STRATEGY 1: REDUCE MORTALITY FROM FISHERIES BYCATCH
Bycatch is still considered the major obstacle to population recovery for East Pacific leatherbacks. The latent impacts of high mortality in swordfish driftnets off Chile in the 1990s are likely further hindering recovery, as possibly thousands of adult leatherbacks were killed annually (Frazier and Montero, 1990; Eckert and Sarti, 1997), which eliminated a significant portion of the breeding population and, therefore, their future offspring as well. In addition, ongoing leatherback bycatch in small-scale fisheries in South America continues to impact adults and subadults (Alfaro-Shigueto et al. 2007; 2011; 2012), the two life stages with the largest per-individual impacts on marine turtle population dynamics (Wallace et al. 2008).
Leatherback bycatch has not been quantified at the regional scale, thus preventing robust estimation of the level of reduction necessary to stabilize and eventually increase population abundance. However, some information about leatherback bycatch is available for some ports and fishing gears (longline gear and gillnets) in South America. In particular, a recent tri-national project to assess sea turtle bycatch in net fishing gear using port-based surveys in Ecuador, Peru, and Chile provided the only available baseline of leatherback bycatch in the region and highlighted high-bycatch ports. Likewise, several ports in Peru have been identified as having high bycatch in both longlines and nets (see below).
Based on existing bycatch assessments mentioned above, between 1,000-2,000 leatherbacks (adult males and females, as well as juveniles) are caught in nets and longlines annually, of which roughly 30%-50% die as a result of these interactions; therefore, estimated bycatch mortality is between 300-600 and as many as 1,000 leatherbacks annually. Though some of these are subadults (e.g., Alfaro-Shigueto et al. 2007), those individuals are included as adults for the purposes of this estimate exercise. Assuming that adult sex ratios reflect those of nesting beaches, roughly 75% of the total number of leatherbacks taken as bycatch are adult females, making the annual mortality of adult female leatherbacks approximately 225 to 450 individuals. These estimates are especially troubling, considering that total abundance of nesting females based on beach monitoring in the region is estimated at fewer than 1,000 individuals. This incongruity between adult female abundance based on beach monitoring and estimates of annual bycatches of adult females means that assumptions affecting abundance and/or bycatch estimates require improvements. More importantly, the low certainty in these estimates makes assigning target reductions in bycatch difficult and tenuous. Nonetheless, because targets are needed to shape the regional Plan of Action, the interim goal for this strategy is to reduce annual bycatch mortality by one-third in the next ten years, or by approximately 150 nesting females per year, in Ecuador, Peru, and Chile combined.
To achieve this goal, enhanced assessments to better quantify leatherback bycatch and track progress toward reduction goals, as well as capacity-building in fishing communities to reduce bycatch and testing of mitigation measures will be supported at priority ports during the first five years of the Plan. During the same period, assessments will be conducted for other countries in the region, particularly those that host leatherback nesting (e.g. Mexico, Nicaragua, Costa Rica), to further refine quantification of leatherback bycatch, and identify important bycatch areas within these countries, as well as opportunities for mitigation. Significant reductions in bycatch mortality will be critical to stabilizing the EP leatherback population trend because saving subadults and adults translates to direct increases in survivorship of the very life stages we use to quantify population trends.
Existing assessments have highlighted particular ports as having significant leatherback bycatch that require more in-depth assessments and community-based mitigation efforts. We recommend that actions be taken at ports identified by previous assessments as high-priority ports for leatherback bycatch. These ports include Manta and Santa Rosa, Ecuador, Salaverry, Pisco, San Jose, and Ilo, Peru, and Coquimbo and Lebu, Chile. For many other ports identified as having significant leatherback bycatch (e.g. several ports in Ecuador [Esmereldas, Anconcito, Puerto Bolivar], Peru [Constante, Chimbote, Pucusana, Morro Sama], and Chile [Iquique, Arica, Antofogasta, Caldera]), we recommend that these efforts also be conducted as funds permit.
1.1.1. Continued assessments of leatherback (and sea turtle) bycatch at ports throughout the three countries using port-based surveys as well as on-board observers (when possible) to establish baselines and follow-up assessments to evaluate progress after mitigation activities.
1.1.2. Establish three new bases (Santa Rosa, Ecuador; San Jose, Peru; Coquimbo, Chile) for the real-time, sea-to-sea and sea-to-shore radio communication program between conservation groups and fishermen to enhance reporting, safe handling and release of leatherbacks caught in fishing gear, and avoidance of leatherback bycatch when possible. Additional bases may be added in later years of the plan based on the success of this strategy and the identification of other priority bycatch areas.
1.1.3. Testing mitigation measures to reduce leatherback bycatch in gillnets and trammel nets in Ecuador and Peru, and in longlines in Peru and Chile.
1.1.4. Providing training and equipment necessary to ensure safe handling and release of leatherbacks caught in fishing gear (e.g., line cutters, dehookers) to at least 30% of artisanal fishermen in key ports in Ecuador, Peru, and Chile, and to 10% of on-board observers in Chilean longline fleet.
1.1.5. Workshops to increase awareness, build capacity, and exchange techniques and experiences between conservation groups and local fishing communities (combined with above).
Although several ports in South America have been established as having high leatherback bycatch, other areas where leatherback bycatch occurs and could be significant must also be identified. In addition to other high bycatch areas, satellite tracking of adult females from nesting beaches has allowed identification of high-use areas for foraging, but virtually nothing is known about long-term habitat use patterns in the region during the 3-4 year period that females are away from nesting beaches, not to mention the complete lack of data on adult males and subadults. Because fishing activities that occur in feeding areas or near nesting beaches would be of particular concern, countries whose waters host these areas should be assessed. We recommend the following actions throughout the region, but particularly in high-use waters adjacent to nesting beaches and potential feeding areas in the region.
1.2.1. Expand port-based bycatch assessments of leatherbacks (and other sea turtles) conducted in Ecuador, Peru, and Chile to all countries throughout the region, particularly those known to host leatherback nesting (Mexico, Nicaragua, Costa Rica) and/or feeding areas (Panama, Colombia) targeting at least 3 ports per country and 10% of vessels per port.
1.2.2. Deploy satellite transmitters on juvenile and adult leatherbacks caught in fishing gear in Peru (and possibly Ecuador and Chile) to elucidate habitat use in feeding areas and to estimate post-release mortality rates, which is a critical piece of information that is essentially unknown for all fishing gears.
1.2.3. Analysis of distributions of juvenile leatherbacks with respect to oceanographic conditions in the region.
1.2.4. Analysis of distributions of jellies, leatherbacks, and fisheries activities in the Humboldt Current system.
In addition to mortality resulting from incidental capture in fishing gear, retention of bycaught leatherbacks for consumption by fishermen is a significant issue in some Peruvian ports, perhaps being the fate for more than 50% of leatherbacks taken as bycatch in some cases. However, as this phenomenon appears to be geographically restricted, we recommend a pilot assessment project to provide insights for future actions to reduce or eliminate this threat.
1.3.1. Pilot study to assess the magnitude of the impact as well as the motivations for consumption at fishing ports in Peru to inform development of approaches that might reduce this practice.
1.3.2. Based on results of pilot study, introduce measures to reduce retention in at least two ports, i.e. those where highest incidence of retention found to occur.
A detailed table including these recommended actions, plus implementation sites, timeframes, costs, and possible implementers was also prepared as part of the Action Plan. Download the table here.