The Gambia Estuary, a “normal” estuary with a decreasing salinity gradient from the mouth towards the head, is moderately exploited by small-scale fisheries and does not receive any severe pollution from either agriculture or industrial activities. Neither the Gambia River nor its estuary are artificially impounded. As the last large West African estuary free of major human disturbance, it is of considerable interest for comparative studies on the effect of major environmental perturbations in West African estuarine ecosystems. The aquatic environment and fish communities of the Gambia Estuary (about 250 km long) were studied by purse seine sampling at different periods in the river cycle, covering all hydro-climatic seasons that are characteristic of West African estuaries. Emphasis was placed on the diversity, composition, structure and distribution of fish assemblages in relation to fluctuations in physico-chemical factors such as water temperature, salinity and turbidity. Results on the aquatic environment, mainly the salinity range (from freshwater to 39) and dissolved oxygen (never a limiting factor for fish in the estuary) and on the main characteristics of the fish fauna (high diversity of life cycles, all the ecological categories represented) indicated that the Gambia Estuary was free of major climatic perturbation and reinforced the choice of this system as a reference for the study of the effects of major perturbations on estuarine tropical fish communities.

In the bay of Marennes-Oléron the dry flesh of Crassostrea gigas ranged from 29 to 52% proteins,10 to 23% ash, 6 to 20% lipids and 0 to 4% carbohydrates of which 48.3 ± 21.6% were glycogen. The energy value ranged from 18.84 to 23.47 joule.mg−1 ash free dry weight (mean 20.27 J.mg−1). Reproductive effort varied from 17.8 to 55.9% dry weight for males, and 43.1 to 61.9% for females during the first and third year of reproduction respectively. A high energy value for female gametes(23.47 to 26.24 J.mg−1 dry tissue) was mainly due to a higher level of lipids (17.3 to 23% of dry tissue) in female gametes as compared to that in male gametes (5.9 to 12.3% of dry tissue). During the period of mass-loss which began in October and finished in March, the poor trophic conditions of the environment resulted in the use of 74.6% of glycogen, 44% of lipids and 36% of proteins to meet more than 50% of the requirements for basal metabolism.

Data from single and multi-frequency active acoustic surveys conducted annually in the vicinity of the South Shetland Islands, Antarctica were re-analyzed using updated procedures for delineating volume backscattering due to Antarctic krill, adjusting for signal contamination due to noise, and compensating for diel vertical migration of krill outside of the acoustic observation window. Intra-and inter-seasonal variations in krill biomass density and dispersion were derived from the re-processed data set for surveys conducted in the austral summers of 1991/1992 through 2001/2002. Estimated biomass density ranged from 1 to 60 g m–2, decreasing from mid-range levels in 1991/1992 to a minimum in 1992/1993–1993/1994, increasing to a peak in 1996/1997–1997/1998, and decreasing again through 2000/2001–2001/2002. Although this variability may be attributed to changes in the spatial distribution of krill relative to the survey area, comparisons with the proportion of juvenile krill in simultaneous net samples suggest that the changes in biomass density are consistent with apparent changes in reproductive success. A truncated Fourier series fit to the biomass density time series is dominated by an 8-year cycle and predicts an increase in krill biomass density in 2002/2003 and 2003/2004. This prediction is supported by an apparent association between cycles in the extent of sea ice cover and per-capita krill recruitment over the last 23 years and indications that ice cover in the winter of 2002 is seasonally early and extensive.

An investigation was carried out into the PAH chemical contamination resulting from the “Erika” tanker fuel spillage of December 1999 along the French coast of the Bay of Biscay. A qualitative and quantitative assessment was conducted of this contamination in water, suspended particulate matter, sediments, and in intertidal molluscs. The chemical composition of PAHs in pre-spill and post-spill samples was determined and used to distinguish the “Erika's” fuel as the source of PAHs in the coastal environment of the Bay of Biscay. Changes in concentrations of PAHs were also assessed. The GC-MS analysis made it possible to identify and quantify parent unsubstituted PAHs, alkyl-substituted PAHs (C-PAH) and sulfur heterocycle unsubstituted and alkyl substituted compounds (SPAH and C-SPAH). The results of this study demonstrated that heavily oil-contaminated shorelines, including beaches, rocky coasts as well as sandy sediments apparently became reservoirs of spilled fuel and these continued to contaminate seawater, suspended particulate matter and mussels with PAHs. These conclusions were borne out by the following observations: (1) the pattern changes in PAH composition after the “Erika” oil spill were consistent in all contaminated compartments (water, suspended particulate matter SPM, intertidal sediments and molluscs), (2) the compositional patterns of PAHs after the “Erika” oil spill in contaminated water, SPM, intertidal sediments and molluscs constantly included alkyl-substituted phenanthrenes, pyrenes, chrysenes and sulfur heterocycle compounds in higher relative abundances than those in the pre-spill samples of these compartments, (3) the relative abundances of different suites of PAHs at contaminated sites were similar to those of weathered “Erika” fuel, (4) consistent and visible temporal decline in concentrations for water, SPM and molluscs, (5) the geographical contiguity of the stations with high concentrations of PAHs in molluscs matched the extent of the shoreline contamination by the spilled fuel.The increase in the contamination levels before and after the spill, together with the significant change in the pattern of PAH composition provide evidence of the intense and long-term chemical contamination of the “Erika's” fuel and of the damage to natural marine resources resulting from such contamination by toxic oil components.

Culture of sturgeons in Russia began in the second half of the 19th century. During the first part of the 20th century, a significant research effort was devoted to the control of reproduction and the rearing of larvae mostly for stock enhancement purpose in rivers. Large-scale construction of hatcheries began in the 1950s after the damming of rivers, and by the 1980s over 130 million 1–3-g juveniles per year were being produced from wild broodstock. Presently, the production is 100 million juveniles. Emphasis is now on optimising stocking results through consideration of fish-specific factors (e.g. behaviour, fitness, size, balance between species) as well as environmental variables (food availability, release sites, salinity, precipitation regime). Food fish production of sturgeon (market size is 1.5–2.0 kg is just beginning using captive broodstock and new growing technologies. In 2000, farm production was about 1650 t, which was higher than sturgeon landing from wild fisheries (1500 t declared in 2000).

An overview is given of our present knowledge on taxonomy, phylogeny and biogeography of catfishes or Siluroidei, one of the worlds economically important groups of fresh and brackish water fishes. In an introductory chapter, the taxonomic position of catfishes in the ichthyological classification is discussed; their external morphology is briefly described and synapomorphies showing their monophyly are listed. In the following chapter, cattish systematics are presented. Thirty three families with 416 genera and 2 584 species are presently recognized, but these numbers are continuously changing; it is therefore obvious that the systematics of many taxa are still rather poorly known. For each family, data (if any) supporting their monophyly are given together with a short description of their external morphology. The valid genera are listed, with for each genus, the number of presently recognized species with a reference (if any) to a recent revisionary study. Contributions to the phylogenetic study of catfishes are scarce, and dealing only with a few families and with a limited number of taxa within the families. As a resultsonly few data on catfish phylogeny are presently known. Therefore, also our knowledge on historicalbiogeography of catfishes is seriously limited, until more date become available on interfamilial and intergeneric relationships.

The functioning of estuaries relies on a natural dynamism imposed on these systems by riverine and marine influences. The increasing abstraction of fresh water from both large and small river catchments in southern Africa has had the effect of forcing some estuaries into artificial cycles, i.e. natural successions now have human imposed trajectories that are changing estuarine variability and forcing some systems into extreme states. The ichthyofauna has responded to these changes in a variety of ways. Where river flow has declined considerably, or ceased altogether for extended periods, fish recruitment has shown a considerable decrease. This can be related to the collapse in planktonic productivity which negatively affects zooplanktivorous fishes, as well as decreased amounts of olfactory cues entering the sea for the attraction of larval and juvenile marine fishes into these estuaries. Hypersaline conditions can result in both a reduced species diversity and abundance. However, where estuaries lose their normal estuarine salinity gradient and become “arms” of the sea, there is often an increase in fish species diversity due to stenohaline marine taxa entering the estuary. Unfortunately the gain in small numbers of marine stragglers is insufficient to compensate for the decline in estuarine dependent fishes that usually dominate these systems. Conversely, major river flooding often causes temporary decreases in both species diversity and abundance due to a rapid decline in salinity, increased suspended sediments, reduced dissolved oxygen levels, and a collapse in the availability of pelagic and benthic food resources. However, the “resetting” of estuaries by episodic events is part of the essential cycle that maintains and enhances estuarine productivity and habitat diversity. Recovery by estuary associated fishes from such events is usually rapid and linked to a variety of factors, especially estuary morphometry which has a direct influence on the flushing or retention of estuarine biota. Freshwater flows interact directly and indirectly with the fishes that inhabit estuaries, e.g. river floods directly influence estuarine morphometry, water temperature, salinity, pH, turbidity, nutrient status, organic inputs, dissolved oxygen concentrations and olfactory cues; and indirectly affect mouth status, tidal prism, habitat diversity, primary and secondary productivity, fish recruitment, food availability and competition. Depletion or removal of components of river flow to an estuary have major short and long-term negative impacts on the ichthyofauna, some of which can be ameliorated by the provision of an environmental freshwater allocation that is appropriate to that particular system.

Eggs from three distinct populations of walleye Stizostedion vitreum, one domesticated (London State Fish Hatchery) and two wild (Lake Erie and Salt Fork Reservoir), were compared in terms of total lipid content and fatty acid profiles (phospholipids and neutral lipids). The concentrations of total lipids in eggs from domesticated broodstock were significantly lower (8.6 ± 1.0 % of wet weight) than those of both wild populations (13.3 ± 0.9 % and 10.9 ± 0.6 % of wet weight for Lake Erie and Salt Fork Reservoir, respectively). The profiles of fatty acids in egg lipids differed significantly among the three investigated populations. Domesticated females fed a formulated diet produced eggs containing significantly higher levels of linoleic acid (18:2n-6), characteristic of plant lipids. However, arachidonic acid (20:4n-6), was at significantly higher levels in eggs of wild walleye stocks. Although eicosapentaenoic acid (20:5n-3) was detected at significantly higher levels in eggs from Lake Erie walleye, docosahexaenoic acid (22:6n-3), the most abundant in polar lipids, was found at similar levels in eggs of all three populations. Survival of walleye embryos was correlated with the concentrations of polyunsaturated long chain fatty acids. Our data suggest that deficiency in n-3 fatty acids might be associated with impaired development of walleye, and thus poor larval and juvenile viability.

Software, MOVIES-B, developed by IFREMER (Institut français de recherche pour l'exploitationde la mer), enables the recognition of echogram features as acoustic detection structures according to spatial-energetic contiguity criteria. These structures (shoals, plankton layers) are described by energetic, morphological, spatial and temporal descriptors. Specifying acoustic detections as individual shoals will allow shoal by shoal echo-integration and may lead to better biomass estimation and shoal species description. The conceptual and operational framework of MOVIES-B is presented in the first part of this paper. The second part presents preliminary work performed in order to assess the feasibility of classification and possible species identification of shoals using MOVIES-B software. This research has studied the data set obtained from four fisheries acoustic surveys, in the Bay of Biscay. The data set is a matrix of 29 descriptors from 13,122 shoals. A limited knowledge of species composition was obtained from trawling. Eight species were captured: Sardina pilchardus, Clupea harengus, Sprattus sprattus, Engraulis encrasicolus, Micromesistius poutassou, Trachurus sp., Scomber sp. and Capros aper. Cluster analysis and linear discriminant analysis were performed on trawled identified shoals data (808 shoals), after a reduction of the space descriptors by a stepwise technique. A partition into 6 clusters was carried out and clusters are described by species composition and continuous variables values. After grouping the six species shoals in two groups, 84% of shoals from the testing data set could be correctly classified using the linear discriminant function.

This paper presents a summary of information on reproduction biology in the scallop, Pecten maximus, which is required for the successful reseeding and intensive aquaculture programs developed in France since 1982. Data are presented on the following subjects: environmental factors that sustain gametogenic activity and the time of year this activity occurs; biochemical changes that are associated with gametogenesis; the consistency of egg quality; and development of a simple test to predict egg quality.

The Eastern Channel (ICES division 7d) is considered a unit for stock management of the common sole Solea solea and the plaice Pleuronectes platessa. At this scale, the aim of this work is to model the juvenile distribution of these flatfish. The database used, based on different surveys undertaken during the two last decades, includes 4500 coastal beam trawl hauls throughout the Eastern Channel coasts. Multivariate analyses are used to study the interannual fluctuations in flatfish recruitment of the region. This approach allows us to separate the Eastern Channel into homogeneous sectors with regard to these fluctuations. The physical parameters that contribute to the observed juvenile sole and plaice distributions are identified and their distributions are modelled using generalized linear models. The results of these models, and the areas of the different populations derived from a geographic information system, are used to identify the main nursery grounds and to compare their respective importance. This quantitative approach identifies the lack of estuarine dependence of the nursery grounds, and highlights those areas where anthropogenic disturbance could influence these populations.

We used a digital stereo-video camera system for three-dimensional monitoring of cultured Pacific bluefin tuna, Thunnus orientalis, swimming freely in a net cage. We estimated the fork length and length frequency distribution of individual fish using the direct linear transformation (DLT) method. Information obtained from stereo images is useful for managing the growth of tuna during rearing. Our aim was to develop a simple method involving a combination of DLT and commercial image-processing software to enable aquaculturists to obtain three-dimensional measurements of fish. In this study, we used a stereo-video camera system to evaluate the precision and validity of fish size estimates determined from repeated measurements. Of the total assessed individuals swimming within a distance of  <5.5 m from the camera system, estimates for 99% (106/107) were found to be valid, with an error ratio (standard error/mean) of  <5%. Therefore, we believe that our proposed simple method for monitoring free-swimming fish could be very useful for aquaculture management.

A reliable anaesthesia and sampling protocol for Pacific oysters will enable experiments to be conducted without sacrificing animals and will facilitate successive sampling of individuals for gametogenesis studies. As no such techniques were available for Crassostrea gigas, the present study aimed to define suitable anaesthetic conditions for use with this species. Three groups of ten oysters (mean weight ± SD, 32.1 ± 9.0 g) were anaesthetised in 5 L containers. Among different chemicals: benzocaine, eugenol and three different types of magnesium chloride (a laboratory one – Flucka® – and two designed for agriculture – DEUSA International® and Dead Sea Works®) and concentrations tested, one laboratory (concentration: 72 g L−1) and one agricultural (Dead Sea Works® 50 g L−1) type of magnesium chloride were the most effective, respectively inducing anaesthesia in 73 ± 3% and 80 ± 3$% after three hours. Lower oyster weight and a two day period of starving prior to treatment significantly increased the number of anaesthetised animals. Using this protocol, losses of 0 to 10% of oysters were observed one week after anaesthesia. Increasing anaesthesia duration from 3 to 16 h resulted in a significant increase in the number of anaesthetised oysters (from 50 ± 10 to 97 ± 7%) but no increase in mortality (7 ± 11%). On the other hand, reducing water temperature from 19.5 °C to 15.3 °C, resulted in a significant decrease in anaesthesia efficacy. A reliable anaesthesia protocol was developed: 100% of Pacific oysters are anaesthetised using 50 g L−1MgCl2 Dead Sea Work®for a 16 h duration. This long duration facilitates tissue sampling and does not increase the working time needed. This protocol was validated by monthly anaesthesia and gonad sampling during a three month period with the loss of only a single oyster. It can thus be used for routine applications.

Since 1991, fishing operations on tuna schools associated with drifting Fish Aggregating Devices (FADs) have become widespread in the purse seine fishery in the Gulf of Guinea. In the offshore South Sherbro area (0–5° N, 10–20° W), FAD-associated catches represent about 75 % of the total catch. This FAD fishery exploits concentrations of skipjack mixed with a smaller amount of bigeye and yellowfin tuna of similar size (46 cm), and some large yellowfin. Catches on unassociated tuna schools are mainly composed of large yellowfin in breeding phase and skipjack. Here we studied tuna diet in relation with the aggregation mode (FAD-associated or unassociated tuna schools), species, and size. The stomach contents of around 800 fish were analysed. Numerous empty stomachs were found, especially in fish caught under FADs. Diets were similar for all small-size tuna sharing the same aggregation type. Small tuna mainly feed on Vinciguerria nimbaria (Photichthyidae), a mesopelagic fish of the micronekton, whereas large tuna mainly feed on Scombridae, mixed with Cubiceps pauciradiatus (Nomeidae) when they were caught in unassociated schools. The feeding habits of tuna are discussed with emphasis on the behavior of V. nimbaria. Estimations of the daily ration of similarly sized tuna with the same aggregation mode were very close. The low estimated rations for small, FAD-associated tuna show that logs do not have a trophic function, but rather are a refuge. In contrast, FADs seem to influence the diet of large tuna because of the Scombridae prey that probably is associated to the FAD.

Changes in the morphology of the ovary are described during maturation and it is established that it is a homogeneous structure for sampling purposes at maturity stages four and five. Several aspects of vitellogenic oocyte growth and recruitement were examined as criteria to ascertain whether the annual fecundity can be determined in Solea solea just prior to spawning. The first criterion was whether a hiatus develops in the size frequency distribution between the previtellogenic and vitellogenic oocytes just prior to spawning. We were unable to demonstrate this feature in sole from division VIId (N = 5) or IVc (N = 5) but it was present in two out of five fish from division VIIe and all fish examined from division VIIa (N = 5) and IVb west (N = 5). The hiates occurred between 175 and 250 µm (cohort size 25 m) in the size frequency distribution and measured between 25 and 75 µm. Oocyte size frequency distribution from mid spawning and late spawning-spent sole from division IVc showed a hiatus in 9 out of 10 fish which became wider as the residual annual potential fecundity declined. Next the rate of recruitment and growth of vitellogenic oocytes was studied in sole sampled at monthly intervals (July 1993 to February 1994) from division VIId in relation to the start and duration of the annual spawning season. The growth rate of the leading oocyte cohort was 2.73 × 10−5 mm3 per day on 20 September and increased to 3.91 × 10−3 at a mean diameter of 839 µm by 10 February just prior to spawning. However, the observed maximum growth rate, even when adjusted for the positive influence of temperature, allowed little scope for previtellogenic oocytes to complete maturation during a spawning period of 60 days. The recruitment of viltellogenic oocytes was 3013 oocytes per day on 3 August and declined rapidly as spawning approached. In the three months prior to spawning no significant increase was found in the annual potential fecundity. An analysis of a sample of spawning fish from IVc demonstrated that 88% had less than 50% of their predicted potential fecundity remaining in the ovary. The mean batch fecundity was 8 400 (SE ± 13 363) and in conjunction with existing data on spawning frequency and duration gave a realised fecundity close to the potential fecundity. It is concluded that for all practical purposes the sole can be regarded as having a determinate fecundity in all the areas studied.

The regulation of potential fecundity by follicular atresia was assessed in pre-spawning and spawning sole. In ICES areas IV and VII the prevalence of atretic oocytes in pre-spawning fish varied between 0.04 and 0.69 and the relative intensity varied between 0.017 and 0.076. During spawning in division IVc the prevalence of atresia varied between 0.45 and 0.57 and the relative intensity between 0.022 and 0.058. If we assume a turnover rate of 9 days the loss from the potential annual fecundity, during spawning, in division IVc would be 12.4%.

The relationships of 25 different populations of the genus Barbus s. str. have been studied using different parsimony grouping methods and similarity indexes. The results indicate that Barbus s. str. is composed of two different groups. They are provisionally placed into two different subgenera (Barbus and Luciobarbus) in order to make the taxonomic work easier. The European species (B. barbus, B. plebejus, B. ciscaucasicus, B. cyclolepis, B. petenyi, B. haasi and B. meridionalis) are included in the subgenus Barbus. Within this group there are two evolutionary lines, one formed by central European species and the other by Mediterranean species which live in mountain fluvialcourses. The subgenus Luciobarbus is constituted by Iberian, northern African and Asian species. The relationships between them are not satisfactorily resolved. Two northern African species (B. nasus and B. magniatlantis) are not included in any subgenus, as their phylogenetic relationships are not clear enough. The fossil record of this genus has been reviewed and new remains from the middle Miocene of Spain are reported as being the earliest known fossils of the genus Barbus. The first known fossils of Luciobarbus date from the Upper Miocene in Spain, Africa and Asia. The dispersion of Barbus intwo main periods is postulated, one of them during the main Alpine orogenic phase at the end of theOligocene, the other during the Upper Miocene transgression. The first one maybe favoured Barbus and the second Luciobarbus. Barriers that might have fragmented the different populations of the genus Barbus have been evaluated and a comprehensive biogeographic model, which minimizes the dispersion events, is proposed.

A number of cephalopod species present substantial ecological and economical importance; however, data on the physiology of stress and on regulatory processes linking stress to immune defence against pathogens remain extremely scarce in these organisms. The present study examined the influence of a 5 min air exposure, a common perturbation associated with handling in aquaculture settings and fisheries, on neuroendocrine and immune parameters in the octopus Eledone cirrhosa. Measurements of circulating concentrations of noradrenaline and dopamine, two hormones that are released in the haemolymph during stress in bivalves and gastropods, showed that the 5 min air exposure represents a real stress to octopus. Indeed, blood levels of both hormones increased by about 2–2.5-fold in stressed animals. Concomitantly, a significant decrease in the number of circulating haemocytes was observed, whereas haemocyte phagocytotic activity and superoxide anion production increased transiently between 5 and 60 min after the beginning of the stress. These results provide a first insight into the effects of stress on catecholamine levels and immune functions in cephalopods and suggest that stress and immunity may be associated in these organisms.

An 84-day experiment assessed the combined effects of two fresh water quality levels (H: 1.71 ± 0.15 mg O2l−1 and 0.28 ± 0.01 mg l−1 total ammonia nitrogen (T-AN), L: 5.15 ± 0.07 mg O2l−1 and 0.54 ± 0.01 mg T-AN l−1) and 3 stabilized stocking densities: 24.8 ± 0.2, 74.2 ± 0.5 and 120.0 ± 0.9 kg m−3) on rainbow trout. Fish were fed using demand feeders with rewards proportional to stocking density. Mass increase was significantly affected by water quality and stocking density, being highest in H water and the lowest at 120 kg m−3. There was no significant difference in final weight between 25 and 74 kg m−3, but at 120 kg m−3 it was 27% and 19% lower in H and L water respectively than at 25 kg m−3. Feed intake (FI) from day 0–85 was significantly affected by water quality, 1.5% in H compared to 1.1–1.0 in L, but there were no significant differences in apparent feed conversion (AFC). FI was not significantly affected by stocking density but AFC was impaired, it increased with stocking density. Marked changes in fish morphology and composition were related to water quality: Condition K factor and fillet fat content were significantly higher in H than in L groups. Dorsal and pectoral fin condition was affected by stocking density and water quality: fins were significantly longer and less eroded in L groups and at low stocking density. Physiological measures were within the usual ranges, but differed between treatments. Changes in plasma osmolarity, hydromineral balance (Na+) and acid base balance (HCO3 –) showed that fish were more affected by water quality than by stocking density. There was no sign of acute stress in acclimated fish as cortisol and glycemia were similar under all experimental conditions. This study highlights the importance of water quality and feeding conditions when considering the effects of stocking density on fish welfare.

Hooking (or “at-haulback”) fishing mortality was analysed in elasmobranchs captured byPortuguese longliners targeting swordfish in the Atlantic Ocean. Information was collectedby on-board fishery observers who monitored 834 longline fishing sets between August 2008and December 2011, and recorded information on 36 067 elasmobranch specimens from 21different taxa. The hooking mortality proportions were species-specific, with some specieshaving relatively high percentages of live specimens at time of haulback (e.g., blueshark, crocodile shark, pelagic stingray, manta, devil and eagle rays), while others hadhigher percentages of dead specimens (e.g., smooth hammerhead, silky shark, bigeyethresher). For the most captured species (Prionace glauca, Pseudocarchariaskamoharai, Isurus oxyrinchus and Alopias superciliosus),logistic generalized linear models (GLMs) were carried out to compare the mortality ratesbetween sexes, specimen sizes and the regions of operation of the fleet. The sex-specificproportions of hooking mortality were significantly different for blue and crocodilesharks, with the males of both species having higher proportions of hooking mortality thanthe females. Specimen size was significant for predicting the hooking mortality for blueand shortfin mako sharks: in both cases, the larger specimens had lower odds of dying dueto the fishing process. There were differences in the hooking mortality depending on theregion of operation of the fleet, but those differences were also species-specific. Forblue and crocodile sharks, the hooking mortality was higher in the Equatorial and southernAtlantic areas (when compared to the NE Atlantic region), while the opposite was observedfor the shortfin mako, with lower mortality rates in the NE tropical area compared withthe other regions. The results presented in this paper can be integrated into futureecological risk assessment analysis for pelagic elasmobranchs. Furthermore, the newinformation can be used to evaluate the impact of recent recommendations prohibiting theretention of some vulnerable elasmobranch species.

The objective of this study was to investigate the impact of cadmium on the structure of gills and epipodites in late juvenile Penaeus japonicus. Cadmium titrations were performed by atomic absorption flame spectrophotometry, and structural observations were performed through light- and electron-microscopy. The cadmium concentration increased in different tissues (mainly gills, epipodites and hepatopancreas) according to the external cadmium concentration and the exposure time. The structural changes which occurred in the gill and epipodite cells appeared to be a function of cadmium accumulation in these tissues. Gill cells of shrimps exposed to 2 and 200 μg Cd·L−1 for 15 d did not display discernible structural changes. An increased number of nephrocytes was noted in gill filaments of shrimps exposed to 200 μg Cd·L−1. Exposure to 2 000 and 4 000 μg Cd·L−1 during 4 d resulted in profound structural changes. The epithelial cells were necrosed, disorganized and vacuolized. Exposure to 2 μg Cd·L−1 for 15 d did not result in discernible structural changes of epitodite cells. Exposure to 200 μg Cd·L−1 for 15 d, 2 000 and 4 000 μg Cd·L−1 during 4 d induced profound alterations of the epipodites: increased thickness, decreased number of apical microvilli, basal infoldings and mitochondria, occurrence of pseudomyelinic structures. These alterations are discussed in relation to the respiratory and osmoregulatory functions of gills and epipodites.