Designing marine reserves to reduce bycatch of mobile species : a case study using juvenile red snapper (Lutjanus campechanus)

Marine reserves have not been widely used to conserve mobile species because species abundance levels can be highly variable over space and time. Here we explore the potential for marine reserves to reduce bycatch of mobile species using red snapper (Lutjanus campechanus) as a case study. Bycatch in Gulf of Mexico shrimp trawls is a major source of juvenile red snapper mortality, and marine reserves may be mandated if bycatch reduction targets are not met. Using geographic information system (GIS) analyses of fishery-independent data, we investigated whether red snapper juveniles concentrate in "hot spots" and examined the trade-offs between abundance within hot spots (intensity) and predictability over time (persistence). These trade-offs allow fishery managers to tailor marine reserves to meet specific conservation goals. For red snapper, hot spots were primarily located around the 30 m isobath, with hot spots spread along the Texas coast in fall and clustered around the Texas-Louisiana border in summer. Increased intensity of hot spots led to lower persistence due to the smaller spatial area of higher intensity hot spots. Hot spots moved annually but generally persisted in the same locations over time, indicating that marine reserves could reduce red snapper bycatch. This approach provides a foundation for making informed decisions about design and placement of reserves for mobile species.