| Summary: | Fishing mortality affects demographic characteristics of a population, and is a major determinant in loss of spawners from a ®sh stock; directly in¯uencing stock productivity and recruitment variability. We investigated the effects of ®shing on the composition of the spawning stock of cod (Gadus morhua) in Icelandic waters by partitioning relative ®shing mortality and spawning stock biomass (SSB) into ®ner spatial components than those used previously. Geographic regions of reproductive importance were identi®ed around the country, in contrast to traditional paradigms of cod stock structure in Icelandic waters. SSB and relative ®shing mortality were unevenly distributed in waters around Iceland, where gill nets selectively removed larger spawners from inshore waters of the main spawning grounds, whose demographic characteristics were more conducive to progeny survival. Changes in stock structure and demographic characteristics caused by changes in spatially explicit exploitation patterns can signi®cantly affect stock productivity through differential loss of reproductive potential. Our approach of partitioning SSB into ®ner spatial units than those used previously, enabled a more detailed analysis of the distribution of spawners and exploitation of the Icelandic cod stock, and will enable the development of spatially disaggregated models of total egg production, that in turn may assist in differentiating the inherent variability within stock±recruitment relationships.
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