Gill-net mesh selectivity of dusky sharks (Carcharhinus obscurus) and whiskery sharks (Furgaleus macki) from south-western Australia

Gill-net mesh selectivity parameters were estimated for C. obscurus and F. macki from catches of an experimental net composed of seven panels of mesh ranging in size from 12.7 cm to 21.6 cm. A maximum-likelihood model was use d to fit a gamma distribution to length data from each of the different-siz ed meshes. Mesh selectivity parameters for the gilled-only data set were th eta(1)=126.90 and theta(2)=20253, and for the data set including gilled and non-gilled sharks theta(1)=130.13 and theta(2)=29237. The advantages of th e parameters from each of these data sets are discussed. Mesh-selectivity p arameters for F. macki were theta(1)=173.70 and theta(2)=26415. The exclusi on of data from the two largest mesh sizes, which had much lower catch rate s than the other mesh sizes, did not significantly change the parameter est imates. Catch rates from the panels in the experimental net that correspond to those used by the commercial gill-net fishery in south-western Australi a were compared and no significant differences were found.