Seasonal and interannual variation in fish assemblages of northern temperate rocky subtidal habitats

Fish assemblages on two inshore rocky subtidal sites on the west coast of Scotland, were studied using diver visual surveys on a monthly basis between September 1995 and December 1999. A total of 17 689 fishes and 26 species were recorded from the two sites, Saulmore Point (056degrees27'N; 005degrees24' W) near Oban and Davy's Rock (055degrees46' N; 004degrees53' W) on the Isle of Great Cumbrae. The gobiid Thorogobius eppiphiatus, dominated the Saulmore Point site; six fish species accounted for >93% of total abundance at that site. At Davy's Rock four species contributed at least 93% of total fish abundance, and the dominant species was the labrid Ctenolabrus rupestris. Total abundance of the dominant species displayed a clear seasonal trend, and this was significantly related to recorded daily average seawater temperature. A maximum abundance of 4.9 fishes m(-2) was recorded in November 1998 at Davy's Rock and 2-5 fishes m(-2) at Saulmore Point in October 1998. Multivariate analysis indicated a degree of variation in assemblage structure between winter and summer at both sites. A number of species showed some degree of interannual variation, in particular the gobiid Gobiusculus flavescens whose abundance increased by over 300 times over a 5 month period in 1998. Correlation analysis showed that variation in annual winter seawater temperature could act as an indicator of interannual variation in abundance of some of the dominant species utilizing rocky subtidal habitats. (C) 2002 The Fisheries Society of the British Isles. Published by Elsevier Science Ltd. All rights reserved.