Discards represent the portion of the total fishery catch rejected at sea, for different reasons; their management has become increasingly important within the framework of the Common Fisheries Policy (CFP), representing a major challenge for commercial fisheries, with significant implications for the sustainable management of fishery resources and marine ecosystems in the Mediterranean Sea. This study aimed to provide a qualitative and quantitative characterization of discards generated by bottom trawl fisheries (OTB) and set nets used in small-scale fisheries (SSF), including trammel nets (GTR) and gillnets (GNS).

Monitoring conducted in the Ligurian Sea during 2025 included 47 observations: 19 from OTB fisheries, divided into three métiers (OTB_DES, OTB_DWS, and OTB_MIX), and 28 from GNS and GTR fisheries, classified according to target species. Results showed that OTB_DES exhibited the highest discard rates, reaching 25% in abundance and 21% in biomass. Among set nets, the highest discard rates were recorded in GTR in terms of abundance (55%) and in GNS in biomass (17%). Shannon and Pielou indices indicated greater multispecificity in trawl fisheries (75 species) compared with set nets. The comparative analysis of length distributions for two target species, Merluccius merluccius (HKE) and Mullus barbatus (MUT), highlighted a marked difference between gear types. OTB_DES captures a significant proportion of juvenile HKE, with a median length (L_MED) of 18 cm, below both the minimum conservation reference size (MCRS) and the length at first maturity (L₅₀); whereas GNS catches are more concentrated on larger specimens ( L_MED 32 cm). For MUT, median sizes are above both the MCRS and L₅₀ in both gears, with an L_MED of 14 cm in OTB_DES and 19 cm in GTR. These findings highlight substantial differences in discard production among fishing gears and provide useful information for developing measures to reduce their impact on fishery resources and environment.