Pathological study of angel sharks (Squatina Squatina) found dead in The Canary Islands

Abstract

The angel shark is listed as critically endangered species. The Canary Islands are considered a unique stronghold for these animals (Barker et al., 2016), but unfortunately some have been found stranded or dead in the recent years. The IUSA-ULPGC together with the Government of the Canary Islands and, in collaboration with researchers of the “Angel Shark Project: Canary Islands”, have performed the necropsies of angel sharks found dead from 2021 to 2022. 10 angel sharks (4 females and 6 males) were studied during this period: 6 in Lanzarote, 2 in Tenerife, 1 in Gran Canaria, and 1 in Fuerteventura. 1 of these animals was in a severe autolytic status, 4 presented advance decomposition and in 3, it was moderated. Only 2 specimens well preserved. The weights ranged: female (10.6-13.8kg) and male (9.6-13kg). According to reproductive status (Osaer et al., 2015), all females were mature with large developing follicles in the ovaries and distended, vascularised uterus. One female was pregnant, with a fetus inside the left uterine horn. The males were mature, with dilated ductus deferent that contained abundant seminal fluid. Other findings were cestodal intestinal infestation and congestion in the stomach mucosa. The necropsy and histopathological analysis resulted inconclusive to determinate the cause of death in eight of the animals. However, two individuals were found entangled with fishing nets and with associated skin lesions. This preliminary research shows new data of potential death causes in angel sharks in the Canary Islands and for future conservation management plans.