| This research investigated key aspects of juvenile loggerhead ecology using a combination of satellite telemetry, fisheries observations, strandings surveys, and diet studies. Though linked both theoretically and thematically, this research was divided into three discrete chapters.;In the first chapter, I used a combination of satellite telemetry and fisheries observations to identify loggerhead high-use areas off the coast of Baja California Sur, Mexico. I used fisheries observations to assess levels of bycatch mortality in local small-scale fisheries. I found that loggerheads frequented a very small area in the Bight of Ulloa at very high densities. I also found that bycatch rates were problematically high in local small-scale fisheries and that they rivaled those reported for industrial scale fisheries spanning the entire North Pacific basin.;In my second chapter, I assessed anthropogenic mortality of endangered North Pacific loggerhead turtles in the coastal waters of Baja California Sur (BCS) through the synthesis of three sources: (1) intensive surveys of an index shoreline from 2003--2007, (2) bimonthly surveys of additional shorelines and towns for stranded and consumed carcasses from 2006-7, and (3) bycatch observations of two small-scale fishing fleets. Through five years of daily surveys of an index shoreline I found that loggerhead carcasses are beachcast along that coast at the highest rates reported worldwide. Through fisheries observations I found that bycatch and mortality rates of loggerheads in both local gillnet and longline fisheries are 1-2 orders of magnitude higher than anywhere else reported worldwide and concluded that conservation action is urgently needed.;In my third chapter, I compared habitat selection, movement, size frequency, and diet between juveniles at the coast of Baja California Sur, Mexico (neritic) with those observed in the Central North Pacific (oceanic). Oceanic juveniles traveled significantly further, faster and straighter and experienced lower SST and surface chlorophyll-alpha concentrations. These findings plus results published elsewhere suggest that neritic juveniles realize higher growth and eventual fecundity rates. Demographic modeling that I conducted suggests however that small advantages in survivorship for oceanic juveniles may balance the large disadvantages in growth and fecundity that result from the oceanic strategy. |
