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The timing and success of spawning in marine fish are of fundamental importance to population persistence and distribution and, for commercial species, sustainability. Their physiological processes of reproduction are regulated, in part, by water temperature, and therefore changes in marine climate may have dramatic effects on spawning performance. Using adult Atlantic cod (Gadus morhua) as a case study, we examined the links between water temperature, body size, vitellogenesis, and spawning time by conducting extensive laboratory and field studies. Our experiments documented that vitellogenesis generally starts at autumnal equinox and that oocyte growth and investment are greater in cod held at warmer temperatures. Furthermore, spawning occurred earlier when oocyte growth was more rapid. Large females spawned earlier than smaller females at warmer temperatures, but this effect vanished at colder temperatures. The experimental results were confirmed by measurements of oocyte growth collected from wild-caught cod in northern (Barents Sea) and southern (Irish Sea and North Sea) populations. The established, general model of oocyte maturation was consistent with published egg production curves of cod from these waters, considering relevant in situ temperatures recorded by individual data-storage tags on cod. These findings have considerable relevance for future studies of fish recruitment in relation to climate change. Resume: Le calendrier et le succes de la fraie chez les poissons marins sont d'importance fondamentale pour la persistance, la repartition et, chez les especes commerciales, la durabilite de la population. Leurs processus de regulation physiologique sont controles, en partie, par la temperature de l'eau, si bien que des changements dans le climat marin peuvent avoir des effets considerables sur la performance de la fraie. Nous servant de la morue franche (Gadus morhua) comme espece de cas, nous examinons les liens entre la temperature, la taille corporelle, la vitellogenese et le moment de la fraie au cours d'experiences en laboratoire et d'etudes de terrain d'envergure. Nos experiences demontrent que la vitellogenese debute generalement a l'equinoxe d'automne et que la croissance des oocytes et l'investissement reproductif sont plus importants chez les morues gardees aux temperatures plus elevees. De plus, la fraie se produit plus tot lorsque la croissance des oocytes est plus rapide. Aux temperatures plus elevees, les femelles de plus grande taille fraient plus tot que les femelles plus petites, mais ce phenomene ne se produit pas aux temperatures plus basses. Nos resultats experimentaux sont confirmes par des mesures de la croissance des oocytes realisees chez des morues capturees en nature dans des populations du nord (mer de Barents) et du sud (mers d'Irlande et du Nord). Le modele general etabli de maturation des oocytes s'accorde avec les courbes publiees de production d'oeufs de morues dans ces eaux, compte tenu des temperatures pertinentes enregistrees in situ par des etiquettes enregistreuses individuelles sur les morues. Ces resultats sont d'une grande pertinence pour les etudes futures du recrutement des poissons en fonction du changement climatique. [Traduit par la Redaction], Introduction Current scenarios of climate change are based on extensive analyses of a suite of environmental variables and have led to the conclusion that many natural systems are being affected [...]

Abstract--Estimation of individual egg production (realized fecundity) is a key step either to understand the stock and recruit relationship or to carry out fisheries-independent assessment of spawning stock biomass using [...]

Life-history theory suggests that animals may skip reproductive events after initial maturation to maximize lifetime fitness. In iteroparous teleosts, verifying past spawning history is particularly difficult; the degree of skipped spawning at the population level therefore remains unknown. We unequivocally show frequent skipped spawning in Northeast Arctic cod (NEAC) in a massive field and laboratory effort from 2006 to 2008. This was verified by postovulatory follicles in temporarily arrested ovaries close to the putative spawning period. At the population level, "skippers" were estimated to be approximately equally abundant as spawning females in 2008, constituting ∼24% of the females 60-100 cm. These females never truly started vitellogenesis and principally remained on the feeding grounds when spawners migrated southward, avoiding any migration costs. The proximate cause of skipping seems to be insufficient energy to initiate oocyte development, indicating that skipped spawning may partly be a density-dependent response important in population regulation. Our data also indicate more skipping among smaller females and potential tradeoffs between current and future reproductive effort. We propose that skipped spawning is an integral life-history component for NEAC, likely varying annually, and it could therefore be an underlying factor causing some of the currently unexplained large NEAC recruitment variation. The same may hold for other teleosts. [ABSTRACT FROM AUTHOR]