NORTH CAROLINA'S STRIPED BASS: A TASTE OF BIGGER THINGS TO COME?

 

North Carolina’s striped bass are not doing well.  More particularly, what is known as the Albemarle-Roanoke stock—fish originating in the Albemarle Sound and Roanoke River—seem to be in real trouble.  The have experienced spawning failure in every year between 2017 and 2022, with 2023 likely to add another failure to the list.  Spawning stock biomass has crashed, and fishing mortality is far above the threshold level.

Yet fishing isn’t the only threat to the stock.  River flows have often been too high during the spawning period, scattering eggs into backwaters and flood plains where the chances of survival are close to nil.  And blue catfish may also be impacting recruitment, either through predation or, perhaps, competition for resources.

State fishery managers are trying to figure out how to turn the situation around; they have already resorted to releasing hatchery-raised fish into the affected waters, although they would prefer to see a recovery based on naturally spawned striped bass.

The question that we may want to ask is whether the current state of the Albemarle-Roanoke stock foretells the fate of striped bass along the greater Atlantic seaboard.

While the Albemarle-Roanoke stock falls within the Atlantic States Marine Fisheries Commission’s Interstate Fishery Management Plan for Atlantic Striped Bass, it is managed separately from the coastal migratory stock; the ASMFC has ceded management of the Albemarle-Roanoke fish to North Carolina.  The relationship between the Albemarle-Roanoke bass and the migratory fish is similarly ambiguous, with the 2018 benchmark stock assessment noting that

“Historically, tagging data indicated very little mixing between the Albemarle Sound/Roanoke River stock and the coastal population…However, recent tagging work indicates that most large [Albemarle-Roanoke] striped bass (<800 mm [total length]) are indeed migratory.”

Still, the contribution of that stock to the coastal population is so small, when compared to that of the Chesapeake Bay and the Hudson and Delaware rivers, that its impact on the health of the coastal stock is negligible.  Even so, it is possible that the trajectory of the Albemarle-Roanoke stock may provide managers with a foretaste of the coastal stock’s future.

Much like the coastal stock, the Albemarle-Roanoke bass experienced poor juvenile abundance from the late 1970s through the 1980s.  Like the coastal stock, the Albemarle-Roanoke population also saw juvenile abundance spike between the mid-1990s and mid-2000s.  And like the coastal stock, the Albemarle-Roanoke stockh as seen juvenile abundance crash again in the past few years.

The peaks and the nadirs of juvenile abundance for the two stocks don’t correspond precisely.  In the Albemarle-Roanoke region, the dearth of juveniles extended much farther into the 1980s.  A big year class was produced in 2005, as opposed to 2003 on the coast.  Both stocks saw strong year classes produced in 2011 and 2015, but spawning began to fail in 2017 for the North Carolina fish, as opposed to 2019 in the Maryland portion of the Chesapeake Bay.

There are also notable differences in the two stocks’ declines.  In the Chesapeake Bay, poor spawns are associated with low water flows, resulting from warm winters and warm, dry springs.  In the Albemarle-Roanoke region, spawning failures have been attributed to flooding rivers although some recent years,  despite very favorable conditions in the rivers, spawning failure nonetheless occurred, a fact that is troubling North Carolina fishery managers.

Overfishing also remains a real issue for the Albemarle-Roanoke stock; it has occurred in 19 out of the last 21 years, with only 2003 and 2008 seeing fishing mortality fall below the threshold level.  The fishing mortality rate exceeded 1.00 in 2020 and was about 0.75 in 2021; both figures were very far above the overfishing threshold of F=0.20.  On the coast, overfishing persisted for all but two years between 2002 and 2019, but ended with the implementation of Addendum VI to Amendment 6 to the Atlantic Striped Bass Interstate Fishery Management Plan in 2020; even when such overfishing was at its worst, the fishing mortality rate never rose above 0.40, and so was nowhere near as severe as what is currently being experienced by the Albemarle-Roanoke stock.

Thus, the status of the Albemarle-Roanoke stock, and the problems which beset it, do not perfectly parallel that of the coastal striped bass population.  The current condition of the Albemarle-Roanoke bass is far more dire.

Responses by North Carolina fishery managers have been correspondingly severe.

The total allowable landings for the Albemarle-Roanoke stock had slowly ramped up from 156,800 pounds during most of the 1990s to a high of 550,000 pounds from 2003 through 2014, tracking an increase in striped bass abundance.  However, as stock status deteriorated, that trend was reversed, with the TAL cut in half, to 275,000 pounds, for the period 2015-2020, then slashed again, to 51,216 pounds, where it stands today.  Beginning next year, the TAL will fall to a mere 8,349 pounds, an amount so small that landings cannot be effectively regulated.  For that reason, the North Carolina Division of Marine Fisheries, in accord with its striped bass management plan, will institute a moratorium on harvest, beginning in 2024.

The Division of Marine Fisheries has also initiated a striped bass stocking program, in an effort to halt, and hopefully reverse, the decline in the spawning stock.

Could the coastal stock find itself in a similar situation?

It’s not impossible, although the coastal stock still enjoys some advantages not enjoyed by the Albemarle-Roanoke fish.  Perhaps most important, the coastal stock is not experiencing overfishing, so fishing mortality alone should not cause a stock decline.  Also, the coastal stock enjoys the benefits of three discrete spawning areas—the Hudson River the Delaware River, and the Chesapeake Bay—which means that even if spawning conditions are unfavorable in one region, they may be better elsewhere.  We are seeing that situation play out with spawning failure in the Maryland portion of the Chesapeake Bay, and poor spawning success in the Delaware River and the Virginia portion of the Chesapeake Bay in both 2021 and 2022, while the Hudson River produced a strong year class in 2020 and reasonably successful spawns in 2021 and 2022.

Even so, unless the Maryland juvenile abundance index begins to show some improvement, the Hudson River will not be able to support the entire coastal stock on its own.  The average Maryland JAI for the past five years is only 2.74, the lowest 5-year average in the history of the Maryland juvenile abundance survey.  Even during the heart of the last stock collapse, no five-year average ever fell below 3.45.  If that trend continues, the coastal stock could well collapse again, and drastically reduced landings—perhaps even a harvest moratorium—might be needed in order to rebuild the stock.

So, if the state of the Albemarle-Roanoke stock might serve as a warning of where the coastal stock could be headed if low recruitment and high fishing mortality combine to deplete population, the decisive action taken by the North Carolina Division of Marine Fisheries stands as an example of how the Management Board must act should the coastal stock approach a collapse.

Hopefully, the Management Board will prove just as resolute, for hesitation, half-measures, and indecisive action can, no less than overfishing and poor recruitment, lead to a collapse of the stock.