title: Body reserves mediate trade-offs between life-history traits: new insights from small pelagic fish reproduction.
abstract: Limited resources in the environment prevent individuals from simultaneously maximizing all life-history traits, resulting in trade-offs. In particular, the cost of reproduction is well known to negatively affect energy investment in growth and maintenance. Here, we investigated these trade-offs during contrasting periods of high versus low fish size and body condition (before/after 2008) in the Gulf of Lions. Female reproductive allocation and performance in anchovy (Engraulis encrasicolus) and sardine (Sardina pilchardus) were examined based on morphometric historical data from the 1970s and from 2003 to 2015. Additionally, potential maternal effects on egg quantity and quality were examined in 2014/2015. After 2008, the gonadosomatic index increased for sardine and remained steady for anchovy, while a strong decline in mean length at first maturity indicated earlier maturation for both species. Regarding maternal effects, for both species egg quantity was positively linked to fish size but not to fish lipid reserves, while the egg quality was positively related to lipid reserves. Atresia prevalence and intensity were rather low regardless of fish condition and size. Finally, estimations of total annual numbers of eggs spawned indicated a sharp decrease for sardine since 2008 but a slight increase for anchovy during the last 5 years. This study revealed a biased allocation towards reproduction in small pelagic fish when confronted with a really low body condition. This highlights that fish can maintain high reproductive investment potentially at the cost of other traits which might explain the present disappearance of old and large individuals in the Gulf of Lions.
authors.affiliation: University of Montpellier, UMR MARBEC (IRD, Ifremer, UM, CNRS), 34203 Sète, France; IFREMER, UMR MARBEC (IRD, Ifremer, UM, CNRS), 34203 Sète, France.
authors.forename: Pablo
authors.identifier: 0000-0002-2561-6560
authors.initials: P
authors.lastname: Brosset
authors.affiliation: Faculty of Sciences , University of Girona , Girona , Spain.
authors.forename: Josep
authors.initials: J
authors.lastname: Lloret
authors.affiliation: Faculty of Sciences , University of Girona , Girona , Spain.
authors.forename: Marta
authors.initials: M
authors.lastname: Muñoz
authors.affiliation: IFREMER, UMR MARBEC (IRD, Ifremer, UM, CNRS) , 34250 Palavas Les Flots , France.
authors.forename: Christian
authors.initials: C
authors.lastname: Fauvel
authors.affiliation: IFREMER, UMR MARBEC (IRD, Ifremer, UM, CNRS) , 34203 Sète , France.
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Van Beveren
authors.affiliation: IFREMER, UMR MARBEC (IRD, Ifremer, UM, CNRS) , 34203 Sète , France.
authors.forename: Virginie
authors.initials: V
authors.lastname: Marques
authors.affiliation: IFREMER, UMR MARBEC (IRD, Ifremer, UM, CNRS) , 34203 Sète , France.
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Fromentin
authors.affiliation: IRD, Mediterranean Institute of Oceanography (MIO) , Aix-Marseille Université/CNRS/IRD/Université de Toulon , UM 110, 13288 Marseille , France.
authors.forename: Frédéric
authors.initials: F
authors.lastname: Ménard
authors.affiliation: IFREMER, UMR MARBEC (IRD, Ifremer, UM, CNRS) , 34203 Sète , France.
authors.forename: Claire
authors.initials: C
authors.lastname: Saraux
keywords: anchovy; maternal effect; northwest Mediterranean; sardine