ISTS Symposium43 Program/Agenda

As a component of the Western Indian Ocean Marine Science Association (WIOMSA) funded Bycatch Assessment and Mitigation in Western Indian Ocean Fisheries (BYCAM) program, a fishing gear specialist accompanied by one Fisheries scientist from the Kenya Marine and Fisheries Research Institute (KMFRI) collected information on catch rates of fish and bycatch from trawls equipped with a 10 cm bar spacing TED constructed In country for testing aboard a Kenyan shrimp trawler. Trawling operations were conducted out of Mombasa (Map 1)on the Kenyan coast in East Africa
between the 20th of April and 3rd of May 2018.

Catch data was collected from TED versus non-TED equipped trawls during a series of 73 consecutive comparative tows (both top and bottom opening TEDs where experimented). The duration of the tows and fishing zones were at the captain’s discretion. The 73 tows can be separated into 3 categories of data since 1) the first 23 tows where used to adjust gear (both the trawls and the TED configuration), 2) the next 30 tows (all. Top opening) considered here to be the preliminary experiment and 3) the last 20 tows (all top opening) which were à continuation of the first 30 tows but this time conducted without the gear specialist onboard the fishing vessel. These 20 tows and the previous 30 tows were considered a data series and so analysis was also conducted on the series of 50 tows.

A statistical analysis of the catch data between a top-opening TED-equipped trawl and non-TED trawl for the second category of data (30 tows) shows no difference in the catch rates of targeted shrimp, fish or bycatch. Large fish specimens of Pawizi (Lobotes surinamensis) were captured less often in the TED equipped trawl.

Adversely, the statistical analysis of the 3rd category of data (50 tows) for the same TED configuration shows a difference in the catch rates of targeted fish and bycatch. Large fish specimens of Pawizi were again captured less often in the TED equipped trawl. Shrimp catch showed no difference in catch rates.

The study culminated in a summary meeting between project personnel, NGO’s, industry and the KMFRI and KEFS representatives. It was noted that members of the fishing industry actively participated in the project and directly contributed to it’s success. The positive results of the study may serve to catalyze an interest in continued TED implementation activities in the region by WIOMSA especially for trawlers operating in Kenya, Tanzania and potentially including Mozambique leading the way for broader TED adoption in shrimp and fish trawls of the sub region.

In Cuba, shrimp trawl fisheries are carried out in the southeastern region, one of the most important areas of distribution of sea turtles on the Cuban shelf. In this paper, the interaction of shrimp trawls with sea turtles is analyzed, taking into account turtles caught, fishing effort and satellite tracking. The study was conducted both during the fishery (January-June) and on survey cruises (January-December) during the years 2021 and 2022. A total of 9 turtles were reported as bycatch (5 green turtles, 3 hawksbills and 1 loggerhead), during the two years. Of these, 7 were alive (77.7%) and 2 were dead. The values obtained indicated low incidence and low mortality of these species by this fishery. Satellite data of hawksbills tracked during different periods in the southeastern region, analyzed to complement this study, allowed us to identify important areas where this species remains, in which, due to the characteristics of the bottom, shrimp trawling operations are not carried out, thus reducing the possibility of their capture by the shrimp fleet. These results confirm the studies carried out over the years on the biodiversity of the fauna accompanying the shrimp fishery in the southeastern region of Cuba, based on the study of its structure and composition, which highlight that more than 90% of the bycatch are fish and crustaceans, the rest are mollusks, sponges and echinoderms; and that the capture of a turtle occurs occasionally and sporadically in this fishery, since, in general, they do not coincide with the areas where shrimp trawling is carried out. Nevertheless, it is vitally important to comply with the established regulations for the return of live turtles or the possibility of saving them as a mitigation measure.

In Malaysia, shrimp trawl fisheries have significantly contributed to the decline of sea turtles, with thousands taken as bycatch annually. Limited ecosystem-based fishery management and insufficient stakeholder involvement exacerbate this issue, affecting not only juvenile and trash fish but also large marine species such as sea turtles. Effective bycatch reduction strategies must protect turtles but not at the expense of negatively impacting fishers’ income and livelihoods, making gear modifications, such as the Turtle Excluder Devices (TEDs) more practical than spatial restrictions. This study focuses on TEDs implementation in Sabah, home to Malaysia’s largest trawl fleets (>1,000 vessels). The Marine Research Foundation conducted 57 paired trials in 2015-2019 to compare catches from TED-equipped and non-TED-equipped trawlers. Each trial involved a minimum of two-hour tow, followed by sorting, weighing, and comparing catches of shrimps, commercial fish, trash fish, and debris. Key findings revealed a slight increase in shrimp catches 4% in absolute catch in kg and 0.02% as an average across all catches in TED-equipped vessels. Commercial fish catches showed a minimal decrease (0.05% absolute and 0.03% average), representing fish that remain available for future trawls. The reduction in trash fish landings (0.24% absolute and 0.21% average) and debris (0.23%) demonstrates significant indirect benefits of TED adoption. By minimizing unwanted bycatch and debris, fishers benefit from shorter sorting times and reduced wear and tear on fishing gear, leading to lower operational costs and improved efficiency. The project also explored innovative TED designs, including a modified TED design featuring a 1m x 1m trapdoor flap to enhance catch retention and a Malaysian-designed frameless TED, a novel approach aimed at improving efficiency and usability. While the modified trapdoor design addressed fishers' concerns about potential catch loss, it is essential to note that TEDs themselves do not reduce the overall number of fish entering a net. The frameless TED underwent a pilot trial, highlighting areas for design refinement, and the need for additional testing to enhance effectiveness. Fishers were generally pleased that TEDs did not result in significant catch losses, addressing a critical perception challenge. While some trials were impacted by low catch volumes outside peak shrimp seasons or equipment damage, the overall results demonstrated that TEDs did not significantly reduce total catches. Instead, TEDs provided indirect benefits, including reduced debris, shorter sorting times, and improved fuel efficiency. The results also indicated that TEDs consistently improved catch quality. One limitation of short-term trials is the variability of fishing conditions, where outcomes can vary between nearby fishing areas. For instance, a TED-equipped vessel might trawl through a school of commercially valuable fish one day, while the non-TED vessel might do so another day. To address this, results across all 57 paired trials were aggregated and fishers were advised to use TEDs for at least a month before assessing their overall effectiveness. This study highlights the potential of TEDs as a low-cost, practical solution for balancing sea turtle conservation efforts with the economic needs of fishers while promoting sustainable fisheries management in Malaysia.

Sabah is home to four turtle species: Chelonia mydas, Eretmochelys imbricata, Lepidochelys olivacea, and Dermochelys coriacea. These species are threatened by accidental captures during fishing activities, particularly in trawl fisheries. In Malaysia, fishers are not allowed to capture sea turtles as they are legally protected. However, this does not protect the sea turtles from being caught accidentally. Fishers often discard the turtles, leaving a gap in information about where and when these capture events occur and whether the turtles are still alive when released. As part of an unrelated comprehensive project to assess shark and ray bycatch, electronic monitoring cameras were deployed on fishing trawlers and purse seiners to capture images of all species that were landed on a subset of 47 fishing vessel decks. Images of green and olive ridley turtles were captured by the cameras, while fishers provided footage of turtles being landed on deck, including leatherback turtles, serving as citizen-contributed data. These images were stamped with date, time and GPS coordinates, and this provides us with accurate location and timing data for each capture. Hotspot areas where most of the capture events occurred were identified by combining and analysing all location data, and overlaying this with fishery pressure. Olive ridley turtles comprised 19% of the bycatch, green turtles accounted for 48%, and the remaining individuals could not be identified. The capture of olive ridleys is a riddle as few have been observed nesting in Sabah. The size of each captured individual will be estimated from accurate measurements of the boat decks, and both the size composition and age-group distribution of the turtles caught by the vessels will be determined. These data will be used to investigate the spatial and temporal trends of these accidental captures, that can be used for future conservation management of the species and address the accidental catches of turtle, such as to protect the species in the hotspot areas from trawling or encourage the trawlers that operate in the hotspot areas to install Turtle Excluder Devices (TEDs).

KEYWORDS. Accidental catch, electronic monitoring cameras, turtles, commercial fisheries, hotspot area

Fisheries bycatch is a major source of anthropogenic mortality for sea turtle populations worldwide. Here, we add to our previous work addressing knowledge gaps in fine-scale behavioral responses of sea turtles to gillnet fishing gear. We conducted binary choice experiments using wild-caught juvenile green and loggerhead turtles in a testing tank at the St. Lucie Power Plant in Jensen Beach, Florida. Each turtle was presented two treatment pathways, one blocked by a gillnet, and one fully open. Individual turtles participated in three consecutive trials with netted and netless choices alternating between each trial. Behavioral metrics included binary choices made, avoidance and escape behaviors, and time spent in each treatment area. To assess potential net avoidance learning, we compared each metric among first, second, and third trials. Our results support a hypothesis that sea turtles learn from encounters with nets, with additional research needed to assess learning retention over longer periods.