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

Bycatch rate and total mortality
Considering the total number of whales recorded (n=349) and the three whales found entangled, a
bycatch rate of 0.0086 was calculated. Extrapolating this value to the entire population estimated to
be 2,917 animals in the period 2003-2004 (Félix et al., 2006), around 25 whales (C.I. 95% 20-32)
could be the total bycatch in the breeding season 2005 in Ecuador.
DISCUSSION
The entanglement of humpback in artisanal gillnets in Ecuador continued in 2005 likely with similar
intensity as previous years. Besides the three cases reported here, the authors knew of two other
cases which occurred in other parts of the country involving beached whales with gillnets around their
bodies. Also, sailors and naturalist guides reported entangled whales off Salinas every year since
whalewatching started here in 2001; at least three cases were reported in 2003 (Félix and Haase,
2003). Other cases of entanglements were reported at La Plata Island, 100km north of Salinas, a calf
in 1998 (Scheidat et al., 2000) and six adults or sub-adults animals in 2001 (Álava et al., 2005).
It is believed that the entanglement of humpback whales in artisanal gillnets in Ecuador and Colombia
have maintained an increasing trend in the last decade (Capella et al., 2001; Álava et al., 2005), but
there not proof as no reliable assessments have been made. So far, data on beached animals have
provided a gross idea of the bycatch level but not its magnitude, since not every entangled or dead
whale ended up on the beach. Our estimate provides a first approach to establish the total bycatch in
Ecuador by using a measurable searching effort and therefore allowing extrapolation for the entire
population that reach Ecuador. However, it is not possible to establish the impact on the population
since no data on survival after the entanglement are available. Photographs of the animals found off
Salinas in 2005 showed different level of seriousness with likely different survival chances for the
whales; therefore, it is not possible to obtain an overall rate.
The fate of the entangled whales was unknown, but previous records of stranded animals on the
coast of Ecuador suggest that at least some whales die few weeks later after the entanglement (e.g.
Félix et al, 1997; Álava et al, 2005). These animals would die of exhaustion or would be easy preyed
upon by orcas and big sharks at sea. In the female with calf case (#2), the impact would be even
bigger, since calves also would die afterwards. Whatever the proportion of animals dying as a
consequence of the entanglement, it may have a significant impact in the recovery of this population.
Since both fishing effort and whale population are increasing in Ecuador (see Félix et al, 2006), it is
expected that the number of entangled whales will continue increasing in the future if measurements
are not taken on short-terms. Several management actions have been proposed by Ecuadorian
researches in order to reduce the level of cetacean bycatch, including directed research; education
programs for artisanal fishermen; use of sound devices; closed seasons; change of fishing gear;
creation of rescue teams; among others (Félix and Samaniego, 2004; Félix et al, 1997; Álava et al,
2005; Félix and Haase, 2005). Some of these measures could be implemented on a temporary basis
during the humpback whale breeding season or in specific sites of higher density of whales. With
exception of a limited number of educative talks during the seasons 2002 and 2003 no other actions
have been taken by fishing authorities.
Considering that such high bycatch rate of a long-migrating species as the humpback whale has
transboundary implicitness, we ask to the Scientific Committee of the International Whaling
Commission to urge Ecuadorian authorities the adoption of measures to reduce the level of bycatch
on short-term. We also recommend that any proposal and or decision to be taken to address the
bycatch problem must be agreed with relevant stakeholders including fishing authorities, artisanal
fishermen associations, NGOs, among others.
ACKNOWLEDGEMENTS
We thank tourist operators in Salinas who allowed us using their vessels for this study. The humpback
whale research in Ecuador is supported by the Whale and Dolphin Conservation Society (WDCS).
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