Elasmobranchs (sharks, skates, and rays) face a significant threat from fishing, often as bycatch but increasingly as target species due to high demand for their products. Global elasmobranch catches peaked at 900,000 tonnes in 2003, subsequently declining but still likely underestimated due to illegal, unreported, and unregulated (IUU) fishing. The unique life history traits of elasmobranchs (large size, slow growth, late maturity, low fecundity) make them particularly vulnerable to overfishing, resulting in approximately one-third of species being classified as threatened by the IUCN. Small-scale fisheries (SSF), employing 90% of the world's fishers and contributing to over 50% of global marine species catch, are often understudied, with limited information on their impact on elasmobranchs. While generally considered less impactful than large-scale fisheries, studies indicate their significant threat to vulnerable marine vertebrates like sea turtles and marine mammals. The potential impact of SSF on elasmobranchs remains poorly understood. Marine Protected Areas (MPAs), including fully protected areas (FPAs) and partially protected areas (PPAs), are proposed as conservation tools. FPAs have been established globally but their effectiveness, especially for mobile species like elasmobranchs, is debated. PPAs, allowing for regulated human activities, represent most MPAs' surface area. Although showing benefits for coastal fish, evidence on their effectiveness for elasmobranchs is limited. The Mediterranean Sea, an elasmobranch biodiversity hotspot, has experienced significant elasmobranch decline due to fishing and habitat degradation. SSF in the Mediterranean, accounting for 83% of fishing vessels, are known to impact elasmobranch populations. While the Mediterranean hosts numerous coastal multiple-use MPAs, mainly PPAs, their role in elasmobranch conservation remains unexplored. This study investigates the interaction between SSF and elasmobranchs within and outside PPAs in 11 Mediterranean MPAs, hypothesizing higher elasmobranch catch per unit of effort (CPUE) in PPAs than in UPAs due to fishing restrictions in PPAs.

Existing literature highlights the severe decline in global elasmobranch populations due to overfishing, with catch statistics significantly underreported. The unique biological characteristics of elasmobranchs, such as slow growth, late maturity, and low fecundity, exacerbate their vulnerability to fishing pressure. The role of small-scale fisheries in this decline is under-researched, though studies indicate their impact on other vulnerable marine species. Marine Protected Areas (MPAs), particularly fully protected areas (FPAs) and partially protected areas (PPAs), are increasingly promoted as effective tools for marine biodiversity conservation. While FPAs hold promise, their application for mobile, long-lived species like elasmobranchs requires further investigation. PPAs, allowing for controlled human activities, represent the majority of MPAs globally. Although evidence exists for positive effects on coastal fish, their influence on elasmobranch populations remains uncertain, particularly in the Mediterranean, a region with a rich history of human exploitation and subsequent decline in elasmobranch biodiversity. Studies on the impact of small-scale fisheries on elasmobranchs within MPAs in the Mediterranean are notably scarce, necessitating further research to understand the effectiveness of different MPA management strategies in protecting these vulnerable species.

The study involved the assessment of elasmobranch catches from 1256 small-scale fishing operations using fixed nets in 11 Mediterranean MPAs across six countries between June 2017 and October 2018. Nine of these MPAs contained partially protected areas (PPAs) where fishing is allowed but regulated, while surrounding areas served as unprotected areas (UPAs) for comparison. Data was collected through a collaborative project involving fishers, MPA managers, and researchers, with fishers voluntarily participating in catch assessments. A photo-sampling technique was employed at landing sites to minimize disturbance and ensure accurate catch recording. Pictures of the entire catch, including a ruler for scale, were taken, allowing for subsequent image analysis using ImageJ software for species identification and measurement. Total length of each individual was measured, and biomass estimated using length-weight relationships from FishBase. Catch per unit of effort (CPUE) was calculated for both abundance (NCPUE) and biomass (BCPUE), standardized by net length. Length at first maturity (L50) data from literature was used to classify individuals as mature or immature. Environmental (chlorophyll a, sea surface salinity, dissolved oxygen, phosphate, nitrate, sea surface temperature, and habitat), geographical, temporal, bathymetric (fishing depth), and anthropogenic data were collected to control for potential confounding variables. Generalized additive models for location, scale, and shape (GAMLSS) were used to analyze BCPUE and NCPUE data, considering protection status and environmental covariates. Partial redundancy analysis (pRDA) explored the relationships between protection, IUCN categories, and BCPUE/NCPUE. Statistical differences in mature/immature proportions between PPAs and UPAs were analyzed separately for each IUCN threat category.

A total of 892 elasmobranch individuals belonging to 24 species were recorded across 1256 fishing operations. Over one-third of the species caught were categorized as threatened (Critically Endangered, Endangered, or Vulnerable) according to the Mediterranean IUCN Red List. The biomass CPUE (BCPUE) was highest for threatened species, while lowest for data-deficient species. Analysis revealed that while the probability of encountering elasmobranchs in fishing operations was higher in UPAs, both BCPUE and NCPUE were significantly higher in PPAs. Generalized additive models (GAMLSS) indicated a significant positive effect of protection on both BCPUE and NCPUE. Chlorophyll a concentration showed a significant positive relationship with both BCPUE and NCPUE, while sea surface temperature exhibited a negative relationship with BCPUE. A positive relationship was found between human impact index and NCPUE. Analysis of maturity indicated a higher proportion of immature individuals for threatened and data-deficient species in PPAs, suggesting potential impacts on recruitment. Partial redundancy analysis (pRDA) highlighted that Endangered and Vulnerable species were significantly correlated with PPAs.

The higher CPUE of threatened elasmobranchs within PPAs suggests that these areas might serve as refuges, despite the presence of fishing activity. This finding indicates that the fishing restrictions within PPAs, leading to potentially reduced fishing effort and the use of less-impacting gear, could positively affect elasmobranch populations. The higher abundance of immature individuals within PPAs suggests these areas may act as important nurseries. The positive relationship between chlorophyll a and elasmobranch CPUE highlights the role of environmental factors in supporting elasmobranch populations. However, the counterintuitive positive relationship between the human impact index and NCPUE could be due to the removal of top predators leading to increased meso-predator populations or juvenile recruitment. The study's findings emphasize the importance of well-managed PPAs as potential tools for elasmobranch conservation, despite the ongoing challenges posed by SSF activities within MPAs.

This study demonstrates that while partially protected areas (PPAs) within Mediterranean MPAs show potential for elasmobranch conservation by exhibiting higher CPUE of threatened species compared to unprotected areas, effective management of small-scale fisheries within these PPAs is crucial. The higher abundance of immature individuals in PPAs suggests these areas may function as important nurseries. Future research should focus on understanding the ecological mechanisms driving these findings, including prey availability and interactions within the food web. Improved data collection on SSF effort, coupled with targeted management measures such as minimum landing size regulations and gear restrictions, are essential to enhance the conservation effectiveness of MPAs and protect threatened elasmobranch populations.

This study is based on fishery-dependent data, meaning CPUE estimations are influenced by fishing practices. The absence of data on elasmobranch prey limits the ability to fully assess the trophic interactions driving observed patterns. Furthermore, the study focuses on a specific region and fishing gear type, limiting the generalizability of the findings. The voluntary participation of fishers may introduce bias, although efforts were made to ensure broad representation.