This study evaluated the genetic variability and traceability potential of farmed European sea bass (Dicentrarchus labrax) and gilthead seabream (Sparus aurata) populations from a fish farm located in Petrosino (Marsala, Sicily) (FAO 37), using microsatellite markers. A total of 64 D. labrax and 63 S. aurata individuals were genotyped with species-specific multiplex panels (9 and 10 loci, respectively). High levels of polymorphism were observed in both species, with an average of 12 alleles per locus in D. labrax and 9.1 alleles per locus in S. aurata. Mean observed heterozygosity (Ho) was 0.530 in D. labrax and 0.459 in S. aurata, while expected heterozygosity (He) reached 0.762 and 0.702, respectively. The fixation index (F) indicated moderate heterozygote deficiency in both populations (0.320 in D. labrax and 0.352 in S. aurata). Significant deviations from Hardy–Weinberg equilibrium were detected at most loci in both species, suggesting non-random mating, genetic drift, or population substructure. The probability of identity (PI) values across loci confirmed the high discriminatory power of the microsatellite panels, supporting their suitability for individual identification and genetic traceability applications in aquaculture. Overall, the results highlight that, despite substantial genetic variability, the observed heterozygote deficiency and deviations from equilibrium may reflect suboptimal breeding management practices. These findings underline the importance of implementing regular genetic monitoring and integrating molecular tools into broodstock management to maintain genetic diversity, reduce inbreeding, and support sustainable aquaculture production.

Multi-year series of surface microplastics at fixed stations are scarce in the Mediterranean, so episodic variability cannot be separated from persistent contamination. This study aimed to quantify the interannual variability of surface microplastics in Sicilian coastal waters, test differences among sites and along the inshore–offshore gradient, and derive indications for monitoring design. Under the Marine Strategy Framework Directive, eighteen stations at 0.5, 1.5 and 6 nautical miles from shore were sampled twice yearly with a Manta net from 2015 to 2025 (329 samples). Particles of 0.3–5 mm were isolated by sieving and identified by stereomicroscopy. Log-transformed concentrations were analyzed with linear mixed-effects models accounting for samples from the same outing, comparing an extended set of candidate models. Year was the only supported factor: model-based concentrations peaked in 2016–2017 and were about nine times lower in 2020–2021 (95% CI 5.4–14.7), whereas sites, distance bands and surveys did not differ and no site-specific trajectories emerged. The median concentration (0.044 n m⁻²) was comparable with other Italian coastal waters, and half of the unexplained variability arose between sampling outings. Contamination varies non-linearly between years rather than progressively. Monitoring precision would gain more from additional outings than from additional stations per outing.