Examinando por Autor "Mangel, J.C."
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Ítem Acceso Abierto 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.Ítem Acceso Abierto Captures of manta and devil rays by small-scale gillnet fisheries in northern Peru(Elsevier B.V., 2017) Alfaro-Cordova, E.; Del Solar, A.; Alfaro-Shigueto, J.; Mangel, J.C.; Diaz, B.; Carrillo, O.; Sarmiento, D.There is a growing global concern for the conservation of manta and devil rays (Mobulidae). Populations of mobulids are falling worldwide and fisheries are one of the main activities contributing to this decline. Mobulid landings have been reported in Peru for decades. However, detailed information regarding the description of mobulid captures is not available. This study provides an assessment of mobulid captures and fish-market landings by small-scale gillnet fisheries from three landing sites in northern Peru. Onboard and shore-based observations were used to monitor captures and landings respectively between January 2015 and February 2016. All mobulid species known to occur in Peru were recorded from landings, with immature Mobula japanica as the most frequent catch. No manta rays (Manta birostris) were reported as caught although one specimen was observed as landed. The mean nominal CPUE was 1.6 ± 2.8 mobulids[km.day]−1 while the average capture per set (fishing operation) was 2.0 ± 8.09 mobulids[set]−1. Smooth hammerhead shark (S. zygaena) and yellowfin tuna (T. albacares) were target species highly associated with mobulid captures. The majority of mobulid captures occurred in nearshore waters and over the continental shelf off Zorritos and San Jose. Mobulid capture showed a temporal trend, increasing between September 2015 and February 2016, with a peak in October 2015 (10.17 ± 0.23 mobulids[km.day]−1), reflected by landings that showed an additional peak in May. A generalized linear zero-inflated negative binomial two-part model (GLM ZINB) indicated that longitude and latitude explained both the zero-inflated binomial model, as well as the count negative binomial model, which also included season as a explanatory variable for differences in mobulid captures. The mean CPUE (mobulids[km.day]−1) and mean Variance values obtained from the fitted final model were 1.73 and 25.51, respectively. Results also suggest that high mobulid captures could reflect an opportunistic behaviour of fishermen who catch mobulids when target species are not as abundant. Considering the global conservation status of mobulids, (Manta and Mobula), and acknowledging that M. birostris was the only species not recorded captured in the study but is the only species legally protected in Peru, further studies are necessary to support the possible inclusion of Mobula species in national management plans. © 2017 Elsevier B.V.Ítem Acceso 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.Ítem Acceso Abierto Feeding ecology of the green turtle Chelonia mydas in northern Peru(Escuela de Ciencias del Mar, 2017) Jiménez, A.; Pingo, S.; Alfaro-Shigueto, J.; Mangel, J.C.; Hooker, Y.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. © 2017, Escuela de Ciencias del Mar. All rights reserved.Ítem Acceso Abierto Filling the gaps in sea turtle research and conservation in the region where it began: Latin America(Escuela de Ciencias del Mar, 2017) Velez-Zuazo, X.; Mangel, J.C.; Seminoff, J.A.; Wallace B.P.; Alfaro-Shigueto, J.The first documented long-term sea turtle research and conservation project in the world was officially launched in Latin America (Tortuguero, Costa Rica) in 1955. Despite the enormous advances in research and conservation in the nearly seven decades since, many questions still remain unanswered about fundamental aspects of ecology and population dynamics that hinder the conservation of sea turtles in the region. To catalyze further dissemination of information and improvement of sea turtle conservation, this Special Issue presents 10 papers solely focused on studies conducted in Latin America. This Special Issue resulted from an initiative launched to celebrate the 36th Annual Symposium on Sea Turtle Biology and Conservation, held in Peru in March 2016 -the first time this event was held in South America. The articles featured present novel results for four of the five species of sea turtles present in this region, with data collected as far back as 1971 and as recent as 2016. The studies cover diverse subjects including the nesting ecology for the most endangered populations of sea turtles in the world - the Eastern Pacific hawksbill turtle (Eretmochelys imbricata) and leatherback turtle (Dermochelys coriacea); the origins and connectivity of nesting and foraging populations of hawksbills and green turtles (Chelonia mydas); the detection of a new foraging ground for hawksbills in the Eastern Pacific; and the pervasive occurrence of incidental capture as well as illegal retention of sea turtles. The recovery of these imperiled marine reptiles relies on information to design and implement sound conservation actions; in this regard, the papers in this Special Issue are making a vital contribution, following the initial efforts launched nearly 70 years ago. © 2017, Escuela de Ciencias del Mar. All rights reserved.Ítem Acceso Abierto Hematologic, morphometric, and biochemical analytes of clinically healthy green sea turtles (Chelonia mydas) in Peru(Chelonian Research Foundation, 2016) Suarez-Yana, T.; David Montes, I.; Zuñiga, R.; Mangel, J.C.; Alfaro-Shigueto, J.Hematologic and biochemistry ranges were established for 31 clinically healthy green sea turtles (Chelonia mydas) incidentally captured in artisanal fisheries in Sechura Bay, Peru. Postcapture stress may have influenced heterophil values and glucose concentration. Sechura Bay provides abundant dietary protein affecting urea and glucose values. © 2016 Chelonian Research Foundation.Ítem Acceso Abierto Incidental capture of sea turtles in the artisanal gillnet fishery in Sechura Bay, northern Peru(Escuela de Ciencias del Mar, 2017) Pingo, S.; Jiménez, A.; Alfaro-Shigueto, J.; Mangel, J.C.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. © 2017, Escuela de Ciencias del Mar. All rights reserved.Ítem Acceso Abierto Isotopic niches of four commercially important pelagic elasmobranch species captured by the small-scale driftnet fishery of northern Peru(Escuela de Ciencias del Mar, 2018) Alfaro-Cordova, E.; Del Solar, A.; Gonzalez-Pestana, A.; Alfaro-Shigueto|, J.; Mangel, J.C.Despite the high landings of elasmobranch in Peru, little is known about some aspects of their basic biology, including their trophic ecology. The present study aims to provide basic information regarding the isotopic niche and trophic interactions of four pelagic elasmobranchs of commercial importance in northern Peru (Alopias spp., Galeorhinus galeus, Sphyrna zygaena, and Mobula japanica). One hundred and twenty-four samples were collected from fishing activities between January and December 2015 and processed for stable isotopes analysis (δ13C and δ15N), using Bayesian statistics to describe their isotopic niche. Differences between species were assessed using PERMANOVA and PERMDISP, allowing testing length, sex, and latitude as covariates. These combined results suggest trophic redundancy among sharks. However, unique areas of no overlap in the SEAC of all species could evidence a broad niche with a low interaction between these sharks. M. japanica had no overlap with any shark species, which indicates a trophic niche that is distinct from other elasmobranch top predators. Increasing sample size and including temporal covariates should help define these isotopic niches better, either by merging or splitting the studied elasmobranchs into more specific groupings. Further complementary studies are required to better understand trophic interactions within the pelagic community ecosystems. © 2018, Escuela de Ciencias del Mar. All rights reserved.Ítem Acceso Abierto Living on the edge: Hawksbill turtle nesting and conservation along the Eastern Pacific Rim(Escuela de Ciencias del Mar, 2017) Gaos, A.R.; Liles, M.J.; Gadea, V.; De Niz A.P.; Vallejo, F.; Miranda, C.; Darquea, J.J.; Henriquez, A.; Altamirano, E.; Rivera A.; Chavarría S.; Melero, D.; Urteaga J.; Pacheco, C.M.; Chácon, D.; LeMarie, C.; Alfaro-Shigueto, J.; Mangel, J.C.; Yañez, I.L.; Seminoff, J.A.Prior to 2007, efforts to monitor and conserve hawksbill turtles (Eretmochelys imbricata) in the eastern Pacific Ocean were opportunistic and records were virtually non-existent. The first abundance estimates were published in 2010, but contained limited data on the species. Ongoing research since that time has led to the identification of several rookeries, including sites containing large proportions of the overall hawksbill nesting currently known to occur in the region. Monitoring projects were established at several sites and have since provided substantial nesting data on the species. Here we summarize data collected between 1983 and March 2016 from all sites (n = 9) confirmed to host >10 nests in any given season to provide an update on hawksbill nesting in the eastern Pacific. We documented a total of 3,508 hawksbill nests, 265,024 hatchlings and 528 individual nesting females in the region. The vast majority of these records (99.4%, 99.9% and 99.6%, respectively) were generated subsequent to 2007, coinciding with the discovery of eight of the nine rookeries included in this study and the organization of monitoring efforts at those sites, which led to the increased documentation conferred here. Our findings should not be misconstrued as increases in actual nesting or signs of recovery, which could diminish the ongoing need for conservation actions, but rather as optimism, that there is still an opportunity to restore the species in the eastern Pacific. The top three sites in terms of average annual number of nests were Estero Padre Ramos (Nicaragua; 213.2 ± 47.6 nests), Bahia de Jiquilisco (El Salvador; 168.5 ± 46.7 nests) and Aserradores (Nicaragua; 100.0 ± 24.0 nests), and all three sites are located in mangrove estuaries in Central America, highlighting the importance of these rookeries/habitats for the survival and recovery of hawksbills in the region. The remaining six sites received between 6.9 ± 7.3 nests (Costa Careyes, Mexico) and 59.3 ± 17.7 nests (Los Cobanos, El Salvador) annually. By integrating data collected on nesting hawksbills with local conservation realities at the most important known hawksbill rookeries in the eastern Pacific, we provide a more holistic view of the conservation status and management needs of the species in this ocean region. © 2017, Escuela de Ciencias del Mar. All rights reserved.Ítem Acceso 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.Ítem Acceso Abierto The intentional harvest of waved albatrosses Phoebastria irrorata by small-scale offshore fishermen from Salaverry port, Peru(Instituto de oceanografia, 2016) Alfaro-Shigueto, J.; Mangel, J.C.; Valenzuela, K.; Arias-Schreiber, M.The waved albatross Phoebastria irrorata is classified by the IUCN as "critically endangered" because of its geographically restricted breeding range and evidence of a substantial decline in adult survival during the 1990s and early 2000s. This decline has been proposed to be a consequence of incidental mortality in the Peruvian small-scale fisheries but also of direct hunting for human consumption by fishermen. This paper uses a trans-disciplinary approach to describe and analyse the intentional capture of waved albatrosses in northern Peru by offshore small-scale fishermen. During 2008, 36 interviews were conducted in the port of Salaverry to understand the extent and reasons for the intentional capture. Sixty-nine precent of the interviewees mentioned occasionally harvesting albatrosses. Considering two to three vessels capture albatrosses regularly in Salaverry, we estimate a total annual mortality between 16 and 24 individuals since 2006. Reasons for capturing albatrosses included insufficient food supplies onboard during long fishing trips, collection of rings from ringed birds, the development of a taste for the bird's meat and even boredom. Interviews with fishermen showed a lack of awareness of the conservation status of albatrosses. We recommend strengthening the role of existing local governmental and non-governmental organizations involved with monitoring and surveillance, education and conservation.Ítem Acceso Abierto Trophic ecology of the smooth hammerhead shark (Sphyrna Zygaena) off the coast of northern Peru(National Marine Fisheries Service, 2017) Gonzalez-Pestana, A.; Acuña-Perales N.; Coasaca-Cespedes J.; Cordova-Zavaleta F.; Alfaro-Shigueto, J.; Mangel, J.C.; Espinoza, P.The smooth hammerhead (Sphyrna zygaena) is the third most captured shark species in Peru, a nation with one of the largest shark fisheries in the Pacific Ocean. We sought to better understand the trophic ecology of this shark in northern Peru by analyzing stomach contents. From 2013 through 2015, we collected 485 samples of gut contents from sharks measuring 53-294 cm in total length. Our results show that the smooth hammerhead is a top predator with a diet dominated by jumbo flying squid (Dosidicus gigas) and the Patagonian squid (Doryteuthis (Amerigo) gahi). Smooth hammerheads displayed different diets with different body size, and this finding indicates that sharks change their distribution and habitat during development. This study represents the most comprehensive investigation to date of the trophic ecology of smooth hammerhead in waters off Peru. We propose that these waters represent an important eastern Pacific Ocean feeding ground for smooth hammerhead. Because this species is commercially important and also preys upon other commercial species, these findings could contribute to the design and implementation of plans for ecosystembased fisheries management. © 2017, National Marine Fisheries Service. All rights reserved.