Tuesday, 26 January 2021

Citizen scientist network records a decline in Whale Shark deaths along the Venezuelan Caribbean coast.

At the beginning of this century, observations of the Endangered Whale Shark, Rhincodon typus, in Venezuelan waters comprised 20 opportunistic records spanning the previous 51 years, suggesting they were present infrequently. A decade later, there were sightings year-round, distributed all along the coast. News of killings of whale sharks also became more frequent. In 2014, the Centro para la Investigación de Tiburones de Venezuela began to systematically document Whale Shark observations and engage fishers linked to Shark encounters. They interviewed 222 people from 17 towns, spanning Maracaibo in the west to Margarita Island in the east. Reports included 142 sightings and 21 deaths of Whale Sharks during 2014-2017, the latter by entanglement in nets, harpooning or other capture methods. Although most encounters were opportunistic or incidental, they generally lead to the killing of Sharks and the sale of their fins.

 
A Whale Shark, Rhincodon typus, off the coast of Venezuela. Centro de Investigación para Tiburones.

In a paper published in the journal Orynx on 21 September 2020, Leonardo Sánchez, Yurasi Briceño, and Rafael Tavares of the Centro de Ecología at the Instituto Venezolano de Investigaciones Científicas, and the Centro para la Investigación de Tiburones de Venezuela, Dení Ramírez-Macías of Tiburón Ballena México, and Jon Paul Rodríguez, also of the Centro de Ecología at the Instituto Venezolano de Investigaciones, present the results of these documenting activities.

In 2016-2020 the organization visited the 17 coastal towns where reports were more frequent. Firstly, they contacted community leaders and fishers connected to Shark kills, built personal relationships, developed trust, and explained the work of the organisation. After one or two visits, workshops at schools, fisher cooperatives or local businesses expanded the visibility of and interest in the project. An invitation to share information on social media followed. Whale Shark sightings now reach the organisation within minutes. Fishers film untangling and releasing of Sharks instead of killing them. Others film themselves swimming with Whale Sharks. Diving operators offer Whale Shark watching tours, increasing their value from a one-time sale of fins to repeat visits with tourists.

The clearest success indicator, however, is a sharp decline in Shark killing. Prior to October 2017, interviews documented 21 Shark kills. In contrast, during 2018-2020, after implementation of workshops, relationship building, and establishment of the social media network, no Whale Shark killings were reported. Although underreporting is possible, it seems likely that the news would reach the organisation, in particular as news of captures of other Shark species rapidly spread. The evidence collected through this citizen scientist network suggests that the Whale Sharks seen are mostly juveniles
(with a mean length of about 7 m), and appear in a number of localities along the Venezuelan coast. Reports have mentioned the presence of 1-10 Sharks simultaneously and during several months. Additional field data would facilitate estimation of seasonality and abundance. Although past records suggest Whale Sharks were only present occasionally along the Venezuelan coast, they are now a common occurrence and perhaps are here to stay.

See also...














Follow Sciency Thoughts on Facebook.

Follow Sciency Thoughts on Twitter