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Visual cues play important roles in sea turtle foraging behavior and likely influence their interactions with fishing gear. Altering these cues may be a useful strategy to reduce the incidental catch of sea turtles in various fisheries. We examined the potential effectiveness of 3 visual cues—shark shapes placed along the length of the gill net, illumination of nets by LED lights, and nets illuminated with chemical lightsticks—in reducing bycatch of green sea turtlesChelonia mydasin gill nets. We then adapted these potential deterrents into commercial bottom gill net fishery to quantify their effects on target fish catch rates and the catch value. Our results indicate that the presence of shark shapes significantly reduced the mean catch rates of green turtles by 54% but also reduced target catch by 45% and, correspondingly, catch value by 47%. In contrast, nets illuminated by LED lights significantly reduced mean sea turtle catch rates by 40% while having negligible impacts on target catch and catch value. Similarly, nets illuminated by chemical lightsticks also significantly reduced mean sea turtle catch rates by 60% while having no significant impact on target catch and catch value. These results illustrate the potential for modifying fishing gear with visual deterrents to effectively reduce sea turtle catch rates.

Bycatch from marine commercial fisheries has been regarded as a global conservation concern for decades. Fortunately, some headway has been made in mitigating bycatch problems in marine fisheries. Freshwater commercial fisheries, however, have been relatively understudied. Although freshwater yields comprise 11% of the global commercial catch, bycatch research focusing on freshwater commercial fisheries represents only about 3% of the total bycatch literature. This paucity of research is particularly alarming given that so many of the world's threatened species live in freshwater. The limited literature that does exist includes examples of population declines attributed to commercial bycatch (e.g., the Yangtze River dolphin) and illustrates that bycatch is substantial in some systems (e.g., lake trout in Laurentian Great Lakes fisheries). Encouraging results from the marine realm can serve as models for bycatch research and development in freshwater and can lead to measurable gains in the conservation of freshwater ecosystems. We summarize existing work on inland bycatch in an effort to draw attention to this understated and understudied conservation problem.

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.

The unintended bycatch of long-lived marine species in fishing gear is an important global conservation issue. One suite of management approaches used to address this problem restricts or modifies fishing practices in areas where the probability of bycatch is believed to be high. Information on the distribution and behavior of the bycaught species is a desirable component of any such scheme, but such observations are often lacking. We describe a spatially explicit approach that combines data on the distribution of fishing effort and observations of the distribution of bycatch species derived from satellite telemetry. In a case study, we used a spatially explicit predator-prey model to investigate real-time interactions between three species of sea turtles (Caret ta caret ta, Chelonia my das, and Lepidochelys kempii) and the fall large-mesh gill net fishery that targets southern flounder (Paralichthys lethostigma) in Pamlico Sound, North Carolina between 2002 and 2004. The model calculates a spatial overlap index, thereby allowing us to identify which fishing areas have the greatest risk of encountering bycatch. In this study, our telemetry deployments (n = 50) were designed specifically to address existing fisheries conservation measures in Pamlico Sound intended to reduce sea turtle bycatch. We were able to predict the spatial distribution of bycatch and evaluate management measures. This approach offers a powerful tool to managers faced with the need to reduce bycatch.

Marine biological hotspots, or areas where high abundances of species overlap in space and time, are ecologically important areas because energy flow through marine food webs, a key ecosystem process, is maximized in these areas. I investigated whether top predators aggregated at persistent spawning sites of a key forage fish species, capelin (Mallotus villosus), on the NE coast of Newfoundland during July and August 2000-2003. By examining the distributional patterns of top predators through ship-based surveys at multiple spatial and temporal scales, I found that the biomasses of birds--dominated by Common Murres (Uria aalge)--and mammals--dominated by whale species--were concentrated along the coast, with a biological hotspot forming near two persistent spawning sites of capelin in all years. The formation of this hotspot was well defined in space and time from middle of July to middle of August, likely coinciding with the spawning chronology of capelin. Within this hotspot, there was a high spatial and temporal overlap of Common Murres and gill nets set to capture Atlantic cod (Gadus morhua). This resulted in breeding murres becoming entangled in gill nets while feeding on spawning capelin. Despite an acknowledged uncertainty of bycatch mortality, estimates for the larger regional-scale area (1936-4973 murres/year; 0.2-0.6% of the breeding population) underestimated mortality relative to estimates within the hotspot (3053-14054 murres/year; 0.4-1.7%). Although fishing effort for Atlantic cod has declined substantially since the groundfish moratorium in 1992, chronic, unnatural, and additive mortality through bycatch continues in coastal Newfoundland. Restricted use of gill nets within this and other biological hotspots during the capelin spawning period appears to be a straightforward application of the \"ecological and biologically significant area\" management framework in Canada's Oceans Act. This protection would minimize murre bycatch and maintain ecosystem integrity.

Very recently, a common cyprinid fish species at northern latitude, the roach (Rutilus rutilus L.) has been observed in the large south-alpine Lago Maggiore for the first time. The colonization of the lake has the characteristics of an invasion. In order to investigate this new fish population, benthic multi-mesh and commercial gill nets were used to sample fish in a wide gulf in the central part of the lake (Golfo Borromeo) from February to October 2006. In total 779 roach (TL: 5.5 – 38.8 cm) were caught, aged, sexed and stomach analyzed. Fecundity was assessed by counting the eggs in ripe gonads of females of age 3 and 4. The roach have become clearly the dominant species in the catches, constituting over 70% of the biomass and 70% of the numbers caught. None of the roach exceeded 8 years in age. They grow very fast (Φ' = 2.55) and have high fecundity (Fabs = 13740 ±4700 S.D. at age 3 and Fabs = 14768 ±5642 S.D. at age 4). The diet spectrum is wide and characterized by a strong seasonality. In early spring algae (benthic and planktonic algae), benthos and detritus prevail, whereas in summer zooplankton is the most frequent food item. In autumn roach switch back to benthos and detritus. Algae occur more frequently in young specimens while zooplankton, benthos and detritus in adults. The roach population is practically unimpacted by fishing. The minimum legal mesh size (25 mm) of gillnets, used by commercial fishermen, selects roach at the mean LT of 21.2 cm, which is over its length at maturity. The results suggest that roach established a viable population in Lago Maggiore less than a decade ago and rapidly became one of the dominant (if not the dominant) fish species. The possible consequence for the fish fauna in general and for the ecological status of the whole lake is briefly discussed.

Commercial and subsistence fisheries pressure is increasing in the Gulf of California, Mexico. One consequence often associated with high levels of fishing pressure is an increase in bycatch of marine mammals and birds. Fisheries bycatch has contributed to declines in several pinniped species and may be affecting the California sea lion (Zalophus californianus) population in the Gulf of California. We used data on fisheries and sea lion entanglement in gill nets to estimate current fishing pressure and fishing rates under which viable sea lion populations could be sustained at 11 breeding sites in the Gulf of California. We used 3 models to estimate sustainable bycatch rates: a simple population-growth model, a demographic model, and an estimate of the potential biological removal. All models were based on life history and census data collected for sea lions in the Gulf of California. We estimated the current level of fishing pressure and the acceptable level of fishing required to maintain viable sea lion populations as the number of fishing days (1 fisher/boat setting and retrieving 1 day's worth of nets) per year. Estimates of current fishing pressure ranged from 101 (0-405) fishing days around the Los Machos breeding site to 1887 (842-3140) around the Los Islotes rookery. To maintain viable sea lion populations at each site, the current level of fishing permissible could be augmented at some sites and should be reduced at other sites. For example, the area around San Esteban could support up to 1428 (935-2337) additional fishing days, whereas fishing around Lobos should be reduced by at least 165 days (107-268). Our results provide conservation practitioners with site-specific guidelines for maintaining sustainable sea lion populations and provide a method to estimate fishing pressure and sustainable bycatch rates that could be used for other marine mammals and birds.

The possibility for fishery-induced evolution of life history traits is an important but unresolved issue for exploited fish populations. Because fisheries tend to select and remove the largest individuals, there is the evolutionary potential for lasting effects on fish production and productivity. Size selection represents an indirect mechanism of selection against rapid growth rate, because individual fish may be large because of rapid growth or because of slow growth but old age. The possibility for direct selection on growth rate, whereby fast-growing genotypes are more vulnerable to fishing irrespective of their size, is unexplored. In this scenario, faster-growing genotypes may be more vulnerable to fishing because of greater appetite and correspondingly greater feeding-related activity rates and boldness that could increase encounter with fishing gear and vulnerability to it. In a realistic whole-lake experiment, we show that fast-growing fish genotypes are harvested at three times the rate of the slow-growing genotypes within two replicate lake populations. Overall, 50% of fast-growing individuals were harvested compared with 30% of slow-growing individuals, independent of body size. Greater harvest of fast-growing genotypes was attributable to their greater behavioral vulnerability, being more active and bold. Given that growth is heritable in fishes, we speculate that evolution of slower growth rates attributable to behavioral vulnerability may be widespread in harvested fish populations. Our results indicate that commonly used minimum size-limits will not prevent overexploitation of fast-growing genotypes and individuals because of size-independent growth-rate selection by fishing.

Various mitigation measures have been implemented to reduce incidental seabird mortality in longline and trawl fisheries but little attention has been given to artisanal fishing. In the 2008/09 breeding season, during a study of foraging of Humboldt, Spheniscus humboldti, and Magellanic Penguins, S. magellanicus, breeding on Puñihuil islets, southern Chile, a Magellanic Penguin equipped with a time-depth recorder became entangled and subsequently drowned in a gill net set for Corvina Drum (Cilus gilberti). The device was returned by fishermen and the data appear to be the first documented case of such a drowning in a marine, air-breathing vertebrate. According to the data, while diving to a depth of more than 50 m, the bird became entangled and drowned, remaining below 60 m for nearly 21 hours until the net was hauled. Although only a single incident is reported, there are indications that incidental mortality of penguins, other seabirds and marine mammals is more common in artisanal fisheries than previously anticipated.

Globally, 6.4 million tons of fishing gear are lost in the oceans annually. This gear (i.e., ghost nets), whether accidently lost, abandoned, or deliberately discarded, threatens marine wildlife as it drifts with prevailing currents and continues to entangle marine organisms indiscriminately. Northern Australia has some of the highest densities of ghost nets in the world, with up to 3 tons washing ashore per kilometer of shoreline annually. This region supports globally significant populations of internationally threatened marine fauna, including 6 of the 7 extant marine turtles. We examined the threat ghost nets pose to marine turtles and assessed whether nets associated with particular fisheries are linked with turtle entanglement by analyzing the capture rates of turtles and potential source fisheries from nearly 9000 nets found on Australia's northern coast. Nets with relatively larger mesh and smaller twine sizes (e.g., pelagic drift nets) had the highest probability of entanglement for marine turtles. Net size was important; larger nets appeared to attract turtles, which further increased their catch rates. Our results point to issues with trawl and drift‐net fisheries, the former due to the large number of nets and fragments found and the latter due to the very high catch rates resulting from the net design. Catch rates for fine‐mesh gill nets can reach as high as 4 turtles/100 m of net length. We estimated that the total number of turtles caught by the 8690 ghost nets we sampled was between 4866 and 14,600, assuming nets drift for 1 year. Ghost nets continue to accumulate on Australia's northern shore due to both legal and illegal fishing; over 13,000 nets have been removed since 2005. This is an important and ongoing transboundary threat to biodiversity in the region that requires attention from the countries surrounding the Arafura and Timor Seas.