Bioenergetic condition of anchovy and sardine in the Bay of Biscay and English Channel

• Published in: Progress in Oceanography
• Main Authors: Gatti, Paul, Cominassi, Louise, Duhamel, Erwan, Grellier, Patrick, Le Delliou, Herve, Le Mestre, Sophie, Petitgas, Pierre, Rabiller, Manuella, Spitz, Jerome, Huret, Martin
• Format: Article in Journal/Newspaper
• Language: English
• Published: Pergamon-elsevier Science Ltd 2018
• Subjects: Energy density; Calorimetry; Small pelagic fish; Engraulis encrasicolus; Sardina pilchardus; Northeast Atlantic
• Online Access: https://archimer.ifremer.fr/doc/00416/52754/53615.pdf; https://doi.org/10.1016/j.pocean.2017.12.006; https://archimer.ifremer.fr/doc/00416/52754/

There is a growing interest in monitoring body condition of marine organisms in the context of the ecosystem approach to fisheries and global change. Fish condition is under the influence of environmental variability on seasonal scale, but also on longer timescales. It represents a good indicator of habitat quality or individual fitness, and is also a relevant parameter to evaluate energy transfer through the trophic chain. However, the sources of variability in fish condition need to be accurately understood and the significance of existing indices has to be correctly assessed. Here, we measured the energy density, a precise and global indicator of fish bioenergetic condition, for anchovy (Engraulis encrasicolus) and sardine (Sardina pilchardus) in the Bay of Biscay and the English Channel, based on an extensive sampling design in 2014. First, we investigated the well-documented relationship between percent dry mass and energy density, and showed that such relationship is species specific. Second, we observed distinct patterns in bioenergetic condition between anchovy and sardine. Both species display similar minimum values at size or age but maximum are significantly higher for sardine, reflecting a higher energy storage capacity that scales more strongly with size. Third, we confirmed the large seasonal variability in energy density of both species. In the Bay of Biscay, energy density values for anchovy and sardine (age 1+) are 5.7 and 5.9 kJ.g-1 (wet weight) in spring and 6.8 and 7.9 kJ.g-1 in autumn, respectively. Our results revealed that fish from the English Channel display significantly higher energy density values in autumn (9.8 kJ.g-1 for anchovy and 10.5 kJ.g-1 for sardine) than those from the Bay of Biscay. When combined with size and weight at age it appears clearly that, after age 1, fish from the northern region display larger growth and energy reserves. This likely results from a higher zooplankton productivity in the English Channel or/and a selection pressure towards faster growing and faster ...