The role of climatic variability on the short-term fluctuations of octopus captures at the Canary Islands

Abstract

The effect of temperature on the common octopus life cycle has been well studied. However, how other climatic patterns affect them is poorly understood. The present work emphasises the importance of the temperature on common octopus catches by the small-scale trap fishery off the Canary Islands, and also highlights the effect of the North Atlantic Oscillation (NAO) pattern. As well as an inverse and significant correlation between octopus abundance (measured as CPUE) and Sea Surface Temperature (SST), a direct relationship between abundance and NAO, off the Canary Archipelago, is reported. Using a linear model (lm) with a stepwise procedure, SST is found to be the most important and significant variable in autumn, accounting for 34.21%. Meanwhile, the NAO became more important in spring with 28.64% and a 31.13% of the explained variance in autumn.

Wavelet analysis of correlation among Canary Islands octopus captures per unit effort, sea-surface temperatures and the North Atlantic Oscillation

“…Hernández-García et al (2002) and Caballero-Alfonso et al (2010) have shown that there is an effect of environmental variability on O. vulgaris abundance off the Canary Islands due to SST. The delay between both variables can be explained alluding to the consequence of the effect of sea water temperature on octopus recruitment, which affects crucial phases in the life cycle of this cephalopod (i.e., paralarvae survival, growth rates, age of juvenile benthic settlement and timing of the reproductive peaks).…”

“…Several realizations (500,000) of an AR(1) process with the corresponding autocorrelation for each of the tested series were created, and the correlation coefficients of segments with the same length as the tested series were used to create an histogram, which represents the distribution of correlation coefficients from AR(1) processes. Values of the correlation coefficient under (above) the 2.5% (97.5%) percentiles in the distribution of correlation coefficients were considered significant (Caballero-Alfonso et al, 2010).…”

“…Solari (2008) suggests that the oscillations in catches of O. vulgaris during the last 50 years in the Northwestern African upwelling system are closely related to variation in NAO index. Consequently, Caballero-Alfonso et al (2010) emphasized the importance of sea surface temperature (SST) and the NAO on common octopus catches in a small-scale trap fishery off the Canary Islands during 1989-2007. This study extends previous result by Caballero-Alfonso et al (2010), who used a linear model.…”

“…On the other hand, it is assumed that cephalopods, due to their short life cycle, around a year (Boyle and Boletzky, 1996;Hernández-López et al, 2001;Mangold, 1983;Doubleday et al, 2006;Leporati et al, 2008), are good indicators of climatic variability (Sims et al, 2001;Zuur and Pierce, 2004;Solari, 2008;Pierce et al, 2008;Caballero-Alfonso et al, 2010).…”

“…The influence could be explained either through growth, food availability or natural mortality due to other causes (Forsythe, 1993;Caveriviere et al, 1999;Robin and Denis, 1999;Waluda et al, 1999;Leporati et al, 2007;Pierce et al, 2008). It could therefore be more feasible to differentiate climatic effects from the influence of fishing in these species, because their response to environmental fluctuations should be faster (Hernández-García et al, 2002;Chen et al, 2006;Caballero-Alfonso et al, 2010).…”