Spatio-temporal patterns of macrourid fish species in the northern Mediterranean Sea

Abstract

The present study describes for the first time the spatial distribution of five macrourid species throughout the Mediterranean Sea and analyses depth, geographical and time-related trends regarding their abundance, biomass and mean fish weight. The data were collected as part of the MEDITS annual bottom trawl survey carried out by several European Mediterranean countries from 1994 to 2015, using the same standardized gear and sampling protocol. The most represented species in terms of abundance and biomass was Coelorinchus caelorhincus. The bathymetric trend was different for each species. The shallowest occurring species was C. caelorhincus, followed by Hymenocephalus italicus and Nezumia sclerorhynchus, while Nezumia aequalis and Trachyrincus scabrus were the deepest. Overall, the mean weight of all the species increased with depth. C. caelorhincus and H. italicus occurred in the entire study area: the first species showed relatively high catches in most areas, while the second was more abundant in the central and easternmost areas. N. aequalis and T. scabrus were mainly reported in the western basin, and N. sclerorhynchus in the central-eastern areas of the Mediterranean. An increasing inter-annual trend in abundance was only detected for C. caelorhincus and N. sclerorhynchus, while variable fluctuations were observed in the other species.

Modelling the Mediterranean Sea ecosystem at high spatial resolution to inform the ecosystem-based management in the region

“…These could be traced back to increases in the biomass of the commercially important bluefin tuna (for CB and TB), and also to increases in biomass of non-commercially important groups like the mesopelagic (for TB) and bathy-demersal fishes (for D/P and TB). Evidence that showed an increase in the biomasses of these functional groups has been observed in other studies, which pointed to changes in environmental conditions and a reduction in fishing effort for bluefin tuna 54 , 55 , and to environmental conditions, low fishing pressure, removals of predators and/or competitors for mesopelagic and bathy-demersal fishes 56 , 57 . However, caution should be taken with these results as most of the information (e.g., distribution and biomass) available for these groups at regional and spatial and temporal scales comes from modelling applications.…”