Weight–Body Length relationships (WLR) of 45 fish species (37 Actinopterygii and eight Elasmobranchii) were investigated. A total of 31,167 individuals were caught and their biological parameters measured during the four quarters from 2013 to 2015, on five scientific surveys sampling the North-eastern Atlantic Ocean from the North Sea to the Bay of Biscay (ICES Divisions IVb, IVc, VIId, VIIe, VIIg, VIIh, VIIj, VIIIa and VIIIb). Among 45 tested species, all showed a significant correlation between total length (L) and total weight (W). The influence of sex on WLR was estimated for 39 species and presented a significant sexual dimorphism for 18 species. Condition factor (K) of females was always higher than for males. Moreover, a spatial effect on the WLR according to five ecoregions (the Bay of Biscay, the Celtic Sea, the Western English Channel, the Eastern English Channel and the North Sea), was significant for 18 species among 38 tested species. The temporal effect was tested according to components (year and quarter/season). The seasonality effect on WLR is more frequently significant than the year especially for the Elasmobranchii species, and can be related to the spawning season. Finally, depressiform species (skates, sharks and flatfish) are characterized by positive allometric growth, whereas there is no such clear pattern regarding roundfishes growth, whatever their body shape is.

-This work focuses on investigating the potential of calcein and manganese as growth markers of the common cockle (Cerastoderma edule) in the bay of Somme (France). Recapture of shells, previously marked using a chemical marking and then bred in natural conditions, was performed in order to determine the shell growth patterns. Calcein marking has shown a fluorescent increment in shells after only 30 min immersion time at 150 mg L −1 , but also for shells immersed 3 h at 50 mg L −1 . Likewise, manganese shell marking was revealed under cathodoluminescence for shells immersed 1 h at 120 mg L −1 as well as for shells which spent 4 h at 90 mg L −1 . A numerical analysis performed on each marked cockles has revealed 23 micro-increments between the mark and the ventral edge of the valves, corresponding to the 23 tides that occurred during the 12 days at liberty post marking. The periodicity of increment formation is thus validated for a tidal frequency. The growth rates of C. edule, ranged from 11.67 to 19.94 μm d −1 , decreased significantly with increasing shell length. This preliminary study gives a clue to the understanding of cockle growth and could be used in shellfish production for cockle age monitoring, but also for chemical analysis to learn more about biomineralization process of this species.

The ornate jobfish Pristipomoides argyrogrammicus Valenciennes 1832 occurs in the Indo-West Pacific Ocean, where it is harvested by small-scale coastal fisheries. Management of this species is hindered by lack of adequate biological data. We sampled a total of 113 individuals from the landings of local artisanal fishers on the island of Réunion (southwestern Indian Ocean), from March 2014 to March 2015. The relationships between two types of body length (total and standard length, cm) and total weight (g) were shown to be significant (p < 0.05). The length-weight relationship was described by a power function, with the scaling factor estimated to be 0.008 and the exponent 3.146. Age was determined using whole otoliths. The von Bertalanffy growth equation was estimated to be TLt = 30.68(1 e-0.52(t)). Otolith morphometry variables (length, width and area) were significantly correlated with age estimates (p < 0.05). No significant difference in age estimates was observed between left and right otoliths used as predictors. Readings from observed age and the estimates from modelled age indicated relatively good agreement, suggesting the potential to use whole otoliths for age estimation.

Arcachon Bay, in the southern Bay of Biscay, is the first French production area of Manila clam (Ruditapes philippinarum) with an annual commercial fisheries production around 400 tons in recent years. This bivalve mollusc was introduced into the bay in the 1980s for aquaculture purpose and quickly succeeded in natural settlement so that its high market value led to the progressive establishment of a perennial fishery from the mid-1990s. Local management plans applied to this species are based on a licensing system for the commercial, protected fishery areas and days of prohibited fishing for both commercial and recreational fishermen. A minimum catch size is also prescribed by European regulation, and so growth rates are an important matter in this context. This work focuses on studying shell growth from the recapture of shells, previously marked using a chemical marker (calcein) and then grown in natural conditions, and was performed in order to determine shell growth patterns. Manila clams were marked by immersion in situ in seawater containing calcein. In order to study the limitations of calcein on the mark readability in situ and manila clam mortality, various exposure times, from 30 minutes to 1 hour, and concentrations, from 50 mg.L -1 to 200 mg.L -1 were tested. After a period of 35 days, 69 growth micro-increments were observed, and, it was found that increment deposition in manila clams occurs with a tidal periodicity. Moreover, this study showed that a method for fast-marking of manila clams, and potentially other species, is feasible in situ.