Science to power conservation & sustainable use

Mote Marine Laboratory research programs represented on this page: Fisheries Ecology & Enhancement Program • Fisheries Habitat Ecology & Acoustics Program • Marine & Freshwater Aquaculture Research Program • Sharks & Rays Conservation Research Program

Stories on this page: Sustaining fisheries—global spotlight on Mote • Sweeping studies, fin-tastic firsts in shark & ray science

SUSTAINING FISHERIES—GLOBAL SPOTLIGHT ON MOTE

• In November 2019, Mote Marine Laboratory was a magnet for fisheries scientists from around the world—drawing more than 80 researchers from the U.S. and 13 other countries for a symposium about fish ecology and the latest methods for enhancing and restoring depleted wild fisheries.
  
  At Mote’s campus in Sarasota, Florida, Mote and Florida State University (FSU) held their 10^th International Symposium on Fisheries Ecology combined with the 6^th International Symposium on Stock Enhancement and Sea Ranching. There, participants shared their latest local and regional research to help address a global problem: Production from capture fisheries peaked in the mid-1990s and has remained relatively stable since then, but the threats to fisheries from climate change, population growth, and pollution are increasing. Science-based fisheries management can and does make a difference. A study of the world’s scientifically-assessed fisheries—areas with more intensive management—showed that many have grown in abundance in recent years. Modern management includes rigorous assessments of fish populations, data-supported laws and regulations, and for many species and ecosystems, it can benefit from the scientific tools presented during the symposium at Mote—fisheries enhancement, sea ranching, and restocking (releasing fish raised in aquaculture), and habitat rehabilitation and restoration.
  
  While aquaculture (fish farming) will supply a growing percentage of seafood in the future, wild fisheries will remain a vital source of food and employment—along with economic value from recreational fishing and eco-tourism—for Earth’s growing population. In 2017, the United Nations Food and Agriculture Organization reported that nearly 40 million people worldwide worked in fisheries. In Florida, saltwater recreational fishing alone is worth $9.2 billion and more than 88,000 jobs.
  
  Symposium participants shared their successes and challenges with understanding and enhancing species fished for seafood and recreation alike, ranging from abalone in New Zealand and France to white seabass in California, queen conch in Puerto Rico, and common snook in Florida—Mote’s longtime focus and model research species for enhancing fisheries responsibly.
  
  Many of the symposium presentations are available online at mote.org/symposium and Symposium proceedings are currently being collected for publication in an upcoming issue of Bulletin of Marine Science.

• Snook success in Mote’s corner of the world:
  This year, Mote scientists released nearly 10,000 common snook into southwest Florida environments, continuing a long-term effort to understand which fisheries-enhancement methods work best and how these popular sportfish interact with their environment.
  
  That total included one group of 7,975 snook—the largest number Mote has ever produced for a single release experiment during more than 20 years of fisheries science by Mote and partners at the Florida Fish and Wildlife Conservation Commission (FWC).Read our to learn about Mote’s success with raising large numbers of snook.
  
  Common snook are the third most targeted fish in saltwater recreational fishing on Florida’s Gulf Coast, FWC reported in 2015. Their populations have long been challenged by habitat loss and recently by severe cold weather in 2010 and a major red tide in 2017-19, both of which led to temporary bans on harvesting snook from Florida’s Gulf of Mexico fishery.
  
  To help snook rebound from such events and improve the outcomes of fisheries enhancement in general, Mote scientists release hatchery-reared juvenile snook (produced by Mote Aquaculture Research Park) and investigate factors that may impact their success, including release habitat, timing, numbers and sizes of fish released, acclimation measures and conditioning of the fish before release. By learning from each release and applying that knowledge later, we can enhance (or “stock”) fisheries strategically.
  
  Mote scientists’ unique methods allow them to conduct timely assessments of snook survival after release, and in turn, develop statistical models of the potential influences on survival. Each released snook is tagged with a passive integrated transponder (PIT tag) that is detected by antenna arrays on shore.
  
  Their research has yielded valuable lessons learned for effective fisheries enhancement:
   
  • Identifying factors/techniques that increase snook survival during the first few weeks after release will have the biggest impact on stocking success.
     
  • Even though creeks provide a refuge for snook during winter, snook releases are more successful when done in spring or fall.
     
  • Mote scientists have seen the highest survival rates for fish released at the mouths of creek systems, notably those with robust shoreline vegetation (e.g., North Creek in Sarasota County).
     
  • Acclimation cages (which contain and protect the snook temporarily within the release site) are helpful for stocking locations that may not be conducive to high snook survival.
     
  • It can take years to learn these valuable lessons using traditional monitoring techniques, but Mote’s novel PIT-tag approach helps the scientists measure their success and identify ways to improve efforts in just a year.
    
    Mote scientists also treat these released snook as “ecological probes”—they help the scientists identify ecosystem features that are important to protect or restore based on their ability to support healthy fish and fisheries. In particular, Mote scientists focus on tidal creek systems in Sarasota County, Florida—some of these creeks have the capacity to support functional fish communities while others are losing this capacity because of human-driven modification. By releasing snook into altered systems, Mote scientists aim to identify areas that may benefit from naturalization.
     
• First study to identify lionfish prey by DNA along western Florida:
  The invasive, Indo-Pacific lionfish preys on many native species in the Gulf of Mexico, Caribbean Sea, and parts of the Atlantic Ocean—and the list of prey might be getting longer, reported a study co-authored by Mote scientists in September 2020 in the peer-reviewed journal Biodiversity and Conservation.
  
  Led by a partner at Thomas University / University of South Florida, Sarasota-Manatee, the study used DNA barcoding to identify the stomach contents of lionfish caught in the 2016 Sarasota Lionfish Derby hosted by Mote.
  
  Study partners dissected 70 lionfish stomachs and secured prey DNA from 49 of them, representing 184 prey fragments. Analyses showed that these lionfish along west Florida had been eating at least 21 fish prey species from 14 scientific families, which accounted for 95.7% of the genetically identifiable prey. The remaining prey identified corresponded to six crustacean species. To the best of the authors’ knowledge, 11 species or groups in the study were identified as lionfish prey using DNA for the first time. Nine were unknown from other DNA barcoding studies of lionfish prey in the western Atlantic: Spotted dragonet (Diplogrammus pauciradiatus), painted wrasse (Halichoeres caudalis, Florida hamlet (Hypoplectrus floridae), sponge cardinalfish (Phaeoptyx xenus), greenblotch parrotfish (Sparisoma atomarium), Atlantic lizardfish (Synodus saurus), redhair swimming crab (Achelous ordwayi), Caribbean velvet shrimp (Metapenaeopsis goodie and Caribbean rock mantis shrimp (Neogonodactylus bredini). Two were unidentified but part of groups with known lionfish prey: fishes in the scientific groups Chaenopsis and Microgobius.
  
  This study and others suggest that lionfish eat a wide variety of prey—part of what makes them such a concerning invasive species. However, they do seem to prefer prey with specific traits—fish that are reef-associated or live close to the seafloor, smaller than 6 inches (15 centimeters) and mostly active at night or during dawn and dusk.
  
  Understanding lionfish is vital for addressing their invasion—a crucial goal because lionfish have been shown to drastically reduce recruitment of native coral reef fishes. This study supplies new data to inform response efforts. It also highlights the way that lionfish derby events—such as the ones hosted at Mote in recent years, which focused on catching lionfish and educating the public—can be a cost-effective way to leverage public events to produce scientific information.
   

SWEEPING STUDIES, FIN-TASTIC FIRSTS IN SHARK & RAY SCIENCE

• A big picture of great white sharks:
  
  Over the past five years, Mote has been part of an intensive, team effort to study great white sharks in the Northwest Atlantic—and the results are producing a whole new understanding of this important species from Canada to the Gulf of Mexico. Great whites, known to scientists as white sharks (Carcharodon carcharias), experienced a serious population decline approaching 90% during the second half of the 20^th century in the Northwest Atlantic. The first federal fishery management plan for sharks was instituted in 1993, and six years later white sharks were declared prohibited from being landed by fishermen in U.S. federal waters. Since then, the population has been rebuilding and white sharks are beginning to slowly increase their numbers on the Atlantic coast of the U.S. and Canada. Their seeming recovery raises important questions about how to protect these animals and their ecosystems—which requires knowledge of their biology, ecology, and behavior, including their long-distance migrations. White shark bites on people are exceptionally rare but can be fatal, which means it’s also important to ensure public safety in areas with growing numbers of white sharks.
  
  To gather the knowledge necessary for white shark management, Mote scientists and dozens of other partners have worked with the nonprofit OCEARCH to capture, sample, tag, and release live white sharks back into their environment, from Florida to Nova Scotia, using a custom lift on OCEARCH’s unique research ship. In the long term, the team aims to sample and tag about 100 white sharks from the Northwest Atlantic population, and of late 2020, they were up to nearly 70. 
  
  In 2020, Mote scientists joined OCEARCH for Expedition Nova Scotia 2020, which included 35 scientists from 24 institutions conducting 21 different white shark studies. During the trip, the team placed a location-tracking satellite tag on their largest white shark to date in the North Atlantic, “Nukumi,” a mature female measuring 17 feet, 2 inches long and estimated to weigh more than 3,500 pounds.
  
  Nukumi and her fellow tagged sharks are helping Mote, OCEARCH and partners develop a model of white shark life in the Northwest Atlantic, which are being detailed in upcoming, peer-reviewed research papers. This model maps out where the sharks travel at each stage of life, based on satellite tags and other sources of shark movement data. In short, Mote scientists and partners surmise that Northwest Atlantic white sharks are born off the coast of Long Island, New York, in a “nursery” habitat where they are relatively safe during this vulnerable stage. They spend their first summer there and migrate south as they are growing, spending their first winter in areas off Florida, north Georgia and the Carolinas. The next year they return north to the nursery area and they continue seasonal north-south movements, slowly expanding their range until they travel as far south as the eastern Gulf of Mexico and north to Newfoundland, Canada, and beyond. They stay near the coast and aggregate in specific feeding areas, which the scientists will describe in their published research. Some sharks move offshore—and the scientists hypothesize that these are pregnant females gestating their young inside them.
   
• In July 2020, white shark discoveries from multiple partners, including Mote, were published in a peer-reviewed article titled “Inconspicuous, recovering, or northward shift: status and management of the white shark (Carcharodon carcharias) in Atlantic Canada,” in the Canadian Journal of Fisheries and Aquatic Sciences. The article highlights that white sharks are found more commonly and consistently in Canadian waters than previously recognized. This finding could relate to more research focused in Atlantic Canada plus better tagging and tracking in the Northwest Atlantic, along with a possible expansion of the sharks’ range that could relate to their population recovery, increasing prey, or even climate change conditions shifting the population northward.
  
  Alongside the tagging and tracking studies led by Mote scientists and their partners, OCEARCH expedition participants are studying white shark reproduction, physiology, ecosystem interactions, genetics, impacts of environmental contaminants, and more.
   
• We *heart* white sharks:
  
  As partners in the OCEARCH expeditions above, Mote scientists were part of the team that produced the first-ever ultrasounds of white shark heartbeats in the Northwest Atlantic—likely the first anywhere. The ultrasounds show that a white shark’s large, two-chambered heart beats just six to 10 times per minute (one-tenth of the resting heart rate typically found in four-chambered human hearts) while the sharks are resting on the OCEARCH lift. This is typical of other large, vertebrate animals, like whales and elephants, and is an indicator of the low stress level of the sharks on the lift.
   
• Major study—reef sharks are in trouble, but there’s hope:
  
  In a study published this year in the prestigious, peer-reviewed journal Nature, scientists surveyed the relative abundance of reef sharks at 371 reefs in 58 nations and found many areas of reduced abundance, with no sharks at 20% of surveyed reefs. This alarming finding is tempered by hope: reef shark abundance has room to rebuild if nations address socio-economic challenges and the need for shark fisheries management and conservation.
  
  Mote scientists co-authored the study, which was led by a first author from Dalhousie University in Canada. The study notes that reef areas with direct management efforts such as shark sanctuaries, catch limits, and reductions in certain types of fishing gear tended to have more reef sharks. However, the study also emphasizes that communities in many nations exploit reef sharks and their ecosystems to cope with socio-economic disparities, which is not sustainable in the long term—a problem that must be addressed by their governments to give reef sharks a shot at recovery. Also, direct management tools may not work equally well everywhere. Shark sanctuaries, a direct management option, have provided vital refuge to reef sharks in many locations, but sanctuaries are often located in nations where shark fishing is less central to the culture or economy.
  
  The study showed that reef sharks are relatively scarce in many places around the world, particularly in areas of the Western Pacific, Indian Ocean and Western Atlantic with more populated coastlines, nearby markets and lower-functioning governments—as described by numeric tools such as the World Bank voice and accountability metric (which examines how much people can participate in their government and engage in free expression, free media and free association).
  
  Understanding declines of reef shark populations—and finding diverse pathways for each nation and culture to respond—is critical. Sharks play important roles in coral reef ecosystems, which are important to economies worldwide. On the flip side, replenishing these sharks may require replenishing their reef habitats, too—a relationship that must be better understood, the authors note.
  
  This study—which estimated sharks’ relative abundance on reefs using more than 15,000 remote, underwater, baited video camera systems called “BRUVs”—helps to fill a major knowledge gap. Coastal environments including coral reefs contain the majority of threatened shark species, but coastal sharks have been studied less consistently than their open-water cousins that are targeted or caught as bycatch in industrial fisheries.
  
  Mote’s participation in this study played a key role in obtaining data from Cuba, where Mote shark scientists have been working since 2003. Cuba’s reef shark population ranges from overexploited in some areas to healthy in marine refuges like their well-known Jardines de la Reina (Gardens of the Queen) on Cuba’s south coast.
   
• Another biggie:
  
  Mote scientists have tagged and tracked many whale sharks (Rhincodon typus), Earth's largest shark species, to support their management and conservation. One amazing whale shark, Rio Lady, was tracked making an epic migration of nearly 5,000 miles by scientists from Mote and Ch’ooj Ajauil AC, who tagged her with a pop-up archival satellite tag in 2007.
  
  Recently, the 26-foot Rio Lady resumed her service to science when she was re-tagged, this time with a real-time position satellite tag, by Nova Southeastern University’s (NSU’s) Guy Harvey Research Institute and Ch’ooj Ajauil AC in 2018. This year, the tagging team reported that Rio Lady has provided 20 months of new scientific data—the latest chapter in a long tale that began with Mote research.
  
  In that 20-month journey, she traveled more than 9,000 miles through the national waters of at least five countries in the Caribbean and Gulf of Mexico. That contrasts with her previous journey, from Gulf of Mexico waters near Isla Mujeres, Mexico, down to the southern Atlantic Ocean near the Rocks of Saint Peter and Saint Paul between the African continent and Brazil.
  
  Whale sharks were classified as Endangered by the International Union for Conservation of Nature and Natural Resources (IUCN) in 2016, due to estimated population declines in some parts of their range. Understanding where whale sharks go is valuable for protecting the habitats and food sources they use while recognizing where they might encounter threats such as ship strikes and fishing impacts in certain areas (catching whale sharks is prohibited in U.S. waters).
   
• New chapter in Mote’s shark tale:
  
  This year marked a milestone for shark science along Florida’s Gulf Coast. Mote scientists launched a year of quarterly shark surveys in the same region where Mote’s founding “Shark Lady,” Dr. Eugenie Clark, first documented sharks in 1955-71, and where Mote scientists surveyed sharks again in 2001-2017. Mote’s long-term data are valuable for understanding changes in shark populations and supporting fisheries management with the best-available science.
  
  These surveys represent one of several Mote projects within the new Pelagic Ecosystem Research Consortium (PERC). PERC—led by the University of Maine with partners including Mote, Auburn University and Nova Southeastern University—launched in 2019 with a competitive, $1.6-million grant awarded through NOAA’s 2019 Sea Grant Highly Migratory Species Research Initiative. Pelagic, or open-ocean, fishes include sharks, tunas, swordfish, and other species that support huge commercial and recreational fisheries. Coastal sharks, also included in PERC, are economically and ecologically valuable as well. However, many of these species are overfished or vulnerable to other pressures, and most are challenging to study and manage because they migrate long distances. PERC partners are studying at least a dozen shark species, five tuna species, and swordfish to deepen knowledge of how their lives play out in the wild and understand the structure of, and threats to, each population.
  
  Mote’s surveys along southwest Florida provide new snapshots of sharks’ relative abundance—for comparison with earlier 2000s surveys—as well as their distribution, habitats, biology (including genetics and parasite samples), the proportions of different species caught, and more. Some sharks are fitted with electronic tags and tracked after release for up to a year.
  
  Mote’s new surveys have continued to document many species Dr. Clark observed six decades ago: blacktip, bull, great hammerhead and sandbar sharks, for example. However, the dusky sharks that Clark documented are absent—having vanished from the area by the time Mote did its 2001-2017 surveys. Local dusky sharks had shifted or died off, part of a broader population decline that motivated the U.S. government to ban harvest of this species starting in 2000. The years have been kinder to other species. For instance, blacktip sharks in the Gulf of Mexico—a primary target in recreational and commercial fisheries—are not overfished or at risk of overfishing, according to a 2018 assessment from NOAA that included Mote data and expertise, and they’ve continued to be found by Mote’s new surveys.
  
  Interestingly, Mote surveys this year and in 2000-2017 have documented blacktip sharks during winter, which Clark’s early surveys did not. Scientists wonder whether the species’ distribution is shifting with a warming climate in the Gulf, something that has already been documented in the U.S. Atlantic. In general, Mote’s winter survey efforts encountered a mixture of warmer-water and colder-water sharks. Potential shifts in shark populations must be understood because they can have significant consequences for ecosystems where sharks are highly influential, top predators.
  
  From December 2019 through December 2020:
  • Mote’s shark survey team deployed 2,673 hooks for their catch-and-release shark surveys, catching 299 sharks.
  • 11 shark species were surveyed including:
    • 118 sandbar sharks
    • 46 blacktip sharks
    • 35 nurse sharks
    • 24 blacknose sharks
    • 21 spinner sharks
    • 20 bull sharks
    • 11 great hammerheads
    • 9 lemon sharks
    • 7 Atlantic sharpnose sharks
    • 5 scalloped hammerheads
    • 3 tiger sharks
      
      Of these sharks, eight great hammerheads were fitted with a specific type of satellite tag designed to help scientists determine their survival after release, along with an acoustic tag that allow the sharks to be detected when they swim by underwater receivers placed by scientists in the Sarasota Coast Acoustic Network (SCAN) as well as other acoustic networks in distant ocean areas. Read about SCAN and Mote’s role in it here. By studying great hammerhead survival after release, Mote scientists aim to better understand how these sensitive sharks are affected by commercial fishing vessels, which sometimes catch the sharks unintentionally, as bycatch, and then release them. Some sharks in Mote’s survey were caught on longlines, which resemble a shorter version of commercial fishing gear.
      
      In addition, the survey team acoustically tagged 10 bull sharks with the help of a Sarasota Dolphin Research Program scientist investigating where the sharks move, how long they stay, and how their movements and diet overlap with those of dolphins in the Sarasota Bay region. Bull sharks sometimes prey on dolphins. This research is part of SCAN (further described here).
       
• Cuban shark discoveries coming up:
  
  Thanks to their years of groundbreaking research, Mote scientists and their colleagues in Cuba and the U.S. produced fascinating new findings about Cuba’s mysterious shark populations this year.
  
  Stay tuned: These discoveries will be featured in three new publications that will be highlighted in Mote’s 2021 annual report, focusing on:
   
  • The first scientific documentation of a shark nursery area in Cuban waters, for the lemon shark.
  • The species and sizes of sharks caught in the open-water longline fishery off northwest Cuba.
  • More details on two important, endangered shark species caught in that longline fishery: the sizes of mature longfin makos and oceanic whitetip sharks.
     
• A new manta ray, plus devil rays in detail:
  
  This year, Mote scientists co-authored a peer-reviewed research paper reporting a possible new species of manta ray in the Gulf of Mexico and Caribbean and better describing the genetic relationships among various endangered manta and devil rays to support conservation.
  
  The study, whose first author is affiliated with Bangor University, The Manta Trust and University of Sheffield in the U.K, includes co-authors from 23 institutions and provides a global picture of these imperiled fishes, which are targeted by fisheries in many areas and area also caught as bycatch by fishers targeting other species. To help protect them, scientists need to recognize which species, subspecies and populations should be managed as units—but rays in these groups can be hard to tell apart and scientists have debated how closely related some of them are. Scientists are working to group the rays more definitively by investigating their genetics, observable physical traits, geographic ranges, behavior and relationships to their ecosystems.
  
  The current study, using a large collection of DNA samples (genetic material) from manta and devil rays at multiple sites around the world, sheds new light on the relationships between recognized species and helps reveal different clusters within species. Notably, study results show that the giant manta (Mobula birostris) has two major genetic clusters: one found around the world including in the Gulf of Mexico, and the second detected in the Gulf of Mexico only—likely a new species, which some scientists have tentatively called the Caribbean manta. The latter has slightly different markings than the widespread cluster of giant mantas.
  
  Giant mantaswere recently listed as threatened under the U.S. Endangered Species Act, and are classified as Endangered, with a decreasing population trend, on the IUCN Red List of Threatened Species. As a result, scientists are ramping up efforts to better understand their presence, movements and critical habitats.
  
  Another IUCN Endangered ray—the lesser devil ray (M. hypostoma)—was demonstrated more clearly to be a single species in this paper, distinct from the related Munk’s devil ray (M. munkiana), thanks to samples collected by Mote scientists in the Gulf of Mexico.
  
  Both the lesser devil ray and the giant manta are listed by CITES, the Convention on International Trade in Endangered Species of Wild Fauna and Flora, which works to protect animals and plants from overexploitation.
  
  Mote scientists aim to continue collecting devil, manta and other ray data from sampling, tagging and community-science efforts that are under way now or will begin soon. Notably, Mote scientists have already monitored the movements of three lesser devil rays and many spotted eagle rays tagged with transmitters through the Sarasota Coast Acoustic Network (SCAN), iTAG and FACT acoustic networks.
   
  • Read the new paper for additional updates on classifying manta and devil rays.
     
  • Be a community scientist (citizen scientist): If you see a manta, devil or spotted eagle ray along Florida’s coastlines, please report it to Mote scientists, who collect sightings data in collaboration with NOAA Fisheries, the federal government authority overseeing wild ray populations in U.S. waters. Submit your sightings to kbhull@mote.org. Please provide the location (with latitude and longitude if possible), the time and date, and a photo or video if available.
     
• First look at spotted eagle ray diving behavior:
  
  Mote scientists co-authored the first peer-reviewed research paper exploring how shallow or deep spotted eagle rays tend to swim and why. To protect mobile animals like spotted eagle rays (Aetobatus narinari)—which are classified by IUCN as Near Threatened with a decreasing population trend—it’s important to understand their movements in both horizontal and vertical space.
  
  In the study, whose first author is from Florida Atlantic University’s Harbor Branch Oceanographic Institute, scientists fitted seven rays with pop-up satellite tags that monitored their depth and horizontal movements for up to 180 days before popping up to the surface and transmitting the data to scientists. Rays were tagged in Atlantic waters off Bermuda and Gulf waters off Sarasota, Florida.
  
  The results: Most rays stayed within 32 feet (10 meters) of the surface, and only one dived deeper than 85 feet (26 meters). That ray, tagged off Bermuda, exceeded 165 feet deep (50 meters)—and provided one example of a key study conclusion: The rays’ depth behavior may depend, in part, on what region they inhabit. The study also showed that the rays swam deeper in the daytime than nighttime, possibly driven by feeding or avoiding predators. Read the study abstract.
   

Image at top of page: A shark is caught, tagged and released by Mote scientists and partners. Credit: Cameron McPhail/Mote Marine Laboratory