Rapid changes in growth, condition, size and age of small pelagic fish in the Mediterranean

Type Article
Date 2014-08
Language English
Author(s) Van Beveren Elisabeth1, Bonhommeau SylvainORCID1, Fromentin Jean-Marc1, Bigot Jean-Louis1, Bourdeix Jean-Herve1, Brosset Pablo1, 2, Roos DavidORCID1, Saraux Claire1
Affiliation(s) 1 : IFREMER, CRH, Res Unit EME UMR 212, F-34203 Sete, France.
2 : Univ Montpellier 2, Res Unit EME UMR 212, F-34203 Sete, France.
Source Marine Biology (0025-3162) (Springer), 2014-08 , Vol. 161 , N. 8 , P. 1809-1822
DOI 10.1007/s00227-014-2463-1
WOS© Times Cited 29
Abstract Since 2007, the ecosystem of the Gulf of Lions has shifted to a different regime, characterised by a low anchovy (Engraulis encrasicolus) and sardine (Sardina pilchardus) biomass and a remarkably high sprat (Sprattus sprattus) biomass. Surprisingly, the abundance and recruitment of anchovy and sardine remained high. To understand which processes (bottom-up or top-down control, etc.) could have caused this shift, we studied the changes in body condition, growth and size and age of anchovy, sardine and sprat over 1984–1985 and 1992–2012, using data from scientific surveys. The annual age structure of anchovy and sardine was estimated using Bayesian mixture models based on size frequency data with priors on the age–length relationship derived from independent otolith readings. The results indicated periods during which anchovy and sardine were in an average (1992–2004), good (2005–2007) or poor (2008–2012) overall state of condition. For sardine, the shift towards smaller fish observed during these past 4 years was explained by a combination of slower growth and the disappearance of older individuals (ages 2+). Despite the increase in biomass of sprat since 2008, indications were found that sprat was also smaller than in the past. As growth and condition decreased and overexploitation has not been documented or suspected for those three species in this area, we propose that the current decline in sardine and anchovy biomass could be due to qualitative and/or quantitative modifications in the planktonic production (i.e. a bottom-up control) or mass mortalities of adults due to an epidemic disease.
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Van Beveren Elisabeth, Bonhommeau Sylvain, Fromentin Jean-Marc, Bigot Jean-Louis, Bourdeix Jean-Herve, Brosset Pablo, Roos David, Saraux Claire (2014). Rapid changes in growth, condition, size and age of small pelagic fish in the Mediterranean. Marine Biology, 161(8), 1809-1822. Publisher's official version : https://doi.org/10.1007/s00227-014-2463-1 , Open Access version : https://archimer.ifremer.fr/doc/00192/30335/