Community structure and zoogeographic affinities of the coastal fishes of the Dampier region of north-western Australia.

Abstract

The species composition and broad trophic structure of the mangrove creek and open shore fish communities of the Dampier region in tropical north-western Australia are described. The habitats are characterized by a lack of freshwater influence, low turbidity and a tidal range in excess of 4 m. Both mangroves and open shores have a diversity of species typical of Indo-west Pacific coastal waters but the physical conditions have modified the community structure both to exclude many families that prefer areas of higher turbidity and reduced salinity, and to include others that usually occur only in clear waters. The fish faunas of the mangroves (113 species) and open shores (106 species) are compared: 54 species were common to both. The deeper waters were dominated by piscivores, which penetrated throughout the mangroves at high tide. Iliophagous species were abundant, particularly in the mangroves where the organic content of the substratum (7.8-8.2%) was not reduced markedly compared with other areas of the Indo-Pacific, despite the lack of freshwater inflow. The clear and deep water in the mangroves at high tide favour predation on juveniles by piscivorous fishes and reduce the effectiveness of such areas as nurseries. There is virtually no overlap of the fauna with that of the deeper waters (>20 m) of the North West Shelf, and the inshore region is not a significant nursery ground for any of the commercially important deeper water species.