Stable isotopes provide evidence of a trophic shift in the lesser spotted dogfish Scyliorhinus canicula from the Central Tyrrhenian Sea

Abstract

Stable isotopes (δ13C and δ15N) were analysed in vertebrae of Scyliorhinus canicula (n=40; 13 males, 27 females) from the central Tyrrhenian Sea to explore a potential trophic shift in relation to sex and maturity condition. Isotopic values were obtained from the centre and the periphery of the vertebra of each individual to test for the effect of maturity condition. The values of δ13C and δ15N showed significant differences between the immature and mature state of the individuals analysed (U’=1392, P<0.0001 for δ13C; U’=1385, P<0.0001 for δ15N). Differences in values of δ15N demonstrated a trophic shift during maturation progress of S. canicula. The peripheral vertebral part, corresponding to the mature state of each individual, showed higher values of δ15N (mean 5.41‰ SD±1.29‰), compared with the lower values of δ15N (mean 2.78‰ SD±1.52‰) observed in the central vertebral part related to the immature state. In contrast, the isotopic signature of δ13C was lower in the vertebral centra, and thus related to areas less enriched in C13 (mean -22.56‰ SD±1.26‰) in comparison with the vertebral periphery (mean -20.03‰ SD±1.34‰) linked to more productive environments. No significant differences in δ13C or for δ15N values were observed between sexes.

Contamination by Trace Elements and Oxidative Stress in the Skeletal Muscle of Scyliorhinus canicula from the Central Tyrrhenian Sea

“…This trend is well-known in fishes [54,55]. In S. canicula, this may be sustained by a growth-related change of the diet [17] and the higher detoxifying activity of the rectal gland observed in relation to animal growth (and the consequent increase in TL) that may contribute to excrete some toxic trace elements, as in the case of Pb [45,46]. Of note, in the skeletal muscle, the levels of Mn and Zn significantly and negatively correlated with the leukocyte count.…”

“…This different sex ratio is not unusual in sharks, being possibly related to the breeding behavior of the species. For example, unisexual aggregations of S. canicula have been observed in certain geographical areas and at different times of the year [17,29,42,43]. The biometric analysis of the samples used in this study showed no significant differences between males and females in terms of length and weight.…”

“…Sharks, due to the high position in the food chain, slow growth rates, and low elimination abilities [10,17], are able to bioaccumulate, or worse, to biomagnify several elements through the food chain [5,15,[18][19][20]. So far, information regarding the influence of the exposure to trace elements on shark health is scarce and fragmentary, often obtained in a limited number of species or in a restricted region of the world [21,22].…”

Bioaccumulation of Trace Elements in the Muscle of the Blackmouth Catshark Galeus melastomus from Mediterranean Waters

“…Sharks are mostly long-lived elasmobranch species and occupy apex-meso-predator roles in their respective food webs (e.g., [25]). Therefore, they are known to accumulate high levels of metals, metalloids, and other pollutants in their tissues [26][27][28]. This feature results in deleterious effects on their normal physiology/biochemistry (e.g., immune and endocrine toxicity, reproductive deficits and tumor promotion) and ultimately on shark population dynamics [29][30][31].…”

Copper, lead and cadmium monitoring via the Small-spotted catshark (Scyliorhinus canicula; Linnaeus, 1758): space-time driven variability in Western Mediterranean populations

“…This demersal elasmobranch species can be found widespread throughout the Mediterranean and north-eastern Atlantic´s continental platform and the upper slopes (Ebert and Stehmann, 2013;Kousteni et al, 2015;Massutí and Moranta, 2003;Ruiz-García et al, 2023;Serena et al, 2020). This opportunistic predator´s diet has been found to be highly generalistic, being comprised mainly of crustaceans, molluscs, and teleosts (Barría et al, 2017;Kousteni et al, 2017;Lyle, 1983;Reinero et al, 2023;Valls et al, 2011). S. canicula captures are a common occurrence among Mediterranean sheries within which, adults are occasionally targeted by shermen due to their greater economic value, while younger individuals are generally discarded at sea (Barausse et al, 2014;Capapé et al, 2008;Carbonell et al, 2003).…”