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.

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The pharaoh cuttle Sepia pharaonis Ehrenberg, 1831 (Mollusca : Cephalopoda : Sepiida) is a broadly distributed species of substantial fisheries importance found from east Africa to southern Japan. Little is known about S. pharaonis phylogeography, but evidence from morphology and reproductive biology suggests that Sepia pharaonis is actually a complex of at least three species.

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Demersal trawl and dredge surveys of the Gulf of Carpentaria in the early summers of 1990 and 1991 provided the first comprehensive assessment of the cephalopod fauna of this shallow, tropical basin off northern Australia. Twenty-one taxa (comprising five loliginid squids, seven cuttlefishes, seven octopuses and two dumpling squids) were recorded. In addition to hosting species distributed broadly in the Indo-West Pacific (e.g. loliginid squids Sepioteuthis lessoniana, Photololigo cf. chinensis and P. cf. edulis; cuttlefishes Sepia eiliptica and Sepia pharaonis), the Gulf of Carpentaria represents the most northwesterly extent of the range of some eastern Australian species (e.g. Loliolus noctiluca and Sepia whitieyana). Squid catches were lower in the north-western gulf in 1990 and higher in shallower water during the more geographically restricted survey in 1991, whereas cuttlefish were more evenly distributed throughout the different sampling areas in both years. Broad size ranges of both sexes of the four most abundant species (P. cf. chinensis (northern form), P. cf. eduiis, S. eiliptica and S. pharaonis) are indicative of extended spawning seasons, and fully mature individuals of these species were evident throughout the gulf. Cephalopods are a minor component in reported domestic fisheries catches from the Gulf of Carpentaria, where penaeid prawns are targeted. High (though seasonal) squid catch rates were reported annually by Taiwanese trawlers targeting butterfish and squid from certain areas prior to 1979. With the observed population structure of the abundant cephalopod species and relatively high catch rates in some localities during these recent surveys, it is suggested that the cephalopod resources of the Gulf of Carpentaria could support increased commercial fisheries exploitation.