Elasmobranch vulnerability to global warming: insights from bioenergetic modelling of catsharks under climate scenarios

Ectotherms are especially vulnerable to global warming due to their temperature-sensitive metabolic processes, impacting survival and reproductive success. Elasmobranchs, with slow life histories and low reproductive rates, may face amplified risks. In this study, we investigated two catshark species with distinct life traits and distributions: the Small-spotted Catshark (Scyliorhinus canicula) and the Nursehound (S. stellaris). Using newly calibrated bioenergetic models, we assessed changes in growth, sexual maturity, offspring production, and population dynamics under two CMIP6 climate scenarios projected for 2100: SSP2–4.5 (Middle of the Road) and SSP5–8.5 (Fossil-fueled Development), comparing these to historical data (1994–2015). Survival rates for early life stages remained similar under historical temperatures (80 %) and SSP2 (83 %) but dropped sharply under SSP5 to 33 % for S. canicula and 23 % for S. stellaris. Under both SSP2 and SSP5, S. canicula showed slight delays

in maturation, yet the proportion of mature individuals ultimately exceeded historical levels in SSP2. Conversely, S. stellaris experienced progressively delayed maturation with warming. In SSP5, reduced growth, reproduction, and survival caused a population crash for S. stellaris, suggesting potential extinction. Our results reveal contrasting climate impacts on these species, underscoring the risk for late-maturing, low-fecundity, and narrowly distributed species. This emphasizes the urgency of conservation strategies tailored to mitigate their vulnerability to global warming.