Study looks at cross-stocking striped bass in struggling N.C. fishery

By on November 12, 2014
Striped bass are launched from a stocking truck into a North Carolina waterway. (Credit: North Carolina Wildlife Resources Commission)

Years of concerted striped bass management in North Carolina’s Roanoke River and Albemarle Sound have built a thriving fishery that draws thousands of anglers a year. A recently published study takes a look at how the striper broodstock that played a role in that recovery have fared when stocked in other rivers in the state where the species continues to flounder.

According to the North Carolina Wildlife Resources Commission, the Roanoke/Albemarle striped bass population dropped as low as 195,000 fish by 1988. But that has since risen to closer to 1 million fish that lure anglers “from all over,” the commission says on its website.

“In the spring, it’s a huge deal,” said Jody Callihan, lead author of the study. “It’s just stacked with boats during the spawning season.”

But it’s a different story to the south in Pamlico Sound and its tributaries, where the striped bass population is a fraction of the size and the fish aren’t as large. The state stopped stocking Albemarle Sound in 1997 but continues to plant fish to enhance the fishery in the Tar-Pamlico and Neuse rivers, both of which flow into Pamlico Sound.

Until 2012, the fish stocked into the southern rivers were hatched from spawners in the Roanoke River to the north. Callihan’s study, published in the North American Journal of Fisheries Management, takes a look at how well the Roanoke River fish performed in the southern rivers based on angler catch reports of tagged fish.

A young striped bass with an internal anchor tag (Credit: North Carolina Wildlife Resources Commission)

A young striped bass with an internal anchor tag (Credit: North Carolina Wildlife Resources Commission)

Raising fish from one waterbody and planting them in another, known as cross-stocking, is a “rather controversial” practice for enhancing fish populations, according to Callihan, who did the research for the study as a post-doctoral researcher in the Department of Applied Ecology at North Carolina State University. There are reasons to believe that fish might not do as well in “non-natal” systems outside of their home range.

“The hypothesis would be that they would do the best in their natal system because that’s where they spend their juvenile life,” Callihan said. “They’re adapted to optimize growth in their natal system.”

But that’s not necessarily what happened here. The results show that the Roanoke River fish were growing just as fast, or even slightly faster, in the Pamlico Sound tributaries. But at the same time, they were disappearing more quickly, which the researchers interpret as a higher mortality rate. The researchers can’t say for certain why that is, but they ventured some guesses in the paper that Roanoke striped bass may encounter more marine predators in the Pamlico Sound system, which is more saline that the Roanoke River and Albemarle Sound, or experience higher fishing mortality in the southern rivers.

Striped bass swimming in the hatchery with tags carrying contact information. (Credit: North Carolina Wildlife Resources Commission)

Striped bass swimming in the hatchery with tags carrying contact information. (Credit: North Carolina Wildlife Resources Commission)

Since 2012, the state has switched from Roanoke River fish to the local broodstock for its stocking program in the Tar-Pamlico and Neuse rivers. This study could help serve as a baseline for further research into which stocking method works best in the system.

“After some years of data come in from that new method, we may be able to evaluate which one seems to be performing better and possibly why,” Callihan said. “The ‘why’ part is always the hardest part.”

Top image: Striped bass are launched from a stocking truck into a North Carolina waterway. (Credit: North Carolina Wildlife Resources Commission)

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