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