title: Timecourse of oocyte development in saithe Pollachius virens.
abstract: Wild caught North Sea saithe Pollachius virens were monitored for growth, sex steroid profiles and oocyte development pre-spawning and measured for egg size and group fecundity during the spawning season in the laboratory. Vitellogenesis commenced in late October-early November, at a leading cohort size (CL) of c. 250 µm, after which oocytes grew rapidly in size until spawning started in February. Notably, a distinct cortical alveoli stage was virtually absent with yolk granules observed in developing oocytes at the very beginning of vitellogenesis. Little atresia was observed pre-spawning, but atretic re-absorption of remnant oocytes containing yolk granules was found in all females immediately post-spawning. As expected, concentrations of sex steroids, oestradiol-17β (females), testosterone (both sexes) and 11-ketotestosterone (both sexes), increased pre-spawning before dropping post-spawning. The present experiment provides the first validation of sex steroid levels in P. virens. Post-ovulatory follicles were visible in histological sections from female gonads 9-11 months post-spawning, but then disappeared. Spawning commenced around a CLof c. 750 µm (700-800 µm). Hydrated oocytes (eggs) measured between 1·04 and 1·31 mm (mean = 1·18 mm) with decreasing sizes towards the end of spawning. The average estimated realized fecundity was c. 0·84 million eggs (median female total length, LT= 60 cm). Spawning lasted from 13 February to 29 March.
authors.affiliation: Institute of Marine Research and Hjort Centre for Marine Ecosystem Dynamics, N-5817, Bergen, Norway.
authors.forename: J E
authors.initials: JE
authors.lastname: Skjaeraasen
authors.affiliation: Institute of Marine Research and Hjort Centre for Marine Ecosystem Dynamics, N-5817, Bergen, Norway.
authors.forename: J A
authors.initials: JA
authors.lastname: Devine
authors.affiliation: Institute of Marine Research and Hjort Centre for Marine Ecosystem Dynamics, N-5817, Bergen, Norway.
authors.forename: J A
authors.initials: JA
authors.lastname: Godiksen
authors.affiliation: Institute of Marine Research, N-5817, Bergen, Norway.
authors.forename: M
authors.initials: M
authors.lastname: Fonn
authors.affiliation: Institute of Marine Research, N-5817, Bergen, Norway.
authors.forename: H
authors.initials: H
authors.lastname: OtterÅ
authors.affiliation: Institute of Marine Research and Hjort Centre for Marine Ecosystem Dynamics, N-5817, Bergen, Norway.|Centre for Ecological and Evolutionary Synthesis (CEES), Department of Biosciences, University of Oslo, PO Box 1066 Blindern, N-0316, Oslo, Norway.
authors.forename: O S
authors.initials: OS
authors.lastname: Kjesbu
authors.affiliation: Institute of Marine Research, Austevoll Research Station, N-5392, Storebø, Norway.
authors.forename: B
authors.initials: B
authors.lastname: Norberg
authors.affiliation: Centre for Ecological and Evolutionary Synthesis (CEES), Department of Biosciences, University of Oslo, PO Box 1066 Blindern, N-0316, Oslo, Norway.
authors.forename: Ø
authors.initials: Ø
authors.lastname: Langangen
authors.affiliation: Institute of Marine Research and Hjort Centre for Marine Ecosystem Dynamics, N-5817, Bergen, Norway.
authors.forename: Ø
authors.initials: Ø
authors.lastname: Karlsen
mesh_terms: D000818:Animals; D005260:Female; D005298:Fertility / Q000502:physiology; D048388:Gadiformes / Q000033:anatomy & histology / Q000097:blood / Q000254:growth & development*; D012739:Gonadal Steroid Hormones / Q000097:blood; D008297:Male; D009659:North Sea; D009865:Oocytes / Q000166:cytology / Q000254:growth & development; D009866:Oogenesis / Q000502:physiology*; D012621:Seasons; D014818:Vitellogenesis / Q000502:physiology
chemical_list: D012739:Gonadal Steroid Hormones
keywords: atresia; egg size; fecundity; oocyte development; post-ovulatory follicles; timing of gonad maturation