Rainfall, river discharges and sea temperature as factors affecting abundance of two coastal benthic cephalopod species in the Gulf of Cádiz (SW Spain)

Abstract

This paper concerns correlations between environmental variables and abundance of two species of benthic cephalopods. Primarily, we aim to reveal putative links between rainfall rates, river discharges, sea surface temperature and landings as indices of abundance. We analysed landings, effort and landing per unit effort (LPUE) patterns of common octopus (Octopus vulgaris) and cuttlefish (Sepia officinalis) from a time series of 18 yrs. We show that both LPUE and landings may be used as suitable indices of abundance by analysing correlations between landings, LPUE and fishing effort. Pearson coefficients of correlation showed that octopus abundance is highly correlated with the rainfall previous to the fishing season, the river discharges of January, February and December, and sea surface temperature of June. Cuttlefish abundance did not show correlatons with any variable. While Octopus seems to be very much affected by the environment, particularly in early-life stages, cuttlefish survival is less susceptible to environment changes or fluctuations. A multivariate regression linear model including rainfall and sea surface temperature variables as predictors was built up. Further applications and uses of this environmental modelling approach for forecasting are discussed.