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.

Short-circuit in the mangrove food chain

“…Fish trap studies in complex habitats, inaccessible to other gears (Sheaves 1992(Sheaves , 1996a, suggest that large, habitat associated predators such as L. argentimaculatus, E. malabaricus and E. coioides may be much more common than the results of netting surveys would suggest. Furthermore, unlike predators such as carangids and carcharhinids that visit mangrove systems temporarily (Blaber et al 1985), these serranids and lutjanids are present throughout the tidal cycle and throughout the year (Sheaves 1995). This line of argument would suggest that the 'few predator' theory may need to be revised.…”

Relationships between latitude and environmental conditions and the species richness, abundance and composition of tropical fish assemblages over soft substrata

“…*Species favouring deep over shallow waters species and providing protection from predation for the juveniles of fish species that move further from the shore as they increase in size and/or become mature (Robertson & Duke 1987, Robertson & Blaber 1992, Blaber et al 1995, Alongi 1998, Manson et al 2005a. Indeed, teleosts such as Siganus fuscescens and Saurida spp., which are abundant as juveniles in mangroves along the Pilbara coast (Blaber et al 1985), were numerous as adults at Cape Preston and Locker Point in the Pilbara (Table 1). As the species richness and density of fishes in deep and shallow waters in the wet season followed the same overall sequential downward trend with latitude between Cape Voltaire in the north and Cape Bossut in the middle of the Canning as occurred in the dry season, the greater productivity in the Kimberley than the Canning, and the benefits derived from the mangrove forests found in that region, presumably likewise played a major role in driving that trend.…”

“…The most northern of these regions lies immediately to the south of the Indo−Australian Archipelago (IAA), in which the species richness of its ichthyofaunas is the greatest of any marine waters (Hughes et al 2002, Connolly et al 2003. The NWA coast also contains a diverse and abundant fish fauna (Blaber et al 1985, Hutchins 2001, Travers et al 2006, 2010.…”

Factors affecting spatial variability in seine net catches of fish in the surf zone of False Bay, South Africa

“…Much attention has been focused on the influence of turbidity on the distribution patterns of fish in inshore waters, chiefly estuarine systems in southern Africa (Blaber & Cyrus 1983, Cyrus 1983, Bruton 1985, Cyrus & Blaber 1987a, b, c, 1992 and Australia (Blaber & Blaber 1980, Cyrus & Blaber 1982, Blaber et al 1985, Weng 1990. It is thought to be the single most important factor influencing estuarine fish distribution patterns, as it provides cover for juveniles through a reduction in light intensity, whlch obscures prey species from visually orientating predators such as piscivorous fish and birds (Blaber & Blaber 1980, Blaber 1981, Cyrus 1983, Cyrus & Blaber 1987a.…”