Patterns and Trends in Cetacean Strandings on the Galician Coast and Their Relationship with Oceanography and Fishing Effort.

Summary: Strandings provide valuable information on the presence and relative abundance of cetaceans in an area. The spatial, inter-annual and seasonal variation in the number of strandings may reflect the variability in cetacean abundance. However, this signal can be masked by other factors which are responsible both for the mortality of the dolphins and the probability that they reach the shore once they are dead. We analysed the time series of cetacean strandings in Galicia (NW Spain), available since 1990, with the aim of determining the trends and variability of strandings. We found that seasonal and inter-annual variation in the number of strandings is highly correlated with the oceanographic conditions most prevalent in each period. Moreover, a more detailed analysis of these effects should be carried out, and the use of further applicable indices (fishing effort rather than landings) may improve the explained part of the models, thus allowing us to disentangle oceanographic effects and to obtain relative seasonal and annual abundances.