Climate change linked to infertility in well‐known shark species

The catastrophic progression of the climate emergency continues, like a speeding freight train, with the brakes only lightly applied (Le Page, 2025); the list of symptoms and casualties reading like a coroner's report (Ripple et al., 2025). Perhaps the most telling statistic of our failure to handle the crisis is that 2025 was the third warmest year on record, continuing a run of the three warmest years ever recorded (Madge, 2026). Needless to say, these rapid shifts in the earth's climate are having a devastating effect on ecosystems across the globe. For fish alone, climate change is set to impact multiple facets, including physiology (McKenzie et al., 2021; Scharsack & Franke, 2022), connectivity (Franklin et al., 2024), behaviour (Candolin & Rahman, 2023) and how we use them as a resource (Feidantsis et al., 2021). One group of fish that are vulnerable to climate change are elasmobranchs. Being ectothermic, their physiology is more sensitive to temperature changes, including elevated metabolic rates, which are compounded when coupled with other climate-driven processes such as ocean deoxygenation (Waller et al., 2024). In addition to this, the typical life history of elasmobranchs, slow growth, late maturity and low fecundity, make them vulnerable to rapid environmental change (O'Brien et al., 2013). Indeed, one emerging and often-overlooked threat to elasmobranchs that intersects these very two vulnerabilities is the impact of climate change on elasmobranch fertility (Coulon et al., 2026). In this issue, Jeanne et al. (2025) explore this phenomenon in male small-spotted catshark (Scyliorhinus canicula) of the English Channel during the summer of 2022, a summer with distinctly higher water temperatures than previous years. Although previous research has demonstrated the detrimental impacts warming temperatures have on growth, fitness and survival of embryos in this species (Musa et al., 2020), Jeanne et al. (2025) show that climate change risk is present even before fertilization. Unlike other sharks, the small-spotted catshark shows little to no seasonal variation in spermatogenesis (Ellis & Shackley, 1997), which makes it an ideal candidate for exploring temperature-induced infertility. When looking at the testis of catshark from September 2022, Jeanne et al. (2025) discovered, using histology and proteomics, that sperm-producing cells were degenerating – an irregular occurrence for this species, and likely linked to observed elevated summer water temperatures. Moreover, the proteomics showed evidence of cell cycle disruption, impaired DNA damage repair, apoptosis and stimulated lipid metabolism. As the North Atlantic continues to warm, work like this will help us understand the risk posed to elasmobranchs, allowing for a better understanding of the climate change winners and losers. Although the small-spotted catshark is abundant in the Northeast Atlantic and Mediterranean Sea, and classified as Least Concern by the IUCN, it shows that no species is immune to climate change. Moreover, although a crash in numbers of this common species seems fantastical, undermining reproductive output in a species with relatively low fecundity and late maturation poses a real risk, especially as warming intensifies.