Sharks in the Parks: Use of MPAs by Silky Sharks, Carcharhinus falciformis, in the Eastern Tropical Pacific
Location
HCAS Guy Harvey Oceanographic Center, Nova Southeastern University
Start
2-13-2025 10:00 AM
End
2-13-2025 10:15 AM
Type of Presentation
Oral Presentation
Abstract
Marine protected areas (MPAs) are increasingly being used to protect at risk species, however, their effectiveness in protecting wide-ranging species is unclear. The silky shark (Carcharhinus falciformis) has experienced large declines in the Eastern Tropical Pacific and may benefit from the network of MPAs in the region. We examined silky shark use of MPAs and fisheries overlap by tracking 38 sub-adult and adult silky sharks tagged within the Galapagos Marine Reserve (GMR) with satellite tags for periods of up to 639 d. Based on movement patterns, sharks were split into three groups: males, eastern females, and western females. Sharks from all groups tended to show site fidelity to the GMR and the GMR was the most used MPA. Use of MPAs varied little between the wet (Dec-May) and dry seasons (Jun-Nov) for males and eastern females; males and eastern females spent ~55% and ~70% of their time within MPAs, respectively. Western females spent more time within MPAs during the wet season (~50%) compared to the dry season (~15%). Combining silky shark space use with fishing effort data from Global Fishing Watch revealed that sharks were most at risk from fisheries during the dry season within the northern Galapagos EEZ. Risk was much lower in the wet season; however, Global Fishing Watch data severely underestimates fishing effort in the region. Overall, for a wide-ranging species, silky sharks spent a great deal of time within the protected waters of the GMR, but much of their movements extended far beyond the GMR and other MPAs, putting them at risk from commercial fisheries operating in the Eastern Tropical Pacific.
Sharks in the Parks: Use of MPAs by Silky Sharks, Carcharhinus falciformis, in the Eastern Tropical Pacific
HCAS Guy Harvey Oceanographic Center, Nova Southeastern University
Marine protected areas (MPAs) are increasingly being used to protect at risk species, however, their effectiveness in protecting wide-ranging species is unclear. The silky shark (Carcharhinus falciformis) has experienced large declines in the Eastern Tropical Pacific and may benefit from the network of MPAs in the region. We examined silky shark use of MPAs and fisheries overlap by tracking 38 sub-adult and adult silky sharks tagged within the Galapagos Marine Reserve (GMR) with satellite tags for periods of up to 639 d. Based on movement patterns, sharks were split into three groups: males, eastern females, and western females. Sharks from all groups tended to show site fidelity to the GMR and the GMR was the most used MPA. Use of MPAs varied little between the wet (Dec-May) and dry seasons (Jun-Nov) for males and eastern females; males and eastern females spent ~55% and ~70% of their time within MPAs, respectively. Western females spent more time within MPAs during the wet season (~50%) compared to the dry season (~15%). Combining silky shark space use with fishing effort data from Global Fishing Watch revealed that sharks were most at risk from fisheries during the dry season within the northern Galapagos EEZ. Risk was much lower in the wet season; however, Global Fishing Watch data severely underestimates fishing effort in the region. Overall, for a wide-ranging species, silky sharks spent a great deal of time within the protected waters of the GMR, but much of their movements extended far beyond the GMR and other MPAs, putting them at risk from commercial fisheries operating in the Eastern Tropical Pacific.