The seafloor of the Mediterranean Sea accumulates marine litter (ML), an area where bottom trawlers operate and can accidentally catch the litter from the seafloor. This study aims to describe and quantify the ML caught by bottom trawlers along the Catalan coast (NW Mediterranean Sea) and estimate the potential of the bottom trawl fleet to extract ML from the area as a Fishing for Litter (FFL) initiative to tackle the ML issue. Marine litter was collected from commercial trawlers and was classified as metal, plastic, rubber, textile, wood, and other waste and weighed (kg) from 305 hauls performed during three years (2019-2021) from 9 different ports at 3 different depths. ML was present in 97 % of the hauls, with plastic being the most abundant material. The composition varied according to zone, port and depth, with the highest densities found in highly urbanized areas (13.75 ± 3.25 kg km^-2), which mainly contained plastics (74.3 %). The port of Barcelona had the highest presence of plastics (23.62 ± 6.49 kg km^-2), mainly wet wipes. Regarding depth, the continental shelf had the highest density of ML, with 12.24 ± 2.40 kg km^-2. The potential ML removal (t year^-1) was calculated using fishing effort (hours). It is estimated that the bottom trawlers may potentially remove 237 ± 36 t year^-1 of ML in the Catalan coast. FFL initiatives should be part of a multidisciplinary approach to tackle marine litter, which must include prevention, monitoring, and cleaning actions.

This study characterized the fishery dynamics of blue whiting, a bycatch species of the bottom trawl Norway lobster fishery, in the NW Mediterranean. Landings and effort data over the last two decades were combined with current information on the spatial distribution of effort and catch, and with the size and age structure of blue whiting over the year. Recruitment to the demersal habitat occurred from 5 cm total length (TL) over the shelf break in spring (April-May), when discards showed the highest values (>95% of the catch). Adults were located over the upper slope, and large individuals (≥26 cm TL) were abundant during the reproductive period (January-March). A decline in landings has been observed in the last decade, probably related to the absence of intense deep convection processes in winter since 2013, which favour recruitment of the species. The effect of exploitation on the decrease in landings cannot be disregarded considering that the bulk of the catch is made up of immature (age 0) individuals, and the presence of old individuals is very low.

Aim: Oviparous elasmobranchs lay benthic eggs with long incubation periods, many of which also require habitat‐forming sessile organisms for their development. However, they are threatened by bottom‐trawling fishing impacts. Here, we aimed to identify the suitable habitat distribution of small‐spotted catshark (Scyliorhinus canicula) egg nursery areas, assess their current protection extent by an existing no‐take MPA network and their coverage by other delimited spatial‐based conservation areas.Location: Balearic Sea, northwestern Mediterranean.Methods: Egg cases were collected over 5 years (2018–2022) by a bottom‐trawling monitoring programme along the eastern coast of the Iberian Peninsula. We used these occurrences and various environmental variables (bathymetry, slope, sea bottom temperature, sea bottom dissolved oxygen and seabed type) to model the habitat suitability of egg nurseries for the species using maximum entropy modelling.Results: Sea bottom temperature was the most important variable explaining habitat suitability of egg nurseries. Small‐spotted catshark eggs were found either attached to or in the same samples as various species of habitat‐forming sessile organisms. We found only 3.6% (381 km²) of the modelled suitable egg nursery habitat in the Balearic Sea to be currently covered by an implemented no‐take MPA network. At the same time, 52% of said MPAs are inadvertently protecting suitable egg nursery habitats (and their associated benthic community), as they were not initially planned with elasmobranchs as conservation targets. Important shark and ray areas (ISRA‐IUCN) were also observed to cover egg nursery habitat (4502 km² or 15.52%) within their boundaries.Main Conclusions: While half of the current MPA surface is providing protection to this elasmobranch species' egg nursery areas and their associated benthic communities, they are not sufficient for their conservation. However, mapping the distributions of these essential fish habitats can help towards the 2030 European conservation target of ‘strictly protecting’ 10% of marine environments.

The establishment of fisheries no-take areas is considered an effective method for the recovery of populations of exploited species and their habitats. Here we study the faunistic composition of decapod crustaceans after the implementation of a no-take area in the Gulf of Roses (NW Mediterranean) in 2014. We studied the occurrence (presence/absence) and density of all decapod crustaceans sampled by trawling inside and outside a no-take area from March 2015 to July 2018. Sizes were assessed for all common species. A total of 33 species of decapod crustaceans were recorded. Four species showed significantly higher occurrences in the no-take area and three in the open area, while significantly higher densities were found for four species in the no-take area and three in the open area. Multivariate analysis showed marked differences between the no-take area and the open area, while also showing that the two areas were undergoing a divergence. The comparison of sizes between the two zones showed species-specific patterns that in many cases showed that both the smallest and the largest individuals were present in the no-take area, suggesting that the closing of this area would be important for recruitment and juvenile development, as well as for protection of large-sized individuals. All evidence indicates that the establishment of the no-take area has led to an improvement in biodiversity and species population descriptors.

The high incidence of anthropogenic impacts in the Mediterranean basin raises concerns on the health and quality of commercial fish species. This study aims to evaluate the health status of the European hake, Merluccius merluccius, from three areas of the Catalan coast (NW Mediterranean Sea) with different anthropogenic impacts (i.e., chemical pollution, litter, …) and assess if hake could serve as a sentinel species. We measured biomarkers of chemical exposure including B-esterases, antioxidant enzymes (GST, GR, GPx, CAT), biotransformation markers (EROD), lipid peroxidation, and macro-parasite assemblages. Hake showed, generally, a good health status across all areas with homogeneous patterns for most parameters. Tissue-specific differences included elevated gonadal cholinesterases and higher brain and hepatic carboxylesterase activities in the south, and increased hepatic EROD but lower lipid peroxidation in the central Barcelona area. Parasite assemblages were dominated by Digenea, Cestoda, and Nematoda, with higher cestode prevalence in both central and south zones. In summary, despite a greater prevalence of environmental pollution in the central region, there was a homogeneous pattern in hake health indicators throughout the three studied fishing zones. These results establish a baseline for hake health in Mediterranean waters and suggest that the species’ high mobility and wide depth range may limit its utility to detect local-scale pollution impacts, though it may serve as a regional-scale bioindicator.