Fish and Invertebrate Ecology

Principal Investigator

Oceans and coastal ecosystems support an incredible diversity of fish and invertebrates that have sustained human societies for millennia through fisheries and aquaculture. These species are key players driving ecosystem structure and function, but human activities threaten the productivity and diversity of marine life. In the Anthropocene, finding a balance between harvest and conservation of fish and invertebrates, and mitigating other human impacts on marine ecosystems, will be key to sustaining productive, resilient, and biodiverse coastal and marine ecosystems. We address broad problems of population and community ecology using long-term quantitative sampling, animal behavior/movement studies, and innovative experiments at multiple spatial and temporal scales. Our studies analyze human impacts and natural change in freshwater, estuarine and marine systems.

Biologists Track Cownose Rays to Florida and Back

 

Aug 23, 2018

Summer and Winter Habitats Pinned Down in Longest Cownose Ray Migration Study on Atlantic

Every summer, cownose rays stream into Chesapeake Bay to mate and give birth to their pups. When autumn comes, they disappear—presumably to migrate south, but no one knew for certain where they spent the winter. Now, after a three-year tagging study published Aug. 23 and led by the Smithsonian Environmental Research Center (SERC), scientists have solved the mystery. Cownose rays all along the Atlantic winter near Cape Canaveral, Florida, and it is likely they return to the same spots each summer.

Cownose rays are large stingrays native to the Chesapeake, with dark brown or olive-gray backs and white bellies. They reproduce slowly. Most mothers give birth to only one pup a year, and they do not mature until age 7 or 8, making them vulnerable to intense fishing or sudden population declines. And yet cownose rays have been dogged by controversy. In the early 2000s, they were saddled with partial blame for oyster declines because their diet includes shellfish. (Later studies cleared their names. Oysters had been declining years before cownose rays became more abundant.) Later, in 2015, bowfishing tournaments for cownose rays began raising alarm among some Marylanders. In response, the Maryland government voted to become the first state to create a fishery-management plan to conserve the cownose ray.

“Because of the slow birth rate, we know that if we don’t manage them, and instead harvest them in a way that heavily impacts the population and causes a population decline, it’ll take a long time for them to recover,” said Matt Ogburn, SERC marine biologist and lead author of the study. “If we lose something important, we could lose it for decades.”

Man and woman on boat
SERC marine ecologist Matt Ogburn (front) and intern Claire Mueller search for bull sharks and cownose rays near Fort Pierce, Florida, in January 2018. (Credit: Jay Fleming/Smithsonian)

The new study, published in Marine Ecology Progress Series, marks the first time scientists have tracked cownose ray migrations along the Atlantic coast for a full year or more. Knowing where they go every year will help fill in some longstanding knowledge gaps about the rays, as Maryland officials decide how to manage them. It is part of the Smithsonian’s new Movement of Life Initiative. Scientists from the Virginia Institute of Marine Science (VIMS) and Savannah State University also joined the effort.

To tag the rays, scientists spent three summer and fall field seasons teaming up with commercial fishers. These fishers were not trying to catch cownose rays, but the animals often appear as accidental bycatch in their pound nets or haul seines. Many of the fishers had worked with the scientists before, partnering with VIMS co-author Bob Fisher or on SERC’s crab-tagging studies.

“Collaborative efforts with commercial fishers are built on trust, straight talk and inclusion to investigate common problems and opportunities,” said Fisher, who has studied cownose rays for nearly three decades.

Man in water holding cownose ray
Bob Fisher, a biologist with the Virginia Institute of Marine Science, releases a tagged cownose ray into the water. (Credit: Sayer Fisher)

After transferring the rays to a holding tank, the researchers gave them general and local anesthesia and inserted a small acoustic tag inside them. Once the rays had recovered from surgery, the scientists released them back into the water. As the rays continued their journeys, the tags emitted a series of “pings” unique to each ray. An array of hundreds of receivers lines the Chesapeake and the Atlantic coast, waiting to pick up their signal. These receivers were placed by dozens of scientists from institutions along the East Coast, all sharing data on different species. If a ray passed within half a kilometer of a receiver, the receiver would record data about the ray’s location. Then the data were shared through the Atlantic Cooperative Telemetry Network and Florida Atlantic Coast Telemetry Network.

The teams tagged 42 rays total. Most were tagged in Virginia, with five in Maryland and two in Georgia. Of those rays, 28 had their signals detected multiple times over a period longer than 90 days, enough time for scientists to get a sense of their migration behavior.

Regardless of where scientists tagged the rays, every ray they detected in winter went to the same spot: a region just off the coast of Cape Canaveral. The greater challenge was figuring out if cownose rays go back to the same places each summer. While most rays returned to the same regions where scientists tagged them the previous year—some even to the same rivers—many rays were tagged in the fall, when they might have already left their summer homes. Only five rays sent out location signals for both summer 2015 and summer 2016. Four of those rays (three from Virginia and one from Georgia) returned to their original regions. The fifth spent both summers in the Chesapeake, but the first summer in Virginia and the second in Maryland.

Cownose ray swimming out of net into water
Scientists release a tagged cownose ray into the water. (Credit: Jay Fleming/Smithsonian)

This pattern could make conservation even more critical. If cownose rays are returning to the same places each summer, that means the Chesapeake likely has its own distinct population. Intense fishing of rays in the Chesapeake, especially during summer, could wipe out a large slice of the species’ genetic diversity.

“If they’re really tied to one specific place, then you’ll be removing a whole piece, a whole unique segment, from the population,” Ogburn said.

While scientists have unraveled one mystery about cownose ray migrations, there are still many unknowns surrounding the animals. Not least, the authors emphasized, is their role in the Chesapeake Bay as a whole. By turning over the sediment, a bit like tilling a garden, they could play a vital role for organisms like shellfish and crabs that live on the bay floor. As Maryland develops the first official management plan for cownose rays, studies like this will offer more guidance on how to manage one of the most enigmatic creatures in the Chesapeake.

The full study is titled "Migratory connectivity and philopatry of cownose rays Rhinoptera bonasusalong the Atlantic coast, USA." It was published in the journal Marine Ecology Progress Series, vol. 602. The abstract is available at https://www.int-res.com/abstracts/meps/v602/p197-211/. For a copy of the paper, images or to speak with one of the authors, contact Kristen Minogue at minoguek@si.edu or (443) 482-2325.

Research Labs

Fish and Invertebrate Ecology

Media Contact

 

Understanding the ecology of fisheries is critical to maintaining resilient, productive and biodiverse coastal and marine ecosystems. Fishing is an important sector of coastal economies, provides an important supply of food for human societies, and is an activity of great cultural and historical importance. But fisheries have also contributed to the decline of coastal and marine ecosystems through changes in biomass and community structure, disruption of food webs, and alteration of habitats. Using the Chesapeake Bay as a model system, we are addressing fisheries issues including the impacts of harvest, restoration, and conservation on populations, communities and ecosystems, habitat use, migrations and connectivity with other coastal ecosystems. To learn more about our fisheries ecology and conservation research, please visit the following webpages:

Our long-term studies of fish and invertebrate communities in the Rhode River, Maryland study site offer a window in the community structure and population dynamics of fish and invertebrate communities in one of the most productive ecosystems on earth, the Chesapeake Bay. Spanning more than three decades, this research tracks seasonal, annual, and decadal variation in species composition and abundance of fishes and macro-invertebrates. Sampling methods include trawling, seining, a fish weir, benthic infauna cores, and tethering experiments. The long-term descriptive data, in combination with our experimental studies, provide an unusual database for exploring populations, communities, predator-prey relationships, impacts of fisheries, and impacts of environmental variability and climate change, and other ecological processes. To learn more about our long-term research, please follow the links below:

Many species on the planet migrate during their lifetime, using different habitats during specific life stages. What habitats are most important and why? How will climate change affect migrations? What are the benefits and costs of migration to individuals? How can we best manage fisheries for migratory species? How do migratory species affect community structure and ecological processes? To learn more about our Movement of Life Initiative research, please visit our Movement of Life Initiative webpage:

Welcome to the Educator Resources page-- below are a collection of lessons, web resources, and videos arranged by subject to help you quickly find resources in your interest area to create lesson plans or activities. Maryland follows the Next Generation Science Standards for K-12 science content standards. Access the Next Generation Science Standards broken down by topic at the National Science Teachers Association website.

Are you a teacher visiting SERC? Click here to learn more about how to prepare for your field trip to our campus and other general resources!

Discover, create, and share more resources and educational experiences on the Smithsonian Learning Lab!

Lesson: Movement of Life Initiative: Discover What Makes Sharks Move
Grade 4
NGSS 
https://learninglab.si.edu/collections/movement-of-life-initiative-discover-what-makes-sharks-move/74MV9mDjnp7PvG9k#r

Lesson: Sharks and Shorelines
Grades 6-10
NGSS 
https://natureworkseverywhere.org/resources/sharks-shorelines/

Activity: Ecosystem Explorer | EARTH A New Wild
Grades 5-8
NGSS
https://www.pbslearningmedia.org/resource/5aeed659-7f0b-417f-81d9-5f2e9c...

Reading/ Video: SERC’s Shorelines Blog "Following the Movement of Life: Tagging Sharks and Rays"
Grades 5-7
https://sercblog.si.edu/?p=8571

Reading/ Video: SERC’s Shorelines Blog "Tracking the Bay’s Cownose Rays"
Grades 5-7
https://sercblog.si.edu/?p=6254

For more information about shark migration, check out Smithsonian's Movement of Life Initiative!

Lesson: The Blue Crab's Chesapeake Journey
Grade 9-12
http://www2.vims.edu/bridge/DATA.cfm?Bridge_Location=archive1102.html

Video: SERC Scientists Video from the Smithsonian Science Education Center, “How do Scientists Track and Monitor blue Crab Populations in the Chesapeake Bay?
Grades 3-8
https://ssec.si.edu/explore-smithsonian-how-do-scientists-track-and-moni...

 

Video: SERC Ecosystems on the Edge video by one of our scientists, called “Blue Crabs: Top Predator in Peril”
Grades 3-8
https://ecosystemsontheedge.org/top-predator/

 

Lesson: Juvenile Oyster Disease: A Growing Problem
Grade 9-12
http://www2.vims.edu/bridge/DATA.cfm?Bridge_Location=archive0103.html

Video: Determining the Resiliency of Juvenile Oysters in the Chesapeake Bay
Grade 3-8