The presence of the angel shark (Squatina squatina) In the Canary Islands, this is no coincidence: the archipelago acts as one of its last refuges, but the stability of that condition is beginning to falter. This species with a flattened body, low fertility and coastal habits, classified as critically endangered by the IUCN, is seeing how the rising sea temperature disrupts their reproductive cycle. The Sharks in general are facing numerous threats, and the angel shark is no exception.
A recent investigation in the La Graciosa Marine Reserve reveals that marine heat waves and sustained warming are altering the arrival of females to breeding areas. According to the team led by Dr. David Jacoby (Lancaster University), and published in Global Change Biology, there is a thermal limit that conditions the presence of females during the mating season.
Thermal threshold and behavioral changes
The study identifies a threshold of 22,5 ° C so that females can normally use key breeding areas. In 2022, the surface of the sea reached 23,81 ° C in the northeast Atlantic, and days above that record tripled compared to the average, causing a anomalous absence of females on crucial dates for mating.
Researchers tracked the movement of 112 copies between 2018 and 2022 (38 males and 74 females) and found a habitat use with sexual preference: Females prioritize suitable environmental conditions, while males tend to locate where they expect to meet them, even if the thermal variables are not ideal. Learn more about the biology of these animals in cartilaginous fish.
Above 20,7 ° C A rapid decrease in females is already observed, and once the 22,5 ° C its presence becomes practically null. This temporal and spatial displacement is interpreted as a change in distribution to avoid unfavorable environments, with direct consequences on the timing of key biological events.
The trend shows that the ocean warming It already modifies the reproductive behavior of the angel shark in the study area and, if the trend persists, it could lead to a local extinction in the archipelago, where the species operates at the thermal limits of its tolerance.
A refuge at risk and the need to adapt conservation
The Canary Islands have remained a bastion of the angel shark, in part, due to the ban on dragging, a fishing technique that has contributed to its disappearance in other regions. Even so, the species was included in 2019 in the List of Endangered Species of Spain (Canary Islands waters) with the category of Danger of extinction, and the latest significant sightings are concentrated in the La Graciosa Reserve (70.700 ha), an enclave of high biodiversity.
The climate scenario for the Northeast Atlantic does not invite optimism: a deceleration of the Atlantic Meridional Circulation, increased acidification and oxygen loss superficial, with a decrease in primary productivity in the Canary Current due to the reduced upwelling of cold, nutrient-rich waters. This situation can also affect protected species, such as the , which shares its habitat with the angel shark.
On small islands and coastal areas, these changes will be amplified by the Rising sea levels, storm surge and episodes of extreme rainfall, accelerating processes such as coral bleaching, loss of seagrass meadows, death of mangroves and beach erosion, especially when they coincide with local human pressures.
Given this situation, the authors urge to actively incorporate the adaptation to climate change in the protection measures for the angel shark: safeguarding thermally suitable areas, dynamic management according to marine heat waves, and reducing existing stressors such as overexploitation and habitat degradation. Learning more about marine habitat conservation can be key in protect endangered species.
The available data clearly show that the marine heat It affects the reproductive calendar of the angel shark in the Canary Islands, and without adjustments to conservation measures, the areas that currently serve as refuge could lose their effectiveness, putting one of the most endangered species in the eastern Atlantic at risk.
