Detection of Ecological Disturbances to Seabed Fauna through Change of Weight Distribution

Abstract

The effect of trawling on seabed fauna in the Northern Prawn Fishery experimental region of Australia is investigated through distributional changes in individual weights for each species. A stochastic growth model is employed to overcome a limited number of effective observations. One statistical challenge is to deal with non-identically distributed observations as only total weights and numbers of individuals caught for each species are observed. A modified Cramér-von Mises statistic is introduced and the p-values are evaluated by random number generation. As a result, the gamma distribution, the equilibrium distribution of the stochastic growth model fits well to 57 out of 80 cases before trawling. We conclude that most of the species are unaffected by trawling but several other species are shifted towards lighter weights. The unevenness of the effect over regions suggests that other environmental effects and ecological factors are involved.