The effect of area closures on the demersal fish community off the east coast of Iceland

Abstract

Abstract The effect of reduced fishing effort on the demersal fish community, following area closures in 1993, was analysed for two protected areas off the east coast of Iceland, Digranesflak and Breiddalsgrunn. The data were collected using a standardized bottom trawl during groundfish surveys in the period 1985–2004. The aspects of the fish community that were analysed included abundance by size class, mean size, species richness, diversity, and composition. The analysis was conducted for closed areas and adjacent reference (fished) areas, as well as for periods before and after the closure (and also after the re-opening in Breiddalsgrunn), using an ANOVA model and planned comparisons. The closure had a favourable impact on abundance of haddock (Melanogrammus aeglefinus) and small long rough dab (Hippoglossoides platessoides) in Digranesflak, and on exploitable sizes of haddock and cod (Gadus morhua) in Breiddalsgrunn. The mean size of haddock increased considerably within the protected areas relative to the reference areas: by 16 cm in Digranesflak and by 10 cm in Breiddalsgrunn. Species richness, diversity, and composition varied over the study period and between areas, but no effect of area closure was found. The observed changes in the fish community in Breiddalsgrunn were reversed within 7 years of the re-opening of the area to fishing. The possible causes for the observed patterns of response to area closures are discussed.