North Carolina Sea Grant
Hook, Line & Science

Hook, Line & Science

March 9, 2020 | Dave Shaw

New modeling suggests why the species hasn’t recovered in the Neuse River.

Researchers at North Carolina Sea Grant and NC State University are collaborating with experts along the Atlantic Seaboard on a new aquaculture project to strengthen the domestic seafood industry: “StriperHub.” Members of the research team will be at the North Carolina Aquaculture Development Conference, which will convene March 12 to 14 in New Bern, to plan for StriperHub’s next stages.

Striped bass have experienced major declines due to overharvesting, water quality degradation, and barriers to reaching spawning habitat. There is little insight, however, as to why some coastal populations of striped bass have yet to rebound despite recovery efforts.

Research Need

Restoration efforts have been successful for specific stocks of striped bass but not all. For example, the fish population in the Neuse River of North Carolina hasn’t recovered despite nearly two decades of reduced harvests, stock enhancement programs, and removal of a dam that had restricted access to the species’ historical spawning grounds.

Low overall population, fewer fish at older ages, and limited younger fish from natural in-river spawning, all are most likely attributable to fishing and environmental causes. Scientists wanted to identify what has kept the Neuse River striped bass population from bouncing back.

What did they study?

Researchers used data from North Carolina resource management agencies on the mortality of wild and hatchery-reared striped bass to develop a predictive population model for the Neuse River. The researchers ran simulations under different scenarios, such as whether the number of fish stocked doubled or if all recreational and commercial harvests were eliminated.

What did they find?

The baseline model predicted few striped bass over age 9, which is consistent with field observations, with a total estimated adult population at a mere 18,457 fish. For context: the state stocked about 125,000 juvenile striped bass in the lower Neuse River annually from 1994 to 2014.

Not surprisingly, eliminating all fishing mortality would have the greatest impact on the population, resulting in a 26-fold increase in older adult fish. The study shows that increasing the number of older and more fertile fish in the Neuse River population may be a prerequisite for successfully building up the numbers of young fish of reproductive ages.

Anything else?

The population model shows that the abundances of adults (age 3+) and older adults (age 6+) were most affected by the natural mortality of juveniles and adults, and, next, by commercial harvest and discard. Doubling the number of fish stocked, however, would have little affect on the number of older adult fish.

Reading

Bradley, C.E., Peterson, Rice, J.A., and D.D. Aday. 2019. “Modeling the Effects of Vital Rate Manipulation and Management Scenarios to Predict the Population Impact of Restoration Programs on an Unrecovered Coastal Population of Striped Bass.” North American Journal of Fisheries Management. 38:639–649.

The N.C. Wildlife Resource Commission’s Federal Aid in Sport Fish Restoration Grant F-100-R funded this project.

Summary compiled by Sara Mirabilio
Above photo courtesy of Coley Hughes/Sea Grant

The text from Hook, Line & Science is available to reprint and republish, but only in its entirety and with this attribution: Hook, Line & Science, courtesy of Scott Baker and Sara Mirabilio, North Carolina Sea Grant. HookLineScience.com

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