Examinando por Autor "Godley, B.J."

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    Abundance estimate of the Amazon River Dolphin (Inia geoffrensis) and the tucuxi (Sotalia fluviatilis) in southern Ucayali, Peru
    (Escuela de Ciencias del Mar, 2017) Campbell, E.; Shigueto. J.A.; Godley, B.J.; Mangel, J.C.
    We present results of the first simultaneous visual and acoustic surveys for Amazon River dolphins (Inia geoffrensis) and tucuxi (Sotalia fluviatilis), undertaken in Yarinacocha Lagoon, Ucayali, Peru (length = 20 km, area = 12 km2). A total of 324 Sotalia observations and 44 Inia observations were recorded in boat-based transects. Based upon total survey effort, we estimated Sotalia had a mean density ± SE of 1.98 ± 4.6 ind km-2and an overall abundance of 34 individuals (95% CI: 28 to 40). Average density for Inia was 0.2 ± 1.2 ind km-2with overall abundance estimated at 3 individuals (95% CI: 0 to 8). Visual surveys observed more Sotalia individuals during earlier hours of the day and during the dry season. Preliminary acoustic surveys undertaken with C-POD passive acoustic monitoring devices indicated a diel pattern in detections of cetacean vocalization with more diurnal activity and with detections ceasing from midnight until 10:00 AM. This work highlights the possibility of monitoring both river dolphin species through visual and acoustic surveys to generate baseline information on abundance trends and distribution patterns in the Ucayali region, an area with high levels of human disturbance. © 2017, Escuela de Ciencias del Mar. All rights reserved.
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    ÍtemAcceso Abierto
    Distribution and habitat use of a cryptic small cetacean, the Burmeister's porpoise, monitored from a small-scale fishery platform
    (Frontiers Media S.A., 2018) Clay, T.A.; Mangel, J.C.; Alfaro-Shigueto J.; Hodgson, D.J.; Godley, B.J.
    There is widespread evidence that small-scale fisheries (SSF) bycatch threatens many populations of small cetaceans, yet conservation efforts are often limited by a lack of basic knowledge regarding their abundance, distribution, and habitat use. Here, we used passive acoustic monitoring from an SSF platform-of-opportunity to better characterize the distribution and habitat use of small cetaceans in northern Peru, focussing on the little-known Burmeister's porpoise Phocoena spinipinnis. From 2009 to 2012, acoustic click detectors (C-PODs) were attached to fishing nets for the duration of 116 fishing sets (30 fishing trips). Dolphins (unspecified delphinids) and porpoises were recorded around 71 and 22% of fishing sets, respectively. The probability of occurrence and buzzing behavior (a proxy for foraging), and time spent, were linked to both static and dynamic environmental variables to examine the drivers of habitat use. Dolphin activity was spread evenly throughout the fishing area and was not linked to any habitat variables. In contrast, porpoises were detected in neritic waters, and habitat models performed well, identifying preferences for shallow (< 200 m depth) and cooler (17-18°C) waters, close (< 50 km) to shore. The high bycatch rate of small cetaceans in Peruvian SSF gave us the unique opportunity to investigate the link between bycatch and cetacean activity around vessels. We found a positive relationship between the likelihood of a bycatch event and acoustic presence for both dolphins and porpoises, however as we did not know the timing of entanglement, we could not link vocalization rates to mortality events. Nonetheless, as small cetaceans (particularly dolphins) frequently encounter fishing boats, the likelihood of entanglements may be reduced through effective efforts to alert animals to the presence of the net, either acoustically (using acoustic alarms) or visually. This study demonstrates that passive acoustic monitoring from a fisheries platform can provide insights into the distribution and habitat use of small cetaceans at relatively low cost, and is likely to be suitable in regions with low monitoring effort and high fishing pressure. © 2018 Clay, Mangel, Alfaro-Shigueto, Hodgson and Godley.
  • Miniatura
    ÍtemAcceso Abierto
    Reducing green turtle bycatch in small-scale fisheries using illuminated gillnets: the cost of saving a sea turtle
    (Inter-Research, 2016) Ortiz, N.; Mangel, J.C.; Wang, J.; Alfaro-Shigueto, J.; Pingo, S.; Jimenez, A.; Suarez, T.; Swimmer, Y.; Carvalho, F.; Godley, B.J.
    Gillnet fisheries exist throughout the oceans and have been implicated in high by-catch rates of sea turtles. In this study, we examined the effectiveness of illuminating nets with light-emitting diodes (LEDs) placed on floatlines in order to reduce sea turtle bycatch in a smallscale bottom-set gillnet fishery. In Sechura Bay, northern Peru, 114 pairs of control and illuminated nets were deployed. The predicted mean catch per unit effort (CPUE) of target species, standardized for environmental variables using generalized additive model (GAM) analysis, was similar for both control and illuminated nets. In contrast, the predicted mean CPUE of green turtles Chelonia mydas was reduced by 63.9% in illuminated nets. A total of 125 green turtles were caught in control nets, while 62 were caught in illuminated nets. This statistically significant re duction (GAM analysis, p < 0.05) in sea turtle bycatch suggests that net illumination could be an effective conservation tool. Challenges to implementing the use of LEDs include equipment costs, increased net handling times, and limited awareness among fishermen regarding the effectiveness of this technology. Cost estimates for preventing a single sea turtle catch are as low as 34 USD, while the costs to outfit the entire gillnet fishery in Sechura Bay can be as low as 9200 USD. Understanding these cost challenges emphasizes the need for institutional support from national ministries, inter-national non-governmental organizations and the broader fisheries industry to make possible widespread implementation of net illumination as a sea turtle bycatch reduction strategy. © The authors 2016.