The catch from bottom longline stations sampled from a series of research cruises around Lanzarote and Fuerteventura (Canary Islands, NE Atlantic) was analysed in terms of fish distribution, density and diversity. The distribution of the number of species and individuals caught per station appeared to fit well the Poisson and Exponential distribution function, respectively. In particular, the parameter of the Poisson’s distribution appeared to provide an index of the point (at station scale) diversity, and its confidence interval, allowing for statistical comparisons. The relationships between point diversity, the alpha diversity (in the depth strata) and the beta diversity (along the depth gradient) were investigated. Around the islands, the density and the point diversity of the predator fish declined with depth down to about 800 m and then increased in the deeper stratum. The alpha diversity was the lowest in the deeper stratum but the taxonomic distinctness was similar to that of shallower strata. The beta diversity showed some faunal breaks along the depth gradient. The carnivorous fish fauna can be understood as comprised of three major assemblages: shelf, upper slope and mid-slope that are different both in terms of species composition and point, alpha and beta diversities. The relevance of this simple method for ecological studies of fish assemblage in the context of non-trawlable grounds is discussed, in particular for the slope and other areas of established or developing deep-water fisheries.

We analysed spatial and temporal patterns of condition factor (CF) of sprat (Sprattus sprattus) between 1986 and 2000 in different areas of the Baltic proper. Results showed a moderate increase in CF between 1986 and 1989. Afterwards, an abrupt decrease in CF, between 22% and 29%, occurred in all the areas of the Baltic proper. However, from 1998 and onwards, CF increased compared to the previous years. Weight-at-age and CF of Baltic herring showed a similar pattern in the same period. Several factors affecting variability of sprat CF were evaluated. Data showed that sprat CF was density-dependent and possibly related to the pelagic fish abundance and individual food intake. Temperature did not influence sprat CF while salinity seemed to affect variability of sprat CF in the northern Baltic proper. Changes in salinity levels may shape pelagic fish growth rates both indirectly changing the zooplankton community structure and abundance and/or directly via fish physiology and metabolisms.

This work is aimed at demonstrating the influence of insulin in the triggering of hepatic cholestasis in young gilt-head sea bream larvae reared under experimental conditions. The results are based on an immunological assay of insulin and an ultrastructural study of the yolk syncytial layer and the liver. Compared to fed larvae, fasting gilt-head sea bream larvae displayed a substantial increase in insulin level correlated with dysfunction of the yolk syncytial layer and hepatic histopathology. This correlation was verified in larvae reared in sea water containing insulin. Ultrastructural observations suggested that insulin affects lipoprotein secretion by the yolk syncytial layer. The failure of plasmatic lipoproteins would then cause dysfunction of the biliary lipid secretion mechanisms and, hence, trigger hepatic cholestasis. These results in gilt-head sea bream show for the first time the influence of insulin in the triggering of hepatic cholestasis during the early development of a vertebrate.

At present, European marine fish farming is based on sea bream and sea bass. A trend for diversification is sustained by the diversity of environmental conditions, by the availability of new production techniques such as recirculating systems, by an increase in rearing yields, by new market trends and by the possibilities to reduce risks of disease outbreak. Already reared fish species were chosen considering a limited number of criteria such as a high selling price and the availability of juveniles or breeders in the wild. This paper proposes a new selection method of fish species as candidates for aquaculture development on the French Atlantic, the Channel and the North Sea coasts. Using a three-phase procedure, candidates were selected among 20000 fish species. Final classification was carried out using a panel of 22 criteria, taking into account inquiries conducted in France with aquaculturists but also with the main actors of distribution and transformation channels and with consumers. Cod (Gadus morhua) was selected by the present work as the first candidate for aquaculture development on the western coasts of France. This work also highlights the high interest of Gadoids for aquaculture development in this area.

In the English Channel, the French cuttlefish landings of the smallest commercial category (body weight < 100 g) indicate that recruitment begins in autumn. Samples of recruits were collected in the Port-en-Bessin (Normandy) fish market once every fortnight from October to December 2000 to determine age-at-recruitment and juvenile growth variability. In addition, pre-recruit samples (mantle length: 53–90 mm) were collected in the Bay of Seine from August. Age was determined by statolith analysis: daily growth increments on the statolith lateral dome were observed under a light microscope. Increments were counted automatically, and manually when necessary, using the image analysis software TNPC. Readable statoliths were obtained in 236 cuttlefish, which revealed changes in age-at-recruitment during the study period. The cohort 2000 is recruited at an age ranging between 2 and 5.5 months (the bulk of recruits are 60–120 d old) and an increasing trend in average age is observed in autumn. The duration of the hatching period was derived from back-calculated hatching dates. A main hatching peak was observed between June and August. Juvenile growth variability was analysed at the individual level and between batches of hatchlings. Growth rates suggest that early hatched individuals grow faster than animals hatched later in the summer.

In the present study, norepinephrine (NE), epinephrine (E), dopamine (DA) and 5-hydroxy-tryptamine (5HT) have been quantified by high performance liquid chromatography (HPLC) in Pecten maximus during larval and post-larval development. With average values ranging from 2 to 5 pg μg–1 of protein, NE remained low through the whole larval life, while epinephrine (E) was undetected. DA and 5HT were the most abundant monoamines with significant variations between larval, pre-metamorphic and post-larval stages. During the first 20 days, corresponding to D larval and umboned larval stages, levels of DA and 5HT increased from 15 to 30 and 10 to 15 pg μg–1 of protein, respectively. Then during the last week of larval life, at the approach of metamorphosis, DA rose sharply from 30 to 50 pg μg–1 of protein and 5HT from 15 to 50 pg μg–1 of protein. Lastly during the first week of post-larval life (day 27 to day 34) DA and 5HT contents declined to levels similar to those detected in the first days of larval life reaching progressively 1 pg μg–1 of protein during the second week of post-larval life (day 34 to day 55). These rapid and transient variations in monoamine contents (5HT and DA) around metamorphosis, present a great interest. However, this relation between neurochemical changes and metamorphosis must be confirmed with future studies in order to verify if such monoamines might be used as indicators of larval competence in P. maximus, a commercially important species.

Gonadal neoplasms (germinomas) in softshell clams, Mya arenaria, have only been reported from locations in Maine, USA despite the fact that the geographic range of M. arenaria extends from Labrador to North Carolina on the east coast of North America. To more accurately determine the geographic distribution of this disease, adult clams (n = 18–60 per sample) obtained between 1989 and 1997 from sites along the entire coast of Maine and from Atlantic Canada (New Brunswick, Nova Scotia, and Prince Edward Island) were examined histologically for the presence of neoplasia. Gonadal neoplasms were present at 10 of the 28 locations sampled, including sites in Maine, New Brunswick, Nova Scotia, and Prince Edward Island, at prevalences ranging from 3.3 to 50% and at all stages of development. Prevalence and stage of development, however, were consistently greater at sites located between Penobscot Bay, Maine and Passamaquoddy Bay, New Brunswick. There was no correlation between mean clam size (shell length) and prevalence. Clams with neoplasia were predominantly female. To assess possible disease transmissibility and subsequent mortality rates, naïve clams were transplanted to a site where neoplasia is enzootic and placed in close proximity to clams having the disease. After 6 months, no evidence of neoplasia was found in the transplanted clams even though cumulative mortality (14.7%) was greater than that in local clams (3.4%). These results suggest that gonadal neoplasms in M. arenaria progress slowly and cause little mortality once present in an individual and may not have an infectious etiology. Loss of reproductive output is a potential long-term effect of the disease.