bycatch of humpback whales in artisanal fishing gear in ecuador ...

50% of the fleet uses multifilament gillnets of 4-5” wide mesh up to 3km in length as main gear to
catch large pelagic fish (sharks and billfish) (Martínez et al. 1991).
Here we present new cases of humpback whales entangled in artisanal gillnets found off Salinas,
Ecuador (2º10’S, 81º’W) (Figure 1). In contrast to previously reported beachings, these new cases
involved live whales. The new approach allowed estimating the magnitude of the total bycatch at
taking into account the survey effort of the season.
METHODS
Figure 1. The study area located at Salinas, Ecuador.
Whalewatching boats have been used as research platform during a long-term study of the
humpback whale in Ecuador (see Félix and Haase, 2001a for details). Data analyzed in this report
was obtained during the breeding season 2005 (late June-early October). Seven different boats were
used with size ranging between 7 and 15 m in length and 10-30 passengers of capacity. Usually
boats departed at 9:00 in the morning and lasting two or three hours. Occasionally trips were also
made in the afternoon. During the trips, information on survey effort, oceanographic conditions, whale
behaviour, heading, group size and composition was filled out on data forms. As a standard
methodology, whales were photographed with a Canon Rebel Digital camera (6.3 megapixels)
equipped with a 70-300mm zoom lens for individual identification.
RESULTS
Effort
Seventy four trips were made between 27 th June and 1 st October 2005. A total of 349 whales in 148
groups were recorded. Total navigation time was 156 hours, of which 59 hours were spent with the
whales. The surveyed distance was 2,031km. Table 1 shows the monthly effort deployed through the
season. July and August were the months with the largest effort with trips almost everyday and then
the effort decreased considerably in September when tourist activities also decreased.
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