In press. Reducing green sea turtle bycatch in small-scale fisheries using illuminated gillnets: the cost of saving a sea turtle. Marine Ecology Progress Series.

A B S T R A C TSmall-scale fisheries can greatly impact threatened marine fauna. Peru's small-scale elasmobranch gillnet fishery captures thousands of sharks and rays each year, and incidentally captures sea turtles, marine mammals and seabirds. We assessed the ability of a dedicated fisheries remote electronic monitoring (REM) camera to identify and quantify captures in this fishery by comparing its performance to on-board observer reports. Cameras were installed across five boats with a total of 228 fishing sets monitored. Of these, 169 sets also had on-board fisheries observers present. The cameras were shown to be an effective tool for identifying catch, with > 90% detection rates for 9 of 12 species of elasmobranchs caught. Detection rates of incidental catch were more variable (sea turtle = 50%; cetacean = 80%; pinniped = 100%). The ability to quantify target catch from camera imagery degraded for fish quantities exceeding 15 individuals. Cameras were more effective at quantifying rays than sharks for small catch quantities (x ≤ 15 fish), whereas size affected camera performance for large catches (x > 15 fish). Our study showed REM to be effective in detecting and quantifying elasmobranch target catch and pinniped bycatch in Peru's small-scale fishery, but not, without modification, in detecting and quantifying sea turtle and cetacean bycatch. We showed REM can provide a time-and cost-effective method to monitor target catch in small-scale fisheries and can be used to overcome some deficiencies in observer reports. With modifications to the camera specifications, we expect performance to improve for all target catch and bycatch species.

Bycatch in net fisheries is recognized as a major source of mortality for many marine species, including seabirds. Few mitigation solutions, however, have been identified. We assessed the effectiveness of illuminating fishing nets with green light emitting diodes (LEDs) to reduce the incidental capture of seabirds. Experiments were conducted in the demersal, set gillnet fishery of Constante, Peru and compared 114 pairs of control and illuminated nets. We observed captures of a total of 45 guanay cormorants (Phalacrocorax bougainvillii), with 39 caught in control nets and six caught in illuminated nets. Seabird bycatch in terms of catch-per-unit-effort was significantly (p < 0.05) higher in control nets than in illuminated nets, representing an 85.1% decline in the cormorant bycatch rate. This study, showing that net illumination reduces seabird bycatch and previous studies showing reductions in sea turtle bycatch without reducing target catch, indicates that net illumination can be an effective multi-taxa bycatch mitigation technique. This finding has broad implications for bycatch mitigation in net fisheries given LED technology's relatively low cost, the global ubiquity of net fisheries and the current paucity of bycatch mitigation solutions.

ABSTRACT. Diet and food preferences of the green turtle Chelonia mydas were analyzed based on digestive tract contents of dead specimens caught incidentally by an artisanal gillnet fishery in Sechura Bay, northern Peru. We examined 27 digestive tracts and identified 35 prey items. The sampled turtles were all juveniles (CCL = 53.7 ± 1.2 cm, range 40.5-67.0 cm). The prey items were grouped into six categories: algae, cnidarians, mollusks, arthropods, chordates and garbage/anthropogenic debris. The items with the highest Frequency of Occurrence values (% FO) were: Caulerpa filiformis (77.8%), Loligo gahi (eggs) (51.9%) and Rhodymenia corallina (44.4%). By weight (% W), the most important items, were L. gahi (eggs) (33.3%), Stomolophus sp. (7.3%) and Aphos porosus (6.5%). According to the Preponderance Index (%IP), the preponderant item was L. gahi (eggs) with 6.1% and 61.2% during winter-spring and summer-autumn, respectively. According to the Resultant Weight index (Rw) of wet items, the most important items were: C. filiformis (13.1%), L. gahi (eggs) (10.5%), R. corallina (7.4%), plastic (7.5%), Gigartina chamissoi (5.1%). Garbage/anthropogenic debris was common in the digestive tracts analyzed. Plastic items had a frequency of occurrence of 44.4%. A greater diversity of food items was observed during summer and autumn. This study shows that juvenile C. mydas forage on a variety of resources. We recommend that conservation plans, land use planning and future management plans in the Sechura Bay include green turtles as a sentinel species for monitoring biodiversity of marine resources and the degree of pollution in the Bay.

ABSTRACT. Gillnets are recognized globally as one of the fishing gears with the highest levels of bycatch and mortality of sea turtles. Through onboard observer monitoring from July 2013 to June 2014 we assessed the bycatch of sea turtles by an artisanal gillnet fishery operating from Sechura Bay, Peru. One hundred and four sea turtles were incidentally caught in 53 observed fishing sets. The observed species composition of bycatch was green turtle Chelonia mydas (n = 100), hawksbill Eretmochelys imbricata (n = 3) and olive ridley Lepidochelys olivacea (n = 1). Bycatch occurred in 62.3% of monitored sets, with an average of 1.96 turtles caught per set. For all sea turtles combined, 28.8% of individuals were dead and 71.2% were alive at the time of retrieval. The majority of individuals caught were classified as juveniles and sub-adults, with an average carapace length (CCL) of 57.3 ± 0.9 cm for green turtles and 40.2 ± 2.4 cm for hawksbills. The mean annual catch per unit effort (CPUE) of sea turtles was 1.11 ± 0.31 turtles km -1 12 h -1), but varied by seasons. These results suggest that Sechura Bay is an important developmental habitat for juvenile and sub-adult green turtles and hawksbill turtles, but one subject to intense fishing interaction pressure. The development of monitoring programs, local awareness-raising activities, and enhanced management and protection of this critical foraging area and developmental habitat is recommended.