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SC/69A/WW/01
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Resource ID
20067
Access
Open
Document Number
SC/69A/WW/01
Full Title
Seasonal occurrence and abundance estimation of sei (Balaenoptera borealis) and other cetacean species in Golfo San Jorge (Chubut Province, Argentina) to be regarded as a new whale watching site in Patagonia.
Author
Mariano A. Coscarella ; Marina G. Riera; Jeremías Galaz; Francisco Yakimovich; Keila Asenié; Santiago Fernández And Nicolás Sueyro
Authors Summary
This is an update of the paper presented last year to the same subcommitee. The advances include an abundance estimation and the inclusion of new tourist related activities in the area
Publisher
IWC
Publication Year
2023
Abstract
In the past few years, different whale species have been increasingly observed in Golfo San Jorge. In Chubut province, Argentina, the occurrence of these whales and dolphins may attract the local community’s attention as a potential resource for tourism-related activities, since the region has a long history of whale watching targeting the southern right whale (Eubalaena australis). To assess the viability of the site as a future whale-watching operation site systematic visual surveys have been conducted from September 2019 to October 2022. The observations were made from the top of a 160 m high cliff to assess the species' seasonal occurrence and relative abundance, following a scan method with the aid of a spotting scope. A total of total of 481 scans were performed in which both large whales and dolphins were spotted, including 1502 were sei whales (Balaenoptera borealis), 51 humpback whales (Megaptera novaeangliae) and 51 southern right whales (Eubalaena australis). Only one fin whale (Balaenoptera physalus) and two sperm whales (Physeter macrocephalus) were spotted during the scans. Regarding dolphins, the dusky dolphin (Lagenorhynchus obscurus) was the most common accounting for 114 individuals, followed by Risso’s dolphins (Grampus griseus) with 92 and Commerson’s (Cephalorhynchus commersonii) dolphins with 35. Also, two killer whales (Orcinus orca) and one Peale’s dolphin (Lagenorhynchus australis) were sighted.
The Sighting per Unit Effort indicates that during the summer and autumn months the frequency of sei whale sightings increases. Sei whales were spotted while feeding on squat lobster, being one of the main observed behavioural states accounting for 30% of the observations. The main behavioural state recorded for humpback and southern right whale was socializing. In the case of dolphins also the Commerson’s and dusky dolphins spend a fair amount of time feeding, while Risso’s also spend time socializating. To obtain estimates of abundance of sei whales using the Distance method, transects were made on board a two engine aircraft surveying 427 kilometres in the central area of the gulf. Two flights were made, one in the low season (December 2021) and other in the high season (May 2022). During the low season 796 (CI 95% 232-2727) sei whales were estimated in a 5000km2 area. For May, this figure was estimated in 2777 (CI 95% 1809-4262). Golfo San Jorge could be regarded as a previously unreported feeding summer ground for the endangered sei whales. The continuation of this study will provide a better understanding of the habitat use and the factors that influence seasonal patterns of rorquals in the area and generate baseline knowledge to contribute to the conservation and assist in developing management actions