Assessment of the seascape suitability along the Iberian Atlantic margin for species exploited by fisheries

• Autor(a) principal: Nunes, Catarina Matos
• Data de Publicação: 2021
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10773/33517
• topic: Ecological niche model; Distribution range shifts; Ensemble model; Merluccius merluccius; Trachurus trachurus; Habitat suitability

One of the most remarkable effects of climate change in marine realm is the shift in the distribution of species. On the other hand, marine ecosystems are also being modified by commercial fisheries (e.g., decline of species with low reproductive rates, alterations in population size structure, habitat loss and decreased habitat quality). Fisheries combined with climate change may cause the redistribution of marine species commercially exploited by fisheries and these changes can cause considerable socio-economic impacts. Therefore, it is crucial to anticipate these changes aiming a sustainable management of marine living resources and food security. The European hake (Merluccius merluccius) is a demersal species while the horse mackerel (Trachurus trachurus) is a pelagic-neritic species, and both are among the most important species commercially exploited in the Northeast Atlantic. In this work, I estimated the habitat suitability along the Iberian Atlantic waters for the European hake and horse mackerel using an ensemble ecological niche model (ENM) approach. Three machine-learning algorithms (Generalized Boosting Model, Random Forest, Maximum Entropy) were selected to estimate the habitat suitability and related uncertainty maps. The predictions of habitat suitability were made for present ocean conditions (2002-2014) and then projected to future scenarios of climate change (RCP 2.6 and 8.5) for the years of 2050 and 2100. The models were fitted using both oceanographic variables (temperature, salinity, and current velocity) and physiographic variables (bathymetry, bathymetric slope, and sea bottom curvature). The variables that most contribute to the model’s predictions were bathymetry, bottom temperature, and salinity for the European hake and bathymetry and salinity for the horse mackerel. Both the ensemble and single models showed high predictive performance, with the ensemble model estimates consistently performing better than the single models. According to the model for the European hake, the most suitable areas were predicted along the continental shelf, especially along the outer edge while the most unsuitable conditions were found in areas off the continental shelf. Moreover, the ENM predicted a decrease on the habitat suitability comparatively to the present conditions for future scenarios of climate change, mainly in the northern and western Iberian Peninsula whilst in the southern areas the habitat suitability is likely to remain constant. These predictions showed high reliability between single models for the most suitable and most unsuitable areas as well as a low uncertainty. For the horse mackerel the most suitable habitat areas were also predicted for the continental shelf and the most unsuitable areas were predicted in offshore area. The projections for the habitat suitability according to future ocean conditions estimated a slightly to moderate increase in the habitat suitability for areas currently offering low habitat suitability for the species. Notwithstanding, these projections were subjected to moderate to high uncertainty. On the other hand, the ensemble prediction for the areas of higher habitat suitability for horse mackerel show low uncertainty. This study brings new insights to the potential impact of climate change in distribution of two economically important species. It is important to be aware that climate change and anthropogenic activities, such as fisheries, will continue to co-exist, putting pressure on the stocks of diverse fish species. Changes in the potential distribution of species may require new management measures for the fishing sector, such as the redefinition of fish stocks and fishing effort. This study provides relevant and spatial explicitly information that may contribute for the development of effective conservative and management measures.