Jeffrey A. Seminoff

Global Conservation Priorities for Marine Turtles

Where conservation resources are limited and conservation targets are diverse, robust yet flexible priority-setting frameworks are vital. Priority-setting is especially important for geographically widespread species with distinct populations subject to multiple threats that operate on different spatial and temporal scales. Marine turtles are widely distributed and exhibit intra-specific variations in population sizes and trends, as well as reproduction and morphology. However, current global extinction risk assessment frameworks do not assess conservation status of spatially and biologically distinct marine turtle Regional Management Units (RMUs), and thus do not capture variations in population trends, impacts of threats, or necessary conservation actions across individual populations. To address this issue, we developed a new assessment framework that allowed us to evaluate, compare and organize marine turtle RMUs according to status and threats criteria. Because conservation priorities can vary widely (i.e. from avoiding imminent extinction to maintaining long-term monitoring efforts) we developed a “conservation priorities portfolio” system using categories of paired risk and threats scores for all RMUs (nu200a=u200a58). We performed these assessments and rankings globally, by species, by ocean basin, and by recognized geopolitical bodies to identify patterns in risk, threats, and data gaps at different scales. This process resulted in characterization of risk and threats to all marine turtle RMUs, including identification of the worlds 11 most endangered marine turtle RMUs based on highest risk and threats scores. This system also highlighted important gaps in available information that is crucial for accurate conservation assessments. Overall, this priority-setting framework can provide guidance for research and conservation priorities at multiple relevant scales, and should serve as a model for conservation status assessments and priority-setting for widespread, long-lived taxa.

Regional Management Units for Marine Turtles: A Novel Framework for Prioritizing Conservation and Research across Multiple Scales

Background Resolving threats to widely distributed marine megafauna requires definition of the geographic distributions of both the threats as well as the population unit(s) of interest. In turn, because individual threats can operate on varying spatial scales, their impacts can affect different segments of a population of the same species. Therefore, integration of multiple tools and techniques — including site-based monitoring, genetic analyses, mark-recapture studies and telemetry — can facilitate robust definitions of population segments at multiple biological and spatial scales to address different management and research challenges. Methodology/Principal Findings To address these issues for marine turtles, we collated all available studies on marine turtle biogeography, including nesting sites, population abundances and trends, population genetics, and satellite telemetry. We georeferenced this information to generate separate layers for nesting sites, genetic stocks, and core distributions of population segments of all marine turtle species. We then spatially integrated this information from fine- to coarse-spatial scales to develop nested envelope models, or Regional Management Units (RMUs), for marine turtles globally. Conclusions/Significance The RMU framework is a solution to the challenge of how to organize marine turtles into units of protection above the level of nesting populations, but below the level of species, within regional entities that might be on independent evolutionary trajectories. Among many potential applications, RMUs provide a framework for identifying data gaps, assessing high diversity areas for multiple species and genetic stocks, and evaluating conservation status of marine turtles. Furthermore, RMUs allow for identification of geographic barriers to gene flow, and can provide valuable guidance to marine spatial planning initiatives that integrate spatial distributions of protected species and human activities. In addition, the RMU framework — including maps and supporting metadata — will be an iterative, user-driven tool made publicly available in an online application for comments, improvements, download and analysis.

Pollutants and the health of green sea turtles resident to an urbanized estuary in San Diego, CA

Rapid expansion of coastal anthropogenic development means that critical foraging and developmental habitats often occur near highly polluted and urbanized environments. Although coastal contamination is widespread, the impact this has on long-lived vertebrates like the green turtle (Chelonia mydas) is unclear because traditional experimental methods cannot be applied. We coupled minimally invasive sampling techniques with health assessments to quantify contaminant patterns in a population of green turtles resident to San Diego Bay, CA, a highly urbanized and contaminated estuary. Several chemicals were correlated with turtle size, suggesting possible differences in physiological processes or habitat utilization between life stages. With the exception of mercury, higher concentrations of carapace metals as well as 4,4-dichlorodiphenyldichloroethylene (DDE) and γ chlordane in blood plasma relative to other sea turtle studies raises important questions about the chemical risks to turtles resident to San Diego Bay. Mercury concentrations exceeded immune function no-effects thresholds and increased carapace metal loads were correlated with higher levels of multiple health markers. These results indicate immunological and physiological effects studies are needed in this population. Our results give insight into the potential conservation risk contaminants pose to sea turtles inhabiting this contaminated coastal habitat, and highlight the need to better manage and mitigate contaminant exposure in San Diego Bay.

Calculating the ecological impacts of animal‐borne instruments on aquatic organisms

Summary 1. Animal-borne instruments provide researchers with valuable data to address important questions on wildlife ecology and conservation. However, these devices have known impacts on animal behaviour and energetics. Tags deployed on migrating animals may reduce reproductive output through increased energy demands or cause phenological mismatches of foraging and nesting events. For marine organisms, the only tagging guidelines that exist are based on lift and thrust impacts on birds – concepts that do not translate well to aquatic animals. Herein, we provide guidelines on assessing drag from animal-borne instruments and discuss the ecological impacts on marine organisms. Of particular concern is the effect of drag from instruments to the welfare of the animals and for the applicability of collected data to wild populations. 2. To help understand how drag from electronic tags affects marine animals in the wild, we used marine turtles as model aquatic organisms and conducted wind tunnel experiments to measure the fluid drag of various marine turtle body types with and without commercially available electronic tags (e.g. satellite, TDR, video cameras). We quantified the drag associated with carrying biotelemetry devices of varying frontal area and design (squared or tear drop shaped) and generated contour plots depicting percentage drag increase as a framework for evaluating tag drag by scientists and wildlife managers. Then, using concepts of fluid dynamics, we derived a universal equation estimating drag impacts from instruments across marine taxa. 3. The drag of the marine turtle casts was measured in wind speeds from 2 to 30 m s 1 (Re 30 9 10 4 – 19 9 10 6 ), equivalent to 01–1 9ms 1 in seawater. The drag coefficient (CD) of the marine turtles ranged from 011 to 022, which is typical of other large, air-breathing, marine vertebrates (008–026). The CD of tags in reference to the turtle casts was 091 018 and most tags caused minimal additional drag ( 100%). The sensitivity of aquatic animals to instrument drag is a dynamic relationship between the fluid flow patterns, or CD, and the frontal area ratio of the animal and tag. 4. In this paper, we have outlined methods for quantifying the drag costs from animal-borne instrumentation considering the instrument retention time (time to release from the animal) and the activity of the instrumented animal. With this valuable tool, researchers can quantify the drag costs from animal-borne instrumentation and choose appropriate tags for their intended study organism and question. Reducing drag will ultimately reduce the impact on the instrumented animals and lead to greater biological realism in the collected data.

Feeding ecology of the green sea turtle ( Chelonia mydas ) in the Galapagos Islands

The Galapagos Islands are among the most important nesting areas for the green sea turtle, Chelonia mydas , in the eastern Pacific Ocean. In addition, the coastal waters of this oceanic archipelago host many important feeding areas for this species, although little is known about green turtle feeding ecology at these sites. The goal of this study was to identify and quantify the most important items in the diet of the green turtle at the foraging grounds of Bahia Elizabeth, Caleta Derek and Punta Nunez. Our analysis was based on 65 oesophageal samples from turtles captured in 2006 and 2007. We compared spatial and seasonal composition of diet using non-metric multidimensional scaling analysis (MDS) and analysis of similarity (ANOSIM). Green turtle diet was composed mainly of the algae species Ulva lactuca, Polysiphonia sp., Hypnea sp. and Dictyota sp. , and the red mangrove Rhizophora mangle . Turtles also consumed animal matter, mainly cnidarians, albeit to a lesser extent. Content of turtle diets was different among feeding grounds and seasons. The ANOSIM showed that diet composition can differ between foraging grounds using presence/absence of diet items. Even though U. lactuca was the most abundant algae consumed in both seasons, changes in species richness of algae were found between both sampling events, with diet during the warm season more varied than the cold season (χ 2 xa0=xa016.84, dfxa0=xa06; P

Coastal habitat degradation and green sea turtle diets in Southeastern Brazil.

To show the influence of coastal habitat degradation on the availability of food for green turtles (Chelonia mydas), we assessed the dietary preferences and macroalgae community at a feeding area in a highly urbanized region. The area showed low species richness and was classified as degraded. We examined stomach contents of 15 dead stranded turtles (CCL=44.0cm (SD 6.7cm)). The diet was composed primarily of green algae Ulva spp. (83.6%). In contrast, the macroalgae community was dominated by the green alga Caulerpa mexicana. We found a selection for red algae, seagrass and Ulva spp., and avoidance for C. mexicana and brown alga Dictyopteris delicatula. The low diversity of available food items, possibly a result of environmental degradation, likely contributed to the low dietary diversity. The nutritional implications of this restricted diet are unclear.

Diet selection by immature green turtles ( Chelonia mydas ) at Bahía Magdalena foraging ground in the Pacific Coast of the Baja California Peninsula, México

In order to determine if eastern Pacific green turtles (Chelonia mydas) exhibit feeding preferences samples of recently ingested food items were compared to the food resources available in the marine environment where C. mydas congregates. Stomach samples were collected by conducting gastric lavage and, at the same time, vegetation transects were conducted during spring and winter. Green turtles in our study selectively consumed seaweeds, with Codium amplivesiculatum and Gracialaria textorii as preferred species. Differences in the consumption of species were found across the two mentioned seasons and were consistent with changes in the availability of different algae species in the environment. Based on these results, it is recommended that sea turtle conservation plans along the Baja California Peninsula include Pacific coastal mangrove channels with a high diversity of algae species as priority areas for protection.

Trace metals in an urbanized estuarine sea turtle food web in San Diego Bay, CA

San Diego Bay is an anthropogenically impacted waterway that is also a critical habitat for many sensitive species such as the green sea turtle (Chelonia mydas). In this study, we quantified trace metal concentrations in sediment and organisms composing the green sea turtle diet, and identified bioaccumulation patterns for a suite of trace metals. We found Ag, Cd, Cu, Mn, Se, and Zn exhibited the highest bioaccumulation levels in this food web. Cu and Mn concentrations in resident biota displayed a strong spatial gradient from the mouth to the head of the Bay, which was different from the patterns found in the sediment itself. Sediment median concentrations followed a general pattern across the bay of Al>Mn>Cu≈Zn>Pb>As>Cd>Ag>Se>Hg. In contrast, eelgrass displayed differential patterns in the mouth versus the back of the Bay (three front Bay sites: Al>Mn>Zn>Cu>Pb>Se>Cd≈Ag>As; five back Bay sites: Mn>Al>Zn>Cu>Pb≈Se>Cd>Ag>Hg>As) with the exception of Shelter Island where levels of Zn and Cu were elevated as a result of anti-fouling paint pollution. Observed differences between sediment and biota metal patterns are likely due to complex processes related to trace metals input and bioavailability, habitat characteristics and specific metabolic functioning of the trace metals for each member of the food web. These data highlight the fact that for the San Diego Bay ecosystem, the current use of toxicity reference values scaled up from sediment and invertebrate testing ex-situ is likely to be inaccurate when transposed to the green sea turtle. Here, we illustrate how identifying spatial variability in metal exposure can improve our understanding of habitat utilization by sea turtles in highly urbanized estuaries. Monitoring contaminants directly in food webs of sensitive vertebrates may greatly improve our understanding of their direct and indirect exposure to potentially deleterious contamination, and should be considered in the future to improve traditional risk assessment approaches.

Small-scale gill-net fisheries cause massive green turtle Chelonia mydas mortality in Baja California Sur, Mexico

The coastal waters of Baja California Sur, Mexico, include some of the most important foraging grounds of the East Pacific green turtle Chelonia mydas . However, they are also important fishing grounds for artisanal fleets, leading potentially to high levels of bycatch mortality. We studied the impact of a small-scale gill-net fishery at San Ignacio lagoon, north-west Mexico, an important green turtle feeding ground. We conducted mortality censuses and interviewed local fishers to estimate total bycatch mortality at the lagoon. We also used marked drifters and carcasses to estimate stranding probabilities of turtles taken as bycatch. During 2006–2009 we found 262 dead turtles; 96% of the mortality occurred in May–August corresponding to the fishing season for halibut Paralichthys californicus and guitar-fish (Rhinobatus sp.). Stranding probability estimated from drifters was 0.062 (95% confidence interval, CI, 0.035–0.094), yielding a minimum mortality of 3,516 turtles during 2006–2008 (95% CI 2,364–6,057) or 1,172 animals per year. This is probably an underestimate of real mortality as the drifters have higher stranding probabilities than carcasses and most of the nets were set in the lower lagoon where carcasses rarely strand. Interviews with local fishers yielded a similar estimate of 1,087 (95% CI 901–1,286) dead turtles per year. This study is emblematic of the impact of artisanal fleets on marine turtles caused by overlap of fishing and turtle feeding areas. In 2009 strandings declined by > 97%, resulting from a change in fishing practices because of increased vigilance by enforcement authorities, underscoring the importance of law enforcement to protect threatened species.

Trading information for conservation: a novel use of radio broadcasting to reduce sea turtle bycatch

Bycatch of non-target animals in small-scale fisheries poses a major threat to seabirds and marine mammals and turtles. This is also a problem for small-scale fisheries in Peru because of the magnitude of these fisheries and the important marine biodiversity in Peruvian waters. Here we describe how we implemented a novel approach to mitigate bycatch impacts on marine turtles in Peru. We used high-frequency (HF) two-way radio communication to exchange information with fishers. We sought data that would afford insights into fishing patterns and levels of turtle bycatch so that we could identify areas of high-density bycatch in real time and warn other fishers. In return we provided oceanographic and atmospheric information useful for the fishers. Radio communication also served as a platform to promote the use of safe handling and release techniques for incidentally caught animals. During the 24 months of the programme we communicated with over 200 vessels and with 200–1,400 fishers, who used primarily longlines, gillnets, jiggers, purse seiners and trawlers. Our findings suggest that HF radio communication is a useful tool (low cost and widely used by fishers, with extensive spatial coverage), helps build links with fishers that potentially reduces fishery impacts on marine turtles, and can also provide information on poorly documented fisheries and the relevant bycatch data associated with small-scale fishing practices.