Factors affecting distribution and abundance of small demersal fishes in the Gulf of Carpentaria, Australia

Abstract

The distribution and abundance of small demersal fishes at depths of 7 to 63 m in the Gulf of Carpentaria were surveyed at 103 stations in 1990 and 60 stations in 1991 with the aid of a Church dredge. A total of 234 species from 70 families was recorded. The most abundant fish groups were cryptic or benthic species such as pleuronectiforms, scorpaenids, apogonids, platycephalids, monacanthids and gobiids. Several species, such as Elates ransonnetti, Pseudorhombus elevatus and Suggrundus macracanthus, are widely distributed; others had a narrower distribution. Apogon poecilopterus, Apogon fasciatus, Arnoglossus waitei and Uranoscopus cognatus were most abundant in the northern Gulf of Carpentaria and Cynoglossus macrophthalmus, Dactyloptena papilio and Paramonacanthus japonicus in the eastern gulf. The dredge is more efficient at catching smaller fish: the smallest individuals of 113 species were caught by the dredge and a further 32 small species were caught only by the dredge. The effects of depth, substratum type and turbidity on the abundance of 17 common species at different stations are described. Neither temperature nor salinity showed significant correlations with catches of the common species. There were significant correlations between the presence of structured benthos and both the number of fish species and the number of fish individuals. The relationship between benthic structure and fish is discussed in relation to the possible effects of trawling, and it is postulated that changes to structure resulting from trawling may affect fish community composition.