All posts by Jonathan Veach

Research Spotlight

Survivorship and Productivity of Florida Sandhill Cranes on Conservation Lands and Suburban Areas in Florida

The Florida sandhill crane (Antigone canadensis pratensis) is a familiar sight for residents and visitors alike to areas of Florida, but unfortunately, they are becoming less familiar. Faced with substantial population decline due to habitat loss, Florida sandhill cranes have also experienced long periods of drought and degradation of remaining habitat, which has all contributed to their decline. This study will compare adult crane habitat use, survival, and reproduction between suburban and conservation areas, with an emphasis on identifying specific causes of mortality. Additionally, researchers will also determine vegetation associations used by cranes in suburban habitats and conservation areas from movement data.

Non-migratory sandhill cranes were once widely distributed across the southeast and into the Caribbean, however, the species was extirpated from most of its natural range by the early 1900s. Conversion of prairie to agriculture or development, draining of wetlands, and overhunting were and are the main factors threatening sandhill cranes. Spatial models suggest the total available Florida sandhill crane habitat declined 42% between 1974 and 2003. The Florida sandhill crane is currently listed as State Threatened and as a Species of Greatest Conservation Need in the state’s Wildlife Action Plan.

Florida sandhill cranes inhabit open areas, typically prairie and pastureland in the uplands and shallow marshes with emergent vegetation in wetland areas. Most preferred Florida sandhill crane habitat is privately owned and can be lost through development at any time. As the amount of preferred habitat has declined, an increasing number of Florida sandhill cranes have inhabited suburban and urban areas, such as airports, residential subdivisions and golf courses. Cranes in these areas may face additional challenges compared to birds in natural areas. For example, cranes require water levels sufficient to protect nests and themselves from terrestrial predators but low enough to prevent nests and roosts from flooding. In suburban areas, cranes often use man-made ponds or water retention areas that can receive large amounts of water run-off from developed sites (e.g., highways, lawns, golf courses and buildings) resulting in rapid increases in water levels that cause nest failure or leave the areas too deep to be utilized. Other threats to suburban cranes include domestic pets, automobile traffic, fences, human disturbance and environmental contaminants. This project was developed to assess threats to the survival and productivity of Florida sandhill cranes in suburban areas compared to the same parameters for conservation areas.

Researchers capturing a suburban Florida sandhill crane with a pneumatic net launcher in Lake County.

To capture cranes, FWRI researchers survey areas for cranes then learn their routine or bait the area if necessary. Researchers then capture the cranes using a hand-held net gun, ground snares or by simple hand grabbing. After capture, cranes are radio-tagged and color-banded, which is helpful for researchers for visual and radio monitoring after release. Cranes are captured and marked from April through October, before the arrival of migratory sandhill cranes that overwinter in Florida. Currently, FWRI has cranes marked from Marion County in the north to Highlands County in the south, Pasco County in the west and to Indian River County in the east.

This project seeks to fill important gaps in our understanding of Florida sandhill crane ecology identified in the Florida Sandhill Crane Species Action Plan. Causes of population decline are not well understood, so this project will benefit cranes by providing habitat use, survival, and productivity data for unstudied habitats (e.g., conservation areas and urban/suburban habitats) needed for development and implementation of management and conservation recommendations.

About halfway complete, this project has radio-tagged their target sample size (n=17) of suburban cranes, and 15 of 17 conservation land birds. Researchers have color-banded 49 cranes, out of a goal of 100+ before the project ends, which is set for June 30, 2021. Data generated from this project will be used to develop conservation recommendations and initiate plans to conserve Florida sandhill cranes. Future research may involve tagging young-of-the-year cranes in suburban and conservation areas to compare survival and movements of these birds to those from past studies of similar aged cranes on improved pastureland.

Key partners for this project include the State Wildlife Grants, the Bernard Lewis Charitable Foundation, Florida State Forest Service, Florida State Parks, Lake County Parks and Trails, Orlando Wetlands Park and St. John’s River Water Management District. FWRI researchers could not have initiated, nor can they complete this project, without the assistance of these partners.

Agency News

FWC Commission Meeting to be Held Online

The FWC Commission Meeting will be held online May 14, beginning at 9 am. The meeting originally scheduled to be held in Miami will now be held online due to COVID-19 (Coronavirus) social distancing guidelines. This meeting is being held by communications media technology, specifically using Adobe Connect with a telephone conference line for accepting public comment during the meeting. The Florida Channel will be broadcasting live video coverage at and participants watching from the Florida channel can utilize the telephone conference line to call in for public comment.

The FWC is committed to providing opportunity for public input. The Commission welcomes public input regarding agenda items requiring action. To accommodate as much input as possible from those attending, the Chairman reserves the right to designate the amount of time given to a topic or speaker, including time donation to other speakers. Because this meeting is being held by video conference and a telephone conference line, the Commission is presenting a reduced agenda and is limiting public comment to one hour per agenda item. Public comment will be taken by telephone conference line on a first call/first serve basis. 

The Commission is also offering the opportunity for stakeholders to provide their comments regarding the agenda item topics in advance. Advanced comments should be submitted no later than Friday, May 1. Those comments can be submitted via email to If you would like to provide written comments, you can mail those comments to:

FWC Commissioners
620 South Meridian Street
Tallahassee, Florida 32399 

For the full May 14 agenda, links to background reports, and ways to participate, go to, or and click on “The Commission” and “Commission Meetings.”

Staff Spotlight

This issue David Steen of Wildlife Research was kind enough to spend some time answering our questions for the Staff Spotlight. Thank you, David!

FWRI Section and Location

Wildlife Research / Reptiles and Amphibians / Gainesville


BS – University of New Hampshire, MS – SUNY College of Environmental Science and Forestry, Ph.D. – Auburn University, Postdoc – Virginia Tech.

Lead Research Technician – Joseph W. Jones Ecological Research Center

Assistant Research Professor – Auburn University

Executive Director – The Alongside Wildlife Foundation

Board of Directors – The Wildlands Network

Research Ecologist – Georgia Sea Turtle Center

What are you working on now?

I see my job as an opportunity to help ensure things are running as smoothly as possible for the folks in my subsection while they work on important projects to understand the imperiled amphibians and reptiles of Florida. Our projects include restoring ephemeral wetlands for rare amphibians in the panhandle, assessing the status and distribution of Diamond-backed Terrapins along the coast, evaluating behavioral shifts of American Crocodiles following translocation in south Florida, and figuring out if Carpenter Frogs are still hanging on in the state, for just a few examples.

How is this information beneficial?

Instead of listing all the usual reasons why it is important to protect and conserve biodiversity, I’ll say that Florida’s wildlife isn’t just a part of our natural heritage, it’s part of our culture too. Florida is changing; to keep our species around today and into the future, we need to understand where these animals are and how they are impacted by our actions. The data we collect feeds directly into management actions and policy recommendations, and we want both to be fully informed by the latest science.

What is your typical workday like?

Most of the responsibilities associated with my position require time in the office, things like brainstorming research plans, checking budget numbers and revising scientific manuscripts, although I’m lucky in that I often have the opportunity to visit the other folks in the subsection as they get dirty outside and do the real work to find and understand Florida’s amphibians and reptiles.

What is your greatest career accomplishment?

I feel as though my greatest career accomplishment is that I’m still here. After a long winding road that almost took a turn right out of science, I have somehow found myself with a job I find rewarding, helping out on projects I feel are important and fulfilling, and surrounded by bright and passionate people working hard to conserve the wildlife of Florida, ground zero for amphibians and reptiles in North America.

What are some of your biggest challenges?

There are so many species that we need to understand better and so many conservation questions that need to be resolved sooner rather than later, it can be a challenge to decide where to focus my efforts.

Was this your original career interest? Why or why not?

I’m lucky in that I’ve always been interested in wildlife, amphibians and reptiles in particular, and have been working toward this career ever since I understood what that means.

What would you be doing if you weren’t involved in science?

If I wasn’t directly involved in science, I would probably pursue science-adjacent writing opportunities (check out Secrets of Snakes, published by Texas A&M University Press late last year) and bartend.

What advice would you give someone interested in pursuing a career in your field?

Recognize that there is no One True Path to obtaining satisfaction and security in this field. Work hard, keep your eyes open for unusual or serendipitous opportunities, and don’t compromise your mental and physical health now because you hope it will pay dividends later.

What do you enjoy doing in your free time?

I like to take it easy with a slow coffee in the morning; I also like movies and doing nothing in particular. Kayaking and hiking are very satisfying, as is spending time around my property thinking about how to restore and maintain it in a way that is beneficial to local wildlife.

Director Message


By Gil McRae, FWRI Director

As I write this our personal and professional lives have been upended by the COVID-19 virus.  We have never seen a pandemic on this scale and response to the virus has challenged our health, economic and social support systems far beyond what they were built to handle.  While it is difficult to speculate at this point, my hope is that we emerge on the other side of this pandemic as a stronger, more peaceful global society focused on proactively addressing health and environmental issues that affect us all.

I want to commend the members of your Institute Leadership Team who have been instrumental in helping us organize ourselves so that we can keep working productively and collaboratively in this new mode.  Harry Norris has done an exceptional job helping us manage data and information while maintaining a personal connection to people and programs that has made a real difference.  I believe our early push to get as many staff teleworking as possible, combined with actions taken at the agency and state level has helped keep our workforce healthy.  As of this writing about 90 % of FWRI staff are teleworking to some extent and close to 80 % are teleworking full time. 

There have been many policy changes associated with this event and I know it can be confusing at times.  The most notable new policy involves the availability of emergency sick leave and emergency family medical leave to all staff.  As I write this, we are still in the discovery mode regarding these policies and our fantastic HR team of Jodi Harner and Betty Heath with the support of Laura Tennant and Rae Ann Hill are simultaneously fielding your questions and working with their HR counterparts in other Divisions and the Office of Executive Director to develop guidance on these policies.  No doubt you will have that guidance by the time you read this, if not you know how to find us, and we are here to help.

Many of you have read about the challenges facing our reemployment assistance program in the state.  With many of our friends and family out of work, this issue hits home hard.  When the call went out for volunteers to assist the state in dealing with the backlog of applications, dozens of you stepped up to assist without knowing what you were getting into.  Our potential role has now been refined somewhat to focus on entry of data received via hardcopy applications and we expect there will be more of you willing to assist.  If so, your ILT member is the point person for getting the information to Harry Norris who is coordinating our volunteer efforts.

In these uncertain times we quickly move to the things that matter most.  As impersonal as things can sometimes seem in a large organization like ours, I am proud of the staff-centric culture we have built over many decades.  I know that some of you have gone through some very difficult, even heartbreaking experiences, and my hope is that you are able to draw some strength from the knowledge that you have a workplace and co-workers that care about you and your family’s well-being.  Collectively, we are the very definition of resilient.  Stay healthy and stay connected.

Assessing temporal and spatial trends in fish assemblages within spring runs of the St Johns River basin

By Phillip Parsley

Springs in the middle St. Johns River basin are known for their clear water, intrinsic beauty and unique wildlife viewing opportunities.  Every year tourists and residents spend countless hours swimming in headspring pools or paddling down spring runs enjoying the breathtaking scenery of wild Florida.  However, recent natural events as well as anthropogenic influences have altered our perceptions regarding the health and vulnerability of some of these springs. Researchers and stakeholders have started to notice that lush aquatic vegetation has been replaced by dense algal mats and fish abundances have drastically reduced and been replaced by exotic fish species as habitat and water quality deteriorates.

While numerous studies exist that describe water quality of springs in the St. Johns River basin and include information on plant and invertebrate communities, information describing the fish communities of these springs is lacking.  In order to better understand the complexities of these fish assemblages, primary goals of this project were to determine an efficient sampling protocol for eight springs and their associated spring runs in the St. Johns River basin that will provide baseline data on community fish assemblages; and to document the presence of exotic fish species utilizing springs and how their abundances may change seasonally.

Figure 1. Locations of study springs within the St. John’s River Basin.

The springs and their associated runs in this study are Alexander Springs, Gemini Springs, Juniper Creek, Rock Springs, Salt Springs, Silver Glen Springs, Spring Garden (also known as DeLeon Springs), and Wekiva Springs (Figure 1). 

FWC standardized river sampling protocols were followed as closely as possible. However, some of the spring runs contained areas of dense aquatic macrophytes and a standard electrofisher boat was not practical.  An airboat electrofisher was used instead in these types of areas to avoid the unnecessary destruction of critical vegetation.  Also, a smaller boat we called the “mini-shocker” (Figure 2) was used in Rock Springs Run due to the narrow nature of the run and shallow areas where an electrofishing boat could not access.

A total of 406 sites spread across the eight study springs have been sampled since this project began in March 2019.  204 sites were sampled during the first round of sampling in summer 2019 collecting a total of 21,933 fish comprising 59 different species.  202 sites were sampled in winter 2019-20 and this netted 15,705 fish and 56 different species.  As one may expect, Bluegill (14.9% of total combined catch), Redbreast Sunfish (13.7%), Spotted Sunfish (12.6%), and Largemouth Bass (6.3%) were the most common sportfish encountered as far as total abundance.  Largemouth bass also comprised over one-fourth (25.3%) of the total percent biomass across all samples, with Bowfin (19.3%), Florida Gar (8.8%), and Lake Chubsuckers (8.7%) the next highest contributors.

Figure 2. “Mini-shocker” boat used to sample Rock Springs Run.

Five exotic fish species were collected during both rounds of sampling.  Blue Tilapia (n=153), Brown Hoplo (n=23), Dimerus Cichlid/Chanchita (n=4), Vermiculated Sailfin Catfish (n=62), and Walking Catfish (n=6) were all found to occur in multiple spring runs, however, they only represented 0.7% of the total catch and 4.3% of total biomass, both very miniscule portions of the entire sample.  Standard electrofishing procedures do not appear to be the best method for capturing an accurate representation of the numbers of exotic fish species occurring in the springs so in the future utilizing alternative methods could provide us with better information. 

The Bluenose Shiner (Figure 3), a state listed threatened species, was collected in Rock Springs Run and the Wekiva River.  Isolated populations of this species occur in the St. Johns River Basin and this fragmentation makes it vulnerable to extirpation from this region.  Finding this species in some of our study waterbodies was a positive and brainstorming is already underway as far as future research projects that could contribute to better understanding how best to conserve this species.

Figure 3. Bluenose shiner collected from Rock Springs Run.

Through days of field work over the past year we believe we have developed efficient sampling procedures for our study systems.  By using those protocols, we now have extensive sampling that yielded a total of 37,638 fish and 63 different species.  Calculating similarity indices between sample seasons will help us better analyze how these community assemblages may change in each spring as well.  Hopefully, the data collected in this study can provide future researchers insights and direction on the best way to make decisions regarding the health and viability of these springs as unique ecosystems. 

Gag Grouper: Where Have All The Cowboys Gone? Evaluating Spatio-Temporal Trends in Male Abundance and Reproductive Dynamics in a Sex-Changing Reef Fish

By Sarah Burnsed, Hayden Menendez, and Sue Lowerre-Barbieri

Gag grouper (Mycteroperca microlepis) are an iconic Florida fish that may be in trouble.  All fish begin as females in estuarine nursery grounds, but as they age they move further offshore, with the oldest, largest fish turning into males (Figure 1).  This life history and spatial ecology pattern makes it difficult to decide on the best measure of reproductive potential.  Based on females-only, the last stock assessment found them to not be overfished or undergoing overfishing. But the same assessment predicted only approximately 2-3% of the population was male and since then commercial fishermen have not been meeting quota, leaving fishermen and scientists concerned that this stock may not be as healthy as assumed.

Figure 1: Conceptual model of gag spatial ecology. Seasonal information is in parenthesis, yr = year, mo = month.

 Beginning in 2015, the Movement Ecology and Reproductive Resilience (MERR) Lab at FWRI began a series of gag studies to evaluate factors affecting gag reproductive potential. Empirical data derived from these studies, including estimates of fecundity-at-age, spawning frequency and sex ratios, and spatio—temporal patterns of sex change and sex ratio, will help to refine estimates of long-term biological productivity of the stock and in turn better manage this important fishery. We describe our three major gag program initiatives below.   

Our initial study (December 2015- May 2018) off the Florida Panhandle targeted the best-known gag spawning habitat ~50-100 miles off Panama City Beach.  Three areas were sampled, with varying protection from fishing: (1) Madison Swanson, an MPA (2) The Edges, open half the year to fishing (3) an open area. Twice monthly during gag spawning season (December-May), we departed lab headquarters in St. Petersburg to drive to Panama City and boarded chartered fishing boats for multiple day cruises. We captured gag using hook-and-line and recorded parameters of time landed, location, depth and ventral pigmentation. We collected video data using an unbaited camera array with a ~360° field of view to assess habitat, spawning behavior and abundance. We evaluated all gag for lengths, weight, genetics, mercury, age, sex, hormones and maturity. Data from our collections were integrated with data from FIM surveys, FDM, and a collaborating commercial fisherman to test assumptions about sex change and spatial management in gag. Results indicate overall gag abundance is low, MPAs do not protect all recruiting males (as previously assumed) and current regulations are not sufficient for males to recover to historic levels. To read more on this study, please see: Lowerre-Barbieri S, Menendez H, Bickford J, Switzer TS, Barbieri L, Koenig C (2020) Testing assumptions about sex change and spatial management in the protogynous gag grouper, Mycteroperca microlepis. Mar Ecol Prog Ser 639:199-214.

To assess how these results might differ with location, a second study was begun in December 2018 (extending through May 2021).  This study uses similar methods but is focused ~100 miles offshore of Tampa Bay at (1) Steamboat Lumps, an MPA and (2) the Sticky Grounds, an open area south of Steamboat Lumps, originally brought to our attention by fishermen and confirmed as a spawning site by preliminary sampling. Both habitats are quite different from those in the Panhandle with Steamboat Lumps having considerably less relief than Madison Swanson and the Sticky Grounds characterized by patchy high relief in depths greater than sites sampled before.  Because gag spawn at these offshore sites in the windy winter months, it is not surprising previous sampling in this area has been limited due to uncooperative seas and day trips requiring 18 hour runs from shore. We are fortunate to again work with an impressive group of captains willing to safely execute these trips and share their knowledge of the gag fishery to increase our success.  By expanding the area of collection, we’ll be able to identify and quantify gag spawning aggregations, sex ratios, and reproductive potential off the West Central Florida Shelf and compare these parameters to those collected in the initial study to determine spatial and temporal differences within and between study areas.

Figure 2: MERR biologist Hayden Menendez sampling blood from the gills of a gag grouper during a directed offshore charter trip. Blood is drawn immediately after capture and processed as part of a companion study to assess if hormones can help indicate transitional fish, which are difficult to determine even with histology.

These studies, and the integration of their results with the larger sampling efforts of the FIM reef fish survey and FDM, changed our understanding of where and when gag change sex.  Previously, it was believed that this occurred only on the spawning grounds and that spawning ground MPAs would protect males.  However, we found fish transitioning from females to males not only on the spawning grounds but also in pre-spawning female-only aggregations. Thus, there is a need to better understand pre-spawning aggregations, their seasonal cues, and spatial consistency, as well as sex-specific movement ecology.  Research on these questions was started in December 2017 when the same fisherman who provided samples from a gag pre-spawning aggregation site for our first study began working with us to dart tag and release gag at his nearshore site. 

 In 2019 and 2020 we increased this effort to include scientific sampling of pre-spawning gag aggregations, dart tagging a larger number of fish, and beginning a program to acoustically tag females (Figure 3 and cover image). Our recaptures so far suggest very high site fidelity of females to pre-spawning aggregation sites, as well as much higher catch per unit effort at these sites than on the spawning grounds. We expect recapture rates at these sites to decrease as fish begin moving offshore. In addition, acoustic tag detections will help us understand where these females move to once they leave these sites. Our ability to detect them throughout the Gulf is made possible because of the iTAG (Integrated Tracking of Aquatic Animals in the Gulf of Mexico) network, which enables researchers to share detections on their receivers that are not their study species.  This network and the data exchange are FWRI initiatives, with the digital exchange developed and maintained by the FWRI Information Science and Management section. These telemetry detections along with dart tag recaptures and reproductive  data will collectively enable us to better understand how this species’ spatial ecology affects vulnerability to fishing and the measures needed to allow more males to recruit to the population, hopefully in turn keeping this valuable fish on dinner plates across the state.

Figure 3: The incision used to insert the acoustic tag is stitched up with one stitch and a series of three knots.

Monitoring and Assessment of Eastern Oyster Growth on Created Oyster Reefs in Tampa Bay

By Dr. Ryan P. Moyer

Oyster reefs, constructed primarily by the eastern oyster (Crassostrea virginica), provide critical ecosystem services to nearly all of coastal Florida. Over many years, multiple generations of oysters settle upon one another, constructing a large reef structure that stabilizes sediment and provides a hard substrate that is utilized as habitat by other species. Oyster reef habitats are crucial components to coastal ecosystems and provide substrate, habitat, and/or food sources to numerous species of gastropods, crustaceans, sponges, worms, fish and birds. Thus, their ability to support recreational and commercial fish species, improve water quality through filtration, and reduce shoreline erosion highlights their significance as critical species within estuarine ecosystems.

In Tampa Bay, continued coastal development, dredging, and historical harvests have led to a reduction in suitable hard substrate for oyster recruitment. Beginning in the early 2000s, several public and private organizations initiated the installation of artificial oyster reefs to mimic the natural substrate oysters need for settlement and growth. These reefs were constructed from shell, concrete domes and mesh shell bags, and were placed throughout Tampa Bay to increase available oyster habitat and oyster populations. In collaboration with Tampa Bay Watch and the Tampa Bay Estuary Program, the Florida Fish and Wildlife Research Institute (FWRI) Coastal Wetlands Research Program implemented a study to assess and monitor oyster growth on old (>5 years), moderate-age (2-5 years), and young (<2 years) constructed oyster reefs.

FWRI Coastal Wetlands staff perform oyster density counts as part of monitoring on a young created oyster reefs (foreground). At the same time ecological surveys are conducted, high-precision elevation surveys are conducted to assess elevation change in newly constructed oyster reefs (background)

Physical assessments of oyster growth (e.g., oyster density, shell height, associated fauna) are coupled with real-time kinematic (RTK) Global Positioning System (GPS) surveys resulting in high-resolution (cm) elevation control of both the reefs and associated shorefaces being sheltered by the reefs. To date, 16 constructed oyster reefs in Tampa Bay with variable substrates (shell bags, concrete domes and loose shell) and ages (old, moderate and young) have been assessed, with young-age reefs being monitored bi-annually. In addition, three nearby natural reefs have been identified to serve as controls, and the same metrics used on created reefs are measured there. Physical oyster growth and faunal information at the 16 sites will be correlated to elevation (depth below mean tide level) and age (young, moderate, old) to further understand how these reefs mature over time.

Oysters are tolerant to prolonged areal exposure, however in order to release toxins and feed they must be submerged; therefore, it is imperative to maintain tight elevation controls during reef construction to ensure proper placement of substrate within the water column. As a result, reef sections situated above, or below suitable oyster settlement depths may experience reduced settlement, increased predation and reduced growth. The conclusions from this study will be used to maximize oyster growth potential and inform adaptive improvement in the planning and design phase of future oyster restoration projects to ensure maximum recovery of healthy oyster populations in Tampa Bay and around Florida.

Spatio-temporal Distribution of Endocrine-Disrupting Compounds in the Florida Keys

By Renee Duffey and Luke McEachron

Water quality throughout the Florida Keys remains a principal management concern because pollutants can have significant impacts on fish, wildlife and sensitive reef systems. In recent years there has been increasing concern regarding environmental effects of endocrine disruptors (EDCs). EDCs are commonly found in pharmaceuticals and personal care products (PPCP), pesticides and other household products. Endocrine disruptors mimic hormones and can cause a wide range of health problems in humans, fish, and wildlife even at small doses.

EDC occurrence has been documented by several studies throughout Florida, however, no single spatial database or map has organized historic and current EDC sampling throughout the FKNMS, or the Florida Reef Tract, despite widespread recognition that EDCs are a threat to biological and economic resources.  To address this need, the Information Science and Management section initiated a one-year project to summarize the type, concentrations, sampling gaps and distribution of endocrine-disrupting compounds (EDC) primarily in the Florida Keys.

We compiled 15 datasets representing approximately 951 unique sampling locations and 621 chemicals. Of the over 600 chemicals included in the database, only 91 chemicals were federally listed by EPA as known endocrine disruptors (2009, 2013). While not federally listed, numerous chemicals have potential endocrine disrupting properties documented in the scientific literature and by non-federal authorities (e.g., World Health Organization (WHO), United Nations (UN)). Consequently, we expanded the scope of the project to include potential EDCs and also chemicals that either indicate human by-products (e.g., caffeine, sucralose, cholesterol and other human waste indicators).

Unlike other routine water quality monitoring programs, EDC sampling was generally isolated to one or two sampling events and/or targeted specific locations. Lack of long-term, consistent sampling presents challenges when assessing spatial or temporal patterns in EDC concentrations. Additionally, very few chemicals of the 621 we identified in this study were sampled by more than one data provider. Differences in laboratory detection limits between data providers also makes comparisons difficult, particularly for EDC concentrations which are often at or below detection limits.

Data compiled by this project are available online via the Endocrine-disrupting compounds (EDCs) in the Florida Keys Story Map. A Story Map combines maps with narrative text, images, and multimedia content to create compelling, user-friendly web apps.

Young Sea Turtles and Floating Debris in Sargassum Habitat

By Tomo Hirama

Sea turtle hatchlings emerge from sandy beaches, swim offshore, and, in a few days, reach Sargassum-dominated surface-pelagic drift communities (or Sargassum habitat). The Sargassum habitat provides protection and food for these sea turtles during the first few years of their lives. We have found that these turtles are opportunistic omnivores, apparently feeding on anything that fits into their mouths including synthetic materials that can harm them. Sargassum, plastics, and other floating objects gather at surface convergence zones that are typically located at the edges of ocean currents. After exposure to ultraviolet rays and other aspects of the ocean environment, large-size plastics are broken down into smaller fragments that are then bite-sized for the young sea turtles in Sargassum habitat. Alarmingly, we have observed a high prevalence of plastics included in the diets of these turtles.

Sargassum habitat with debris.

Because of late-summer to fall storm events, some post-hatchlings, which are only a few weeks to a few months old and have been living in Sargassum habitat, are washed back on the beaches, mainly along the East Coast of Florida. These wash-backs are often in poor condition. Some are found dead and others die later at rehabilitation facilities. Since the early 2000s, we have been examining the gut contents of wash-backs that died. The percentage that had ingested plastics was about 80 % during the early 2000s but has reached 100 % during recent years. When ingesting plastics, the wash-backs seem to have no preference in color; we see a wide range of colors of plastic in their GI contents, with the majority being translucent and white as these are the most abundant types in the Sargassum habitat. By dry weight, about 30 % of the gut contents from these turtles were plastics.

The gastro-intestinal content of a wash-back that was 7.8 cm straight carapace length.

In addition to our study of wash-backs, we have also been capturing and studying post-hatchlings in the offshore Sargassum habitat. When comparing these two groups, we’ve found that the body condition index of the wash-backs was significantly lower than that of the post-hatchlings that were captured offshore.  Although the relationship between plastic ingestion and cause of death is often not clear, the ingestion of plastic may result in nutritional dilution (non-nutritious material contributing to a feeling of satiation and reducing the urge to continue feeding) or may cause an impaction of the digestive tract.

FIM’s Marine Fish Mercury Program — Indian River Field Lab

By Richard Paperno and Deb Leffler

The Florida Fish and Wildlife Conservation Commission’s Fish and Wildlife Research Institute (FWC-FWRI) Mercury Program conducted by the Fisheries-Independent Monitoring (FIM) Program is one of the most comprehensive efforts in the United States for monitoring mercury concentrations in marine and estuarine fishes. Mercury is a toxic metallic element that has been shown to bioaccumulate in fish tissue. Humans and wildlife that consume fish can potentially ingest significant levels of mercury in their diet. In 1989, the FWC-FWRI began to examine total mercury levels in fish muscle tissue from many economically and ecologically important species to better understand mercury contamination in Florida’s marine fishes. With analytical cooperation from the Florida Department of Environmental Protection, the program’s initial goal was to document mercury levels in Florida’s commercial and recreational fishery species to assist the development of regional Fish Consumption Advisories. In 2006, the FWC-FWRI began analyzing mercury samples in-house at the Indian River Field Laboratory. This addition expanded the program’s analytical capabilities and its focus to now include ecologically important predator and prey species in marine and estuarine habitats.  Currently, the Indian River Field Laboratory is responsible for all analyses of marine fish mercury samples within the waters under Florida’s jurisdiction.  

To date, we have examined the concentration of total mercury in more than 113,000 fish representing over 350 species. These species represented all major trophic groups from primary consumers (e.g., anchovies, herrings, mullets) to apex predators (e.g., mackerels, tunas, billfish, sharks). Most individuals we examined contained low concentrations of mercury, but concentrations in individual fish varied greatly within and among species. Overall, fish concentrations ranged from 0.001 ppm to 32.0 ppm, yet only 10% of all individuals analyzed had tissue concentrations above the U.S. EPA “Choices to Avoid” consumption guideline of approximately 0.47 ppm. Species with very low average mercury concentrations tended to be those that feed on plankton, detritus, invertebrates, or small fishes. Apex predators typically had the highest mercury concentrations. In most species, mercury concentration increased as fish size and age increased.

The data generated by the FWC-FWRI Mercury Program have been used to inform the public and to weigh the potential risks and health benefits of consuming common fishery species in Florida. These data have also advanced scientific research regarding ecological tracers and ecosystem function. Indian River Field Laboratory scientists have shared Florida mercury results through numerous professional presentations at scientific conferences, technical reports, and more than 20 publications in scientific journals. Ongoing cooperative collaborations regarding mercury with researchers within and outside of the FWC-FWRI currently involve stable isotope applications, point- and non-point source identification, ecosystem-wide assessments, and evaluation of mercury effects on marine fishes at the sub-cellular level.  Sampling in Florida waters is continuing, and FWC-FWRI research relating mercury to fish age, feeding ecology, and the trophic structure of Florida’s marine and estuarine ecosystems will help us better understand concentrations of this element in marine fishes and their habitats.