Inshore demersal fish stocks in Australia’s north-west face increased exploitation pressure by an ever increasing number of recreational fishers in direct competition with an adjacent commercial fishing industry. There is, therefore, an urgent need to determine the species distribution and the composition of demersal scalefish resources in the inshore region of north-western Australia in waters outward from the shoreline to depths of 30 metres, including the documentation of the abundance and diversity of any significant finfish by-catch of prawn trawlers operating within the region, as a basis for formulating rational management plans for the exploitation of the demersal scalefish resource among user-groups.
The sharing of the inshore demersal fish resource in this region will require careful future management to ensure sustainability and avoid conflict among these user groups. This project will provide baseline information on the species composition and relative abundance of the inshore fishes of Australia’s north-west and identify possible nursery areas of species of commercial and recreational fishing significance which may need protection, possibly as nursery closures, in the future. Furthermore, in order to facilitate sagacious management plans and to safeguard the interests of commercial and recreational fishers, the baseline information on the nearshore fishery resources of the north-west provided by this study can be used to assess the impact of any possible access restrictions that may be imposed in areas nominated as future marine reserve sites in north-western Australia.
Final report
The catches of the main fish species obtained by commercial, recreational and charter boat fishers along the Pilbara and Kimberley coasts have been determined by analysing the Department of Fisheries Western Australian Catch and Effort Database System (CAES), the results of a recreational creel survey and the statutory monthly reports of catch and effort by charter boat operators.
The weight of finfish caught by nearshore and inshore commercial fishers along this coast during 2002 was approximately 590 tonnes. The total annual recreational fishing effort along the coast between Onslow and Broome in 2002 was estimated as 190,000 fisher days, which yielded approximately 320 tonnes of fish. The 111 licensed charter boat operators in the Pilbara and Kimberley undertook 3628 tours in 2002, during which they caught 53 tonnes of fish. Thus, the total catch from all three sources approached 1000 tonnes.
Nearshore, shallow waters on beaches and in mangroves and intertidal pools in three regions along the Pilbara and Kimberley coasts were sampled during the wet and dry periods of two consecutive years. Data derived from the resultant catches were used to determine the ways in which fish species use the different habitat types and how the characteristics of the fish faunas varied with latitude, habitat type and season.
The fish catches from all habitat types collectively yielded 170 species representing 66 families. Fifty three of these species are fished commercially and recreationally along the Pilbara and Kimberley coasts, and a further 17 fish species are caught solely by recreational fishers. The most abundant species included the blue and king threadfin salmons, salmon-tailed catfish, the blue-spot and large-scale mullets, queenfish, western school whiting, Quoy’s garfish, Moses snapper and estuary rockcod.
Some species, such as the two threadfin salmons, spend the whole of their life cycle in nearshore, shallow waters, whereas others, such as Moses snapper and estuary rockcod, use those waters solely as a nursery area. Species such as the two threadfin salmons and also whiting species were caught predominantly over bare sand, whereas species such as the large-scale mullet and the nervous shark were obtained mainly from mangroves, and Moses snapper and estuary rockcod were collected almost exclusively from intertidal pools.
The species compositions of the fish assemblages were influenced not only by habitat type, but also by season and region and also apparently the extent of tidal action and thus turbidity. Differences between the compositions in the extreme wet and dry periods found in the region were attributable to emigrations and immigrations of large numbers of particular species at certain times. For example, mature catfish aggregate in nearshore, shallow waters during the wet period.
This project has synthesised the available data from commercial, recreational and charter boat fisheries with baseline survey data throughout the region. In order to build on the outcomes of this project a number of priority areas for research in this nearshore zone have been identified.
These priority areas of research include; estimation of biological parameters of key species for the purposes of fisheries management (a list of key species is provided in the Further Development Section of this Report); evaluation and assessment of recreational and aboriginal netting activities in the Pilbara and Kimberley region of north-western Australia; determination of the genetic stock structure of the key species of commercial and recreational fishing significance in the nearshore areas throughout north-western Australia to define the appropriate spatial scale for fisheries management; and refinement of commercial and recreational data collection programs in the Pilbara and Kimberley region of north-western Australia.
Keywords: Tropical, commercial, recreational, nursery habitats, nearshore reefs, estuaries, beaches, intertidal, rockpools.
