Ecology and behavior of the spiny butterfly ray (Gymnura altavela) in coastal waters of Gran Canaria, Canary islands

Abstract

The spiny butterfly ray, Gymnura altavela, also known as Mantelina in the Canary Islands, is an occasional benthic species that migrate to very shallow waters of some beaches of the Canary Islands during the summer months. In order to record ecology and behavioural data of this species in these areas, monthly sampling campaigns were carried out between May 2017 and March 2020 in four sandy beaches: Sardina del Norte, Salinetas, El Cabrón and Pasito Blanco, located respectively in the northwest, east, southeast, and south of the island of Gran Canaria. Visual censuses were carried out and were counting the number of specimens present on the beach, identifying sex, and behaviour, but also the water temperature and salinity. The spiny butterfly rays show a preference for shallow water, decreasing their abundance with depth. Displacements of this ray to shallow waters seem to follow a temperature gradient between 19 and 24 Cº, remaining on the coast from June to October. Pasito Blanco beach shows the highest aggregations of individuals per square metre, and the largest individuals were recorded there, while those from Salinetas were the smaller ones. The estimated sex ratio was 1:18.9, with a predominance of females, larger than males.