ABSTRACT
Sea turtles spend the majority of their lives in coastal or pelagic waters, making in-water sources of mortality critical to population viability. Sea turtles have been negatively impacted by a number of human-mediated factors including oil spills (Antonio et al., 2011), contaminants (van de Merwe et al., 2010; Swarthout et al., 2010; Komoroske et al., 2011; Stewart et al., 2011), and other types of marine pollution, namely debris ingestion and entanglement (Lazar and Gracan, 2011; do Sul et al., 2011). Coastal and in-water shoreline development also have been shown to degrade ocean habitat, which can negatively affect resident turtles (Harewood and Horrocks, 2008; Pike, 2008). While all of these factors likely have some negative effect on sea turtle populations, the human activity that has the largest impact on sea turtles is sheries bycatch (Lewison et al., 2004a; Wallace et al., 2011). Although directed take of turtles is one form of sheries impact, and in some regions opportunistic take of captured turtles is still prevalent (Alfaro-Shigueto et al., 2011), turtles are generally an
12.1 Biology and Signicance of Sea Turtle Bycatch .................................................................. 329 12.2 Understanding How Sea Turtle Bycatch Happens ................................................................ 330
12.2.1 Differences among Fishing Gears ............................................................................ 331 12.2.2 Bycatch Rates and Mortality among Gears .............................................................. 333
12.3 Interpreting the Bycatch Landscape ..................................................................................... 334 12.3.1 Characterizing Bycatch ............................................................................................ 334 12.3.2 Mapping the Bycatch Landscape .............................................................................. 335
12.4 Assessing Population-Level Impacts of Bycatch .................................................................. 337 12.5 Bycatch in Different Fisheries Sectors ................................................................................. 338
12.5.1 Bycatch in Large-Scale Fisheries ............................................................................. 338 12.5.2 Bycatch in Small-Scale Fisheries ............................................................................. 339
12.6 Bycatch Reduction ................................................................................................................340 12.6.1 Bycatch Reduction in Large-Scale Fisheries ............................................................340 12.6.2 Bycatch Reduction in Small-Scale Fisheries ............................................................ 342
12.7 Social Science of Bycatch ..................................................................................................... 343 12.8 New Approaches and Directions in Bycatch Research ........................................................344 References ...................................................................................................................................... 345
unwanted and unwelcome byproduct of shing activities. Because shing is an important source of protein and livelihood for millions of people worldwide, incidental capture, or bycatch, of sea turtles continues to be the most pressing human impact on sea turtle populations globally. In this chapter, we review the current state of knowledge about global marine turtle bycatch, including how characteristics of sea turtle biology and shing practices interact to result in bycatch, assessments of population-level impacts of turtle bycatch, descriptions of where and how turtle bycatch occurs across distinct sheries sectors, a summary of techniques and approaches to bycatch reduction, and new ways forward for bycatch research and management.
