Browsing by Author "Tserpes, George"
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- The diet and feeding habits of lagocephalus sceleratus in the eastern Mediterranean: a case study carried out off the island of Crete (southern Greece)Publication . Vieira de Carvalho Gomes, Rita; Christidis, Georgios; Peristeraki, Panagiota; Somarakis, stylianos; Tserpes, GeorgeThis study focused on the diet and feeding habits of the invasive pufferfish Lagocephalus sceleratus in the coastal waters of Crete (Cretan and Libyan Sea, eastern Mediterranean). The diet was composed of a wide variety of organisms, while the number of specimens with empty gastrointestinal tracts was low (14.41%). In total we were able to identify 38 different species of fish and invertebrates within the tracts analysed. Fish were the main diet component, followed by crustaceans and mollusks (mostly gastro- pods and cephalopods). At family level, the most significant preys were Sparidae and Mullidae teleosts, along with Cavoliniidae gastropods. The trophic level of L. sceleratus was estimated to be 4.13. The trophic niche breadth was intermediate, whereas the L. sceleratus population exhibits a mixed feeding strategy. Spatiotemporal differences in diet composition were also identified. The application of generalized additive models (GAMs) revealed that depth at which the fish were captured, season, region and total length, were significant predictors of the probability of occurrence of its most frequent prey groups. Fish prey occurrence was more probable in autumn and summer and at circa 20-25 m depth. In contrast, the probability of consuming crustaceans was higher in spring and winter and in specimens measuring 450-500 mm in length, and lower at 20-25 m, whilst increasing until a maximum at 40 m. The probability of non-cephalopod mollusks consumption was higher in winter and in the Libyan Sea, as well as at greater depths. Fish size had a significant effect on the likelihood of consuming photosynthetic organisms (algae and seagrass) and cepha- lopods, which was higher in larger fish. This study presents further evidence of the negative impact of L. sceleratus on the fisheries sector, revealing both predation on commercial species and the ingestion of various fishing gear parts.
- Marine spatial closures as a supplementary tool to reduce discards in bottom trawl fisheries: examples from southern European watersPublication . Despoti, Smaragda; Milisenda, Giacomo; Ligas, Alessandro; Bentes, Luis; Maynou, Francesc; Vitale, Sergio; Garofalo, Germana; Sbrana, Mario; Erzini, Karim; Tserpes, George; Tsagarakis, Konstantinos; Maina, Irida; Pyrounaki, Maria-Myrto; Papadopoulou, Nadia; Machias, Athanassios; Colloca, Francesco; Fiorentino, Fabio; Stergiou, Konstantinos, I; Giannoulaki, MariannaDiscards is an important issue in fisheries around the world. the spatial management of discards has attracted interest as a potential tool for minimizing the unwanted catch. the aim of the present work was to identify areas with high quantities of bottom trawl discarded catch regarding species subjected to MCRS, in six areas of southern European waters (southern Portuguese waters, Catalan Sea, Ligurian and northern Tyrrhenian Seas, Strait of Sicily, eastern Ionian Sea, and Aegean Sea). Analyses were based on two types of data: (a) the undersized catch of species subjected to MCRS from bottom trawl surveys and (b) the actual discarded catch (including undersized and non-undersized individuals) of species subjected to MCRS from commercial bottom trawling. Geostatistical analysis techniques were applied to the first type of data and Generalized Additive Models using environmental variables were applied to the second one. Subsequently, areas that persistently presented high quantities of discarded catch (i.e., "iDC grounds") or undersized catch (i.e., "iUC grounds") were identified and mapped. the "iDC grounds"/"iUC grounds" were located either over the slope or within the continental shelf and over marine plateaus, largely depending on the main target species of each fishery. Next, the overlap of "iDC grounds"/"iUC grounds" with the existing Fisheries Restricted Areas (FRAs) and the proposed Marine Protected Areas (MPAs) was estimated aiming to explore how spatial closures could contribute to the reduction of bottom trawl discarded catch/undersized catch. Certain spatial closures were more effective in the Central Mediterranean and others to the Eastern Mediterranean. the overlapping of existing FRAs with "iDC grounds"/`iUC grounds" did not exceed 24 % in any study area, whereas proposed MPAs, like the CIESM Marine Peace Parks, reached up to 90 % for the same study area.