Changes in the demersal fish assemblages of British coastal waters during the 20th century

摘要: Catches of demersal fish from research vessel surveys in three areas around the British Isles 1901 to 1907 were compared with survey catches same 1989 1997. Mesh size and other characteristics trawls used suggested that some these data comparable, could be describe changes assemblages over last 80 years. In Start Bay (NW English Channel) Irish Sea, species diversity was both periods, although most abundant each period not same. coastal regions southern North populations became more diverse, as plaice Pleuronectes platessa whiting Merlangius merlangus less abundant, relative abundance several non-target such dragonet Callionymus spp., bib Trisopterus luscus, bull-rout Myoxocephalus scorpius increased. The proportion catch small (maximum body length 30 cm) decreased all during time period, except Sea where replaced grey gurnard Eutrigla gurnardus a dominant species. There decline large sharks, skates rays, including common skate, Raja batis, white skate R. alba angel shark Squatina squatina. During historic surveys, 60% elasmobranch fauna consisted thornback ray clavata, whereas contemporary lesser spotted dogfish Scyliorhinus canicula elasmobranch. Changes length-frequency distribution target categories, observed changes, thought response commercial exploitation, corresponded similar observations recorded elsewhere. (C) 2000 Crown Copyright.