of several drivers and should be studied. Size-spectra (the distribution of a community metric across individual body size classes) provide a simple modelling method to capture aspects of marine communities such as trophic structure and productivity. Biomass size-spectra parameters have been used as indicators of fishing exploitation. Also diversity size-spectra (the distribution of a diversity metric across individual body size classes) can be informative of fishing induced changes in ecological dynamics. In fact, since fish change diet and aggregation patterns as they grow in size, different ecological constraints may determine the number of species coexisting (species richness) and their relative abundances (species evenness) at different fish size ranges. To test the effects of fishing on both size and trait-based aspects of demersal fish of the South Aegean Sea, the heavily fished area of the Cyclades plateau was compared with the lightly fished area of Northern Crete. To account for the role of environmental parameters, the spatial distribution of primary productivity was also explored.
While the spatial distribution of large fish biomass and diversity was found to be highly correlated with primary productivity, fishing effort provided a better explanation for small fish spatial patterns. This suggests that the size structuring of fish community biomass and diversity must be taken into account to understand and monitor human impacts and that both habitat and fishing need to be taken into account.
Cetaceans and climate change in northwest Europe: What, where, why, when?
School of Biological Sciences (Zoology), University of Aberdeen, Tillydrone Avenue, Aberdeen, AB24 2TZ, UK.
As top predators, cetaceans can be used as indicators for environmental impacts on marine ecosystems. Climate change can potentially affect cetaceans in a number of ways. Currently, the best studied impact is the effect of changes in water temperature on species ranges. It has been predicted that the ranges of 91% of marine cetacean species will be affected by climate change, and that certain ecological characteristics make some species more vulnerable than others. In terms of the waters around northwest Europe, the species at the greatest risk is thought to be the white-beaked dolphin, while the common dolphin is expected to benefit the most. Given this framework, we studied the distribution of cetacean species in northwest Europe and found a number of past and current changes