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Research article2013Peer reviewed

Egg production of turbot, Scophthalmus maximus, in the Baltic Sea

Nissling, Anders; Florin, Ann-Britt; Thorssen, Anders; Bergström, Ulf

Abstract

In the brackish water Baltic Sea turbot spawn at similar to 6-9 psu along the coast and on offshore banks in ICES SD 24-29, with salinity influencing the reproductive success. The potential fecundity (the stock of vitellogenic oocytes in the pre-spawning ovary), egg size (diameter and dry weight of artificially fertilized 1-day-old eggs) and gonad dry weight were assessed for fish sampled in SD 25 and SD 28. Multiple regression analysis identified somatic weight, or total length in combination with Fulton's condition factor, as main predictors of fecundity and gonad dry weight with stage of maturity (oocyte packing density or leading cohort) as an additional predictor. For egg size, somatic weight was identified as main predictor while otolith weight (proxy for age) was an additional predictor. Univariate analysis using GLM revealed significantly higher fecundity and gonad dry weight for turbot from SD 28 (3378-3474 oocytes/g somatic weight) compared to those from SD 25 (2343 oocytes/g somatic weight), with no difference in egg size (1.05 +/- 0.03 mm diameter and 46.8 +/- 6.5 mu g dry weight; mean +/- sd). The difference in egg production matched egg survival probabilities in relation to salinity conditions suggesting selection for higher fecundity as a consequence of poorer reproductive success at lower salinities. This supports the hypothesis of higher size-specific fecundity towards the limit of the distribution of a species as an adaptation to harsher environmental conditions and lower offspring survival probabilities. Within SD 28 comparisons were made between two major fishing areas targeting spawning aggregations and a marine protected area without fishing. The outcome was inconclusive and is discussed with respect to potential fishery induced effects, effects of the salinity gradient, effects of specific year-classes, and effects of maturation status of sampled fish. (C) 2012 Elsevier B.V. All rights reserved.

Keywords

Reproductive potential; Fecundity; Egg size; Salinity gradient; Spawning fishery; Life-history traits

Published in

Journal of Sea Research
2013, Volume: 84, pages: 77-86
Publisher: ELSEVIER SCIENCE BV