Some of these families probably persist into deeper shelf water, being joined by some of the upper slope taxa such as the Squalidae. Thus depth, too, (as a proxy for other physico-chemical parameters such as temperature, salinity, etc.) The shelf communities are probably quite distinct from those on the slope, as described generally by Longhurst and Pauly (1987). Thus, the association of demersal fish communities with particular substratum types has not been demonstrated in the WIO, other than in a general sense by Bianchi (1992), and by Fennessy (in press) in a South African study with limited scope.