Early Life Stages Of Fish Research Articles

Stable isotope analysis reveal hidden reliance on scyphozoan jellyfish in a commensal fish: editorial comment on the feature article by D’Ambra et al.

often found in association with a diverse range of commensal organisms, including invertebrates (e.g. crabs, amphipods) and early life stages of fish, many of which are ecologically and economically important (Doyle et al. 2014). A long debate has revolved around the precise form of the primary relationship between commensal taxa and their jellyfish hosts. Does the host provide habitat in the form of a refuge for commensal taxa in the otherwise open pelagic habitat, allowing them to feed on prey from the surrounding waters whilst providing protection from predators? This seems reasonable, especially when the mobile refuge comes equipped with the added capacity to sting or kill potential predators. Alternatively, the host may also provide a source of food for commensal taxa: indeed commensal fish and other taxa have been observed to feed on their jellyfish hosts. Pulling the relative importance of these potential relationships (which are not mutually exclusive) apart has been complicated by the fact that gelatinous tissues are digested quickly and are not easily identified in gut or stomach contents (Arai et al. 2003). Furthermore, such tissues are considered to be of limited nutritional value (Pitt et al. 2009), and it has been generally considered that they do not contribute significantly to the diet of commensal fish (Purcell and Arai 2001). Hence, to date, many workers have concluded that the primary interaction between commensal taxa and their jellyfish hosts is likely to be one of the provisions of habitat. The feature article by Isabella D’Ambra and her coauthors successfully turns this assumption on its head, at least in the case of their study system. In a short but solid study, they examine the assimilated diet of Atlantic bumper (Chloroscombrus chrysurus), an abundant carangid fish from the Gulf of Mexico that lives commensally with jellyfish hosts (Aurelia sp. and Drymonema larsoni) during the fish’s juvenile life stage (Tolley 1987). Rather than examining stomach contents, D’Ambra et al. compared the stable We know very little about the ecology of jellyfish and other gelatinous zooplankton and how they interact with other taxa: many biologists consider that their role in ecosystems is likely underestimated (Pauly et al. 2009). As citizens and marine biologists, we are continually exposed to stories (via the news media and even the scientific literature) where jellyfish are shown in a negative light and even as indicators of impending ecological doom. The negative impacts of jellyfish blooms on aquaculture and fisheries are well documented, but sometimes I feel that we are approaching a point where (to some observers) the presence of normal densities of jellyfish in marine ecosystems is considered an indication of perturbation, even though jellyfish and associated taxa are natural components of such systems. Some marine biologists have worked hard to counter the consistent negative spin regarding jellyfish. Condon et al. (2013) examined the veracity of the well-reported global rise of jellyfish, and in a recent book chapter, Doyle et al. (2014) highlighted the positive side of jellyfish in terms of their important ecological roles and the goods and services they provide to human society. The wider public are well aware of the importance of jellyfish as prey to some charismatic megafauna including leatherback turtles and sunfish (although recent studies show that relationship between jellyfish and sunfish may be less clear than previously thought (Harrod et al. 2013; Nakamura and Sato 2014)). Less well known, at least by those not working on jellyfish, is the fact that individual jellyfish are

Diversity, distribution and nature of faunal associations with deep-sea pennatulacean corals in the Northwest Atlantic.

Anthoptilum grandiflorum and Halipteris finmarchica are two deep-sea corals (Octocorallia: Pennatulacea) common on soft bottoms in the North Atlantic where they are believed to act as biogenic habitat. The former also has a worldwide distribution. To assist conservation efforts, this study examines spatial and temporal patterns in the abundance, diversity, and nature of their faunal associates. A total of 14 species were found on A. grandiflorum and 6 species on H. finmarchica during a multi-year and multi-site sampling campaign in eastern Canada. Among those, 7 and 5 species, respectively, were attached to the sea pens and categorized as close associates or symbionts. Rarefaction analyses suggest that the most common associates of both sea pens have been sampled. Biodiversity associated with each sea pen is analyzed according to season, depth and region using either close associates or the broader collection of species. Associated biodiversity generally increases from northern to southern locations and does not vary with depth (∼100–1400 m). Seasonal patterns in A. grandiflorum show higher biodiversity during spring/summer due to the transient presence of early life stages of fishes and shrimps whereas it peaks in fall for H. finmarchica. Two distinct endoparasitic species of highly modified copepods (families Lamippidae and Corallovexiidae) commonly occur in the polyps of A. grandiflorum and H. finmarchica, and a commensal sea anemone frequently associates with H. finmarchica. Stable isotope analyses (δ13C and δ15N) reveal potential trophic interactions between the parasites and their hosts. Overall, the diversity of obligate/permanent associates of sea pens is moderate; however the presence of mobile/transient associates highlights an ecological role that has yet to be fully elucidated and supports their key contribution to the enhancement of biodiversity in the Northwest Atlantic.

Assessment of trifloxystrobin uptake kinetics, developmental toxicity and mRNA expression in rare minnow embryos

Trifloxystrobin (TFS) is the widely used strobilurin fungicide. However, little information is so far available regarding the uptake kinetics and developmental toxicity of TFS to fish. The present study was conducted to investigate the uptake kinetics, potential environment risk and toxicity of TFS on Gobiocypris rarus embryos. Results revealed that increased malformation, decreased body length and heart rate, affected spontaneous movement and swimming speed provide a gradual concentration-dependent manner; values of 144h LC50 (median lethal concentration) and EC50 (median effective concentration) were 1.11 and 0.86μgL−1. Continuous exposure to TFS resulted in a steady accumulation with no evidence of elimination. Enzyme activities were significantly changed; reactive oxygen species and DNA damage were significantly induced after TFS treatment. Certain genes related to cell apoptosis (p53), metabolism (cyp1a), stress response (hsp70) and blood vessels (vezf1) development were all significantly up-regulated. This is the first study to define uptake kinetics and to focus on behavioral consequences, physiological changes and mRNA expression following TFS exposure in the early life stages of fish. Our results suggest that TFS is highly toxic to fish embryos.

Development toxicity of functionalized single-walled carbon nanotubes on rare minnow embryos and larvae

Carbon nanotubes (CNTs) are widely used in industrial and commercial applications, but few studies systematically evaluate their developmental toxicity on aquatic organism. Using rare minnow (Gobiocypris rarus) at early life stages as experimental models, developmental toxicity of functionalized single-walled CNTs (SWCNTs) was investigated following exposure to 0–320 mg/L for 144 h. Results revealed that significantly increased in mortality and malformation was only observed after hatching. Decreased body length, heart rate and swimming speed provide a concentration-dependent manner on larvae; values of 144 h LC50 and EC50 were 140.8 and 109.8 mg/L, respectively. Antioxidant enzyme activities (superoxide dismutase, catalase and glutathione S-transferase) and antioxidant enzyme related mRNA expressions were significant changed; cell apoptosis activities (caspase-3, -8, -9) and cell apoptosis related mRNA expressions were significant up-regulated; reactive oxygen species and DNA damage were significantly induced when the concentration of SWCNTs above 100 mg/L. Fluorescence and electron microscopy sliced observation show that SWCNTs were well dispersed in larvae within 0.5 h, eventually cleared from the larvae at 144 h. This is the first study to define uptake kinetics and to focus on behavioral consequences, physiological changes and mRNA expression following SWCNTs exposure in the early life stages of fish. The results obtained in the present study demonstrated that functionalized SWCNTs have the potential to affect aquatic life when released into the aquatic environment and reached high concentration. In the increasing economical context of SWCNTs, complementary studies must be undertaken, especially including mechanistic and environmental investigations.

Estimating the impact of petroleum substances on survival in early life stages of cod (Gadus morhua) using the Dynamic Energy Budget theory

To estimate the impact of accidental oil-spills on cod fisheries a model framework is developed in which a Dynamic Energy Budget (DEB) model is applied to assess mortality caused by petroleum substances in early life stages. In this paper we report on a literature search and DEB analyses, aiming for cod specific DEB-parameters. Furthermore, we explored the relevance of Fathead minnow DEB-parameters as surrogate by comparing LC50 values calculated from DEB-parameters with literature. Cod specific DEB-parameters could not be estimated based on available literature. LC50 values calculated from Fathead minnow DEB-parameters were higher than literature LC50 for early life stages of fish. Applying an extrapolation factor of 50 to the DEB-parameters resulted in LC50 values that were below literature irrespective of life stage. Therefore, we propose to use the last as an estimate for early life stages in cod and recommend relevant experiments with individual petroleum substances on cod.

In situ and laboratory toxicity of coalbed natural gas produced waters with elevated sodium bicarbonate.

Some tributaries in the Powder River Structural Basin, USA, were historically ephemeral, but now contain water year round as a result of discharge of coalbed natural gas (CBNG)-produced waters. This presented the opportunity to study field sites with 100% effluent water with elevated concentrations of sodium bicarbonate. In situ experiments, static renewal experiments performed simultaneously with in situ experiments, and static renewal experiments performed with site water in the laboratory demonstrated that CBNG-produced water reduces survival of fathead minnow (Pimephales promelas) and pallid sturgeon (Scaphirhynchus albus). Age affected survival of fathead minnow, where fish 2 d posthatch (dph) were more sensitive than 6 dph fish, but pallid sturgeon survival was adversely affected at both 4 and 6 dph. This may have implications for acute assays that allow for the use of fish up to 14 dph. The survival of early lifestage fish is reduced significantly in the field when concentrations of NaHCO(3) rise to more than 1500 mg/L (also expressed as >1245 mg HCO(3) (-) /L). Treatment with the Higgin's Loop technology and dilution of untreated water increased survival in the laboratory. The mixing zones of the 3 outfalls studied ranged from approximately 800 m to 1200 m below the confluence. These experiments addressed the acute toxicity of effluent waters but did not address issues related to the volumes of water that may be added to the watershed.

Larval fish assemblage recovery: a reflection of environmental change in a large degraded river

AbstractEstuaries are globally important to fisheries but face many anthropogenic stressors that reduce water quality and degrade benthic habitat. The Maumee River estuary has been degraded by industrial contaminants, high sediment and nutrient loads, channelization and elimination of surrounding wetlands, lessening its value as spawning habitat for fishes of Lake Erie. Regulation and better management practices (BMPs) in the watershed have improved the water quality in this estuary, which should result in a response of the biotic community. We compared recent (2010/2011) larval fish assemblage data to similar data from the 1970s (1976/1977) in order to identify changes due to improved water and habitat quality. Family‐level diversity was greater in recent study years compared to the 1970s and family richness increased from 6 to 10. In addition, the abundance of lithophilic spawning fishes was significantly greater in the recent study years. Increased diversity and family richness were consistent with increased water quality in the Maumee River whereas the observed increase in abundance of lithophilic spawners was consistent with an increase in the amount or quality of benthic habitat used by species in these families for spawning. Better wastewater management and agricultural practices in coastal watersheds can benefit the early life stages of fishes, thus benefitting coastal fisheries. Furthermore, larval fish assemblages may be useful indicators of biological integrity because of their sensitivities to environmental change. Routine sampling of estuarine larval fish assemblages could provide practitioners with insight into ecosystem changes and measure the response of the biotic community to restoration.

Impact of dietary selenium on methylmercury toxicity in juvenile Atlantic cod: A transcriptional survey

Selenium (Se) and its derivatives are known to have protective effects against mercury (Hg) toxicity in mammals. In this study we wanted to evaluate whether Se co-exposure affect the transcription of methylmercury (MeHg) toxicity-relevant genes in early life stages of fish. Juvenile Atlantic cod were exposed to regular feed (control), Se-spiked feed (3mg Sekg−1), MeHg-spiked feed (10mg Hgkg−1) or to Se- and MeHg-spiked feed (3mg Sekg−1 and 10mg Hgkg−1, respectively) for ten weeks. Liver tissue was harvested for transcriptional analysis when the fish were weighing 11.4±3.2g. Accumulated levels of Hg in liver of the two groups of fish exposed to MeHg were 1.5mg Hgkg−1 wet weight, or 44-fold higher than in the control group, while the Se concentrations differed with less than 2-fold between the fish groups. Selenium co-exposure had no effect on the accumulated levels of Hg in liver tissue; however, MeHg co-exposure reduced the accumulated level of Se. Dietary exposure to MeHg had no effect on fish growth. Interaction effects between Se and MeHg exposure were observed for the transcriptional levels of CAT, GPX1, GPX3, NFE2L2, UBA52, SEPP1 and DNMT1. Significant effects of MeHg exposure were seen for DNMT1 and PPARG, while effects of Se exposure were seen for GPX4B and SEPP1A, as well as for DNA methyltransferase activity. The transcriptional results suggest, by considering up-regulation as a proxy for negative impact and at the tested concentrations, a pro-oxidative effect of Se co-exposure with MeHg, rather than an antioxidative effect.

Assessing the quality of four inshore habitats used by post yolk‐sac Alosa sapidissima (Wilson 1811) in the Hudson River: a prelude to restoration

AbstractHabitat restoration within large rivers to enhance early life stages of fish is an emerging field. Prior to restoration, assessment of what constitutes “good” habitat is needed. We exemplify this with a study of larval Alosa sapidissima (American shad) in the Hudson River estuary in New York State, United States, which examines the quality of four main shallow water habitat types that have been reduced greatly by dredging activities. The larval stage has been identified as a sensitive period in need of mortality reduction. Habitats were examined as nursery habitat by comparing ambient conditions to known suitability indexes and by comparing relative abundance, loss rate, daily growth, and relative condition among habitats. Areas of lower velocity had greater abundances of shad ≤15.0 mm in length and shad growth was significantly higher. As shad became larger, those in areas of higher velocity had significantly higher relative condition, suggesting a shift in habitat use as larvae metamorphose into the juvenile stage. Contiguous backwater and secondary channel habitats had reduced loss rates during 2011 when there was high river discharge. No single habitat type examined in this study was found to be overall poor quality, and it is recommended that restoration sites be examined on an individual basis. More broadly, habitat diversity appears needed both for within‐year ontogeny as well as for longer‐term resiliency in the face of disturbance, such as storm‐driven high flows.

An evaluation of fish early life stage tests for predicting reproductive and longer-term toxicity from plant protection product active substances.

The chronic toxicity of chemicals to fish is routinely assessed by using fish early life stage (ELS) test results. Fish full life cycle (FLC) tests are generally required only when toxicity, bioaccumulation, and persistence triggers are met or when there is a suspicion of potential endocrine-disrupting properties. This regulatory approach is based on a relationship between the results of fish ELS and FLC studies first established more than 35 yrs ago. Recently, this relationship has been challenged by some regulatory authorities, and it has been recommended that more substances should undergo FLC testing. In addition, a project proposal has been submitted to the Organisation for Economic Cooperation and Development (OECD) to develop a fish partial life cycle (PLC) test including a reproductive assessment. Both FLC and PLC tests are animal- and resource-intensive and technically challenging and should therefore be undertaken only if there is clear evidence that they are necessary for coming to a regulatory decision. The present study reports on an analysis of a database of paired fish ELS and FLC endpoints for plant protection product active substances from European Union draft assessment reports and the US Environmental Protection Agency Office of Pesticide Programs Pesticide Ecotoxicity Database. Analysis of this database shows a clear relationship between ELS and FLC responses, with similar median sensitivity across substances when no-observed-effect concentrations (NOECs) are compared. There was also no indication that classification of a substance as a mammalian reproductive toxicant leads to more sensitive effects in fish FLC tests than in ELS tests. Indeed, the response of the ELS tests was generally more sensitive than the most sensitive reproduction NOEC from a FLC test. This analysis indicates that current testing strategies and guidelines are fit for purpose and that there is no need for fish full or partial life cycle tests for most plant protection product active substances.

Oil Pollution in the Marine Environment II: Fates and Effects of Oil Spills

Part I of this three-part set of articles focused on the various types and amounts of oil inputs to the marine environment. The complexity of the mixture of chemicals making up crude oils, fuel oil...

An experimental study of Aurelia aurita feeding behaviour: Inference of the potential predation impact on a temperate estuarine nursery area

Temperate estuaries are nursery areas for economically important fisheries resources. The common jellyfish Aurelia aurita is a resident species in many of these areas, where it can reach high abundances. This work aimed to determine the potential for predation of A. aurita on zooplanktonic organisms and early life stages of fishes, measuring feeding rates at concentrations that mimic those occurring for zooplankton, fish eggs and larvae in an estuarine nursery area. A set of experiments was aimed at determining the feeding selectivity of jellyfish when offered a mixture of fish eggs and larvae and wild plankton. Clearance rates varied markedly with prey availability and concentrations. When given mixtures of different prey types, jellyfish preferentially elected some taxa (copepods and fish eggs). Data obtained in the laboratory experiments were used to infer the potential impact of jellyfish predation upon zooplankton and ichthyoplankton in the Guadiana estuary (Southern Iberia). Repeated sampling of zooplankton, fish eggs and medusae was undertaken during the summer season of 2011. Abundance determinations were combined with experimentally estimated clearance rates of individual medusa to infer the potential jellyfish-induced mortality on prey in the area. In June and early August jellyfish-induced mortality rates were very high, and half-life times (t1/2) were consequently short for the zooplankton and ichthyoplankton. Although the potentially overestimation of our feeding rates typical of confined laboratory experiments, the results show high ingestion and clearance rates at high temperatures, typical from summer condition, and results also suggest that either by predation on early life stages of fish, or by competition for food resources, jellyfish may have a significant impact on estuarine communities and its nursery function.

The effects of dietary xylooligosaccharide on mucosal parameters, intestinal microbiota and morphology and growth performance of Caspian white fish (Rutilus frisii kutum) fry

The present study investigates the effects of different levels of dietary xylooligosaccharide (XOS) on skin mucus bactericidal activity and protein content, intestinal microbiota and morphology as well as growth performance of Caspian white fish (Rutilus frisii kutum) fry. The specimens (1.54 ± 0.03 g) were fed experimental diets supplemented with different levels of XOS [0% (control), 1%, 2% and 3%] for 8 weeks. The results revealed that feeding on XOS significantly increased skin mucus antibacterial activity and protein levels (P < 0.05) and the highest levels were observed in 3% XOS treatment. The total autochthonous intestinal heterotrophic bacteria significantly increased following XOS administration in diet (P < 0.05). Administration of 2 or 3% XOS in fry diet significantly elevated the autochthonous lactic acid bacteria (P < 0.05). However, dietary XOS had no significant effect on intestinal morphology, growth performance and diet utilisation of Caspian white fish fry (P > 0.05). These results demonstrate beneficial effects of dietary XOS on different parameters of mucosal immunity (both skin mucus and intestinal microbiota) and encourage further studies regards various aspect of XOS administration in early life stages of fish.

Physical–biological coupling and the challenge of understanding fish recruitment in freshwater lakes

Marine fisheries recruitment research has emphasized approaches that explore physical–biological interactions during early life stages (ELS). Herein, we review evidence that such approaches would benefit our understanding of fish recruitment in large freshwater lakes, which exhibit similar physical processes and contain fishes with comparable life-history characteristics as marine ecosystems. A review of the primary literature (1965–2008) for freshwater and marine ecosystems revealed that coupled biophysical research on fish ELS (i) has benefited our ability to understand and predict fish recruitment in marine ecosystems; (ii) has been virtually absent from small lake ecosystems but has been growing in the Laurentian Great Lakes; and (iii) has shown that similar to marine ecosystems, physical processes can control fish recruitment in large lakes through direct and indirect pathways, often involving interactions between biological processes and physicochemical conditions. In addition to identifying specific research gaps and opportunities, this perspective points to the need for increased research on physical–biological coupling in large lake ecosystems, as well as the continued erosion of barriers between marine and freshwater fisheries recruitment science.

Developmental toxicity of PAH mixtures in fish early life stages. Part I: adverse effects in rainbow trout

A new gravel-contact assay using rainbow trout, Oncorhynchus mykiss, embryos was developed to assess the toxicity of polycyclic aromatic hydrocarbons (PAHs) and other hydrophobic compounds. Environmentally realistic exposure conditions were mimicked with a direct exposure of eyed rainbow trout embryos incubated onto chemical-spiked gravels until hatching at 10 °C. Several endpoints were recorded including survival, hatching delay, hatching success, biometry, developmental abnormalities, and DNA damage (comet and micronucleus assays). This bioassay was firstly tested with two model PAHs, fluoranthene and benzo[a]pyrene. Then, the method was applied to compare the toxicity of three PAH complex mixtures characterized by different PAH compositions: a pyrolytic extract from a PAH-contaminated sediment (Seine estuary, France) and two petrogenic extracts from Arabian Light and Erika oils, at two environmental concentrations, 3 and 10 μg g(-1) sum of PAHs. The degree and spectrum of toxicity were different according to the extract considered. Acute effects including embryo mortality and decreased hatching success were observed only for Erika oil extract. Arabian Light and pyrolytic extracts induced mainly sublethal effects including reduced larvae size and hemorrhages. Arabian Light and Erika extracts both induced repairable DNA damage as revealed by the comet assay versus the micronucleus assay. The concentration and proportion of methylphenanthrenes and methylanthracenes appeared to drive the toxicity of the three PAH fractions tested, featuring a toxic gradient as follows: pyrolytic < Arabian Light < Erika. The minimal concentration causing developmental defects was as low as 0.7 μg g(-1) sum of PAHs, indicating the high sensitivity of the assay and validating its use for toxicity assessment of particle-bound pollutants.

Developmental toxicity of PAH mixtures in fish early life stages. Part II: adverse effects in Japanese medaka

In aquatic environments, polycyclic aromatic hydrocarbons (PAHs) mostly occur as complex mixtures, for which risk assessment remains problematic. To better understand the effects of PAH mixture toxicity on fish early life stages, this study compared the developmental toxicity of three PAH complex mixtures. These mixtures were extracted from a PAH-contaminated sediment (Seine estuary, France) and two oils (Arabian Light and Erika). For each fraction, artificial sediment was spiked at three different environmental concentrations roughly equivalent to 0.5, 4, and 10 μg total PAH g(-1) dw. Japanese medaka embryos were incubated on these PAH-spiked sediments throughout their development, right up until hatching. Several endpoints were recorded at different developmental stages, including acute endpoints, morphological abnormalities, larvae locomotion, and genotoxicity (comet and micronucleus assays). The three PAH fractions delayed hatching, induced developmental abnormalities, disrupted larvae swimming activity, and damaged DNA at environmental concentrations. Differences in toxicity levels, likely related to differences in PAH proportions, were highlighted between fractions. The Arabian Light and Erika petrogenic fractions, containing a high proportion of alkylated PAHs and low molecular weight PAHs, were more toxic to Japanese medaka early life stages than the pyrolytic fraction. This was not supported by the toxic equivalency approach, which appeared unsuitable for assessing the toxicity of the three PAH fractions to fish early life stages. This study highlights the potential risks posed by environmental mixtures of alkylated and low molecular weight PAHs to early stages of fish development.

English

Determination of early life stages of fish for thermal tolerance, optimum temperature for growth, rate of oxygen consumption is becoming essential for aquaculture industry in the climate change scenario due to long-term and short term (seasonal and diurnal) variability in temperature. Emphasis was made to understand the response of early of rohu (0.09 to 0.1 g) to thermal acclimation. Three hundred early fry stage rohu, Labeo rohita (initial weight 0.097&plusmn;0.01 g) were equally distributed at four different temperatures (28, 30, 32 and 34&deg;C) each with three replicates for a period of 40 days. Highest body weight gain was between 30 and 32&deg;C and lowest feed conversion ratio (FCR) was at 30&deg;C. The percentage weight gain and specific growth rate at 30&deg;C were 382&plusmn;8.01 and 0.88&plusmn;0.03% respectively, significantly higher than other acclimation temperatures. Thermal tolerance and oxygen consumption rate were analyzed to determine the temperature tolerance limits and metabolic activity at four acclimation temperatures. Critical thermal maxima (CTmax) was 42.86&plusmn;0.04, 43.3&plusmn;0.02, 44.45&plusmn;0.02 and 45.42&plusmn;0.03; critical thermal minima (CTmin)&nbsp; was 13.07&plusmn;0.04, 14.35&plusmn;0.02, 14.92&plusmn;0.04 and 15.64&plusmn;0.03 and oxygen consumption rate was 110.75&plusmn;0.44, 126.57&plusmn;0.60, 146.22&plusmn;0.68, 166.47&plusmn;0.86 mgO2 kg-1h-1 at 28, 30, 32 and 34&deg;C respectively and increased with increasing acclimation temperatures. Oxygen consumption rate for four acclimatization temperatures increased significantly, 110.75&plusmn;0.44, 126.57&plusmn;0.60, 146.22&plusmn;0.68, 166.47&plusmn;0.86 mgO2 kg-1h-1 at 28, 30, 32 and 34&deg;C respectively. Temperature preference of the early fry of rohu derived from relationship between acclimation temperatures and Q10 values for 28 to 30&deg;C, 30 to 32&deg;C, 32 to 34&deg;C were 1.94, 2.05, and 1.91 respectively. The optimum temperature range for growth was 30 to 32&deg;C and Q10 value was 32 to 34&deg;C. Survival at different acclimation temperatures was between 98.7&plusmn;2.31, 96.0&plusmn;4.0, 93.3&plusmn;2.31 and 94.7&plusmn;4.62%, from lower to higher acclimation temperatures. Key words: Acclimation temperature, critical temperature, critical thermal maxima (CTmax), critical thermal minima (CTmin), Labeo rohita.

Limitations of waterborne exposure of fish early life stages to BDE-47

2,2′,4,4′-Tetrabromodiphenyl ether (BDE-47) is acknowledged as the most abundant congener of all polybrominated diphenyl ethers (PBDEs). Despite its limited residence in the water column, most ecotoxicological research using fish early life stages (ELS) has focused on its waterborne bioavailability. These studies have been supported either by chemical analysis in solutions or in tissues after ≤168h exposures to relatively high waterborne concentrations with dimethyl sulfoxide (DMSO) as solvent carrier (≤0.5%). Using noninvasive physiological and anatomical features in medaka ELS, we investigated the viability of waterborne BDE-47 exposures (100–10,000μg/L; 1% DMSO) and evaluated the developmental effects in relation to the actual BDE-47 present in water. Embryos were exposed for 10 days under semi-static (24-h renewal) conditions and waterborne BDE-47 concentrations (i.e., dissolved) were quantitated daily and their accumulation in eleutheroembryonic tissues was analyzed 4 days after exposures finished. BDE-47 in solution rapidly decreased after each renewal by >50% in 24h. This was confirmed by discernible precipitation occurring at ≥5000μg/L on the bottom of the container and attached to the chorionic filaments of eggshell. The fast dissipation from water may explain why, besides the subtle, yet significant effects on post-hatching growth (short length at ≥5000μg/L), no other significant deleterious developmental effects were observed despite the fact that BDE-47 accumulated in tissues in response to BDE-47 treatment. Waterborne BDE-47 exposure was unachievable under traditional semi-static exposure conditions, but was achievable in repeated pulse exposures lasting a few hours whenever the medium was renewed. Hence, this research encourages the use of alternate – more realistic – exposure routes (e.g., particulate matter or sediments) when evaluating early developmental toxicity of BDE-47 or any other PBDE sharing similar properties.

The early life history of fish—there is still a lot of work to do!

Abstract The themed set of articles that follows this introduction contains a selection of the papers that were presented at the 36th Annual Larval Fish Conference (ALFC), convened in Osøyro, Norway, 2–6 July 2012. The conference was organized around four theme sessions, three of which are represented with articles in this collection: “Assessing the relative contribution of different sources of mortality in the early life stages of fishes”; “The contribution of mechanistic,behavioural, and physiological studies on fish larvae to ecosystem models”; “Effects of oil and natural gas surveys, extraction activity and spills on fish early life stages”. Looking back at the main themes of earlier conferences about the early life history of fish reveals that they were not very different from those of ALFC2012. Clearly, we still have a lot of work to do on these and other topics related to the biology and ecology of fish early life stages.

해수 중 이산화탄소의 증가가 감성돔( Acanthopagrus schlegelii)의 초기성장에 미치는 영향

Since the industrial revolution, seawater has increased in temperature and acidity due to the increase in anthropogenic carbon dioxide in the atmosphere. To understand the effect of elevated <TEX>$CO_2$</TEX> on the early life stages of fish, we reared fertilized eggs of black sea bream Acanthopagrus schlegelii under three <TEX>$CO_2$</TEX> concentrations (400, 850 and 1550 ppm) for 3 weeks. The standard length and wet weight of black sea bream larvae declined with enhanced <TEX>$CO_2$</TEX> concentration in the rearing water (P<0.05). However, chemical analysis using ICP-OES on internal tissues of black sea bream larvae indicated that the whole-body calcium concentration increased with <TEX>$CO_2$</TEX> concentration in the rearing water. These conflicting results suggest that future experiments should examine the acid-base balance to investigate the formation of bone and otolith during larval growth.