Skeletochronology, age at maturity and cause of mortality of loggerhead sea turtles Caretta caretta stranded along the beaches of Campania (south-western Italy, western Mediterranean Sea)

Abstract

Information on demographic and life-history traits of endangered vertebrate species, such as sea turtles, is crucial for planning management and conservation actions. We applied skeletochronology of phalanges to estimate the age of loggerhead turtles, Caretta caretta, found dead stranded along the beaches of Campania (western Mediterranean) from 2013 to 2017. To obtain maturity data, we examined gonads from a subsample of 7 males and 11 females. Overall, curved carapace length (CCL) ranged from 5.6 to 90.8 cm, but for most turtles (89%) it was 50-79.9 cm. Predominance of stranded females (62%) was recorded. Ten out of the eighteen histologically examined gonads allowed estimating maturity. Based on the lines of arrested growth counting, the estimated age of the examined specimens ranged from 0 (hatchling) to 26 years. The modal age was 14 years for males and 17 years for females. The smallest male with spermatogenetic activity had a CCL of 65 cm and was estimated to be 16 years old. The smallest female with follicular development stage, characterising the transition towards adulthood, had a CCL of 69.5 cm and was estimated to be 20 years old. Anthropogenic factors were responsible for 36% of the mortality of individuals, followed by parasitic/infective pathologies (20%).

First study of sea turtle strandings in Algeria (western Mediterranean) and associated threats: 2016–2017

“…Our study shows that fisheries interactions are the most important cause of strandings. This finding is consistent with other reports elsewhere in the Mediterranean (Casale et al 2008;Tomás et al 2008;Guarino et al 2020). This species is still experiencing the heaviest mortality record.…”

“…The impact of bycatch on sea turtle populations depends on the fishing areas (Clusa et al 2016), which explains the heterogeneity of sizes along this coast. Similar heterogeneity in size was reported around the western Mediterranean Sea (Casale et al 2011;Piovano et al 2011;Guarino et al 2020). Small size turtles spend most of their time in oceanic waters (Cardona et al 2005;Revelles et al 2007b) which makes them vulnerable to swordfish driftnets; this technique is applied more on the west and central coast, while large size turtles, feeding mainly in neritic areas (Casale and Margaritoulis 2010;Casale 2011), are exposed to small-scale fishing which operates closer to the coast.…”

Bone histology of Broad-snouted Caiman Caiman latirostris (Crocodylia: Alligatoridae) as tool for morphophysiological inferences in Crocodylia

“…As in other reptiles, LAGs provide clues to both skeletochronology and the growth rates of specimens on an annual basis (Castanet et al, 1993;Guarino et al, 2020). These thin lines that occur parallel to the periosteum margin (Wilson and Chin, 2014) are observed in greater quantities with increasing age.…”

Age estimation and growth of striped dolphinsStenella coeruleoalbastranded along the coasts of south-western Italy

“…To conclude, although this study was limited by the number of animals examined, it provides interesting information toward understanding the demographic traits of S. coeruleoalba from the Mediterranean Sea. The results reported here can useful for future research aimed at understanding mortality patterns and the effects of anthropogenic activity on the survival of this species in this marine area, as performed also for other cetacean species (Maio et al, 2016) and other marine vertebrates (see Guarino et al 2020).…”