title: Oogenesis and reproductive investment of Atlantic herring are functions of not only present but long-ago environmental influences as well.
abstract: Following general life history theory, immediate reproductive investment (egg mass × fecundity/body mass) in oviparous teleosts is a consequence of both present and past environmental influences. This clarification questions the frequent use of season-independent (general) fecundity formulas in marine fish recruitment studies based on body metrics only. Here we test the underlying assumption of no lag effect on gametogenesis in the planktivorous, determinate-fecundity Atlantic herring (Clupea harengus) displaying large plasticity in egg mass and fecundity, examining Norwegian summer-autumn spawning herring (NASH), North Sea autumn-spawning herring (NSAH), and Norwegian spring-spawning herring (NSSH). No prior reproductive information existed for NASH. Compared with the 1960s, recent reproductive investment had dropped markedly, especially for NSAH, likely reflecting long-term changes in zooplankton biography and productivity. As egg mass was characteristically small for autumn spawners, although large for spring spawners (cf. different larval feeding conditions), fecundity was the most dynamic factor within reproductive investment. For the data-rich NSSH, we showed evidence that transient, major declines in zooplankton abundance resulted in low fecundity over several subsequent seasons, even if Fulton's condition factor (K) turned high. Temporal trends inKslope(Kon total length) were, however, informative. These results clarify that fecundity is defined by (i) dynamics of primary (standing stock) oocytes and (ii) down-regulation of secondary oocytes, both processes intimately linked to environmental conditions but operating at different timescales. Thus, general fecundity formulas typically understate interannual variability in actual fecundity. We therefore argue for the use of segmented fecundity formulas linked to dedicated monitoring programs.
authors.affiliation: Institute of Marine Research, N-5817 Bergen, Norway.|Department of Biology, University of Bergen, N-5020 Bergen, Norway.
authors.forename: Thassya C
authors.initials: TC
authors.lastname: Dos Santos Schmidt
authors.affiliation: Institute of Marine Research, N-5817 Bergen, Norway.
authors.forename: Aril
authors.initials: A
authors.lastname: Slotte
authors.affiliation: Marine Research Institute, 121 Reykjavik, Iceland.|Biopol, 545 Skagaströnd, Iceland.
authors.forename: James
authors.initials: J
authors.lastname: Kennedy
authors.affiliation: Institute of Marine Research, N-5817 Bergen, Norway.
authors.forename: Svein
authors.initials: S
authors.lastname: Sundby
authors.affiliation: Department of Biology, University of Bergen, N-5020 Bergen, Norway.
authors.forename: Arne
authors.initials: A
authors.lastname: Johannessen
authors.affiliation: Marine Research Institute, 121 Reykjavik, Iceland.
authors.forename: Gudmundur J
authors.initials: GJ
authors.lastname: Óskarsson
authors.affiliation: Tohoku National Fisheries Research Institute, Miyagi 985-0001, Japan.
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Kurita
authors.affiliation: Centre for Ecological and Evolutionary Synthesis, Department of Biosciences, University of Oslo, N-0316 Oslo, Norway; n.c.stenseth@ibv.uio.no olav.kjesbu@imr.no.|Institute of Marine Research, Flødevigen, N-4817 His, Norway.|Centre for Coastal Research, University of Agder, N-4604 Kristiansand, Norway.
authors.forename: Nils C
authors.initials: NC
authors.lastname: Stenseth
authors.affiliation: Institute of Marine Research, N-5817 Bergen, Norway; n.c.stenseth@ibv.uio.no olav.kjesbu@imr.no.
authors.forename: Olav Sigurd
authors.initials: OS
authors.lastname: Kjesbu
mesh_terms: D000818:Animals; D005298:Fertility / Q000502:physiology*; D005399:Fishes; D007814:Larva / Q000502:physiology; D009659:North Sea; D009664:Norway; D009865:Oocytes / Q000502:physiology*; D009866:Oogenesis / Q000502:physiology*; D012098:Reproduction / Q000502:physiology*; D017747:Seafood; D015048:Zooplankton
keywords: fecundity; fishery; lag effect; recruitment; zooplankton