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Recent research on ocean health has found large predator abundance to be a key element of ocean condition. Fisheries can impact large predator abundance directly through targeted capture and indirectly through incidental capture of nontarget species or bycatch. However, measures of the global nature of bycatch are lacking for air-breathing megafauna. We fill this knowledge gap and present a synoptic global assessment of the distribution and intensity of bycatch of seabirds, marine mammals, and sea turtles based on empirical data from the three most commonly used types of fishing gears worldwide. We identify taxa-specific hotspots of bycatch intensity and find evidence of cumulative impacts across fishing fleets and gears. This global map of bycatch illustrates where data are particularly scarce-in coastal and small-scale fisheries and ocean regions that support developed industrial fisheries and millions of small-scale fishers-and identifies fishing areas where, given the evidence of cumulative hotspots across gear and taxa, traditional species or gear-specific bycatch management and mitigation efforts may be necessary but not sufficient. Given the global distribution of bycatch and the mitigation success achieved by some fleets, the reduction of air-breathing megafauna bycatch is both an urgent and achievable conservation priority.fisheries bycatch | trophic downgrading | longlines | gillnets | trawls

Background. Although bycatch of industrial-scale fisheries can cause declines in migratory megafauna including seabirds, marine mammals, and sea turtles, the impacts of small-scale fisheries have been largely overlooked. Small-scale fisheries occur in coastal waters worldwide, employing over 99% of the world's 51 million fishers. New telemetry data reveal that migratory megafauna frequent coastal habitats well within the range of small-scale fisheries, potentially producing high bycatch. These fisheries occur primarily in developing nations, and their documentation and management are limited or non-existent, precluding evaluation of their impacts on non-target megafauna. Principal Findings/Methodology. 30 North Pacific loggerhead turtles that we satellite-tracked from 1996-2005 ranged oceanwide, but juveniles spent 70% of their time at a high use area coincident with small-scale fisheries in Baja California Sur, Mexico (BCS). We assessed loggerhead bycatch mortality in this area by partnering with local fishers to 1) observe two small-scale fleets that operated closest to the high use area and 2) through shoreline surveys for discarded carcasses. Minimum annual bycatch mortality in just these two fleets at the high use area exceeded 1000 loggerheads year 21 , rivaling that of oceanwide industrial-scale fisheries, and threatening the persistence of this critically endangered population. As a result of fisher participation in this study and a bycatch awareness campaign, a consortium of local fishers and other citizens are working to eliminate their bycatch and to establish a national loggerhead refuge. Conclusions/Significance.. Because of the overlap of ubiquitous small-scale fisheries with newly documented highuse areas in coastal waters worldwide, our case study suggests that small-scale fisheries may be among the greatest current threats to non-target megafauna. Future research is urgently needed to quantify small-scale fisheries bycatch worldwide. Localizing coastal high use areas and mitigating bycatch in partnership with small-scale fishers may provide a crucial solution toward ensuring the persistence of vulnerable megafauna.

The green turtle Chelonia mydas is a circumglobal species that is susceptible to overexploitation as a food resource and incidental mortality in fisheries. Efforts to recover regional green turtle populations have been hampered by a lack of information on their biology. In particular, turtle movements and home ranges in neritic foraging habitats are not well understood. Thus, wildlife managers cannot accurately determine the habitat needs of green turtle populations. To address these understudied aspects, we carried out the first ever investigation of green turtle home range in neritic foraging habitats of the eastern Pacific Ocean. Twelve turtles, ranging from 50.9 to 82.5 cm in straight carapace length and from 17 to 70 kg in mass, were tracked with radio and sonic telemetry for 34 to 96 d at the Bahía de los Angeles foraging area in the Gulf of California, Mexico. Home range areas determined with minimum convex polygon and fixed kernel density estimator methods ranged from 584 to 3908 ha (mean = 1662 ± 324 ha) and 409 to 3231 ha (mean = 1537 ± 280 ha), respectively. There was no evidence that straight carapace length, mass, sex, tracking duration or number of re-sightings influenced the size of the home range. Green turtle home ranges contained from 1 to 3 activity centers ranging from 3.8 to 642.2 ha in area (mean = 178.8 ± 62.0 ha). Turtles were re-sighted in all depth-class regions (0 to 10 m to 40+ m) in the study area but were not found with equal frequency among these regions. The distribution of re-sightings among depth classes varied significantly between diurnal (05:00 to 18:59 h) and nocturnal (19:00 to 04:59 h) periods. While the greatest frequency of diurnal re-sightings occurred in the 10 to 20 m depth class, nocturnal encounters were most frequent in the 0 to 10 m depth class. This study shows that Bahía de los Angeles remains an important feeding ground; thus, underscoring the need to develop conservation strategies that address the impacts of ongoing commercial marine-algae harvests and net fisheries that threaten green turtles in this region.