Aggregative Behaviour of Spiny Butterfly Rays (Gymnura altavela, Linnaeus, 1758) in the Shallow Coastal Zones of Gran Canaria in the Eastern Central Atlantic
by
, , and
Ana Espino-Ruano
1,*
,
Jose J. Castro
1,
Airam Guerra-Marrero
1,*,
Lorena Couce-Montero
1,
Eva K. M. Meyers
2,
Angelo Santana-del-Pino
3 and
David Jimenez-Alvarado
1 1
Biodiversidad y Conservación, IU-ECOAQUA, University of Las Palmas de Gran Canaria, Edf. Ciencias Básicas, Campus Universitario de Tafira, 35017 Las Palmas de Gran Canaria, Spain
2
Zoological Research Museum Alexander Koenig, 53113 Bonn, Germany
3
Department of Mathematics, University of Las Palmas of Gran Canaria, 35018 Las Palmas, Spain
*
Authors to whom correspondence should be addressed.
Animals 2023, 13(9), 1455; https://doi.org/10.3390/ani13091455
Submission received: 1 March 2023
/
Revised: 16 April 2023
/
Accepted: 18 April 2023
/
Published: 25 April 2023
(This article belongs to the Special Issue Sharks and Skates: Ecology, Distribution and Conservation)
Simple Summary
The presence of batoids in Gran Canaria, Canary Islands, Spain, in the Mid-Eastern Atlantic Ocean, is quite common depending on the species and time of year. For that reason, we examined the behaviour of spiny butterfly rays (Gymnura altavela) in the shallow waters of Gran Canaria, where the species’ affinity to certain beaches was analysed according to the time of year and preference for the type of ocean environment. Such knowledge is important given the lack of information available on the species that is nevertheless vital for its sufficient management and conservation.
Abstract
The presence of spiny butterfly rays, Gymnura altavela, in waters less than 20 m deep off the Canary Islands shows marked seasonality, with relatively high abundances in the summer and autumn. Large aggregations of sometimes hundreds of individuals, primarily females, appear in specific shallow areas of the archipelago and seem to be associated with the seasonal variation in water temperature. This seasonal pattern of presence or absence in shallow areas suggests that spiny butterfly rays migrate into deeper waters or other unknown areas during the rest of the year. G. altavela shows sexual dimorphism; in our study, females were larger and more abundant than males, with a sex ratio of 1:18.9. The species’ estimated asymptotic length, L∞, was 183.75 cm and thus close to the common length reported for the species (200 cm). The von Bertalanffy growth constant (k) oscillated between 0.210 and 0.310 year−1, as similarly described for the species in the Western North Atlantic off the U.S. coast. From June to November, the seawater temperature oscillated between 19 and 24 °C, and massive aggregations of females occurred at 22–24 °C and in a few specific sandy beaches on the islands. Spiny butterfly rays, mostly females, show a preference for aggregating in shallow waters during summertime, probably conditionate to mating or breeding behaviour.
Keywords:
Gymnura altavela; butterfly ray; visual census; ecology; elasmobranchs; Canary Islands
