Hook, Line & Science
Oyster Reefs, Self-Releasing Hooks, and the Mysterious Wanderings of Southern Flounder



Does Protecting Oyster Reefs Benefit Other Marine Organisms?

Creating no-harvest zones on oyster reefs also helps the fish and crustaceans that live on the reefs.

by Aiman Raza, biology major at the University of Maryland, Baltimore County, and former intern at the Smithsonian Environmental Research Center in the Fisheries Conservation Lab.

Research Need

In the 19th century, the Chesapeake oyster fishery was the largest in the world. However due to habitat degradation, disease-causing parasites, and over-harvesting, the number of oysters in the bay has significantly decreased.

Oysters have been the subject of intensive management efforts, but there are many gaps in our understanding of oyster reef ecosystems. We know oysters provide many ecological services, such as water filtration, nitrogen removal, and habitat for other species.

At the Smithsonian Environmental Research Center, we were interested in seeing how protecting oyster reefs affects other species that live around them, specifically fish and crustaceans

What did I study?

I was interested in seeing whether there was a higher abundance and diversity of fish and crustacean species on harvested or non-harvested oyster reefs.

To answer this question, I analyzed GoPro video footage of oyster reefs from three tributaries in the Chesapeake Bay: the James, Great Wicomico, and Choptank rivers. Each tributary had one reef that was actively harvested and a neighboring reef where harvesting was prohibited. After watching the videos, I compared the number and types of fish and crustaceans in oyster sanctuaries compared to harvested zones.

What did I find?

There was a higher abundance of fish and crustaceans, as well as higher diversity, on protected reefs compared to harvested reefs.

This study provides evidence that fish and crustacean species benefit from creating no harvesting areas and highlights the importance of oyster reefs for healthy ecosystems. Expanding this study to more sites could provide new data to help guide oyster reef management in the future.

Anything else?

The James River had a higher abundance and diversity of organisms compared to the other two sites.

In addition, I was able to identify many different species of fish and crustaceans in the GoPro videos of the tributaries, including striped bass, summer flounder, and black sea bass, as well as blue crabs and grass shrimp. What’s more exciting is that some of these species, like striped bass and blue crabs, are federally managed. Spotting them in our videos is a good indicator that the species benefit from no-harvest zones.

So what?

Focusing our efforts on protecting valuable oyster reef habitat not only will benefit oysters but also the important fish and crab species that depend on them. As the demand for oysters increases and affects the oyster fishery, it is critical to understand how this might impact the broader ecosystem of the Chesapeake Bay.

An easy release off a bite-shortened hook. Credit: UF/IFAS Nature Coast Biological Station.

An easy release off a bite-shortened hook. Credit: UF/IFAS Nature Coast Biological Station.

Can Self-Releasing Hooks Minimize Fish Injuries During Catch-and-Release? 

A bite-shortened hook, designed to release fish without handling, shows promise.

by Holden Earl Harris, postdoctoral research associate at the University of Florida’s Nature Coast Biological Station.

Research Need

Releasing fish can help conserve their populations, but the process of capturing and handling fish also can result in injuries or death. These “discard effects” present a major conservation issue in recreational fisheries. Even if the percentage of injuries and mortalities are relatively small, fisheries where large numbers of fish are released can have cumulative effects that impact the population.

Fishing practices and gears that minimize handling, hook injuries, and air exposure can considerably improve the chances for survival of released fish. In particular, efficient dehooking substantially reduces the physiological stress in fish that typically occurs during the landing and release process.

Earlier field trials with bonefish on Palmyra Atoll found the species would “spit out” bite-shortened hooks once they were reeled in toward the angler and the angler gave slack in the fishing line. The idea appeared promising and prompted the researchers at the Nature Coast Biological Station to begin more rigorous testing.

What did we study?

To our knowledge, these are the first assessments of hooks designed to self-release from fish and to fully eliminate fish handling.

On 150 spotted seatrout, we tested whether standard, barbless, or bite-shortened hooks would allow anglers to reel in the popular coastal sport fish and then allow the fish to selfrelease while still in the water.

What did we find?

We found promising results for the bite-shortened modified hook, which enabled anglers to land 91% of hooked spotted seatrout and then release 87% of those fish without direct handling. In comparison, the self-release success rates were 47% using barbless hooks and 20% using standard, unmodified hooks.

We also found that smaller fish could be self-released without handling at higher rates. Length-regulated fisheries often protect smaller fish, and reducing mortality in these fish especially can help conserve resources.

So what?

A proven and effective self-releasing hook could have broad conservation and management applications in recreational fisheries as a means of minimizing or eliminating injuries and mortalities in catch-and-release fishing. Foreseeable uses of self-releasing hooks could include cases of restricted fishing in sensitive fishing areas, such as no-take aquatic protected areas or areas experiencing unsustainable fishing pressure. Further research with different lures, species, and anglers can inform conservation strategies.

Mason Collins, graduate student in marine biology at UNC Wilmington.

Mason Collins, graduate student in marine biology at UNC Wilmington.

Where Do Southern Flounder Go in the Winter?

Southern Flounder move offshore to spawn, but their migration patterns might be more mysterious than we thought.

by Mason Collins, a graduate student in marine biology at UNCW, formerly with the South Carolina Department of Natural Resources and with the U.S. Forest Service in Alaska. 

Research Need

Working with other U.S. South Atlantic states, the N.C. Division of Marine Fisheries recently concluded that not only is the state’s southern flounder population overfished but also that overfishing is still occurring. The poor status of the stock requires considerable reductions in harvest to allow rebuilding.

Determining how much these fish mix across states will help to better understand the impacts of present and future fishing practices, informing strategies to rebuild and sustain the stock.

Adult southern flounder leave estuaries for the ocean during the fall and spend the winter in offshore habitats, where they presumably spawn. As waters warm in spring, flounder return to coastal and estuarine habitats, but conventional tagging data has shown that their return locations often are hundreds of miles away from their original tagging sites.

More recent studies of flounder genetics and chemical tracers indicate a well-connected flounder population throughout the South Atlantic. But how does this happen? Are flounder from Florida estuaries spawning in the same offshore locations as fish from North Carolina? Or are flounder merely wandering back inshore in different states?

What did we study?

We used pop-up satellite tags to estimate the offshore locations of southern flounder during the winter. In fall of 2020, we cooperated with fishermen to tag 100 fish captured at several inshore sites close to ocean inlets along the North Carolina coast.

We programmed the tags to pop off the fish on specific dates between mid-January and mid-March to cover most of the winter spawning period. Upon release, the tags floated to the surface and transmitted their locations via satellite.

What did we find?

Most southern flounder left the estuaries and went to the ocean. However, some fish remained in the estuary or stayed very close to the ocean shoreline. The absence of offshore movements by these fish could be related to stress from capture and tagging or could mean that individual southern flounder might not spawn every year.

The offshore movements of southern flounder were not as extensive as we expected, with many fish still using nearshore habitats during the winter. We did observe some fish near the outer edge of the shelf, in deeper waters, where past egg and larval collections suggest that spawning occurs. However, the offshore movements were generally straight off the North Carolina coast, as opposed to southward migrations that we expected, based on past tagging studies.

Results are still preliminary, with additional tagging planned for 2021 and 2022, but the early returns reveal a different picture of where southern flounder travel during the winter.

read the full studies and more at HookLineScience.com

lead photo courtesy of NC State University Photos


from the Autumn 2021 issue of Coastwatch