Habitat Use and Diet of Juvenile Eastern Pacific Hawksbill Turtles (<i>Eretmochelys imbricata</i>) in the North Pacific Coast of Costa Rica

ABSTRACT.Hawksbill sea turtles (Eretmochelys imbricata) inhabiting the eastern Pacific Ocean are one of the world's most threatened marine turtle management units. Despite the fact that knowledge about the status of sea turtles at foraging grounds is a key element for developing the effective conservation strategies, comprehensive studies of hawksbills at foraging habitats in the eastern Pacific remain lacking. For many years anecdotal information indicated Coiba Island National Park in Panama as a potentially important hawksbill foraging ground, which led to the initiation of monitoring surveys in September 2014. Ongoing mark-recapture surveys to assess population status, generate demographic data and identify key foraging sites have been conducted every six months in the park since that time. To date, a total of six monitoring campaigns consisting of four days each have been conducted, leading to the capture and tagging of 186 hawksbills, 51 of which were recaptured at least once. The size range of captured individuals was 30.0 to 75.5 cm and largely comprised of juveniles. Somatic growth rates of individual hawksbills were highly variable, ranging from -0.78 to 7.1 cm year -1 . To our knowledge, these are the first published growth rates for juvenile hawksbill turtles in the eastern Pacific Ocean. When these growth data are combined with information on hawksbill demography and distribution, our findings indicate Coiba Island National Park is one of the most important known foraging sites for hawksbill sea turtles in the eastern Pacific Ocean.

Section: Discussionmentioning

confidence: 81%

Distribution, size range and growth rates of hawksbill turtles at a major foraging ground in the eastern Pacific Ocean

Llamas¹,

Flores

Abrego

et al. 2017

“…Hawksbills that forage at coral reefs primarily consume sponges and macroalgae, which are typically found at highest densities in shallow water (Meylan, 1988;Leon & Bjorndal, 2002;Bell, 2013), and rarely utilize habitats deeper than 20 m (Houghton et al, 2003;Witt et al, 2010). Similar to their conspecifics in other ocean regions, juvenile (Carrión-Cortez et al, 2013) and adult (Gaos et al, 2012c) hawksbills in the eastern Pacific predominately use shallow water habitat <20 m deep, where 92% (n = 18,389.4 effort units and 654 sets) of total fishing effort and 97% (n = 30) of total hawksbill captures occurred in our study, further highlighting the threat of lobster gillnet fishing activities operating in nearshore waters of El Salvador and Nicaragua.…”

Section: Discussionmentioning

confidence: 99%

“…Indeed, Aucoin & León (2007) reported the capture of three juvenile hawksbills in a 640 m lobster gillnet used in experimental bycatch trials during 24-h periods over four days in the Dominican Republic, and encountered a lobster gillnet with an additional seven dead juvenile hawksbills. In the eastern Pacific, small-scale fishers primarily use gillnets to capture lobsters (FAO, 2007;Pérez-González, 2011;Salas et al, 2011;Carrión-Cortez et al, 2013), although in Mexico, Colombia, and Ecuador lobster fishers also employ traps and diving (Beltrán, 2005;Salas et al, 2011). We expect hawksbill bycatch to be greatest in lobster gillnet fisheries along the coast of Central America, where intense use of lobster gillnets occurs in areas relatively adjacent to major nesting grounds for this species in the region (Gaos et al, 2017), which employs short migrations between nesting and foraging areas (Gaos et al, 2012a).…”

Section: Discussionmentioning

confidence: 99%

“…Little is known, however, about the spatiotemporal distribution and bycatch rates at Los Cóbanos and similar rocky reef systems at Punta Amapala in El Salvador and La Salvia in Nicaragua, where previous research signaled hawksbill bycatch occurs in lobster gillnet fisheries (Liles & Thomas, 2010;Gaos et al, 2014b). Further, eastern Pacific hawksbills are considered a high risk Regional Management Unit (RMU; Wallace et al, 2011) with high vulnerability to bycatch mortality and, therefore, a top priority for bycatch monitoring and mitigation, particularly in small-scale fisheries operating in or near critical hawksbill habitats (Wallace et al, 2010, such as at rocky reefs where eastern Pacific hawksbills congregate (Gaos et al, 2012a;Carrión-Cortez et al, 2013;Tóbon-López & Amorocho-Llanos, 2014).…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Survival on the rocks: high bycatch in lobster gillnet fisheries threatens hawksbill turtles on rocky reefs along the Eastern Pacific coast of Central America

Liles¹,

Gaos

Bolaños³

et al. 2017

Self Cite

ABSTRACT. Small-scale coastal fisheries can cause detrimental impacts to non-target megafauna through bycatch. This can be particularly true when high-use areas for such species overlap with fishing grounds, as is the case with hawksbill turtle (Eretmochelys imbricata) aggregations at lobster gillnet fishing sites in El Salvador and Nicaragua. We quantified hawksbill bycatch by partnering with local fishers to record data for 690 gillnet sets on rocky reefs at Los Cóbanos Reef Marine Protected Area ) and Punta Amapala (2012 in El Salvador, and La Salvia (2012)(2013)(2014) in Nicaragua. Based on 31 observed hawksbill captures, the mean bycatch-per-unit-effort (0.0022; individuals per set = 0.0450) and mortality (0.74) are among the highest reported for the species across fishing gear types and oceanic regions worldwide, and we conservatively estimate that at least 227 juvenile hawksbill captures occurred in lobster gillnet fishing fleets at our sites during the study. Estimated mortality for the 227 hawksbills -which could approach the 74% observed mortality of total capturesfrom interactions with lobster gillnet fisheries at these sites during the study period may constitute the greatest single source of human-induced in-water mortality for juvenile, sub-adult, and adult hawksbills in the eastern Pacific, and is of grave concern to the population. Based on our findings, we discuss neritic habitat use by hawksbills during their 'lost years' and offer recommendations for bycatch reduction strategies, including community-based efforts to enhance sustainable self-governance via the establishment of locally crafted conservationist norms and marine protected areas at important developmental habitat.

“…These escalated efforts led to ongoing discoveries of hawksbill nesting and foraging grounds throughout the region (Alfaro-Shiqueto et al, 2010;Gaos & Urteaga, 2010;Quiñones et al, 2011;Brittain et al, 2012;Carrión-Cortez et al, 2013;Chacón-Chaverri et al, 2014;Tobón-López & Amorocho, 2014;Heidemeyer et al, 2014;Kelez et al, 2016). The rapid surge in data has quickly improved researchers' understanding of the species and their critical habitats, behooving updated regional assessments.…”

Section: Introductionmentioning

confidence: 99%

Living on the Edge: Hawksbill turtle nesting and conservation along the Eastern Pacific Rim

Gaos

Liles

Gadea

et al. 2017

ABSTRACT. 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 572 2 Latin American Journal of Aquatic Research Pacific, we provide a more holistic view of the conservation status and management needs of the species in this ocean region.