Appendix H: Sea Turtles

Note: Scientific and ecological terminology and agency/organization acronyms are used throughout this chapter. A List of Definitions and Acronymsis included at the end of the chapter.

H.1 Sea turtle species in the RWSC study area

All sea turtles in the U.S. are federally protected by the Endangered Species Act (ESA) and most states adopt the federal status for management purposes. In the U.S., sea turtles in water (foraging, migrating, oceanic dispersal, mating, disentanglement and stranding response) are managed federally by NOAA Fisheries and on land (nesting, rehabilitation and captive display) by the U.S. Fish and Wildlife Service.

Sea turtles have a unique life history. They are generally long lived and, besides incubating eggs and emergent hatchlings, only adult females spend a brief period on beaches while nesting. For all six species found in U.S. waters combined, sea turtles can be found in the northwest Atlantic from shallow coastal waters, including brackish and inshore bays, sounds and river mouths to offshore pelagic waters. Collectively sea turtles may be the ESA listed species most commonly affected by offshore wind. They range in size from <10cm Kemp’s ridley hatchlings to >2m adult leatherbacks. In the oceanic dispersal stage, they feed in surface waters often associated with floating algae such as sargassum, as larger juveniles-adults, diets range from herbivorous adult green turtles to leatherbacks feeding primarily on gelatinous prey to Kemp’s ridley and loggerhead turtles that feed primarily on benthic crustaceans and mollusks.

In the U.S. Atlantic, sea turtles are migratory in temperate and northern sub-tropical areas and may live in relatively static or seasonally shifting home ranges in sub-tropical and tropical waters depending on the species and habitat.

On the U.S. Atlantic coast, loggerhead and green turtles regularly nest from Florida to North Carolina. Loggerheads nesting in the U.S. belong to the NW Atlantic DPS, and greens belong to the N Atlantic DPS. Small numbers of loggerheads annually nest in southeastern Virginia and occasional nests of both species have been reported north of Virginia. In the same region, leatherback turtles nest primarily in Florida and numbers have fluctuated at index beaches but have generally increased since the late 1980s. Occasional Kemp’s ridley and hawksbill turtles nest on the U.S. Atlantic coast, hawksbills in Florida and Kemp’s ridleys from FL to VA. Extralimital nesting outside of known nesting areas have been documented for all turtle species.

There is no parental investment after a nest is laid and hatchlings emerge from nests, make their way to the water and swim frenetically until they reach offshore habitat where they spend several years to over a decade in an oceanic dispersal stage. For northwest Atlantic green and loggerhead turtles, we believe this life stage is spent primarily in the Gulf Stream and Sargasso Sea. Little is known about NW Atlantic leatherbacks in the oceanic dispersal stage. Most Kemp’s ridleys nest in the Gulf of Mexico and some of these turtles exit the Gulf and are dispersed into the northwest Atlantic most likely via the Gulf Stream.

Healthy juvenile through adult life stage sea turtles are considered ‘surfacers’ instead of ‘divers’ meaning that most of their time is spent below the surface, and, with a couple of exceptions, they only come to the surface briefly to breathe (Kooyman, 1989). One exception to this mostly subsurface lifestyle is basking behavior which has been exhibited by loggerhead turtles on the outer continental shelf, mostly in the spring months as they are migrating north to summer foraging areas (Hochscheid et al., 2010). Post-hatchling turtles in the dispersal phase (Phillips, 2022) also appear to spend most of their time in the top several meters of the water column.

Movement from the oceanic dispersal life stage to the juvenile-adult neritic life stages occurs at different age and size for loggerhead, green, and Kemp’s ridley turtles. Little is known about leatherback distribution from hatchling to sub-adult life stages.

Because their behavior and distribution varies among life stages, the Science Plan will address research priorities by species, life stage and subregion (Table 1). Thus, for the remainder of this document, sea turtle life stages will be defined as:

Egg/hatchling – for the conservation purposes of the RWSC, we are combining incubating egg in nests with hatchling emergence and swimming frenzy; beach phase including incubation, emergence & swim frenzy that results in arrival in offshore pelagic habitat.

Juvenile dispersal – ‘lost years’ life stage, post-hatching dispersal where turtles are near the surface, in open water. Off the U.S. Atlantic coast these small turtles are thought to be distributed primarily in the Gulf Stream and Sargasso Sea. Little is known about the dispersal life stage for leatherback turtles, and this life stage primarily occurs in the Gulf of Mexico for Kemp ridley turtles (Phillips, 2022).

Juvenile-subadult (post dispersal)– foraging phase of sexually immature turtles (neritic habitat for Kemp’s ridley, green and loggerhead turtles in the NW Atlantic; pelagic and neritic for NW Atlantic leatherbacks), characterized in some species and subregions by north/south and/or inshore offshore seasonal migrations or seasonally shifting home ranges.

Adult – sexually mature; loggerheads nest in the Central Atlantic and Southern Atlantic subregions, green and leatherback turtles almost exclusively in the Southern Atlantic, occasional nests of all species are found outside normal nesting areas. Females of most populations have an inter-nesting period of >1 year. Non-breeding and post-breeding/nesting adults may behave seasonally much like juveniles and sub-adults. Tracking data suggest foraging occurs outside of nesting areas in post-nesting females.

Table 1: Sea turtle species and life stage covered by this plan by subregion (UN=unknown, NA=not applicable, Winter=Jan-Mar, Spring=Apr-Jun, Summer=Jul-Sep, Fall=Oct-Dec).

Gulf of Maine

Species ESA Status egg/ hatchling juvenile dispersal juvenile-subadult adult nesting females Annual occurrence Habitat use Seasonal timing
leatherback endangered NA UN ✔️ ✔️ NA common neritic & pelagic foraging spring-fall
loggerhead threatened NA NA ✔️ ✔️ NA common neritic foraging spring-fall
Kemps ridley endangered NA NA ✔️ NA NA rare neritic foraging summer-fall
green threatened NA NA ✔️ NA NA rare neritic foraging summer-fall

Southern New England

Species ESA Status egg/ hatchling juvenile dispersal juvenile-subadult adult nesting females Annual occurrence Habitat use Seasonal timing*
leatherback endangered NA UN ✔️ ✔️ NA common neritic & pelagic foraging spring-fall
loggerhead threatened NA NA ✔️ ✔️ NA common neritic foraging spring-fall
Kemps ridley endangered NA NA ✔️ NA NA rare neritic foraging summer-fall
green threatened NA NA ✔️ NA NA rare neritic foraging summer-fall

New York Bight

Species ESA Status egg/ hatchling juvenile dispersal juvenile-subadult adult nesting females Annual occurrence Habitat use Seasonal timing
leatherback endangered NA UN ✔️ ✔️ NA common seasonally neritic & pelagic foraging spring-fall
loggerhead threatened NA NA ✔️ ✔️ NA common neritic foraging spring-fall
Kemps ridley endangered NA NA ✔️ NA NA common neritic foraging summer-fall
green threatened NA NA ✔️ NA NA common seasonally neritic foraging summer-fall

Central Atlantic

Species ESA Status egg/ hatchling juvenile dispersal juvenile-subadult adult nesting females Annual occurrence Habitat use Seasonal timing
leatherback endangered NA UN ✔️ ✔️ NA common seasonally neritic/pelagic foraging, migration spring-fall
loggerhead threatened UN UN ✔️ ✔️ NA common seasonally neritic/pelagic foraging, migration, nesting spring-fall
Kemps ridley endangered NA NA ✔️ ✔️ NA common seasonally neritic foraging, migration spring-fall
green threatened NA NA ✔️ UN NA common seasonally neritic foraging, migration, nesting late spring-fall

Southern Atlantic

Species ESA Status egg/ hatchling oceanic dispersal juvenile-subadult adult nesting females Annual occurrence Habitat use Seasonal timing
leatherback endangered ✔️ ✔️ ✔️ ✔️ ✔️ common neritic/pelagic foraging, migration, nesting year round
loggerhead threatened ✔️ ✔️ ✔️ ✔️ ✔️ common neritic/pelagic foraging, migration, nesting year round
Kemps ridley endangered NA UN ✔️ UN NA common neritic foraging, migration year round
green threatened ✔️ UN ✔️ ✔️ ✔️ common neritic foraging, migration, nesting year round

H.1.2 RWSC Sub-regions and regional scale sea turtle distribution

RWSC is organized by subregion along the U.S. Atlantic coast, roughly aligned with current offshore wind development planning areas. RWSC subregions and map are described in the Chapter 1.

In this document, region wide ongoing, pending and recommended field research is briefly described, discussed and organized into one of several research themes described in the Chapter 1. Details of ongoing and pending research and long-term monitoring efforts informative to the questions regarding OSW are available in the searchable RWSC Offshore Wind and Wildlife Research Database, and links to queries for each research project are included in the tables describing projects in the chapter. Following regionwide field research, is discussion of field research specific to each subregion. Following subregion field data collection discussion, are on-going, pending and recommended non-field efforts by research theme and action. Non-field data collection actions include: 1) outreach and platforms to provide data products/results to stakeholders; 2) coordination and planning; 3) standardizing data collection, analysis, and reporting; 4) study optimization; 5) historic data collection/compilation; 6) model development and statistical frameworks; 7) technology advancement; 8) manipulative experiments, and 9) meta-analysis and literature review and are further described in Chapter 1.

H.1.2.1 Regional-scale distribution information

Consistent data to capture spatial and temporal distribution is provided via survey effort. In addition, tag, sighting, stranding and bycatch data contribute to distribution information, especially in areas and times where survey effort is limited and under conditions where turtles are not likely to be detected. While there has been a substantial amount of survey effort conducted to detect large sea turtles in the NW Atlantic, turtle distribution and behavior is variable both within and between seasons and is likely affected directly and indirectly by a combination of environmental factors. As such, abundance estimates should be based on multiple years and seasons of data (NOAA Fisheries, 2020). Currently, a thorough understanding of surface availability and abundance is lacking for all species in much of the NW Atlantic. For some species and subregions, especially sub-adult loggerheads in shelf waters of USCA through SNE subregions, availability estimates are based on relatively large data sets, but still contain some data gaps (Hatch and al., 2022). Importantly, most recent distance sampling aerial surveys (AMAPPS) have been conducted using parameters appropriate for detecting a variety of species. The speed and altitude at which most of these surveys were conducted prevent detection of smaller turtles (<40cm carapace length) (NOAA Fisheries, 2020; Palka et al., 2021), and all turtle detections decrease in sub-optimal conditions, especially with increasing sea state. Regardless of the survey effort level, substantial data gaps on sea turtle distribution and abundance exist for all species, seasons and subregions.

Efforts to develop an index of abundance and distribution using satellite tag data for loggerhead turtles by month were conducted by Winton et al. (Winton and al., 2018). Loggerheads used nearly all shelf waters from Long Island, NY south to near the tip of peninsular FL. In winter months, loggerhead turtles were largely south of the Virginia-North Carolina border. This analysis was possible due to a large tag dataset with similarly programmed tags for animals captured and tagged with broad temporal and spatial variation. Similar efforts may yield better results for other species if undertaken as a coordinated effort.

The U.S. Navy recently completed a sea turtle surface density modeling project along the U.S. Atlantic coast from shore to the EEZ which produced estimates for the NW Atlantic for juvenile-adult stage turtles large enough to be detected from a variety of platforms (DiMatteo and Sparks, 2022), those surveys are available as East Coast Turtle Density Models on OBIS SEAMAP. Estimates of sea turtle abundance are not yet available from AMAPPS surveys. Tagging results of loggerhead and leatherback turtles from AMAPPS surveys are available in AMAPPS reports (Palka et al., 2021).

H.1.2.2 Biologically Important Areas for sea turtles within U.S. Waters

Biologically important areas in the United States for NW Atlantic sea turtle species/populations have not been determined. State space modeling applied to telemetry studies suggest that inshore and coastal continental shelf habitat are important foraging areas for loggerhead (Braun-McNeill et al., 2008; Evans et al., 2019) and Kemp’s ridley (Bean and Logan, 2019) turtles in the Central Atlantic and New York Bight subregions. Work is underway through AMAPPS research to establish similar areas of importance for leatherback turtles (C. Sasso pers comm). Although all established Kemp’s ridley nesting areas are in the Gulf of Mexico, the coastal and inshore waters of the NW Atlantic appear to be important foraging areas for juvenile and subadult Kemp’s ridley turtles although the contribution of this region to the population remained unclear in the 2015 status review for the species (NOAA and USFWS, 2015). A new proposed critical habitat designation for N Atlantic green turtles was released in July 2023 (NOAA Fisheries, 2023). It is expected that findings will discuss the northward expansion of the species as well as increases in nesting on Southern Atlantic beaches since the previous review in 2015 (Seminoff and al., 2015).

Better understanding of biologically important in-water sea turtle habitat is needed for all species in US Atlantic waters.

H.2 Potential effects of offshore wind on sea turtles

The subcommittee recognizes that there may be positive, negative and/or mixed impacts of offshore wind development and operation on sea turtles. These effects may directly affect individual animals or indirectly affect them through changes to the environment, prey/predator distribution and/or changes in human activities. Animals and populations may be impacted by multiple, cumulative, effects, some positive and some negative.

As ectothermic, mostly migratory populations in U.S. Atlantic waters, some sea turtle population’s foraging, breeding, nesting, and migratory ranges overlap the areas proposed for offshore wind development in the Atlantic Ocean. In addition, sea turtle species are exposed to multiple and cumulative stressors throughout their life cycles, including climate and non-climate threats (Fuentes et al., 2013; Fuentes et al., 2020). The cumulative effect of these and other stressors are likely to create biologically significant population level responses.

There have been no studies describing the effects of construction and operation of windfarms on sea turtles, largely because most research has come from European and U.K. waters, where sea turtles do not commonly occur. Discussion of potential impacts of offshore wind on each sea turtle species are, therefore, based on data from other species groups or other potential stressors. The subcommittee is concerned that this lack of knowledge for sea turtle species, which have a very different life history, compared to other species groups, plays into sea turtle risk assessments and adds potential for more unexpected results, compared to other wildlife impacted by OSW. Without risk assessment specific to sea turtles, unidentified impacts cannot be assessed or mitigated with enhanced monitoring and adaptive management. The subcommittee recommended exploring the use of cumulative impact assessment whereby multiple threats to sea turtles were quantified allowing for effective mitigation and restoration recommendations following the Gulf of Mexico Deep Water Horizon Oil Spill. Love et al. (Love et al., 2017) categorized, quantified, and assessed the threats to (stressors) sea turtles to identify the most effective restoration actions for the recovery of sea turtle populations in the Gulf of Mexico. The authors were able to quantify poor and missing information in their assessment through use of proxy and modeled data. A similar approach to identifying sea turtle threats and quantifying the potential impact of OSW may be helpful in determining the most effective methods for assessing and addressing threats in U.S. Atlantic waters.

OSW, like other human activities in the marine environment, will have effects on sea turtles. Positive effects will most likely be related to reef effects of physical structures supporting turbines. Structures are expected to attract invertebrate fouling organisms and reef/wreck fishes, which will likely attract small schooling fishes (Glarou et al., 2020). Sea turtles have been documented around underwater structures and are likely attracted to them (Broadbent1 and al., 2020; Reimer et al., 2023). These structures will also attract anglers and some commercial fishers such as pot/trap fishers which may increase the likelihood of interactions with active and discarded gear. The most probable direct negative effects of offshore wind construction and operation are serious injury and mortality from increased vessel interaction and increase in fishery interaction because of attraction to turbines due to reef effects. It is likely that there will be direct, indirect and/or temporary negative effects related to noise, EMF, as well as changes in prey distribution, oceanographic parameters, fishing and shipping distribution. Other oceanographic and substrate impacts are not well understood, and impacts are yet to be determined.

Since little is known about effects of OSW on sea turtles, the subcommittee must look to studies on large marine vertebrates for comparison. In European waters, researchers have documented avoidance and displacement effects, primarily of harbor porpoises (Phocoena phocoena). These effects occurred at ranges of 10-26 km from the whole footprint of offshore windfarms during construction (Benhemma Le Gall et al., 2021; Brandt et al., 2018; Graham et al., 2023, 2019; dähne2013a?). All of these studies indicate that the distance and duration of avoidance is related to received noise, which is further influenced by source level, sound propagation conditions (environmental parameters, substrate type, etc.), hearing range of the studied species, distance to the noise source, duration of exposure, level and type of mitigation, and presence of other noise sources like construction vessels.

For harbor and grey seals, tagging data around wind energy sites in Europe showed behavior consistent with foraging after construction was completed (Russell et al., 2016; Russell et al., 2014). Pinnipeds appeared to either habituate quickly or to take advantage of wind farm physical structures as a foraging opportunity, whereas small dolphins and porpoises showed high variability in displacement and recovery response to wind farm construction and operations. Considerable research is still needed to understand sea turtle hearing sensitivity and behavioral responses to noise. Effects of noise associated with OSW construction and operation may be more similar to pinnipeds than cetaceans, which, as a species group, are more highly auditory and vocal in nature than sea turtles. To date, however, there is not a complete understanding of the ranges of sea turtle hearing or their physiological and behavioral responses to underwater noise such as pile driving associated with turbine construction or that associated with turbine operation.

Kraus et al. (Kraus et al., 2019) summarized the potential short-term and long-term effects of offshore wind development on marine mammals and sea turtles in Massachusetts and Rhode Island Wind Energy Areas. The list below is also relevant to the entire Atlantic coast. Any specific concerns related to sea turtle species in each subregion will be further described in the following sections of this chapter.

Potential short-term effects of offshore wind construction activities (Kraus et al., 2019)

Potential short-term effects include reaction to noise from pile driving, vessel operating noise, and impacts of an increased presence of vessels. These stressors could influence:

  • Displacement from wind energy areas

  • Disruption to critical behaviors such as feeding, socializing, or nesting 

  • Elevation of stress hormone levels

  • Changes in vertical distribution, density, or patch structure of prey

Potential long-term effects of offshore wind operation (Kraus et al., 2019)

Potential long-term effects include wind turbine presence, and increased vessel activity to/from and near turbine fields. These stressors could influence:

  • Exclusion from or attraction to wind energy areas

  • Changes to feeding opportunities

  • Enhancements to marine productivity due to artificial reef effect around wind turbine foundations

The Sea Turtle Subcommittee also discussed potential impacts to sea turtles across the entire RWSC region. The Kraus et al. (Kraus et al., 2019) report addressed MA and Rhode Island, and thus only listed potential impacts in the GOM and SNE subregions which are limited to seasonal foraging habitat for neritic hard-shelled and leatherback turtles. Loggerhead, green and leatherback turtles have mating and nesting habitat in the USCA and USSEA subregions in addition to foraging and migratory habitat.

Below is an additional list of potential effects of concern identified by the subcommittee

  • Increased vessel interactions, lethal and non-lethal

  • Acoustic disturbance

  • EMF effects from underwater cables linking turbines and distributing electricity to shore

    • Prey distribution – Some evidence of attraction to EMF (Albert et al., 2020)

    • Navigation disturbance in foraging and migratory areas

    • Nesting disturbance (south of Chesapeake Bay)

    • Hatchling dispersal disturbance (south of Chesapeake Bay)

  • Other

    • Changes in habitat from structure effects on water column stratification, frontal field, current velocity/direction, thermocline, halocline

    • Reef effects

    • Temporal and/or spatial changes in turtle and/or prey distribution due to warm water effluent from underwater DC substations

    • Changes in entanglement/ingestion risk because of changes in distribution of fishing gear and aquaculture structures (especially increased fixed gear in lease areas)

    • Interaction with floating/surface components and/or rotor intakes that could trap sargassum in off shelf planning areas

H.3 Methods and approaches

To address questions about sea turtles and the potential concerns with respect to offshore wind development, the Science Plan describes commonly used methods and approaches for data collection and research in Chapter 1. The following categories of methods are used throughout this chapter, but the Subcommittee recognizes that different tools, technologies, and/or procedures could be implemented with respect to each.

H.3.1 Aerial and vessel-based line transect observational surveys

Large scale abundance data for sea turtles is generally collected using distance sampling surveys conducted from aerial, shipboard, and, in future, unmanned platforms such as drones.

In order to accurately estimate turtle abundance and/or density, aerial and vessel surface turtle counts are corrected for bias including perception bias and availability bias. Perception bias is the likelihood that observers will detect a turtle at the surface. Unlike small cetaceans such as dolphins and porpoises, turtles do not travel in groups and are relatively cryptic at the surface with no visible blow (exhalation) to cue observers. Thus, it is likely that a proportion of turtles that are at the surface are missed by observers and the proportion that are missed is correlated with increasing sea state, turbidity and glare. Availability bias incorporates the likelihood that an animal will be at the surface and available to be detected compared with the likelihood it will be subsurface and unable to be detected (unavailable). It is imperative to understand the relationship between number of turtles detected at the surface, those that are available to be detected, and the proportion of the population that is below the surface and unavailable to be detected. Again, compared to cetaceans which often travel in groups, detection of one individual in a group cues the observer to focus on a particular area increasing the likelihood of detection. A single diving turtle may only be perceived as a surface disturbance and not be identified to the species level.

Unlike cetaceans, sea turtles surface time is highly variable by species, season, habitat, behavioral state, and other co-variates such as depth and water temperature. Because they are ectothermic, surface time is variable for sea turtles and complicates abundance estimation for these marine vertebrates over other species (Hatch and al., 2022). Surface time is estimated using tagged individuals, and, for sea turtles, should ideally be assessed at the time and location that surveys are being conducted. Minimally, tag data used to determine availability should include multiple years and individuals of all species being detected and include a range of animal sizes in all survey strata and seasons. Poor understanding of both perception and availability bias increases uncertainty in abundance estimates.

Because sea turtle abundance may be low and CV high for some species in some seasons of the RWSC study area, ability to detect changes in abundance and assigning causality to detected changes may be difficult. In a tech memo summarizing a workshop on estimating loggerhead turtle abundance in the NW Atlantic, NOAA estimated that ten years of survey data may be needed to develop robust loggerhead turtle abundance estimates in the NW Atlantic and that current protocols are unable to detect turtles less than 40cm carapace length (NOAA Fisheries, 2020).

On page 15 of NOAA Tech Memo NMFS-OPR-67, authors list several next steps that are important elements in developing robust estimates for NW Atlantic loggerheads (NOAA Fisheries, 2020):

  • Define management needs relative to the ability of aerial surveys to detect changes in abundance across appropriate timeline(s). Define desired level of confidence in those abundance estimates.

  • Establish the optimal survey altitude for sea turtles by conducting additional experiments at altitudes between 500–1,000ft to examine/understand the size of turtles that can be seen and turtle behavior relative to the survey platform.

  • Conduct additional field testing to determine detectability of a range of turtle sizes under varying water clarity and sea state conditions.

  • Explore the pros and cons of high resolution aerial photogrammetry and use of automatic pattern recognition, considering likely improvements in the next 5-10 years. Establish whether calibration or ground-truthing is needed for aerial photogrammetry using side-by-side flights with both photogrammetry and observers.

  • Ensure relevant aspects of sea turtle life history (e.g., seasonal migrations, behavioral state) are considered appropriately in the development of the survey design.

  • Design and conduct an experiment to assess variability of abundance estimates through repeat aerial surveys.

  • Explore whether existing satellite telemetry data are sufficient to assess the effects of sea state on surfacing behavior.

  • Refine measures of surface availability

    • Take stock of satellite telemetry data and identify data gaps relative to location, life stage, and behavioral state (foraging, migrating, interesting intervals).

    • Design appropriate satellite telemetry experiment(s) to fill identified data gaps. o Assess the value of repeated counts to inform surface availability; compare to satellite telemetry approach; integrate methods to improve surface availability estimation.

  • Mine data from all relevant existing aerial surveys to inform a new survey design, including block identification if appropriate. Develop simulations to refine survey design.

  • Coordinate survey design and implementation with other ongoing efforts to maximize efficiency and reduce duplication/overlap.

  • Develop funding estimates and consider potential funding sources, including leveraging existing funding. Develop a plan for and approach to seek funds.

[Note that loggerheads are the most abundant sea turtle species in the NW Atlantic, perhaps by an order of magnitude over other species, making the complexity of developing robust abundance estimates for other species greater than for loggerheads.]

The subcommittee believes that few of the suggestions made at the workshop in 2016 have been fully accomplished and believes that most are needed for loggerheads as well as other turtle species. Providing funding and effort to better understand which turtles are being detected under what conditions, small turtle occurrence for green and Kemp’s ridley turtles estimates, and developing robust surface time estimates for all sea turtle species, in all subregions and seasons is critical for developing baseline abundance of sea turtle species.

Without this basic knowledge, assessing and mitigating impacts to sea turtles from a variety of sources, including offshore wind, will be extremely difficult.

H.3.2 Tagging

For the purposes of this document, tagging refers to active tagging where tags transmit or archive data related to the tagged animal’s location, physiology and/or behavior. This is in contrast to passive tags such as flipper (Inconel) and subdermal (PIT) tags which are applied to an animal and must later be detected on that animal during subsequent observations. Tagging individual sea turtles includes the use of satellite and acoustic telemetry and may be paired with animal born and/or autonomous underwater cameras. The size of some turtles restricts the use of larger and heavier tags which limits battery life and additional instrumentation such as time depth recorders (TDRs) and GPS chips. To take advantage of the long battery life of tags used in acoustic telemetry, tags are often inserted internally into the target animals. Currently this methodology is not an accepted permit activity for research on wild turtles and has been experimentally allowed on stranded, rehabilitated and released turtles. The results of a recent pilot project conducted by the New England Aquarium may further the use of this method for sea turtle research (Innis et al., 2023).

H.3.3 eDNA

Environmental DNA (eDNA) is DNA released from an organism into the environment via feces, mucus, shed skin, hair, etc. It is detected in air, water, and substrate samples and requires assays from the organisms to be detected. eDNA is useful for determining presence of a species, population, or individual, but its utility as an index of abundance is unclear. Several organizations are developing eDNA assays for sea turtles and are ground truthing use of this technology in providing an index of abundance. Pilot studies at several sites are pending.

H.3.4 Long-term monitoring - Stranding response, nest surveys, sightings databases, and observed takes (dredge & fishery)

Sea turtles only come ashore to nest, at the time of hatching, and when stranded (sick, injured, or dead). Nesting sea turtles in the U.S. are monitored annually on many beaches from Virginia through the U.S. Gulf coast, and several index beaches are established to provide long term indices of nesting turtle presence which are correlated with abundance. Nesting trends from index beaches which have been consistently monitored over decades are the primary data available for long-term population trend analysis for sea turtles in the U.S. Atlantic. An index of abundance has been established from long term nest monitoring data at specific sites in the Southern Atlantic subregion and in areas where turtles are resident or have relatively small seasonally shifting home ranges through capture/recapture studies.

Although many caveats exist with use of stranding data, the U.S. Sea Turtle Stranding and Salvage Network may be another source of distribution and phenological trend information.

In addition, where survey data have few detections, citizen science sightings databases can add information on sea turtle presence. There is at least one curated long-term sightings database curated by Mass Audubon that can provide information about individual sightings of species that are small and are not easily detected with most survey methodologies.

Finally, dredge and fishery observers record takes associated with permitted and authorized activities in many regions. Observers follow established protocols and receive substantial training. Though relatively rare, observed takes may also provide information on turtle presence in areas where abundance data are low. This is particularly true of offshore areas where distribution data may be poor for some species.

Analyses of long-term data sets may provide the basis for future hypotheses regarding baseline population and distribution trends for sea turtle species, but these data sets have not always been consistently collected or reviewed and experience of data collectors for some monitoring data sets varies widely.

H.4 Sea turtle research topics

The RWSC Sea Turtle Subcommittee recognizes that impacts to sea turtles associated with OSW have not been studied since much of the previous work has been done in European waters where sea turtles are not commonly observed. The subcommittee also recognizes that impacts to sea turtles individually and at population levels are likely to be indirect, cumulative, synergetic and difficult assign to a single cause. Disentangling the effects on sea turtles of climate change from any potential effects from offshore wind development will be a major challenge.

RWSC has established several Research Themes for the study of impacts to wildlife by OSW that build on work conducted by previous groups, on other wildlife species. In subsequent sections, many of the detailed questions, hypotheses, and potential approaches that correspond to these Research Themes are described for regional-scale studies and for each subregion (Gulf of Maine-GOM; Southern New England-SNE; New York/New Jersey Bight-NYB; US Central Atlantic-USCA; US Southeast Atlantic-USSEA).

H.4.1 Regional Field data collection and analysis

Ongoing and pending regional field data collection and analysis projects are listed in the RWSC Research Database. Below are recommendations for regional field data collection and analysis for sea turtles.

  • NMFS Long-term protected species, fisheries, and ecosystem surveys form the backbone of the scientific monitoring system needed for the management of wildlife, fisheries, habitats, and ecosystems. In order to understand potential changes in wildlife and habitats from offshore wind energy development, it is critical that long-term standardized surveys provide timely, accurate, and precise data on wildlife, habitats, and ecosystems. The need to fully implement the NMFS and BOEM Survey Mitigation Strategy (Hare et al., 2022) and review the strategy to directly affect sea turtle survey needs is critical to putting site and regional level studies in the context of population trends and ecosystem conditions. The Strategy calls for the development of a Northeast Survey Mitigation Program.  This largely unfunded strategy should be fully funded and be a significant priority for the region as well as for the Atlantic waters of the Southeast region.

  • Increase level of regional-scale sea turtle species data collection including surveys designed to detect all sizes of sea turtles and at sea tagging through AMAPPS, BOEM, and US Navy projects

  • Employ recommendations by NMFS to enhance AMAPPS sea turtle abundance estimates listed in (NOAA Fisheries, 2020), especially detection studies of all sea turtle species and sizes under a variety of conditions

  • Enhance and expand abundance estimation, surface density estimates and habitat modeling using all appropriate forms of turtle occurrence data, including, but not limited to, verified sightings, strandings, bycatch data and prey distribution to determine biologically important areas for each sea turtle species in each RWSC subregion

H.4.2 Regional Non-field research by type of action

H.5 List of Definitions and Acronyms

AMAPPS – Atlantic Marine Assessment Program for Protected Species; a joint project funded by BOEM, NOAA Fisheries, US Navy, and US Fish and Wildlife Service to provide seasonal abundance estimates that incorporate environmental habitat characteristics for marine mammals, turtles, and seabirds in the western North Atlantic Ocean

AMSEAS – Atlantic Marine Conservation Society, Hampton Bays, NY

ARGOS - a global satellite-based location and data collection system dedicated to studying and protecting our planet’s environment. The polar-orbiting satellites making up Argos fly at an orbit of 850 km above the earth. They pick up the signals, store them on-board, and relay them in real-time back to earth. Receiving stations then relay data from satellites to processing centers. These processing centers collect all incoming data, process them and distribute them to users.

benthic – adjective describing species, habitat, etc. associated with the ocean bottom

BOEM – Bureau of Ocean Energy Management, the federal agency regulating OSW planning areas, auctions and leases

CFF – Coonamessett Farm Foundation, East Falmouth, MA

CV – coefficient of variation; a measure of confidence in statistical calculations such as density and abundance. A low CV suggests higher confidence that the true value is close to the estimated value

DPS – distinct population segment, in the US some turtle species are managed in distinct population segments usually defined by distribution of nesting females

ectothermic – ‘cold-blooded;’ refers to animals such as fish, amphibians, and reptiles whose core body temperature is correlated with the environment, some ectothermic species such as leatherback turtles are able to maintain body temperatures up to 10 °C above ambient environmental temperatures but their body temperature is still correlated with ambient temperature

endothermic – ‘warm blooded;’ refers to animals whose core body temperature is maintained within a narrow range regardless of ambient environmental temperatures. Birds and mammals are endothermc.

EMF – electromagnetic field; a classical (i.e. non-quantum) field produced by accelerating electric charges. The field can be viewed as the combination of an electric field and a magnetic field. The electric field is produced by stationary charges, and the magnetic field by moving charges (currents); these two are often described as the sources of the field.

ESA – U.S. Endangered Species Act

Gelatinous zooplankton – group of macroscopic zooplankton including jelly fishes, comb jellies, salps and other similar species that are prey for some sea turtles, especially leatherback turtles.

GOM – Gulf of Maine the northernmost subregion described in the RWSC study area

GPS – global positioning system

MARCO – Mid-Atlantic Regional Council on the Ocean

NEAq – New England Aquarium, Boston, MA

Neritic – adjective describing ocean habitat over the continental shelf. Following their oceanic dispersal stage, most sea turtle species enter a juvenile neritic foraging stage that may continue for 3 to more than 20 years.

NEFSC – Northeast Fisheries Science Center for NOAA Fisheries, Woods Hole, MA

NMFS – see NOAA Fisheries

NOAA Fisheries – formerly called National Marine Fisheries Service (NMFS), federal agency tasked with managing protected marine species in their in-water marine habitats. Jurisdiction of species that spend time in freshwater and/or terrestrial habitat is shard with the U.S. Fish and Wildlife Service (USFWS). For sea turtles, NOAA Fisheries manages all behavior and life stages except for nesting and nest protection which falls under USFWS.

NROC – Northeast Regional Ocean Council

NY/NJB – New York/New Jersey Bight subregion of the RWSC study area

NYSERDA – New York State Energy Research and Development Authority

pelagic – adjective describing ocean habitat over the deep ocean. In the NW Atlantic the oceanic dispersal stage of a sea turtle’s life is spent in the pelagic environment, most notably in the Sargasso Sea

(the) Plan – RWSC Science Plan

Project WOW – Wildlife and Offshore Wind: A multi-organization research project with the goal of creating a system for the comprehensive evaluation of potential effects of offshore wind energy development on marine wildlife. Project WOW is led by the Duke University Marine Geospatial Lab (https://offshorewind.env.duke.edu/)

PTT – Platform Transmitting terminal, the part of a satellite tag that sends user-defined periodic messages to satellites.  

SNE – Southern New England subregion of the RWSC study area

telemetry – measurement of wireless transmission of data from remote sources, in this context animal borne tags such as satellite and acoustic tags

USCA – US Central Atlantic subregion of the RWSC study area

USFWS – U.S. Fish and Wildlife Service

USSEA – US Southeast Atlantic subregion of the RWSC study area