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Ecology Seminar: Integrating science and management into a strategy to reduce bycatches of mobulid rays (Dr. Nerea Lezama Ochoa, Inter-American Tropical Tuna Commission)

10/31/2018 - 12:15pm
Hubbs Hall #4500
Event Description: 

In the eastern Pacific Ocean (EPO), the tropical tuna purse-seine fishery captures high numbers of five mobulid species; all of which are considered as mortalities by the Inter-American Tropical Tuna Commission due to uncertainties in post-release survival rates, and following a precautionary approach. Despite the low frequency of mobulid captures per set, the large worldwide distribution of purse seiner sets combined with the low reproductive rates of these species make them vulnerable to the fishery impacts. In addition, the apparent association of mobulids with productive habitats that overlap with the main tuna fishing grounds and in some cases their distribution in coastal waters makes them highly susceptible to capture by purse seiners. In this context, reducing the mortality of mobulid species in the tropical tuna purse-seine fishery has become a challenge for their conservation in the eastern Pacific Ocean. To date, the impacts of the fishery on the populations are not well understood, since their abundances, and other mortality factors are not known. However, the decision to reduce these impacts are part of the Fishery Improvement Projects active in the region. We will discuss the options to reduce their mortality. One of them, the modification of fisher’s behavior and techniques in the handling of the rays appear to be crucial for their survival. In this context, some improvements have already been made by the IATTC, banning harmful release practices. Very encouraging results, showing significant reductions in capture mortality when good practices are implemented, are driving the efforts to extend these practices to all oceans, and complement them with additional actions. To assess the impacts of the mortality, we need to know more about life history (age, growth, natural mortality, reproductive rates), population trends, movements and spatial dynamics that should be core components of robust stock assessments. Among the alternatives to explore, spatial, temporal and environmental preferences of mobulid rays may help identify other management actions, to further reduce the impacts. Habitat and Species Distribution Models may help pinpoint those options.

For more information on this event, contact: 
Olivia Pereira
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