Interactions between the Galápagos Marine Reserve and Tropical Tuna Purse-Seine Fisheries

Abstract

In times of worldwide increasing overfishing, marine reserves are a vital tool of marine conservation and fisheries management. Benefits of marine reserves can extend beyond reserve boundaries to adjacent fishing grounds through spillover of fish. Anticipating higher catch rates, fishers try to capitalize on spillover by increasingly fishing along reserve boundaries, a behavior known as fishing the line. Empirical studies on fisheries behavior in response to marine reserves exist mostly for small-scale costal reserves, whereas studies on larger off shore reserves are few. To fill this gap, using fisheries observer data provided by the Inter-American Tropical Tuna Commission (IATTC), fisheries patterns of the industrial tropical tuna purse-seine fisheries in the eastern tropical Pacific (ETP) were examined in relation to the Galápagos Marine Reserve (GMR). By conducting hot spot analyses in ArcGIS, temporal and spatial hot spots of fishing effort and catch patterns before and after GMR establishment and enforcement were analyzed. Hot spots in fishing effort and catch were identified south-west of the reserve border, whereas catch rate hot spots were found further off-shore, towards the western Pacific Ocean. Using Bayesian spatio-temporal models for the period after fully established reserve enforcement, trends in fisheries patterns immediately adjacent to the GMR were analyzed. Fishing effort along the south-west border of the GMR increased above average over time compared to other areas around the GMR. This indicates that fishermen seem to be fishing the line of the GMR. Overall, catch per unit effort (CPUE) decreased over time adjacent to the GMR boundary. However, CPUE along the south-west reserve border decreased below average over time compared to other areas around the GMR. This means the GMR has the potential to buffer declining catch rates in adjacent fishing grounds, indicating fisheries benefit of the reserve. This study provides empirical evidence of fishing the line behavior in response to the establishment of a large scale marine reserve and potential fisheries benefits of marine reserves for industrial tuna fisheries. These findings can help to effectively evaluate and improve GMR conservation outcomes and increase recognition of marine reserves as fisheries management tools, especially among industrial fisheries.

Popular Abstract

Marine reserves are recognized as powerful tools for both conservation and fisheries management. It is well established that marine ecosystems benefit from established marine reserves in terms of higher density, biomass, and species richness within the protected area. While in terms of fisheries management it remains controversial whether marine reserves have the potential to benefit fisheries operating adjacent to reserve boundaries or not. To be useful as a fisheries management tool, marine reserves need to positively affect fisheries in adjacent fishing grounds. In this context, marine reserves are predicted to support adjacent fisheries through spillover, the net emigration of marine organisms across reserve boundaries. However, the establishment of marine reserves has implications on fishing behavior among fishers in the respective region. Anticipating fisheries benefits due to spillover fishing effort often aggregates near reserve boundaries, known as fishing the line behavior. Unregulated fishing the line behavior can be of great concern for ecosystems and targeted fish stocks both in-and outside marine reserves. Thus, understanding fisheries dynamics in the context of spatial marine conservation is of great relevance to effective fisheries management and successful conservation measures; both on a regional and global scale. In my research I investigated interactions between the Galápagos Marine Reserve and tropical tuna purse-seine fisheries in the Eastern Tropical Pacific. By analyzing temporal and spatial fisheries dynamics using fisheries observer data I demonstrated fisheries behavior in relation to the Galápagos Marine Reserve and provided information concerning fisheries benefits from marine reserves. The tropical tuna purse-seine fishery in the Eastern Tropical Pacific showed a fishing the line behavior in relation to the Galápagos Marine Reserve suggesting fisheries benefits for vessels fishing adjacent to the reserve. It is considered that fisheries benefit from marine reserves when catch rates increase along reserve boundaries. In this context, established catch rate patterns along the Galápagos Marine Reserve suggested a real potential of the Galápagos Marine Reserve to buffer declining catch rates in adjacent fishing grounds, in terms of higher catch rates along the south-west border of the Galápagos Marine Reserve compared to other areas adjacent to the reserve. Overall, analyzed fisheries patterns in relation the Galápagos Marine Reserve have to be considered in the context of environmentally variability. The Galápagos Marine Reserve is inherently dynamic, located in the pathway of major ocean currents and directly affected by strong climatic events such as El Niño events, which in turn influence effort distribution and catch patterns in associated tuna fisheries. Finally, in times of ineffective conventional tuna fisheries management, examining spatio-temporal responses to the Galápagos Marine Reserve in the eastern tropical tuna purse-seine fishery, which represents one of the largest tuna fisheries in the world, provides important empirical information on interactions between marine reserves and industrial fisheries, and has the potential to improve the recognition of marine reserves as tools for industrial fisheries management.

Supervisor: Johan Hollander

• author: Buchholz, Andrea
• supervisor: Johan Hollander
• organization: Degree Projects in Biology
• course: BIOP35 20142
• year: 2015
• type: H2 - Master's Degree (Two Years)
• subject: Biology and Life Sciences
• language: English
• id: 8055476
• date added to LUP: 2015-10-13 11:39:37
• date last changed: 2015-10-13 11:39:37