Warming oceans a turn-off for female Critically Endangered sharks

Feminine angels in critical danger of being (Squatina Squatina) modify the normal mating routines in the warming oceans while they favor the stay at the expense of visiting the reproduction ground when things become too hot.

These changes create a potential discrepancy in coupling behaviors between the sexes of the angel shark which could have serious consequences for the future of the species, according to scientists.

A team of marine scientists, co-directed by researchers from the University of Lancaster and the Angel Shark project: Canary Islands (a collaboration between the Leibniz Institute for the Analysis of Biodiversity Change, the Universidad de Las Palmas de Gran Canaria and ZSL), used acoustic trackers to discover that the prolonged warming of the mers Reproduction behavior.

Their research appears in World change biology.

During an unusual and extremely high sea temperature period in 2022, the researchers found that female angels sharks were largely absent from the traditional mating fields of the species in the Graciosa marine reserve – which is located off the coast of Lanzarote and is the largest marine reserve in Spain.

That year, sea surface temperatures in the study area reached more than 23.8 ° C and remained above 22.5 ° C for almost three times longer than in previous years. Above all, these very high temperatures have persisted throughout the all season of shark airs, which traditionally starts at the end of autumn, when the seas should be cooler.

However, while the warmer seas seemed to dissuade female angels sharks, the men were not pushed back and returned to the sites in November as usual, looking for mating opportunities.

Dr. David Jacoby, lecturer in zoology at the University of Lancaster and principal study of the study, said: “These more frequent and extreme heat waves are potentially ocean forest fires and have incalculable effects on sea species.

“With angels sharks, we have observed important sexual differences in behavior, women being disproportionately influenced by sea temperature increases, which makes them absent from their traditional mating sites during this long period of warming.

“The males were much more resistant to temperature increases and glued to their regular models of arrival and departure, apparently prioritizing coupling despite these extreme temperatures.”

The Canary Islands are in the extreme south of the distribution of angels sharks and the archipelago is a unique bastion for the species, which is listed as in danger in a critical manner by the International Union for Nature Conservation (IUCN). Adults and juveniles have regularly seen and are a flagship species in the local diving industry.

Between 2018 and 2023, the research team was able to monitor the movement and distribution of more than 100 individual angels sharks using acoustic monitoring and link this data to environmental conditions.

Before 2022, the presence of male angels and female sharks in the marine reserve constantly culminated in November and December of each year.

However, in 2022, the number of male angel sharks culminated as usual, but female figures remained weak all year round. The study has shown that the female presence of the Angel shark is strongly linked to temperature and that 22.5 ° C can be an approximate upper thermal limit for women.

During the five -year surveillance period, scientists observed a general rise in the maximum temperatures of the sea surface and an increase in the number of days with temperatures above 22.5 ° C, from 30 days in 2019 to 85 days in 2022.

Above all, sea surface temperatures in 2022 have remained above 22.5 ° C at the end of November, falling only until the year observed the previous year. Unusually high temperatures have remained throughout fall and the season of winter accessories.

Scientists believe that the reason why female angels sharks prioritize respect for coupling are probably due to their biology. Feminine angels have more energetically demanding lifestyles due to reproductive biology and, therefore, are more sensitive to temperature because they must regulate metabolic processes and energy expenditure.

Researchers fear that these disturbances in reproduction behavior in angels sharks can have serious consequences for the future of the species.

“The fact that environmental extremes lead hours of male and female arrival on coastal mating sites are particularly concern for this critical endangered species,” said the main author of the study, Dr. Lucy Mead, researcher at the ZSL ZSL Institute and Lancaster.

“Angels sharks – like most other sharks – are ectothermic, which means that their body temperature depends directly on the surrounding water temperatures. It seems that male angels sharks give priority to mating even when the conditions are unfavorable, while women favor respect for their favorite temperature range.

“The Canary Islands are already at the warmer end of tolerable temperatures for angels sharks, and with significant warming projected here, our concern is that key areas can become inhospitable for women. Events in the oceans.”

Eva Meyers, a co -director of the Angel Shark project and researcher at the Leibniz Institute for the analysis of the biodiversity change (Lib), added: “These results are a reminder of how climatic extremes already rehapes the behavior of threatened marine species. The main bastions of this species – the protection of these waters are more urgent than ever.”

Dr. David Jiménez Alvarado, co-directed by the Angel Shark project and postdoctoral researcher at the Ecoaqua Institute (University of Las Palmas of Gran Canaria), noted: “It is important to understand how changes under the physico-chemical conditions of the Ocean can affect the species that lived in ecosystems.