Abstract
The Pacific Sailfish (Istiophorus platypterus) and Blue Marlin (Makaira nigricans) are vital resources to Central American economies along the eastern tropical Pacific Ocean through recreational catch-and-release fisheries and as retainable bycatch in commercial fisheries. Because of observed stock declines and a lack of a formal stock assessment research, there exists an immediate need to understand sailfish and blue marlin population dynamic characteristics to design fishery regulations to protect both species and fisheries. Therefore, the goal of this dissertation was to understand the sailfish and blue marlin behavior and dynamic habitat use in the Eastern Pacific Ocean (EPO) in support of billfish conservation programs. This dissertation utilized newly developed methods to assess sailfish behavior using advanced technologies and data collection in accelerometry never before applied to non-captive animals. A behavioral modeling technique applied for the first time to billfish was incorporated into migratory analysis revealing differentiated behavioral characteristics between sailfish and blue marlin relative to migratory speed, distances, and spatial foraging/searching behavioral patterns. Billfish behavioral parameter estimates and geo-referenced purse seine catch statistics were analyzed via generalized additive models (GAM) using divergence, vorticity, sea surface temperature, and chlorophyll-a as explanatory variables revealing billfish preferences for these habitat characteristics. Finally, an analysis of dispersal range of sailfish and blue marlin revealed the extent and residency of sailfish and blue marlin migratory ranges within exclusive economic zones, indicating a need for management to be applied over large transnational spatial scales.