The Gulf of Manfredonia: a new neritic foraging area for loggerhead sea turtles in the Adriatic Sea

Casale, Paolo; Simone, G. De; Conoscitore, Ciro; Conoscitore, Michele; Salvemini, Pasquale

doi:10.13128/acta_herpetol-9897

Cited by 5 publications

(7 citation statements)

References 32 publications

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“…Bycaught turtles spanned a wide size range, from small juveniles to adults, as also reported by previous studies (Casale et al, 2012b;Casale & Simone, 2017). Compared with other Mediterranean areas, large turtles were the majority (Turkey: 13-35%, >60 cm CCL; this study: 70%, >60 cm CCL), with among the highest mean CCL (Egypt, Greece, Tunisia: x ̅ = 51.3-73.4 cm; this study: x ̅ = 64.4 cm; see Casale (2011) for comparisons).…”

Section: Discussionsupporting

confidence: 82%

Section: Introductionmentioning

confidence: 78%

“…To obtain information of turtle distribution from bycatch data, the latter should be representative of the turtle population and possible confounding factors should be excluded. Turtle distribution and/or turtle susceptibility to be captured may be affected by temperature and season (Casale et al, 2012b;Lucchetti, Vasapollo & Virgili, 2017).…”

Section: Spatio-temporal Distribution Of Fishing Effort and Turtle By...mentioning

confidence: 99%

“…Although the South Adriatic was thought to be mainly an oceanic development area for small juveniles (Casale & Margaritoulis, 2010), the shallow waters of the Gulf of Manfredonia have been identified recently as an important neritic foraging ground for large turtles, including adults (Casale et al, 2012b), in some cases showing high fidelity to restricted areas (Casale & Simone, 2017). Here, the bycatch rate from bottom trawlers appears to be equal to, if not greater than, other Mediterranean areas (Casale et al, 2012b). Turtles captured by trawlers are subject to forced apnoea and drowning, resulting in direct (turtles dead at gear retrieval) and post-release mortality (turtles still alive when released but eventually dying), with the chance of mortality increasing with the duration of the haul (Sasso & Epperly, 2006).…”

Section: Introductionmentioning

confidence: 99%

“…Various studies conducted in Adriatic waters reported that turtles foraging here originate predominantly from rookeries in Greece, and to a lesser extent from Turkey and Libya (Giovannotti et al, 2010;Clusa et al, 2014;Splendiani et al, 2017;Tolve et al, 2018). Several studies have investigated sea turtle ecology and fisheries interaction in the Adriatic, and great attention has been given to turtle bycatch levels and hotspot areas for bottom trawlers, mostly in the northern part (Casale, Laurent & De Metrio, 2004;Casale et al, 2012b;Lucchetti, Vasapollo & Virgili, 2017;Vasapollo et al, 2019). More than 12,000 loggerhead turtle bycatch events by bottom trawlers are estimated to occur annually in the Adriatic, of which around 2,000 are probably fatal (Lucchetti, Vasapollo & Virgili, 2017).…”

Section: Introductionmentioning

confidence: 99%

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Voluntary fishing logbooks are essential for unveiling unsustainable bycatch levels and appropriate mitigating measures: The case of sea turtles in the Gulf of Manfredonia, Adriatic Sea

Baldi

Salvemini²,

Attanasio³

et al. 2022

Aquatic Conservation

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1. Studying the impact of bycatch on marine megafauna, including sea turtles, is challenging for a variety of technical and biological reasons. The Mediterranean Sea has among the highest levels of turtle bycatch globally, notably of the loggerhead sea turtle (Caretta caretta), and bottom trawling represents a particularly relevant threat.2. Bottom trawlers from a recently discovered neritic foraging area, the Gulf of Manfredonia, reported 1,152 loggerhead turtles incidentally caught in the period 2015-2020. Capture locations were available for 497 turtles. These data were complemented by the distribution of fishing effort obtained by the vessel monitoring system.3. High bycatch rates were observed, leading to more than an estimated 5,600 annual captures and to the death of a minimum of 560 large individuals with high reproductive value. These findings are extremely concerning for the affected population and require immediate action. A strong seasonality of turtle bycatch was observed, with most captures occurring in November-March when fishing effort occurs in shallow waters where turtles concentrate all year round. 4. Therefore, a seasonal approach (e.g. adopting measures only in the high-turtle bycatch season) can be pursued as long as the spatial distribution of fishing effort varies among seasons. However, such a spatio-temporal pattern should be monitored; then, in the case of change, although more difficult to implement, an area-based conservation approach should be pursued. Several recommendations are provided, including the urgent implementation of turtle excluder devices, at least on a seasonal basis.

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Section: Discussionsupporting

confidence: 82%

Section: Introductionmentioning

confidence: 78%

Section: Spatio-temporal Distribution Of Fishing Effort and Turtle By...mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Voluntary fishing logbooks are essential for unveiling unsustainable bycatch levels and appropriate mitigating measures: The case of sea turtles in the Gulf of Manfredonia, Adriatic Sea

Baldi

Salvemini²,

Attanasio³

et al. 2022

Aquatic Conservation

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A comprehensive mitochondrial DNA mixed-stock analysis clarifies the composition of loggerhead turtle aggregates in the Adriatic Sea

et al. 2018

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Diet of loggerhead turtles in the Gulf of Manfredonia, South Adriatic Sea: evidence of winter feeding and anthropogenic impacts

Baldi,

Miglianti,

Salvemini

et al. 2023

Mar Biol

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Investigating biological aspects of migratory marine animals like sea turtles is challenging. The Adriatic Sea is a key Mediterranean foraging ground for loggerhead turtles, yet certain feeding behaviors remain poorly known, including winter feeding and foraging within the neritic area of the Gulf of Manfredonia. With high fishing effort, this area experiences considerable turtle bycatch from trawlers during winter, representing an important conservation issue. Insights on how and to what extent the species interacts with anthropogenic threats such as trawlers and debris can be obtained from diet analysis. We examined feces and gut contents from 57 bycaught or stranded turtles to assess active feeding and digestion time during winter, identify and quantify prey items, evaluate feeding patterns among size classes, and ascertain the anthropogenic impact via debris and fishing discard ingestion. Our findings show that turtles feed actively during winter, primarily on benthic items, starting from a small size (32 cm Curved Carapace Length). No size effect was observed on dietary diversity or biomass percentage. We identified 37 Operational Taxonomic Units (OTUs) across 10 dietary groups, with crustaceans and mollusks being most prevalent. Osteichthyes and cephalopods, likely scavenged from trawl discard, were also common, implying intensive local trawling may attract turtles, increasing bycatch and mortality rates. The frequency of anthropogenic material ingestion was comparable to other Mediterranean regions and its presence in feces suggests non-lethal effects, if any. This study shows how information on seasonal feeding behavior can provide insights into how the relationship of the species with the environment and threats changes over time, ultimately steering conservation efforts.

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The Gulf of Manfredonia: a new neritic foraging area for loggerhead sea turtles in the Adriatic Sea

Cited by 5 publications

References 32 publications

Voluntary fishing logbooks are essential for unveiling unsustainable bycatch levels and appropriate mitigating measures: The case of sea turtles in the Gulf of Manfredonia, Adriatic Sea

Voluntary fishing logbooks are essential for unveiling unsustainable bycatch levels and appropriate mitigating measures: The case of sea turtles in the Gulf of Manfredonia, Adriatic Sea

A comprehensive mitochondrial DNA mixed-stock analysis clarifies the composition of loggerhead turtle aggregates in the Adriatic Sea

Diet of loggerhead turtles in the Gulf of Manfredonia, South Adriatic Sea: evidence of winter feeding and anthropogenic impacts

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