Carlos Rodríguez-García

Despite their ecological importance, discarded species with low commercial value are often overlooked in marine research. This study examined the age structure and feeding habits of the large-scaled gurnard (Lepidotrigla cavillone) and the spiny gurnard (Lepidotrigla dieuzeidei) in the Gulf of Cádiz (SW Iberian Peninsula). A total of 225 specimens were collected during 19 fishing trips at depths of 15–550 m. Ages were estimated from otolith readings, and stomach contents were analysed to describe diet composition, niche breadth, and overlap. Both species showed positive allometric growth, with the most frequent age class being 5+ in L. cavillone and 5+–6+ in L. dieuzeidei. Crustaceans dominated the diet, with mysids accounting for >80% of the index of relative importance (IRI) in L. cavillone, but L. dieuzeidei displayed a broader diet including mysids (45% IRI) and decapods (32% IRI). Feeding patterns varied with time of day, depth, and size, reflecting ontogenetic and environmental influences. Levin’s index indicated stronger specialization in L. cavillone (BA = 0.090) than in L. dieuzeidei (BA = 0.208), while the Schoener index (0.575) showed moderate overlap. These findings provide the first biological insights into these discarded species in Atlantic waters, contributing to ecosystem-based fisheries management.

Beaches are among the world's most important coastal ecosystems, within which surf zones are crucial providers of essential ecosystem services to humans. We completed the first estimate of current and potential monetary value of fishery resources in surf zones of beaches on the southwestern Iberian Peninsula. Over 1 year, five beaches in the Gulf of Cádiz were sampled using a beach seine. For monetary valuation, average first‐sale prices were used, with a capital update based on the Consumer Price Index (CPI). The 189.16 kg of 38 commercial species captured had a potential monetary value (PMV) of 408.63 €/ha. The annual value of adult fish (19 species) averaged 115.05 €/ha and juvenile fish (33 species) averaged 293.58 €/ha. Our findings highlight the value of surf zones and beaches as fishery resources, similar to other marine ecosystems. Our findings are useful for ongoing monitoring and research to enhance knowledge of these areas and the array of ecosystem services they provide.

Various commercial fish species utilize different coastal habitats as nurseries in their juvenile stages, with surf zones being particularly crucial due to the protection and abundant food resources they offer. Among the species that rely on these areas are the spotted seabass (Dicentrarchus punctatus) and the European seabass (Dicentrarchus labrax). This study aimed to investigate the age and feeding habits of surf zone specimens of these species and explore their environmental adaptations. The average size for D. punctatus was 16.94 ± 4.05 cm, and for D. labrax, it was 23.23 ± 6.30 cm. The length–weight relationship for D. punctatus was TW = 0.013*TL^2.885 (parameter a: 95% CI: 0.012–0.014; parameter b: 95% CI: 2.854–2.917), and for D. labrax, it was TW = 0.008*TL^3.095 (parameter a: 95% CI: 0.006–0.009; parameter b: 95% CI: 3.040–3.151). In both D. punctatus (79.20%) and D. labrax (75.92%), the predominant age classes were 1+ and 2+. Significant variations in age class abundance were observed in D. punctatus based on the time of day, lunar phase, and season, while D. labrax showed variations only by season. A diet analysis revealed that both species primarily consume mysids and fish, with D. punctatus showing dietary variations related to the time of day, lunar phase, and season, and D. labrax showing variations with the time of day and season.

In many fisheries, such as trawl fisheries, sharks appear among the catches as bycatch or discards, and these species include velvet belly (Etmopterus spinax) and blackmouth catshark (Galeus melastomus). The objective of this study was to research the feeding habits of both species in the Gulf of Cádiz and to identify possible differences in diet depending on size and time of day. The most frequent sizes were 12–16 cm for E. spinax and 14–20 cm for G. melastomus. Both species preyed mainly on euphausiaceans and teleosts; their Index of Relative Importance (IRI) per species were as follows: E. spinax 42.30% IRI, 21.66% IRI; G. melastomus 52.33% IRI, 27.26% IRI, respectively. Only Etmopterus spinax showed significant variation in diet as a function of the time of day (p < 0.05), although both species showed similar patterns of feeding throughout the day. With respect to size, E. spinax consumes more cephalopods and teleosts as its size increases, while G. melastomus increases its consumption of decapods.