RED SNAPPER MANAGEMENT JUST GOT MORE COMPLICATED

 

Red snapper has long been one of the more contentious  issues in United States fisheries management.

In the Gulf of Mexico, an expanding red snapper population has attracted more anglers to the fishery, leading to chronic recreational overharvest, the threat of significant paybacks in some states, and militant industry and anglers’ rights organizations which seem willing to overthrow the federal fishery management system in order to put a few more dead fish on the dock.

In the South Atlantic, the population is also expanding, but is still at such a low level of abundance that bycatch in other fisheries is coming dangerously close to causing overfishing, so that the directed red snapper fishery, both recreational and commercial, has been nearly shut down.  Again, controversy prevails.

While anglers, commercial fishermen, for-hire operators, conservation advocates, and fishery managers have often been in stark disagreement about the size of red snapper stocks and how they ought to be managed, they were more or less in agreement on at least one thing:  There are two stocks of red snapper, one in the South Atlantic, one in the Gulf of Mexico.

Now, research recently presented to the South Atlantic Fishery Management Council has blurred that line, and strongly suggests that some red snapper spawned in the western Gulf of Mexico end up in South Atlantic waters, and enhance the South Atlantic population.

The presentation was based on work done by Dr. Mandy Karnauskas, et al, and presented in a paper titled “Source-sink recruitment of red snapper:  Connectivity between the Gulf of Mexico and Atlantic Ocean,” which was published in the journal Fisheries Oceanography earlier this year.  (As the paper explains, “source-sink” recruitment occurs when “recruitment of the sink population (or stock) is subsidized by larvae from the source population;” in this case, the Gulf stock of red snapper is subsidizing the South Atlantic stock.)

The researchers began with known red snapper spawning areas in the western Gulf of Mexico, and then applied models that predicted how particles (i.e., red snapper eggs and larvae) would be transported in the water column during the 26 to 30 days that pass between time when the eggs are produced and the time when the larvae settle onto the bottom.  By doing so, they determined that red snapper spawned in the Gulf of Mexico make a significant contribution to the South Atlantic stock, with the precise contribution differing from year to year.

As a result, as the abstract of the paper notes,

“effective management of the Gulf of Mexico red snapper stock, particularly the spawning population in southwest Florida, may have important consequences for the sustainable harvest of red snapper off the Atlantic coast.”

That adds another dimension to red snapper management, both in the Gulf and in the Atlantic.

In the Gulf, it means that managers can’t only be concerned with maintaining Gulf red snapper numbers.  

Right now, Gulf of Mexico red snapper—at least, those in United States waters—are managed as a single stock, whether those fish are located off Galveston, Texas or Destin, Florida.  The current goal of the fishery management plan is to increase spawning stock biomass until the spawning potential of the stock equals 26% of the spawning potential of an unfished population (26% spawning potential ratio, or “SPR”).

But if red snapper spawned in a particular part of the Gulf are also needed to bolster the stock in the South Atlantic region, then managing the entire Gulf under the same set of regulations might not produce the best possible results.  While the current targeted level of removals might make sense for red snapper caught off Texas or Louisiana—and probably off Mississippi and Alabama, too—because those fish spawn too far west to make an appreciable contribution to the South Atlantic stock, Florida red snapper may be an entirely different issue.

The study recently presented to the South Atlantic Council’s Scientific and Statistical Committee advised that larvae from red snapper that spawn on the West Florida Shelf, which is located offshore, south of Tampa Bay, makes a significant contribution to the South Atlantic stock, and may provide as much as one-third of the recruitment to that stock in some years.  In the recent past, severe overfishing had badly depleted the number of red snapper that populated, and spawned on, the West Florida Shelf, but as the overall Gulf of Mexico stock has rebuilt, the West Florida Shelf has become largely repopulated as well, a circumstance that has probably benefited red snapper in the South Atlantic region.

But given the importance of that area to the South Atlantic red snapper, and the lesser but still real contributions to the South Atlantic stock made by areas both north and south of the West Florida Shelf, does it make sense to keep managing Gulf of Mexico red snapper as a single stock?  

While all Gulf of Mexico red snapper are spawned somewhere within the Gulf (although larvae may be transported some distance from where they were spawned, while other populations are supported largely by local spawning), does the fact that many snapper spawned off the West Coast of Florida end up in the South Atlantic justify managing red snapper from Florida’s portion of the Gulf more conservatively than those caught off other Gulf states, because of their potential contribution to the South Atlantic stock?

And if the answer to that question is yes, then managers need to figure out just how to do so.

Then, there is the question of red snapper that spawn in the South Atlantic.

It appears that many of the red snapper off eastern Florida were spawned locally; the models disagree on whether the greater proportion of the snapper off Georgia and South Carolina are probably also of eastern Florida origin, or whether they were spawned locally, too.  The models seemed to suggest that red snapper spawning off North Carolina was strong enough to justify calling the area a spawning “hotspot,” although some of the models also suggested that larvae from eastern Florida, and perhaps even from the Gulf of Mexico, were settling off North Carolina in substantial numbers.

Given the significant percentage of South Atlantic red snapper recruitment that is attributable to fish spawned in the Gulf—somewhere between 11.0% and 34.5% of recruitment in any given year, depending on the ratio of egg production off western Florida compared to egg production in the Atlantic—can the South Atlantic stock be managed to a somewhat lower spawning potential ratio, given that some percentage of its recruitment comes from the Gulf, and is not affected by the South Atlantic stock’s SPR?

Or might the opposite be the case:  Because the South Atlantic stock is currently being subsidized by Gulf recruitment, should the target SPR of the South Atlantic red snapper be higher than it currently is, so that the stock might continue to support itself should the Gulf stock experience unforeseen recruitment issues?

Those are things for the biologists to decide.

Right now, the published study advises

“Our simulation results characterize the primary source and sink locations of red snapper recruits in the Eastern Gulf and Atlantic and can guide future monitoring of key areas of spawning stock biomass as well as likely areas of settlement to develop recruitment indices.  In the Atlantic, there is essentially no published information documenting the occurrence, distribution, and habitat preferences of red snapper juveniles.  Identifying red snapper probably settlement locations, as done here, is a critical first step toward developing surveys to generate recruitment indices, which could subsequently be incorporated into stock assessments.  Probably source populations in the Gulf have only recently been studied, and source-sink dynamics in the Atlantic were previously unstudied.  From a stock assessment perspective, substantial input of recruits from an external population would complicate detection of any spawner-recruit relationship…

“Our results also have implications for red snapper management, both among jurisdictions and within.  Given that productivity of the Atlantic stock seems to be significantly impacted by dynamics of recovery and exploitation in the southern extent of the West Florida Shelf, more insights into these patterns could improve management advice.  Recent research initiatives with improved monitoring in these areas may lead to additional insights into patterns of abundance and may improve predictions of recruitment subsidies in the region.  In the Atlantic, the center of biomass off the coast of Florida may be relatively robust to localized depletion, so long as it is subsidized by recruits from Southwest Florida.  The compact area of high red snapper biomass off the coast of North Carolina may be even less susceptible to localized depletion as it appears to be only a sink location; it receives substantial input from both East and West Florida centers of red snapper abundance…  [internal references omitted]”

Thus, the recently released study has opened the door on a new line of inquiry for red snapper managers.  By providing insights into the contribution of Gulf-spawned red snapper to the South Atlantic population, it has provided a foundation for additional research into the relationship between red snapper in the Gulf and the Atlantic, into new approaches to red snapper management, and into other areas germane to the health of the red snapper stocks.

At this point, there’s no way to be sure where such inquiries will lead.  Yet one thing seems certain—while red snapper management has never been easy, the new study will probably lead to a more complex, more nuanced sort of management, a sort never imagined by spokesmen for the anglers’ rights crowd, who mostly bang on the tables while seeking to take home more fish.