Sea turtle strandings, sightings and accidental catch along the Croatian Adriatic coast

Abstract

The northern Adriatic Sea has long been known as the foraging and developmental habitat of loggerhead sea turtles. Previous literature on stranded, floating, sighted, and accidentally caught sea turtles is fragmentary and mainly obtained from this shallower northern part. This work presents data on 272 records of stranded, floating, sighted and accidentally captured turtles within the entire Croatian Adriatic. The data was collected through the national stranding network for strictly protected marine species run by the Croatian Agency for the Environment and Nature during a six-year period (2010-2015). We focused on analysing spatial and temporal observations, age structure, and reporting sources. The collected morphometric data revealed that most measured C. caretta (85%) were immature individuals found stranded and floating at sea. These observations were location-dependent with a tendency towards the shallow northern areas (≤200 m). Most of the stranded individuals were severely decomposed preventing the determination of possible mortality causes. Most non-decomposed individuals had fishery- or boat-inflicted mechanical injuries confirming fishing activities and boat collisions as threats to young C. caretta individuals in the Croatian Adriatic Sea. Results also revealed an important contribution of local people in reporting the C. caretta strandings and sightings whereas most accidentally caught individuals were reported by unknown sources. Altogether, the data presented in this paper indicate possibilities for improving the ongoing sea turtle monitoring and conservation activities along the entire Croatian Adriatic coast.

Strandings of loggerhead sea turtles south of the Po River delta: insights from a highly impacted area

“…It would be interesting to explore in greater detail such year-to-year variability once a more prolonged time series will become available, a step that will allow us to better understand sea turtles strandings in relation to parameters such as sea surface temperature, chlorophyll concentration and fishing effort, an approach recently exploited in the Adriatic Sea for fishery by-caught individuals (Pulcinella et al, 2019;Bonanomi et al, 2022). The number of stranded sea turtles•km -1 as well as absolute numbers of strandings during three years, clearly confirmed that the area south of the Po River delta is the most impacted in Italy (Casale et al, 2010) and perhaps in the whole Mediterranean Sea (Tomás et al, 2008;Türkozan et al, 2013;Belmahi et al, 2020;Hama et al, 2020;Dimitriadis et al, 2022). Indeed, it is important to highlight that monitoring activities spanned only about 18 km of coastline and the numbers presented herein represented underestimates as we are aware of other and partly overlapping monitoring programs for which data could not be accessed.…”

“…The number of stranded sea turtles•km -1 as well as absolute numbers of strandings during three years, clearly confirmed that the area south of the Po River delta is the most impacted in Italy (Casale et al ., 2010) and perhaps in the whole Mediterranean Sea (Tomás et al ., 2008; Türkozan et al ., 2013; Belmahi et al ., 2020; Hama et al ., 2020; Dimitriadis et al ., 2022). Indeed, it is important to highlight that monitoring activities spanned only about 18 km of coastline and the numbers presented herein represented underestimates as we are aware of other and partly overlapping monitoring programs for which data could not be accessed.…”

Nowhere to hide: Sea turtle bycatch in Northwest Africa

“…Reports from industrial fisheries bycatch include green turtles, leatherbacks, loggerheads and olive ridleys (IMROP, 2020), while artisanal fisheries primarily catch green turtles and the occasional leatherback (Wolff et al, 1993; Mint Hama, Fretey & Aksissou, 2013; Fretey & Mint Hama, 2014). A single mention of a stranded hawksbill is found in the literature from the last two decades (Hama et al, 2019); however, local coastal fishers interviewed by Mint Hama, Fretey & Aksissou (2013) between 2009 and 2011 recognized the hawksbill as one of four species encountered along the coast, along with green turtles, loggerheads and leatherbacks.…”

“…From 2009 to 2016, Hama et al (2019) retrieved 1,787 stranded carcasses, of which 1,654 were green turtles. Four of these were found entangled in fishing nets or ropes/lines, 10 others presented flipper and neck injuries of unspecified cause and eight had been killed for consumption in fishing villages or camps.…”

“…There is a clear overlap between fisheries and sea turtle distribution owing to their use of vast areas for foraging and nesting (Patrício et al, 2022) as well as the known number of fishing vessels operating in the region (Figure 2a; Jabado, 2021). Bycatch rates appear to be particularly high for green turtles and loggerheads (Figure 2b), especially in Mauritania and Cabo Verde, where these species are most abundant (Marco et al, 2011;Hama et al, 2019).…”