Participatory Risk Assessment of Humpback Whale (Megaptera novaeangliae) and Leatherback Turtle (Dermochelys coriacea) Bycatch in Northern Peru

Uncertainties about the magnitude of bycatch in poorly assessed fisheries impede effective conservation management. In northern Peru, small-scale fisheries (SSF) bycatch negatively impacts marine megafauna populations and the livelihoods of fishers which is further elevated by the under-reporting of incidents. Within the last decade, accounts of entangled humpback whales (HBW) (Megaptera novaeangliae) off the northern coast of Peru have increased, while Eastern Pacific leatherback turtles (LBT) (Dermochelys coriacea) have seen over a 90% decline in nesting populations related in large part to bycatch mortality. By leveraging the experience and knowledge of local fishers, our research objectives were to use a low-cost public participation mapping approach to provide a spatio-temporal assessment of bycatch risk for HBW and LBT off two Peruvian fishing ports. We used an open-source, geographic information systems (GIS) model, the Bycatch Risk Assessment (ByRA), as our platform. Broadly, ByRA identifies high bycatch risk areas by estimating the intersection of fishing areas (i.e., stressors) with species habitat and evaluating the exposure and consequence of possible interaction between the two. ByRA outputs provided risk maps and gear risk percentages categorized as high, medium, and low for the study area and seven subzones for HBW in the austral winter and LBT in the austral summer. Overall, the highest bycatch risk for both species was identified within gillnet fisheries near the coast. Bycatch risk for most gear types decreased with distance from the coast. When we separated the ByRA model by port, our map outputs indicate that bycatch management should be port specific, following seasonal and spatial variations for HBW, and specific fishing gear impacts for HBW and LBT. Combined with direct bycatch mitigation techniques, ByRA can be a supportive and informative tool for addressing specific bycatch threats and marine megafauna conservation goals. ByRA supports a participatory framework offering rapid visual information via risk maps and replicable methods for areas with limited resources and data on fisheries and species habitat.

Presence and the global implications of plastics in wild commercial fish in the Alboran Sea

The presence of plastic in the environment has become a major problem for marine megafauna. The identification of the global micro and mesoplastic uptake by commercial fish populations may allow for a better understanding of their impact. This study aims to: (i) determine the presence and composition of plastic in two pelagic fish (Engraulis encrasicolus and Scomber scombrus) and two demersal species (Scyliorinus canicula and Mullus barbatus) from the Alboran Sea (western Mediterranean) to quantify the relationship between plastic prevalence and habitat and feeding behavior in the selected fish species, (ii) compare local measurements made of the presence of plastics ingested by these four fish species with published values from a across their range literature review, and (iii) identify the methodologies used in similar studies of plastic pollution in fish. Across their range, the highest occurrence of plastics was found in E. encrasicolus, which contrasts to that found in S. scombrus at the Alboran sea. Material analysis of the collected data showed the most predominant fiber color was black and the predominant plastic polymer was polyethylene. The increasing emerging risk of plastics and the levels of macro- and micro-plastic ingested by seafood in this study support the suggest that quantifying plastic presence and composition may be essential as a food safety measure.

Incorporating Geographical Scale and Multiple Environmental Factors to Delineate the Breeding Distribution of Sea Turtles

Temperature is often used to infer how climate influences wildlife distributions; yet, other parameters also contribute, separately and combined, with effects varying across geographical scales. Here, we used an unoccupied aircraft system to explore how environmental parameters affect the regional distribution of the terrestrial and marine breeding habitats of threatened loggerhead sea turtles (Caretta caretta). Surveys spanned four years and ~620 km coastline of western Greece, encompassing low (<10 nests/km) to high (100–500 nests/km) density nesting areas. We recorded 2395 tracks left by turtles on beaches and 1928 turtles occupying waters adjacent to these beaches. Variation in beach track and inwater turtle densities was explained by temperature, offshore prevailing wind, and physical marine and terrestrial factors combined. The highest beach-track densities (400 tracks/km) occurred on beaches with steep slopes and higher sand temperatures, sheltered from prevailing offshore winds. The highest inwater turtle densities (270 turtles/km) occurred over submerged sandbanks, with warmer sea temperatures associated with offshore wind. Most turtles (90%) occurred over nearshore submerged sandbanks within 10 km of beaches supporting the highest track densities, showing the strong linkage between optimal marine and terrestrial environments for breeding. Our findings demonstrate the utility of UASs in surveying marine megafauna and environmental data at large scales and the importance of integrating multiple factors in climate change models to predict species distributions.

Revealing Sea Turtle Behavior in Relation to Fishing Gear Using Color-Coded Spatiotemporal Motion Patterns With Deep Neural Networks

Incidental capture, or bycatch, of marine species is a global conservation concern. Interactions with fishing gear can cause mortality in air-breathing marine megafauna, including sea turtles. Despite this, interactions between sea turtles and fishing gear—from a behavior standpoint—are not sufficiently documented or described in the literature. Understanding sea turtle behavior in relation to fishing gear is key to discovering how they become entangled or entrapped in gear. This information can also be used to reduce fisheries interactions. However, recording and analyzing these behaviors is difficult and time intensive. In this study, we present a machine learning-based sea turtle behavior recognition scheme. The proposed method utilizes visual object tracking and orientation estimation tasks to extract important features that are used for recognizing behaviors of interest with green turtles (Chelonia mydas) as the study subject. Then, these features are combined in a color-coded feature image that represents the turtle behaviors occurring in a limited time frame. These spatiotemporal feature images are used along a deep convolutional neural network model to recognize the desired behaviors, specifically evasive behaviors which we have labeled “reversal” and “U-turn.” Experimental results show that the proposed method achieves an average F1 score of 85% in recognizing the target behavior patterns. This method is intended to be a tool for discovering why sea turtles become entangled in gillnet fishing gear.

A socio-psychological approach for understanding and managing bycatch in small-scale fisheries

Fisheries bycatch is the greatest threat to migratory, long-lived marine animals. Managing bycatch can be particularly problematic in small-scale mixed-species fisheries, where perceptions of target and non-target vary widely, and all catches have economic or subsistence value. Such fisheries are ubiquitous throughout the world’s oceans, and represent a cross-disciplinary challenge for biodiversity, food security and livelihoods. We offer a novel approach for addressing this challenge, drawing on well-established theories from behavioural and social sciences. We first typify bycatch as a spectrum rather than a clearly delineated component of catch, where the position of a species on this spectrum depends on fishers’ beliefs regarding the outcomes of bycatch-relevant behaviour. We then outline an approach to diagnose the underlying socio-psychological drivers of bycatch, based on the Theory of Planned Behaviour. Finally, we illustrate the approach using an empirical case study, exploring fishers’ beliefs regarding bycatch-relevant behaviour for three endangered species in a small-scale gill net fishery in Indonesia. We show how a socio-psychological approach can help to identify conflicts and synergies between bycatch mitigation and fishers’ beliefs, thus informing more effective and socially-just interventions for marine megafauna conservation. We emphasize the need to understand human dimensions of bycatch, especially in SSFs, where technical fixes alone will be insufficient to change behaviour. Rather, interdisciplinary approaches are needed to align fishers’ needs with conservation objectives. Our spectrum and approach could be widely applied for disentangling drivers of bycatch in other SSFs, and designing interventions which support effective and equitable marine conservation.

Designing locally-appropriate conservation incentives for small-scale fishers

Large, long-lived marine animals (‘marine megafauna’) play critical roles in ocean ecosystems, however, they are threatened by overfishing. Technologies and practices that reduce fisheries’ impacts on marine megafauna are well documented, yet less is known about how to encourage their adoption. This is particularly challenging in small-scale fisheries (SSFs), where endangered species can have important consumptive use values. We used a novel combination of methods – scenario interviews with contingent valuation (CV) – to investigate how incentive-based interventions might influence fisher behaviour and reduce mortality of Critically Endangered taxa (hammerhead sharks (Sphyrna spp.) and wedgefish (Rhynchobatus spp.)) in two case study SSFs in Indonesia. Scenario interviews revealed that positive performance-based incentives were almost unanimously supported (98% and 96% of fishers would stop landing hammerheads and wedgefish, respectively). This is in contrast to 1% and 6% under a business as usual control scenario, and 52% and 46% in response to a regulation with a fine. Using CV, we estimated that an incentive-based scheme for catch mitigation of all hammerheads and wedgefish across both sites could cost US$71,620-298,820 annually, and save up to 18,500 hammerheads and 2,140 wedgefish relative to current catch baselines. This study provides empirical evidence that performance-based payments could offer a cost-effective, legitimate and socially-just approach for marine conservation in SSFs, and support “a sustainable and equitable blue economy” and “living in harmony with nature”. This is particularly important with the growing adoption of net-outcome goals for biodiversity, with studies such as this providing the basis for locally-appropriate investment ready schemes for bycatch-neutral seafood supply chains.

Culturing Putatively Obligate Epizoic Diatoms: Insights for the Evolution and Ecology of Diatoms and Their Host

Background: Our understanding of the importance of microbiomes on large aquatic animals—such as whales, sea turtles and manatees—has advanced considerably in recent years. Recent activity describing the epizoic diatoms growing on marine vertebrates suggests that these epibiotic diatom communities constitute diverse, polyphyletic, and compositionally stable assemblages that include both putatively obligate epizoic and generalist species. Here, we outline a successful attempt to culture putatively obligate epizoic diatoms without their hosts and propose further applications and research avenues in this growing area of study. Results: We cultured cells of epizoic diatoms from multiple host species sampled in the wild and captivity. Analyzing the DNA sequences of these cultures, we found that several unique diatom taxa have independently evolved to occupy in epibiotic habitats. We created a library of reference sequence data for use in metabarcoding surveys of sea turtle and manatee microbiomes that will further facilitate the use of environmental DNA for studying host specificity in epizoic diatoms and the utility of diatoms as indicators of host ecology and health. Conclusions: Our discovery that epizoic diatoms can be cultured independently from their hosts raises several questions about the nature of the interaction between these diatom species and their hosts. We encourage the interdisciplinary community working with marine megafauna to consider including diatom sampling and diatom analysis into their routine practices.