural subsides by manipulating dissolved nutrients and sediment inputs in a 2 × 2 factorial design in experimental mesocosms. We predicted that larval fish success would be greater under elevated nutrients. However, we propose two alternative hypotheses with respect to the overall effect of allochthonous sediment inputs. If sediment inputs negatively affect larval gizzard feeding success, larval success would be highest when only nutrients are added and lowest when only sediments are added (+N > +N+S ≥ C > +S). If high turbidity enhances larval foraging activity (due to greater contrast between prey and background), we predict that larval success would be highest when both subsidy types (nutrients and sediment) are elevated, intermediate when either nutrients or sediments are added and the lowest when no subsidies are added (+N+S > +N ≥ +S > C). 3. Our results indicate that elevated nutrient and sediment conditions enhanced larval gizzard shad biomass, but the overall nutrient addition effect was greater than the sediment addition effect (+N ∼ +N+S > +S > C). We observed differential effects of nutrient and sediment inputs on larval survival, growth and condition factors. 4. The enhancement of fish biomass in elevated nutrients (+N, +N+S) relative to control conditions was associated with improved gizzard shad survival and not greater growth. The enhancement of fish biomass in the elevated sediment treatment (+S) relative to the control conditions was caused by an increase in survival that more than compensated for a negative effect of sediment addition on growth. 5. Our findings support the recommendation that reservoir management practices must consider the links between land use practices and food web dynamics. Our results suggest that reduction of subsidies of nutrients and sediments to productive reservoirs would decrease survival of larval gizzard shad due to lower food availability. [ABSTRACT FROM AUTHOR]

Abstract: To better understand the role of the German Bight (GB) as a nursery area for juvenile North Sea sprat Sprattus sprattus we sought to determine whether the area may receive only locally or also externally produced offspring. We sampled juveniles during 3 trawl surveys in the GB in August, September, and October 2004 and applied otolith microstructure analysis in order to reconstruct their distributions of the day-of-first-increment-formation (dif). These were contrasted with spatial and seasonal patterns of sprat egg abundance in the GB and its adjacent areas, observed during 6 monthly plankton surveys. It was found that the majority of juveniles originated mainly from April/May 2004, coinciding with high spawning activity west of the GB, whereas spawning and larval production inside the GB peaked notably later, in May/June. This indicated that a large proportion of juveniles was produced outside the GB and transported subsequently into it through passive and/or active migration. Shifts to later mean difs from one survey to the next and length distributions indicative of the simultaneous presence of multiple cohorts, supported the notion that the GB is a complex retention and nursery area for sprat offspring from different North Sea spawning grounds and times. Later born juveniles had significantly faster initial growth rates than earlier born conspecifics, which was likely temperature-mediated, given the strong correlation between back-calculated growth histories and sea surface temperature as a proxy for thermal histories of juveniles (r 2 =0.52). [Copyright &y& Elsevier]

Abstract: Growth and mortality rates of juvenile anchovy (Engraulis encrasicolus) were estimated from monthly samples collected in the coastal waters off Ortona (central Adriatic Sea). Otolith microstructure analysis was conducted on specimens ranging from 10 to 60mm TL, including the transition from larval to juvenile stages (i.e. at metamorphosis). Fish were aged by growth increment counts on sagittal otoliths, presuming they were laid down with a daily periodicity. Age estimates ranged from 16 to 96 days, with a good consistency between readings. The hatch date distribution, back-calculated from the date of capture, was spread over a long period (April–February), with three main cohorts hatched in May, August and November. The instantaneous growth rate, calculated for the whole fish sample, was 0.68mm/day. Nevertheless, the growth rate estimated for each of the main cohorts showed a seasonal trend, being higher in May and decreasing in August and November. The allometric relationship between otolith and fish size changed markedly during the transition from larval to juvenile stages, with a slight decrease of otolith growth rate after metamorphosis. The instantaneous total mortality rates of anchovy, calculated for each of the main cohorts, was lower in May and progressively increased in August and November cohorts, showing an opposite seasonal trend respect to the growth rate. [Copyright &y& Elsevier]

Abstract: The near-surface distribution of young-of-the-year perch was observed with a towed upward beaming echosounder system (SIMRAD EK60 with a circular 7° transducer). Perch aggregated densely in the epilimnion during daytime and dispersed evenly below the surface at night. Shoaling commenced in late June when perch metamorphosed from the larval to juvenile stage. Average shoal width was 6.6m and average shoal height was 2.35m in July, when perch were observed for the last time in the pelagic zone of Lake Constance. Upward echosounding revealed the presence and near-surface distribution of pelagic juvenile perch and therefore this method can be used as a complementary survey tool to get more precise information about the distribution, behaviour and abundance of near-surface fish. [Copyright &y& Elsevier]

Many fish species are zooplanktivorous at the onset of exogenous feeding, but distinct shifts in their foraging biology may occur with development. This study investigated the food and feeding relationships of the larvae and 0+ year juveniles of 13 fish species in ‘main river’, ‘marina’ and ‘pond’ macrohabitats in the lower River Trent, England. Young larvae had narrow diet spectra, with feeding diversity and the importance of species-specific traits increasing with development. Two main ontogenetic shifts in diet were differentiated, corresponding with the transition from finfold to finformed larvae, and from the larval to the juvenile period. Dietary overlap was generally greatest among ecologically similar species, with competition and resource partitioning most likely where prey availability was lowest. The greater availability of zooplankton in connected waterbodies compared with main river channels provides suitable prey for a wide range of fish species, and may enhance recruitment success. [ABSTRACT FROM AUTHOR]

The relative importance of taxa- and size-specific prey selection, and the influence of gape on the prey consumed by the larvae and 0+ year juveniles of four fish species were investigated in ‘main river’, ‘marina’ and ‘pond’ macrohabitats in the lower River Trent, England. A general sequence of ontogenetic shifts in food consumption was reflected in the electivity indices of particular prey taxa, partly due to the restrictions imposed by the gape of 0+ year fishes. Certain taxa, however, were consistently selected over others, irrespective of size, suggesting that taxa-specific, as well as size-specific, prey characteristics may be important in the selection process. There were significant, positive relationships between maximum prey (zooplankton) length and maximum gape height for larvae, but not for 0+ year juveniles. The majority of fishes, however, consumed prey substantially smaller than the maximum theoretically possible inferred from their gape. The greater size ranges of zooplankton in connected waterbodies compared with main river channels provide suitable prey for a range of developmental steps and fish species, and may, thus, enhance recruitment success. [ABSTRACT FROM AUTHOR]

Lampreys in the Columbia River basin are a conservation concern, and understanding their status is a priority among managers. Many population assessment techniques depend on the ability to tag fish so that these tags are retained for the duration of the study with minimal effect on survival. There are several methods for tagging small fishes in streams, including passive integrated transponders, coded wire tags, and visible implant elastomer (VIE) tags. Of these, VIE tags have not been extensively tested on larval or juvenile lampreys. We evaluated the performance of uncured VIE tags on ammocoetes of Pacific lampreys Lampetra tridentata in a laboratory experiment to determine tag detection and the influences of color and tag position on detection. Additionally, we examined the effects of transformation (ammocoete to macrophthalmia) on tag detection. Though survival was not specifically tested, 0 of the 84 lampreys died as a result of tagging. Tag detection was 87% after 168 d in lampreys that did not transform; in those that did transform, however, tag detection was reduced to 38%. Tag position did not affect detection, but red and orange tags were detected more consistently than green tags. Overall, uncured VIE tags can be used effectively to tag larval lampreys; however, studies that depend on long-term tag detection either should be conducted at a time when lampreys are not expected to transform or should only use ammocoetes that are not likely to transform during the study. [ABSTRACT FROM AUTHOR]

We provide experimental evidence for a direct link between embryonic metabolism and longevity in the larval stage of a marine fish when food resources are limited. Since growth rates of otoliths are closely related to metabolic rates, the area inside the hatch check (i.e., deposition of otolith matrix during embryonic development) is representative of inherent differences in metabolic rates. When exposed to food limitation, larvae with larger hatch check areas died earlier than larvae with smaller hatch check areas. This relationship did not occur in larvae that fed at saturated levels. A simple explanation for these observations is that larvae, which consumed metabolic fuel at higher rates died earlier unless energy derived from food was not limiting. Since high growth rates are linked to high metabolic rates, this mechanism could efficiently counteract selection for faster average growth but only when resources are limiting. [ABSTRACT FROM AUTHOR]

Otoliths have frequently been used to reconstruct growth histories in larval, juvenile and adult fish. However, there is growing evidence that otolith growth is directly determined by metabolic intensity and, consequently, only indirectly related to somatic growth. By performing measurements of oxygen consumption rate and other early life-history traits on individual eggs of zebrafish (Danio rerio), we found that oxygen consumption explained residual variance in otolith size that is not accounted for by egg size. Total oxygen consumption during the embryonic stage explained 34% of the variance in sagitta size at hatch, whereas larval size at hatch (as a proxy for growth during the embryonic period) was not significantly correlated with sagitta size. This strongly suggests that otolith growth is directly related to metabolic rate, and yields a mechanism that may explain recent observations of a link between otolith size at hatch and viability in larval fish. [ABSTRACT FROM AUTHOR]

Intertidal movements of fish larvae and juveniles on a mudflat in the Tama River estuary, central Japan, were investigated by comparing the abundance and sizes of fishes caught in the intertidal zone during flood tides with those in the subtidal zone during low tides. A total of 28 465 individuals, belonging to 9 families and 20 species, were collected by small purse seine. Among the abundant species, planktonic larvae and juveniles of gobiids and Konosirus punctatus were more abundant in the intertidal zone at flood tide than the subtidal zone at low tide. Similar occurrence patterns were found in juvenile Plecoglossus altivelis altivelis and Lateolabrax japonicus, having fully developed swimming abilities. In contrast to these species, much higher abundances of epibenthic juveniles of 2 gobiids (Acanthogobius flavimanus and Gymnogobius macrognathos) were found in the subtidal zone at low tide, although they also utilized the intertidal zone at flood tide. [ABSTRACT FROM AUTHOR]

We examined 1,825 bongo-net samples collected during Southeast Area Monitoring and Assessment Program (SEAMAP) ichthyoplankton surveys of United States Gulf of Mexico waters (1982-1986) for carangid larvae. Objectives were to describe the distribution of carangid larvae and to examine distribution patterns relative to areas of higher zooplankton volumes in order to reveal areas that may be important nurseries. Samples contained about 29,200 carangid larvae from 13 species or species complexes in 11 genera.Chloroscombrus chrysurusandDecapterus punctatusaccounted for 91.7% of all larvae. We found that the ‘scads’ (D.punctatus,Trachurus lathami, andSelar crumenophthalmus) utilize temporally and/or spatially distinct spawning strategies to reduce co-occurrence of larvae. Samples contained fewer larvae than expected of the amberjacks (Seriolaspp.),Caranx crysos, andC. hippos/latusgiven the abundance of adults in the survey area, possibly due to inadequate sampling at appropriate times and locations, gear avoidance, or gear bias. Zooplankton displacement volumes (ZDVs) differed among regions and seasons and were inversely related to surface salinity and station depth. Differences among years were not significant. ZDVs were consistently highest near the Mississippi River delta and along the western Louisiana/eastern Texas shelf, and moderately high during summer and fall along the shelf break, with localized pockets of elevated volumes over the eastern Gulf shelf. We suggest thatChloroscombrus chrysurus,D.punctatus,T.lathami, and possiblyOligoplites saurus,Hemicaranx amblyrhynchusandCaranx crysosspawn in frontal areas and/or along other hydrographic features that promote higher productivity. We provide new illustrations and descriptive information for the larvae ofH.amblyrhynchusand discuss characters that separate early larvae of several species ofCaranx. [ABSTRACT FROM AUTHOR]

The otolith microstructure from North Sea autumn-spawned herring larvae and Norwegian spring-spawned herring larvae is described. The distance from the nucleus to the hatch check is on average 1.5 μm longer in the spring-spawned larvae (11.6 μm) than in the autumn-spawned (10.1 μm), and the average increment size is larger. The greatest difference is observed in the zone between 20 and 60 increments from the nucleus. This corresponds to a distance of 20 to 60 μm from the nucleus in the autumn-spawned herring larvae and of 28 to 132 μm in the spring-spawned larvae. A combination of distance to the hatch check and increment size in otolith from 30 to 60 μ from the nucleus could be a valuable method of distinguishing between the progeny of spring- and autumn-spawning herring. [ABSTRACT FROM PUBLISHER]

A Monte Carlo simulation model was used to investigate uncertainty in estimates of the production of newly hatched larvae by a fish population when the estimates are derived from samples of larval abundance. The model simulates (1) hatching, growth, and mortality of a population of larvae; (2) a series of cruises which sample the population; (3) back-calculation to estimate the number hatched; and (4) comparison of estimates of the production of hatched larvae (LP). The model is applied for several combinations of (a) the time interval between cruises; (b) the coefficient of variation of larval concentration within a cruise (CVWC), which depends on sample size; and (c) for several other variables which characterize the simulated population. The coefficient of variation of estimates of the number of larvae produced (CVLP) increases sharply if the interval between cruises is greater than twice the standard deviation of the temporal distribution of the larval hatching. It is equally sensitive to CVWC. For example, doubling sample size by increasing the number of samples within cruises or by halving the interval between cruises has a similar effect. Of the random variables that characterize the population, CVLP is most sensitive to variability in growth rate. There is a bias in the estimate of larval production if mortality rate is length-dependent, or if estimates of growth rate used in calculations are incorrect. The simulations show that estimates of larval production are inherently uncertain. [ABSTRACT FROM PUBLISHER]

La question du rôle de la privation de nourriture dans la mortalité des premiers stades larvaires des poissons marins dans leur milieu naturel a suscité d'importants travaux. Les méthodes proposées font appel à différentes techniques dont aucune n'a jusqu'alors réuni tous les avantages recherchés. Le rapport ARN/ADN, prôné par de nombreux auteurs, semble présenter une variabilité qui nuit à l'efficacité de son application in situ. Quelques arguments conceptuels simples conduisent à proposer un nouvel indice biochimique, la teneur de la larve en ADN, exprimee en μg/mg de poids sec (ADN/PS). Plusieurs élevages expérimentaux de larves de sole (Solea solea L.) ont été entrepris pour tester cette approche: des privations totales ou différées de nourriture leur ont été infligees à deux températures. Il est tout d'abord vérifié que l'évolution du rapport ARN/ADN au cours du développement ontogénique d'individus témoins nourris montre une forte variabilité qui, de plus, n'est pas reproductible, pour un même stade de développement, d'un élevage à l'autre, pourtant menés dans des conditions standard rigoureusement identiques. A I'inverse, ADN/PS s'av ère beaucoup plus stable chez les témoins et présente essentiellement deux niveaux, identiques pour les deux températures testées et caractéristiques respectivement de la larve à symétrie bilatérale, puis de l'animal en cours de métamorphose pleuronecte. L'effet de la privation de nourriture est tr ès marqué chez les premiers stades, caractérisé par une élévation rapide, nettement au-del à du seuil significatif que Ion détermine à 30; pour les larves en cours de métamorphose, bien que l'effet soit moins manifeste, le dépassement du seuil de 15 révéle l'inanition. Ces résultats sont discutés en regard des travaux antérieurs, en particulier ceux fondes sur le rapport ARN/ADN. On y trouve des valeurs d'ADN/PS montrant une faible variabilité interspécifique. L'intrét de la méthode proposée est renforcé par le fait que les techniques fluorimétriques actuelles de mesure permettent de l'appliquer sans difficulté au niveau individuel.Much work has been devoted to the study of the role played by starvation in the natural field mortality of the early larval stages of marine fishes. Although different methods have been proposed, none have succeeded in including all the various advantages found. The RNA/DNA ratio suggested by many authors seems to show a variability which adversely affects its application in situ. Some conceptual considerations have led us to propose a new biochemical index, the DNA amount in the larva (expressed in μg/mg dry weight; DNA/DW). Several rearing experiments were carried out with fed and starved Dover sole (Solea solea L.) larvae under two temperature conditions. It is confirmed that the RNA/DNA ratio during ontogenetic development of fed individuals exhibits a strong variability which, moreover, is not reproducible for the same development stage between experiments carried out in strictly identical standard conditions. On the other hand, DNA/DW is proving much more stable in fed individuals and shows two main levels which are similar under the two tested temperature conditions and peculiar to symmetrical and metamorphosing larvae respectively. The effect of starvation is very sharp in the early stages, characterized by a rapid increase beyond the significant threshold of 30; for metamorphosing larvae, this effect appears to be less important and the threshold falls to 15. These results are discussed and compared with previous works, especially those based on the RNA/DNA ratio. The literature gives DNA/DW values showing a weak interspecific variability. The interest of the method is reinforced by the fact that recent fluorometric techniques allow DNA determination in ... [ABSTRACT FROM PUBLISHER]

The temporal and spatial patterns of species composition and abundance of fish larvae and juveniles in the Tanshui River mangrove estuary (Taiwan) were studied monthly using a drift bag-net in daylight. A total of 44591 individuals representing 55 families and 105 species were collected over 12 mo (August 1989 to July 1990). The community was dominated numerically by a few species. Sardinella melanura was most numerous, making up 70.15% of the total catch, followed by Stolephorus buccaneeri (19.59%), Thryssa kammalensis (2.96%), and Gerres abbreviatus (2.61%). These four species constituted ca. 95% of the total catch, the remaining 5% consisted of another 101 species. This estuary functions as a nursery and feeding area in the early life history of these fish. There was a separation in peak-immigration and seasonal utilization of the estuary by the dominant species. The abundance of fish larvae and juveniles decreased in an upstream direction. [ABSTRACT FROM AUTHOR]

Milt of common carp, Cyprinus carpio L. was cryopreserved in pellet form with the use of 12 extenders. Most efficient were: BE2 original extender (containing 85 nM NaCl, 50 mM KCl, 3 mM CaCl2, 1 mM MgCl2 with 10% dimethyl-acetamide (DMA) and 10% addition of hen's egg yolk) and Kurokura et al.'s extender with 15% DMA and 10% yolk (about 73% and 69% of eyed eggs, about 61% and 52% of swim-up larvae, respectively). Within the most effective treatments, survival from the eyed-egg stage to the swim-up stage was similar to that observed in the control group. Survival from the eyed-egg stage to the swim-up stage (percentage of eyed eggs was considered as 100%) was highly significantly and positively correlated with the actual rate of swim-up larvae. [ABSTRACT FROM AUTHOR]

Mortality during the early stages is a major cause of the natural variations in the size and recruitment strength of marine fish populations. In this study, the relation between the size-at-hatch and early survival was assessed using laboratory experiments and on field-caught larvae of the European sardine (Sardina pilchardus). Larval size-at-hatch was not related to the egg size but was significantly, positively related to the diameter of the otolith-at-hatch. Otolith diameter-at-hatch was also significantly correlated with survival-at-age in fed and unfed larvae in the laboratory. For sardine larvae collected in the Bay of Biscay during the spring of 2008, otolith radius-at-hatch was also significantly related to viability. Larval mortality has frequently been related to adverse environmental conditions and intrinsic factors affecting feeding ability and vulnerability to predators. Our study offers evidence indicating that a significant portion of fish mortality occurs during the endogenous (yolk) and mixed (yolk /prey) feeding period in the absence of predators, revealing that marine fish with high fecundity, such as small pelagics, can spawn a relatively large amount of eggs resulting in small larvae with no chances to survive. Our findings help to better understand the mass mortalities occurring at early stages of marine fish. [ABSTRACT FROM AUTHOR]