Life Stages Of Marine Fish Research Articles

Chronic exposure to environmental concentrations of benzo[a]pyrene causes multifaceted toxic effects of developmental compromise, redox imbalance, and modulated transcriptional profiles in the early life stages of marine medaka (Oryzias melastigma)

Polycyclic aromatic hydrocarbons (PAHs) accumulate and integrate into aquatic environments, raising concerns about the well-being and safety of aquatic ecosystems. Benzo[a]pyrene (BaP), a persistent PAH commonly detected in the environment, has been extensively studied. However, the broader multifaceted toxicity potential of BaP on the early life stages of marine fish during chronic exposure to environmentally relevant concentrations needs further exploration. To fill these knowledge gaps, this study assessed the in vivo biotoxicity of BaP (1, 4, and 8 μg/L) in marine medaka (Oryzias melastigma) during early development over a 30-day exposure period. The investigation included morphological, biochemical, and molecular-level analyses to capture the broader potential of BaP toxicity. Morphological analyses showed that exposure to BaP resulted in skeletal curvatures, heart anomalies, growth retardation, elevated mortality, delayed and reduced hatching rates. Biochemical analyses revealed that BaP exposure not only created oxidative stress but also disrupted the activities of antioxidant enzymes. This disturbance in redox balance was further explored by molecular level investigation. The transcriptional profiles revealed impaired oxidative phosphorylation (OXPHOS) and tricarboxylic acid (TCA) cycle pathways, which potentially inhibited the oxidative respiratory chain in fish following exposure to BaP, and reduced the production of adenosine triphosphate (ATP) and succinate dehydrogenase (SDH). Furthermore, this investigation indicated a potential connection to apoptosis, as demonstrated by fluorescence microscopy and histological analyses, and supported by an increase in the expression levels of related genes via real-time quantitative PCR. This study enhances our understanding of the molecular-level impacts of BaP's multifaceted toxicity in the early life stages of marine medaka, and the associated risks.

Projecting marine fish distributions during early life stages under future climate scenarios

AbstractChanges to Earth's climate affect organisms globally; in marine systems, these impacts are seen through warming water temperatures, ocean acidification, hypoxia and frequent marine heatwaves. These effects may lead to the movement of species to more favourable conditions. While climate‐driven movement is well studied at the adult stage, how the early life stages of marine fish will respond to future variability is less clear. Many fish species are constrained by specific spawning locations or phenology. Spawning in certain locations allows for local retention of offspring, while precise timing can facilitate transport of offspring to nursery locations through seasonal circulation patterns. Our research investigates how changing oceans impact the location and timing of spawning of Bering Sea groundfishes over the next century. We used ROMS SST and SSS model output and NOAA survey data in species distribution models to hindcast and project distributions and centre of gravity for eggs and larvae of six groundfish species. Our analyses found that most of our study species exhibit flexible geography. However, the speed and direction of egg and larval movement did not track the speed and direction of their respective thermal niches. Hence, the projected distributional patterns of adult stages may be limited by their early life stages. This response is likely to be mirrored globally by other species with planktonic eggs and larvae. These results indicate that life history considerations are critical for the management of commercially important species, as effects on early life stages are strongly connected to the success or failure of adult populations.

Development and application of a bioenergetics growth model for multiple early life stages of an ecologically important marine fish

Spatial and temporal variability in temperature and food availability are key drivers of growth of marine fishes. Growth during the early life stages (ELS's) is tightly coupled to survival, and in turn, can set year-class strength (i.e. annual recruitment) and overall stock productivity of populations and fished stocks. Ontogenetic changes in physiology, dietary preferences, and growth across ELS's can be accounted for within bioenergetics models, but existing models lack resolution within larval and early juvenile stages. We leveraged daily output from a coupled physical-biogeochemical model to force a highly resolved ontogenetic bioenergetics model parametrized for an ecologically important rockfish in the California Current System. Size-at-age predictions closely track empirical growth trajectories of the ELS's. Scenario testing revealed that growth performance is disproportionately driven by changes in temperature compared to food availability. We then expanded the model to incorporate spatial climatological differences in temperature and prey concentration and found that preflexion growth potential is maximized in areas of historical spawning, suggesting the timing and location of reproduction is an adaptive strategy that places larvae in habitat favorable for survival. Growth potential for late-stage larvae (postflexion) is greatest over a broad areal extent, implying that if a particle tracking algorithm was coupled to the bioenergetics model, a wide range of larval dispersal pathways would place postflexion larvae in habitat suitable for rapid growth. Finally, growth potential of pelagic juveniles is maximized over the continental shelf and shelf-break, aligning with high juvenile catch rates from a fisheries-independent survey. In summary, this study (i) serves as a proof of concept that a bioenergetics model with high ontogenetic resolution can reproduce life stage-specific growth trajectories even though the underlying physiology data for model parameterization is imperfect and (ii) can aid future studies aimed at understanding how ecosystem processes interact with ontogenetic growth and changes in year class strength of early life stages of marine fishes.

Temperature-dependent spawning behaviour and larval thermohaline associations of Bering Sea groundfish

Abstract The Bering Sea is a productive large marine ecosystem that supports numerous commercial fisheries, while climate change is introducing rapid warming and freshening, especially in coastal water. The success of early life stages of marine fish can impact adult abundance levels; little is known about how behavioural or physiological plasticity in relation to environmental changes at one stage (e.g. spawning) may affect survival during subsequent stages (e.g. larvae), nor whether trade-offs exist that affect how a species demonstrates such plasticity. We utilized a statistical approach to examine phenological and geographical flexibility in spawning behaviour for four species of groundfish. In situ sea surface temperature (SST) and salinity (SSS) associations were also estimated by statistical models for six species of groundfish larvae. All species exhibited greater spawning geography flexibility than phenological flexibility during the egg stage. All larval stages exhibited specific temperature and salinity associations across unique combinations of SST and SSS. These species-specific patterns, in the context of potential climate change impacts, suggest that flexibility in spawning behaviour may not adequately compensate for the presence of unfavourable habitats at the larval stage.

Impact of squid predation on juvenile fish survival

Predation is a major source of mortality during the early life stages of marine fishes; however, few studies have demonstrated its impact—especially that of squid predation—on survival processes. Here, we examined the feeding habits and predation impacts of swordtip squid on a major prey fish, juveniles of jack mackerel, in the East China Sea. Otoliths of the juveniles extracted from the squid stomach were used to reconstruct the age–length relationship and the growth trajectory of the consumed juveniles, and they were compared to those of juveniles collected with a net using a newly developed statistical framework. The juveniles consumed by squid had significantly shorter body lengths and smaller body sizes during the late larval and early juvenile stages than the netted juveniles, suggesting that smaller juveniles with slower growth rates have a higher probability to be selected. The body mass ratio of the predator squid to prey juveniles (predator–prey mass ratio, PPMR) ranged from 7 to 700, which was remarkably lower than the PPMR reported in various marine ecosystems based on analyses of fishes. Our findings demonstrate that squid predation can significantly impact the early life survival of fish and the trophodynamics in marine ecosystems.

Embryonic development and effect of temperature on larval growth of the Peruvian anchovy Engraulis ringens.

Understanding aspects of the biology of early life stages of marine fish is critical if one hopes to reveal the factors and processes that impact the survival and recruitment (year class) strength. The Peruvian anchovy (Engraulis ringens) is a key species in the Humboldt current system, and the present study provides the first description of the embryonic and larval development of this species reared in captivity. Embryonic and early exogenous feeding stages of larvae were illustrated in detail at 18.5°C. Hatching was completed within 42 and 48 h post-fertilization at 18.5 and 14.5°C, respectively. Mean ± 95% C.I. standard length (LS ) at hatch (3.40 ± 0.10 mm at 18.5°C and 2.76 ± 0.34 mm at 14.5°C) was significantly different between the two temperatures. Larval behaviour was assessed at 18.5°C; at the onset of exogenous feeding [3 days post-hatch (dph)], larvae were fed small, motile dinoflagellates, Akashiwo sanguinea. At 7 dph, larvae started to feed almost exclusively on zooplankton (rotifers and Artemia nauplii). Larval activity increased with age, and the first sign of schooling was noted at 31 dph (18.56 mm LS ) at 18.5°C. Temperature had a significant effect on size-at-age, but not on body shape (depth to LS ratio). The size-at-age data for larvae (this study) was used to parameterize a temperature-corrected von Bertalanffy growth function for Peruvian anchovy, the accuracy of which was assessed for juveniles and adults (literature values).

Diel and tidal periodicity in the responses of early life stages of marine fishes to an estuary opening event in temperate South Africa

Early life stages of fish were monitored in a breach channel during an opening event of the temporarily open/closed East Kleinemonde Estuary. For comparison, early life stages were also collected in the surf zone and estuary mouth region before, during and after the breaching event on a weekly basis. The breach channel was sampled day and night at each midtide state for five consecutive days using a larval fish seine net (mesh 500 µm). Catch per unit effort (CPUE) of mostly postflexion stage larvae increased in the surf zone during opening events with a concomitant peak in abundance in the breach channel. Catch composition included many estuarine associated species typically found in temporarily open/closed estuaries. Predominantly postflexion stage larvae and newly settled juveniles were caught. No overall patterns of diel and tidal use across species were found in the breach channel suggesting some degree of plasticity in recruitment that could be opportunistically driven for most species. However, for the abundant Rhabdosargus holubi (Sparidae), nocturnal flood tides were favoured for movement into the estuary. Natural estuary opening events, especially during peak rainfall in the recruitment season are critical to the early life history strategy of estuary-associated marine fish species.

Teratogenic effects of environmentally relevant concentrations of phenanthrene on the early development of marine medaka (Oryzia melastigma)

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous pollutants in marine environments and have arouse great concern since they pose adverse effects to marine ecosystem. To determine the potential impacts of environmentally relevant PAHs on early life stages of marine fish, this study exposed embryos of marine medaka (Oryzias melastigma) to 0, 2, 10, 50, and 250 μg/L of phenanthrene (Phe), one of the most abundant PAHs. The results demonstrated that Phe exposure decreased hatching rates, delayed hatching time of embryos, and increased deformity rate of newly-hatched larvae. Exposure to 10 and 50 μg/L Phe decreased the survival rate of marine medaka larvae at 28 days post-fertilization (dpf), and no embryo successfully hatched in 250 μg/L Phe exposure group. Morphology results showed that 10, 50, and 250 μg/L Phe exposure significantly retarded the development of embryos, and 2, 10, and 50 μg/L caused yolk sac edema and pericardial edema in newly-hatched larvae, indicating that low concentrations of Phe could induce developmental cardiac toxicity. Furthermore, the changes in the expression of heart development-related genes were determined, and the results showed that Phe-induced cardiac malformation might be related with fgf8, bmp4, smyd1, ATPase and gata4 genes. Overall, environmentally relevant PAHs could disrupt heart morphogenesis and hatching process of marine medaka, which might have profound consequences for sustainability of fish population.

Developmental toxicity of copper in marine medaka (Oryzias melastigma) embryos and larvae

Copper as developmental toxicants have been reported extensively in freshwater fish, however, the sublethal and chronic toxic effects of Cu to the early life stages of marine fish are not clear. Embryo (3–5 hpf) and newly hatched larvae of marine medaka (Oryzias melastigma) were exposed to 0.01–1.28 mg L−1 waterborne Cu to investigate the developmental toxic effects. The results showed that Cu accumulation in the whole embryos presented a dose- and time-response increase while it decreased dramatically once hatching. Most of Cu accumulated in the chorion suggests that chorion is an effective barrier to Cu absorption. However, Cu that penetrated chorion and entered embryo still caused significant lethal and sublethal effects. Cu concentrations at ≥0.16 mg L−1 led to low hatchability, delayed hatching, high mortality, morphological abnormalities and increased egg size in the embryos. Heart beats and the total body length of the newly hatched larvae were significantly increased when exposed to ≥0.02 mg L−1. Cu exposure accelerated early development and promoted or delayed hatching of embryo. High Cu concentration (≥0.16 mg L−1) exposure induced morphological abnormalities of embryo and larvae, particularly skeletal and vascular system abnormalities and reduction of pigmentation. The 30 d-LC50 for embryo development was 0.138 mg L−1 and 7d LC50 for larvae survival was 10.15 mg L−1, demonstrating that embryos were more sensitive to Cu than larvae. In summary, O. melastigma embryos development is highly sensitive to Cu exposure, and the sublethal effects occurred at low Cu concentration might be as potential biomarkers in marine fish.

Swimming performance of marine fish larvae: review of a universal trait under ecological and environmental pressure

The larval phase of marine teleost fishes is characterized by important morphological and physiological modifications. Many of these modifications improve the larvae’s ability to swim, which satisfies a suite of crucial biological and ecological functions. Indeed, larval fish swimming performance has been considered a good proxy for overall condition, a predictor for growth and survival, and particularly helpful in assessing effects of natural and anthropogenic stress. Several methodologies have been developed to test larval fish swimming performance; however, measured swimming capabilities can strongly depend on the methodology utilised and developmental stage investigated. The aims of this review were, therefore, to link the ontogenetic development of swimming performance in early life stages of marine fishes, particularly the anatomical and physiological processes around the fins, muscles, and gills, with both the experimental methodologies used and the environmental stressors tested. We conducted a literature search and found 156 research papers relevant to swimming performance of marine teleost fish larvae. We found swimming performance to be highly variable among species and driven by temperature. In a meta-analysis focusing on the impacts of environmental stress on larval swimming performance, we found that prey reduction had the greatest impact on swimming. Methods used to evaluate swimming should keep the ontogenetic stage a focus, as forced swimming experiments are unfit for larvae prior to flexion of the notochord. Overall, while the data are deficient in some areas, we are able to highlight where the field of larval fish swimming could be directed and provide insight into which methods are best used under certain ecological scenarios, environmental stressors, and developmental stages.

Ocean acidification and hypoxia can have opposite effects on rockfish otolith growth

Climate change is predicted to alter ocean chemistry through warming temperatures, increases in CO2 (i.e., ocean acidification), and reductions in dissolved oxygen (DO) (i.e., hypoxia). Past research has shown that early life stages of marine fishes are sensitive to all three stressors, but with sometimes different directions of response. In this study, we examined the separate effects of ocean acidification and hypoxia on otolith growth in two species of juvenile rockfish (copper rockfish, Sebastes caurinus, and blue rockfish, Sebastes mystinus). Fishes were collected at settlement stage from kelp forests on the central California coast and reared in the laboratory for up to 6 months in 4 separate pH treatments (pH = 7.3, 7.6, 7.8, and a control of 8.0), simulating the effects of ocean acidification through the addition of CO2, and 4 separate dissolved oxygen treatments (DO = 2.2, 4.1, 6.0, and a control of 8.7 mg/L), simulating the effects of hypoxia. For both species, otoliths were smaller for a given fish length in response to hypoxia but were larger (trend was non-significant for copper rockfish) in response to elevated CO2. The results suggest that otolith growth may respond differently to ocean acidification and hypoxia for some species, which has implications for sensory development, ecological performance, and interpretations of the permanent record of fish growth in hard parts such as otoliths.

Nearshore environmental conditions influence larval growth and shape changes for a temperate rocky reef fish

Coastal upwelling and other oceanographic processes, exert influences on phenotypic traits of early life stages of marine fishes. However, it remains to elucidate the environmental effects on the morphology of fish larvae. Using geometric morphometrics and otolith microstructure of a temperate rocky reef fish, the labrisomid blenny Auchenionchus crinitus (Labrisomidae), we studied the larval growth, mortality and morphospace of four consecutive cohorts, hatched between austral winter and summer off central Chile. We hypothesize that coastal environmental conditions will influence early life traits of this cryptobenthic fish. The winter cohort, which inhabited colder and well-mixed nearshore waters, grew more slowly and had a more hydrodynamic head shape, while the summer cohort, which lived in warmer and stratified waters, grew faster, but had a more robust shape. Cohorts expressed less ontogenetic allometry as seasons progressed, suggesting that the seasonal increment in water temperature reduces the shape changes with size during larval development. Also, slower- and faster-growing larvae showed large variation from the consensus shape, e.g. had the largest shape disparity. Nonetheless, all cohorts showed similar mortality rates during the first month of life. Finally, increases in zonal wind stress (i.e. sea breeze) and decreases in the sea temperatures (i.e. upwelling events) increased the growth rates of older (> 15 days old) larvae. Therefore, for this cryptobenthic species, differences in growth rate and body shape are related to the seasonal increase in water temperature, and local-scale meteorological conditions.

Toxicity Test Assay of Waterborne Methylmercury on the Japanese Flounder (Paralichthys olivaceus) at Embryonic-Larval Stages.

Methylmercury (MeHg) is a widespread pollutant in aquatic ecosystems, but its toxicity to the early life stages of marine fish has not been adequately investigated. This study used acute toxicity tests on embryonic-larval stages of a marine flounder Paralichthys olivaceus to determine the LC50 values for embryos and larvae and evaluate the responses of several biological endpoints to subacute MeHg exposure. Under exposures (0-15μgL-1) below LC50 values ( < 15.3μgL-1 for embryos and 16.3μg L-1 for larvae), embryos were more sensitive to MeHg than were the larvae. MeHg exposures at ≥ 13μg L-1 increased morphological deformities and mortality, reduced growth and yolk absorption rate of the embryonic-larval flounder. These endpoints were sensitive to MeHg and their responses were dose-dependent. They could be used as bioindicators for assessing MeHg toxicity to the ELS of the flounder. Embryonic-larval flounder could be a useful fish for ecotoxicological assessment of MeHg in marine ecosystems.

Trophic plasticity of larval notothenioid fish Harpagifer antarcticus in shallow waters from the South Shetland Islands, Antarctica

Adaptive plasticity in foraging of early life stages of marine fishes is highly relevant, particularly in environments such as the Antarctic inshore waters. In this study we analyzed the trophic habits, feeding success and selectivity of larval spiny plunderfish Harpagiferantarcticus (Osteichthyes: Harpagiferidae) collected weekly in austral summer 2014 and 2015 at Bahia Chile, Greenwich Island, South Shetland Islands. Based on the stomach contents of 202 individuals ranging between 5.97 and 10.66 mm, the spiny plunderfish was omnivorous, with chain-forming diatom Thalassiosiraminuscula, euphausiid eggs and copepodites as the main prey items. The feeding success, measured as prey number per gut and total volume per gut, and the trophic niche breadth were independent of the standard length. Only the maximum prey size (width) was positively correlated with larval size, suggesting a preference for larger prey as larvae grow. At the interannual scale, significant differences were only detected in the ingested prey per gut, with higher values during summer 2014. In this season, trophic niche breadth increased with larval size. At the weekly scale, and after storm winds from southeast and high turbulence in surface waters, H. antarcticus larvae switched their selective feeding based on large prey (i.e., copepodites) to a more opportunistic feeding strategy, relying on large abundance of small (i.e., T. minuscula) to medium-size prey (euphausiid eggs). The present results suggest that larval spiny plunderfish exhibit feeding behavior plasticity, ensuring higher feeding rates after major changes triggered by meteorological conditions in a shallow embayment of the South Shetland Islands.

European sea bass, &amp;lt;i&amp;gt;Dicentrarchus labrax&amp;lt;/i&amp;gt;, in a changing ocean

Abstract. Ocean acidification, caused by rising concentrations of carbon dioxide (CO2), is widely considered to be a major global threat to marine ecosystems. To investigate the potential effects of ocean acidification on the early life stages of a commercially important fish species, European sea bass (Dicentrarchus labrax), 12 000 larvae were incubated from hatch through metamorphosis under a matrix of two temperatures (17 and 19 °C) and two seawater pCO2 levels (ambient and 1,000 μatm) and sampled regularly for 42 days. Calculated daily mortality was significantly affected by both temperature and pCO2, with both increased temperature and elevated pCO2 associated with lower daily mortality and a significant interaction between these two factors. There was no significant pCO2 effect noted on larval morphology during this period but larvae raised at 19 °C possessed significantly larger eyes and lower carbon:nitrogen ratios at the end of the study compared to those raised under 17 °C. Similarly, when the incubation was continued to post-metamorphic (juvenile) animals (day 67–69), fish raised under a combination of 19 °C and 1000 μatm pCO2 were significantly heavier. However, juvenile D. labrax raised under this combination of 19 °C and 1000 μatm pCO2 also exhibited lower aerobic scopes than those incubated at 19 °C and ambient pCO2. Most studies investigating the effects of near-future oceanic conditions on the early life stages of marine fish have used incubations of relatively short durations and suggested that these animals are resilient to ocean acidification. Whilst the increased survival and growth observed in this study supports this view, we conclude that more work is required to investigate whether the differences in juvenile physiology observed in this study manifest as negative impacts in adult fish.

Assessing the nursery role for marine fish species in a hypersaline coastal lagoon (Mar Menor, Mediterranean Sea)

The shallow inshore areas of coastal lagoons function as nursery grounds for the early life stages of marine fish. Multi-species approaches and the assessment of several population variables are of great value in studies focused upon the ecological importance of estuarine systems as fish nursery areas. Therefore, the objective of this study was to analyse the spatial differences in the abundance, biomass, growth and condition indexes of juveniles from three marine species: Sparus aurata, Liza aurata and Liza ramada, in order to assess the nursery role of the Mar Menor coastal lagoon for these species. Results showed high spatial variability of the studied variables, with higher abundance and biomass values at those sites closest to the inlet connecting the lagoon with the Mediterranean Sea. Moreover, there were significant relationships between the growth and condition of the fish with hydrographical circulation patterns within the lagoon, indicating the suitability of the Mar Menor as a nursery area for the three studied fish species.

Effects of chronic exposures to the herbicides atrazine and glyphosate to larvae of the threespine stickleback (Gasterosteus aculeatus)

Atrazine (ATR) and glyphosate (GLY) are among the most widely used herbicides in Canada, yet there is relatively little information concerning their toxicity to early life stages of marine fish. The threespine stickleback (Gasterosteus aculeatus) reproduces in coastal habitats which receive runoff of pesticides during the summer, the peak season of herbicide use. Sticklebacks have biomarkers for effects of both estrogenic and androgenic contaminants. Stickleback adults from a clean reference site were allowed to reproduce in the laboratory and the fertilized eggs were incubated until hatching. Larval sticklebacks (<24h old) were exposed for 42d to four concentrations (0.1, 1, 10 and 100μg/l) of either ATR or GLY, a seawater control, a carrier (acetone) control and positive controls for estrogenic (0.05μg/l ethinylestradiol, EE2) and androgenic (3μg/l dihydrotestosterone, DHT) effects. The survivors were measured (length, wet weight) then conserved for biochemical (vitellogenin, VTG, and the male nest-protein spiggin, SPG) and histological (phenotypic sex determination) analyses. There were no significant effects of ATR and GLY exposures on larval survival or growth. Exposure to 3μg DHT/l resulted in a significant effect on growth (body lengths) but did not induce SPG, possibly because of DHT degradation after the 24h solution renewal. VTG was induced after the EE2 exposure, yet neither ATR nor GLY induced production of VTG and SPG. The proportion of mixed sex individuals was higher in the positive controls compared to the negative controls. A single mixed sex individual was found in the group exposed to the lowest dose of atrazine and none in glyphosate expositions. We conclude that these herbicides do not show estrogenic or androgenic effects to early life stages of sticklebacks at environmentally realistic concentrations.

气候环境因子和捕捞压力对南海北部带鱼渔获量变动的影响

带鱼(<em>Trichiurus japonicas</em>)是南海北部的重要经济鱼类,其渔获量的变化不仅与捕捞压力有关,还与气候环境变化有关。为了研究气候变化和捕捞对南海北部带鱼渔获量变动的影响,使用长时间序列渔业统计资料和气候变化数据对1956-2006年的南海北部带鱼渔获量变动进行了分析。南海北部的带鱼渔获量变化可划分成因捕捞效应所产生的趋势变化和因气候环境变化所导致的渔获量变动。捕捞效应所产生的趋势变化可用Fox模型拟合,Fox模型拟合结果显示南海北部带鱼渔获量与捕捞努力量关系显著(<em>P</em><0.01),说明捕捞压力的增长显著影响到南海北部带鱼渔获量的变化。移除捕捞效应所产生的趋势变化后,渔获量变动与中国南方降雨、南海北部海表水温、南海北部夏季季风以及南海北部冬季季风等气候因子呈显著正偏相关(<em>P</em><0.04),与热带气旋影响指数呈显著负偏相关(<em>P</em><0.03),这种相关说明南海北部带鱼渔获量变动还受气候环境因子的影响。南海北部带鱼渔获量可用捕捞努力量和气候变量来拟合,且拟合效果显著(<em>R</em>²=0.958,<em>P</em><0.01),表明南海北部带鱼渔获量的变动归因于捕捞压力的单调增长和气候环境的变化。在南海北部的捕捞压力维持在现有水平下,未来的气候变化和人类活动引起营养盐的增加都可能有利于南海北部带鱼渔业产量的增加,且由于未来极端天气事件的频繁发生,可能还会引起带鱼渔获量的变动幅度加剧。;Hairtail (<em>Trichiurus japonicas</em>) is one of the most important kinds of commercial fishes in the northern South China Sea (NSCS). Changes to hairtail catches are not only related to fishing pressure but also to changes in the climatic environment. To understand the influence of climatic environmental factors and fishing pressure on the changes of hairtail catches in the NSCS, we have used long-term fisheries statistical data and climate change data to analyze the changes of hairtail catches between 1956 and 2006 in the NSCS. Hairtail catches in the NSCS can be divided into two parts: the trend of catches caused by fishing pressure and the alteration of catches influenced by climate change. Fitting the trend of catches to the Fox model shows significant relationships between fishing effort and hairtail catches in the NSCS (<em>P</em><0.01), which in turn demonstrates that growing fishing pressure has significantly affected the changes of hairtail catches in the NSCS. Before 1986, the growth of fishing effort was slow in the NSCS, and correspondingly, the growth rates of hairtail catches increased by a small margin. However, after 1986, with the rapid growth of fishing efforts and improved techniques for fishing, hairtail catches in the NSCS grew continuously and rapidly. After removing the effect of fishing pressure on the changing trends, we found that the alteration of catches had a significant positive partial correlation with precipitation in the southern China, as well as sea surface temperature, summer wind speed and winter wind speed in the NSCS (<em>P</em><0.04). Alteration of catches also had a significant negative partial correlation with the index of tropical cyclone influences (<em>P</em><0.03). This correlation showed that the alteration of hairtail catches was also affected by climatic and environmental factors. Rainfall runoff inputs a vast amount of nutrients into the estuary and adjacent waters. However, the monsoon-driven confluence and mixing between coastal and surface waters, as well as vertical mixing between the upper and lower waters, diffuses the distribution of nutrients in the NSCS, aides the efficient use of nutrients, and is conducive to the growth of phytoplankton in the sea. In addition, changes in ocean temperatures directly or indirectly had an effect on the various life stages of marine fish, particularly on the metabolism of fish and the rate of the reproductive cycle. Finally, the tropical cyclone changed the living environment of the hairtail, which would in turn affect its concentration, feeding and migration. Hairtail catches in the NSCS can be highly significantly fitted to fishing efforts and climatic variables (<em>R</em>²=0.958,<em>P</em><0.01). That is to say, changes of hairtail catches in the NSCS can be confidently attributed to a monotonic growth in fishing pressure and changes of the climatic environment. If the fishing pressure stays unchanged, the future climate changes and human activities that cause the increase of nutrients in the seas are likely to result in an increase in hairtail catches in the NSCS. Moreover, the increased frequency in extreme weather events that is predicted in the future may also cause larger fluctuations of hairtail catches.

Larval fish distribution, growth and feeding in Patagonian fjords: potential effects of freshwater discharge

In fjord systems, freshwater inputs occur by ice melting and river discharge, affecting seawater salinity along fjord and adjacent waters, and poten- tially the ecology of early life stages of marine fish occurring in the area. During austral spring 2008, a bio-oceanographic cruise was carried out in southern Chile between 47°00' and 50°09'S, an area influenced by Baker River discharge and ice melting of Northern and Southern Ice Fields, the largest glaciers from Patagonia. Surface salinity and temperature ranged from 1.22 to 32.80, and from 8.11 to 10.68°C, respectively. Larval lightfish Maurolicus parvipinnis (Sternoptychidae) and Falkland sprat Sprattus fuegen- sis (Clupeidae) were the dominant species, with abundances of 2.2-39.9 larvae 10 m �2 and 3.4-77.1 larvae 10 m �2 , respectively. Postflexion stages of both species were collected mainly in surface density fronts. Otolith-based growth analyses estimated linear growth rates of 0.136 mm day �1 for M. parvipinnis of 4.1-15.1 mm, and 0.448 mm day �1 for S. fuegensis of 5.4-20.5 mm. Recent Otolith Growth Index (ROGI), based on the residual analysis of the relationship between increment width of outermost five micro- increments and otolith radius, indicates that larval M. parvipinnis collected in low salinity waters showed a reduction of its recent growth rate compared those collected in saltier waters. Also, ROGI was positively correlated with salinity of the water column for larval M. parvipinnis. Gut content analysis showed that large larvae collected near sources of freshwater had lower number of prey in its guts and preyed on different items than fish larvae collected in saltier waters. Therefore, freshwater inputs from rivers and glaciers from Patagonia affected horizontal distribu- tion, recent growth and feeding of larval fish in fjords and channels of southern Chile.

Isotopic Correlation (δ18O versus δ13C) of Otoliths in Identification of Groundfish Stocks

AbstractThe management of many marine fish stocks suffers from a lack of genetic data or insignificant genetic differentiations, particularly for the commercially important groundfish along the U.S. Pacific coast. In this study, we investigated a large number of otoliths of various groundfish species from the coasts of Washington and Oregon and analyzed them for stable oxygen (18O/16O, or δ18O) and carbon isotope ratios (13C/12C, or δ13C). The isotopic results and correlation of δ18O versus δ13C of Pacific hake Merluccius productus, sablefish Anoplopoma fimbria, Pacific halibut Hippoglossus stenolepis, and Pacific cod Gadus macrocephalus indicated that most of the groundfish we examined had two or more spawning stocks or subpopulations; the only tested species that might belong to a single coastwide stock was yelloweye rockfish Sebastes ruberrimus. Compared with genetic methods of stock identification, the isotopic signatures of otoliths have distinct advantages in determining (1) a time series to separate the different life stages of marine fish and (2) the oceanographic and environmental conditions to which fish are exposed. Thus, stable isotopic signatures in otoliths appear to be an alternative for marine fish stocks when there is little genetic differentiation between populations or no genetic data are available.