Long term oscillations of Mediterranean sardine and anchovy explained by the combined effect of multiple regional and global climatic indices

This study is a contribution to the PELWEB project (“Winners, losers and shifts of PELagic food WEB changes in the western Mediterranean Sea: from ecosystem consequences to future projections”, CTM2017-88939-R,2018–2020), and to “Fostering the capacity of marine ecosystem models to PROject the cumulative effects of global change and plausible future OCEANS” (PROOCEANS): Funding by Ministerio de Ciencia e Innovación, Proyectos de I+D+I (RETOS-PID2020-118097RB-I00).It is widely known that the abundance and distribution dynamics of populations of small pelagic clupeid fish, such as sardines and anchovies, are affected by large-scale climate variability, which may lead to changeovers to new regimes of small pelagics. However, long-distance climatic oscillations, such as El Niño/La Niña and the Pacific Decadal Oscillation, have been little explored in the Western Mediterranean Sea. We investigated the possible effects of the South Oscillation Index (i.e. the atmospheric oscillation coupled with the El Niño/La Niña) and Pacific Decadal Oscillation on fluctuations in catches of European anchovy (Engraulis encrasicolus) and sardine (Sardina pilchardus) in the Western Mediterranean Sea, and their association with regional climate oscillations (i.e. the Atlantic Multidecadal Oscillation, the North Atlantic Oscillation, the Western Mediterranean Oscillation index, and the Arctic Oscillation)

Using mobile device’s sensors to identify fishing activity

Fisheries management is generally based on the regulation of the fishing effort, by limiting fishing capacity and activity. The fishing capacity can be quantified objectively, however, the calculation of the fishing activity requires knowing the effective fishing time, for which it is essential to monitor the vessels activity. The European Vessel Monitoring System (VMS) only describes the geographical position, course and speed of the vessel at 2-h intervals, it is an expensive system used only in vessels over 12 m in length and there are no common criteria to infer the fishing activity from the VMS data. To evaluate more precisely the fishing activity, we propose to incorporate new sensors in the vessels that provide additional information. The sensors of mobile devices offer an economic solution that would allow their implementation throughout the fishing fleet. The objective of this work is to evaluate whether the most common sensors integrated in current mobile devices: GPS, accelerometer, gyroscope, and magnetic field, offer relevant information to identify the different phases of bottom trawling fishing activity. The results obtained indicate that these sensors detect, with very high precision, foreseeable changes in the movement of the vessel during the towing manoeuvre

Hook selectivity models assessment for black spot seabream. Classic and heuristic approaches.

Size selectivity of the deep water longline used in the black spot seabream (Pagellus bogaraveo) fishery in the Strait of Gibraltar was studied with data of four sizes of hooks. Logistic (classic) and Artificial Neural Networks (heuristic) selectivity models were fitted for two experimental fishing trials. Logistic selectivity model was adequate for only one of the two periods analysed and the inferior results obtained with the classical approach were significantly improved by ANNs. These results indicate that in the event that the classic models do not fit well, perhaps due to poor quality of the data (such as a smaller sample size or highly overlapped distributions), the simpler ANNs models, with capacity to combine linear relationships and highly non-linear, are most appropriate to establish the functional relation between variables

Selectividad del arte de pesca del voraz de Tarifa

Species and size selectivity of the deep water longline traditionally used in commercial fishing of the black spot seabream (Pagellus bogaraveo) were studied in the Strait of Gibraltar with four sizes of hooks. Black spot seabream contributed up to 88% of the catch by number. Catch and by-catch rates differed for the different hooks and fishing trials. Significant differences in average fish length between all hooks, except in one case, were found. The comparison of two experimental fishing trials within 4 years indicates a displacement towards smaller sizes in the size frequency distributions. The results of this study show that the fishing gear can be size selective depending on hook size. The fitted selectivity models for each experiments were very different despite having two hooks in common. This is probably due to the very different catch size distributions in the two periods, which suggests that the population size structure changed significantly between 2000/2001 and 2004/2005