Benthic Habitats and the Effects of Fishing

Symposium Abstract: The Sensitivity of Fish and Macro-Epifauna to Habitat Change: An Analytical Approach

S. M. Freeman and S. I. Rogers


Increased use of seabed resources and greater awareness of the effects of fishing on the seabed call for an urgent need to assess the extent and diversity of seabed habitats affected by such activities. Existing methods that describe and predict the distribution of benthic habitats using either substrata or depth are generally inadequate. When other factors such as tidal velocity, temperature and salinity are combined with substrata and depth, they more clearly characterize these habitats. Principal components analysis (PCA) was used to evaluate the distribution and abundance of fish and macro-epifauna using a suite of factors. Characteristic habitat types were identified and provided a mechanism for predicting their spatial extent. A new analytical approach to link species to their habitat was constructed using a combination of PCA and a generalized additive model (GAM). The method predicts the habitat preferences of an individual species based on their association with the environment. Preferences were used to describe the likelihood of a species occurring across a range of different habitats; this was called the habitat-envelope. The strength of the association between species patchiness and its habitat-envelope indicated the potential sensitivity of the species to habitat change. Generally, fish had larger habitat-envelopes and more likely to exploit a wider range of habitats than crustaceans, whereas echinoderms were more selective, and hence more sensitive to habitat change.