Evaluation of the frequency of skipped spawning in Norwegian spring-spawning herring |
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| Authors: | James Kennedy Jon Egil Skjraasen Richard DM Nash Aril Slotte Audrey J Geffen Olav S Kjesbu |
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| Institution: | a Department of Biology, University of Bergen, P.O. Box 7803, 5020 Bergen, Norway;b Institute of Marine Research, P.O. Box 1870 Nordnes, 5817 Bergen, Norway |
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| Abstract: | Based upon an under-representation of second time spawners on the spawning grounds between 1935 and 1973, researchers have suggested that Norwegian spring-spawning (NSS) herring (Clupea harengus) frequently skip their second spawning event. In order to evaluate this claim with direct evidence, herring were collected over a period of three years from statutory surveys and commercial catches over a wide area covering the feeding, over-wintering and spawning grounds. The development stage of the ovaries was assessed and the intensity of atresia quantified. Only a negligible number of the analysed herring caught were considered likely to skip spawning, thus this phenomenon does not appear to be a common feature of the NSS herring stock at present. In addition, considering the reproductive strategy of herring, it seems doubtful that skipping the second spawning event has ever frequently occurred in this stock. |
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| Keywords: | Skipped Spawning Herring Clupea harengus Reproduction Maturation Life History |
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