Scottish lobster fisheries and environmental variability

Abstract

Variability in the fluctuations of two Scottish lobster populations, the Hebrides and Southeast, was investigated from available long dataseries of fishery and environmental variables. In a multivariate context, relationships between selected environmental variables and the fishery data were studied at different spatial and temporal (annual, spring, and autumn) scales and from individual and overall sampled fleet. Multivariate techniques such as cross-correlation function, principal components analysis, and redundancy analysis confirmed that the capture of lobsters was strongly influenced by sea surface temperature, windspeed, and sea level pressure throughout the year, and this dependence affected the duration of the fishery. There were evident differences in the patterns of environmental variables for both regions. In the Hebrides, the total variation (42%) of the interaction fishery-environmental variables for spring and autumn fisheries could be attributed to the environmental variables in an 89%. For the Southeast, spring fishery was more affected by changes in the environment, with a total variation of 34%, from which 85% could be explained by the environmental variables tested, than autumn fishery where catches and catch rates may be more affected by the way individual vessel and sampled fleet operate. Two elements were identified, Hebrides and Southeast spring and autumn fisheries. The Hebrides lobster population is strongly influenced by density-independence processes at all spatial scales. The Southeast fishery is also driven by environmental processes, with higher correlations for recruits with differences at small and large spatial scales.