Hook ingestion in cetaceans 2000-2021 in Canary Islands

Abstract

Estimating cetacean interactions with fishery activities is challenging (Kuiken, 1996; Moore et al., 2013). Bycatch is responsible for thousands of cetacean deaths per year globally (Young & Iudicello, 2007; Dolman & Moore, 2017). This study updates the data on fishery interaction in stranded cetaceans in the Canary Islands, from the last review (Puig- Lozano et al. 2020), focusing on the cases of ingested hooks. Between January 2000 and December 2021, 741 cetaceans have been necropsied. During this period, a total of 8 cetaceans died due to the severity of the lesions caused by an ingested hook. Additionally, 3 cetaceans have been counted with ingested hooks during this year 2022. The most affected species was the Atlantic spotted dolphin (Stenella frontalis) [88% (7/8)]. This species is very frequent in the canary waters all year round. All the cases (8/8) were found stranded or floating dead, in different decomposition codes (3/8 fresh, 3/8 moderate autolytic, and 2/8 very autolytic). The hooks were identified during the external examination (3/8), being lodged in the oral cavity, or observed during the dissection of the carcass (5/8), perforating the oesophagus (2/8), and the trachea (2/8), and producing haemothorax (3/8). The majority of the cases were mature animals [48% (6/8)] in a good or moderate body condition [88% (7/8)]. The most common gross finding was the hemoabdomen [75% (6/8)]. The most frequently described histological finding in these cases was alveolar oedema [40% (5/8)]. Histological examination confirms the gross lesions and excludes other possible causes of death. Hooks founded are of different types and can measure up to 7cm long and 4cm wide. This study updates the data about the presence of interaction with hooks in cetaceans and the importance of marine conservation policies in the Canary Islands.