|Author(s)||Gatti Paul1, Cominassi Louise1, Duhamel Erwan2, Grellier Patrick3, Le Delliou Herve4, Le Mestre Sophie1, Petitgas Pierre3, Rabiller Manuella3, Spitz Jerome5, Huret Martin1|
|Affiliation(s)||1 : Ctr Ifremer Bretagne, Unite Sci & Technol Halieut, Lab Biol Halieut, ZI Pointe Diable CS 10070, F-29280 Plouzane, France.
2 : Stn Ifremer Lorient, Unite Sci & Technol Halieut, Lab Technol & Biol Halieut, 8 Rue Francois Toullec, F-56100 Lorient, France.
3 : Ifremer Nantes, Unite Ecol & Modeles Halieut, Rue Ile dYeu,BP 21105, F-44300 Nantes 3, France.
4 : Ctr Ifremer Bretagne, Unite Physiol Fonct Organismes Marins, Lab Adaptat Reprod & Nutr Poisson, ZI Pointe Diable CS 10070, F-29280 Plouzane, France.
5 : Univ La Rochelle, CNRS, UMS 3462, Observ PELAGIS, 5 Allees Ocean, F-17000 La Rochelle, France.
|Source||Progress In Oceanography (0079-6611) (Pergamon-elsevier Science Ltd), 2018-09 , Vol. 166 , P. 129-138|
|WOS© Times Cited||10|
|Keyword(s)||Energy density, Calorimetry, Small pelagic fish, Engraulis encrasicolus, Sardina pilchardus, Northeast Atlantic|
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 reserve building individuals, to be able to survive a longer winter than in the Bay of Biscay. Finally, we described a dome shaped evolution of energy density with body size in case of sardine. Increase with size has been well documented but not the decrease at largest sizes. Several mechanisms may explain such a pattern, i.e. increasing investment in spawning, shift in diet or a metabolic trade-off between temperature and food availability, with regard to maintenance requirements.
Gatti Paul, Cominassi Louise, Duhamel Erwan, Grellier Patrick, Le Delliou Herve, Le Mestre Sophie, Petitgas Pierre, Rabiller Manuella, Spitz Jerome, Huret Martin (2018). Bioenergetic condition of anchovy and sardine in the Bay of Biscay and English Channel. Progress In Oceanography, 166, 129-138. Publisher's official version : https://doi.org/10.1016/j.pocean.2017.12.006 , Open Access version : https://archimer.ifremer.fr/doc/00416/52754/