title: Frequent skipped spawning in the world's largest cod population.
abstract: 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.
authors.affiliation: Department of Biology, University of Bergen, N-5020 Bergen, Norway. jon.skjaeraasen@bio.uib.no
authors.forename: Jon Egil
authors.initials: JE
authors.lastname: Skjæraasen
authors.forename: Richard D M
authors.initials: RD
authors.lastname: Nash
authors.forename: Knut
authors.initials: K
authors.lastname: Korsbrekke
authors.forename: Merete
authors.initials: M
authors.lastname: Fonn
authors.forename: Trygve
authors.initials: T
authors.lastname: Nilsen
authors.forename: James
authors.initials: J
authors.lastname: Kennedy
authors.forename: Kjell H
authors.initials: KH
authors.lastname: Nedreaas
authors.forename: Anders
authors.initials: A
authors.lastname: Thorsen
authors.forename: Peter R
authors.initials: PR
authors.lastname: Witthames
authors.forename: Audrey J
authors.initials: AJ
authors.lastname: Geffen
authors.forename: Hans
authors.initials: H
authors.lastname: Høie
authors.forename: Olav Sigurd
authors.initials: OS
authors.lastname: Kjesbu
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001110:Arctic Regions; D049628:Body Size; D016002:Discriminant Analysis; D005260:Female; D048389:Gadus morhua / Q000502:physiology*; D008099:Liver / Q000254:growth & development; D009866:Oogenesis / Q000502:physiology; D009929:Organ Size; D006080:Ovarian Follicle / Q000502:physiology; D010053:Ovary / Q000254:growth & development; D011157:Population Dynamics; D012098:Reproduction / Q000502:physiology*; D012726:Sexual Behavior, Animal / Q000502:physiology*