Modelling relationships between fisheries landings and oceanographic variables: A case study in adjacent areas of Gibraltar Strait

Small pelagics are one of the most important groups of fishes in the world due to their ecologic significance in the trophic web. Small pelagics are the main target of the world’s fishery industry and European anchovy, European sardine, mackerel and horse mackerel represent 43.7% of the total landings in Andalusia (southern Spain). The main objective of this study was to analyse the different factors that could be affecting the abundance of these small pelagics in the two main andalusian fishing areas: Gulf of Cadiz and North Alboran Sea. For this purpose, multiple Generalised Additive Models (GAM) were performed using different oceanographic variables and landing time series as explanatory variables. The explanatory variables were also included with up to a three-year lag. A total of 4776 partial models were performed and eight models (the best for each species per area) were extracted for analysis. GAM models explained up to 61% of the total variance. Most of the models showed a strong non-linear relationship between different fish landings, and all models showed primary production as a key environmental factor to explain variations in the abundance of these small pelagics. However, results also revealed differences in the fishing pressure for all species in both fishing grounds. The use of non-linear models as an analytic tool could be useful for improving the knowledge on small pelagics and the management of the small pelagics fishing industry.