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Learning from Summer Flounder's Successful Recovery

David Newman

Posted December 15, 2011 in Living Sustainably, Reviving the World's Oceans, Saving Wildlife and WIld Places

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Summer Flounder - NOAA Fisheries

There’s good news to report: a recent scientific assessment has confirmed that summer flounder, or fluke as it’s more commonly known, has been restored to a healthy population level after decades of overfishing.  The reasons for this success: disciplined restrictions on fishing in recent years, as required by the nation’s marine fisheries law, coupled with some fortunate biological conditions.  However, the same scientific assessment that confirmed fluke’s recovery also cautions that catch limits must not be ratcheted up too quickly, lest we’ll begin overfishing once again. 

Summer flounder’s lean, white meat and delicate flavor makes it a natural favorite.  It also conveniently summers close to shore making it an easier target for recreational anglers.  Fluke, like all flatfish, has evolved with two-eyes on one side of its head so it can swim along the seafloor.  Remarkably, they’re born with eyes symmetrically located on both sides, but then one eye migrates to the other side of the head by the juvenile stage.  Fluke’s chameleon-like skin allows it to literally change color to blend in with the seabed (check out this cool video).  This specialized physiology allows the carnivorous fish to lie undetected until an oblivious bluefish or shrimp swims into striking distance.

I remember fishing for fluke with my Grandpa Leo as a kid.  It was the early ‘80s and the fishing seemed great.  In fact, 1983 was a record year with nearly 60 million pounds of summer flounder hauled in.  But, the record catch belied the true condition of the stock.  As would soon become apparent, we were quite simply removing fish much faster than they could replenish themselves.

Average annual catch from 1982 to 1988 was over 48 million pounds, well above the overfishing level.  These unsustainably high catch levels were the result of significant increases in fishing effort (i.e., more boats and more fishermen pursuing a dwindling number of fish) and an expansion of the commercial trawl fishery targeting fluke’s winter spawning grounds.  In 1988, fishery managers established the first federal plan for summer flounder, including requiring a modest increase in the minimum size of fish permitted to be landed.  But by 1989, summer flounder biomass had plummeted to just 12% of a healthy population.  And a year later, fishermen were catching about one-third of what they were hauling in seven years before.

Clearly something needed to be done.  The first step toward recovery, albeit modest, came in 1993 with the establishment of “soft” (i.e., non-binding) fishing mortality targets and associated catch levels.  Two years later, a formal rebuilding plan was established with a deadline of a rebuilt population by 2005.  Despite these steps, the actual fishing mortality rate continued to exceed the sustainable rate by 4 to 7 times.

The rebuilding plan was again amended in 1999, extending the deadline to 2010.  However, that same year, fisheries managers decided to set a catch level with a mere 18% chance of success in ending overfishing.  NRDC, EDF, National Audubon Society and the Center for Marine Conservation (now the Ocean Conservancy) took the National Marine Fisheries Service to court.  In 2000, the D.C. Circuit Court of Appeals found in our favor, writing:

"Only in Superman Comics’ Bizarro world, where reality is turned upside down, could the [Fisheries] Service reasonably conclude that a measure that is at least four times as likely to fail as to succeed offers a ‘fairly high level of confidence’” of preventing overfishing.

For a couple of years, catch was reduced to acceptable levels.  But it didn’t last.  Fishery managers significantly ratcheted up catch levels and by 2005-2006 progress toward rebuilding had once again stalled.  Catch needed to be cut back again for 2007 and 2008, but these efforts finally did the trick, and, helped by a particularly large number of young fish in recent years, population levels have been on the increase ever since. 

In October, after decades of depletion, the government announced that the species has finally rebuilt.  But, the October assessment told a cautionary tale as well.  The rebuilding had happened, for sure, but not to the extent projected a year earlier.  The new estimate, based on the most recent year of data, shows the population is at 100% of the target instead of 123%.  Unfortunately, this new information became available only after the Mid-Atlantic Fisheries Management Council and Atlantic States Marine Fisheries Commission had recommended increasing the catch limit for next year based on the older, more optimistic population estimate.  In response, they’ve now prudently decided to pull back from the large increase to ensure the population does not begin declining once again.     

These fluctuations cause understandable frustration and confusion among the public, but can be avoided if we heed some of the lessons of recent history.  Obviously, it would be good for the Council to be able to get the most updated data before it votes on catch limits.  But, more importantly, the Council must set catch with greater precaution to account for the expected uncertainties of scientific modeling. 

We all know that anything uncertain merits precaution.  Take your family’s budget as an example.  You try to account for all anticipated costs, but inevitably something unexpected pops up – maybe the car needs new brakes – and all of the sudden you need a little flexibility to buffer the shock of overshooting your budget.  Fisheries management is similar.  Every year, we set catch limits that are akin to a budget comprised of the amount of fish that a specific population can provide on an ongoing basis.  The goal is to live off the interest and not eat into the principal.  But, because we can’t literally count the exact number of fish in the sea, we base catch limits on scientific estimates, called stock assessments.  These assessments model population sizes based on the number, size, and age of fish being caught relative to the amount of effort fishermen make, independent surveys that count samples of fish from the same spots year after year, and our understanding of the life history characteristics of the species and ecosystems in which they live.  Yet, no matter how robust the data and sophisticated the calculations used to derive the resulting population estimates, there is inevitably some degree of error, or uncertainty, which must be buffered against.

This scientific uncertainty must be taken into account when setting catch limits to ensure that overfishing doesn’t occur and to help cushion the management response if it does.  Unfortunately, managers have not adequately taken this into account when setting catch limits for summer flounder over the past decade.  With every bit of good news – such as a survey indicating an abundant “year class” of juvenile fish – fisheries managers have set catch limits too close to the line of the projected population, only to have to cut catch when new information shows the population is not growing quite as quickly as thought. 

Fortunately, Congress understood this when it amended the law in 2006 requiring precautionary buffers that account for scientific uncertainty.  These provisions are just now being implemented, along with a push for more timely stock assessments.  These changes will make fishing more predictable and sustainable.  And, hopefully, with continued sound management, I’ll be able to take my two-year-old son fishing for jumbo fluke someday, and actually catch some.    

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Switchboard is the staff blog of the Natural Resources Defense Council, the nation’s most effective environmental group. For more about our work, including in-depth policy documents, action alerts and ways you can contribute, visit NRDC.org.

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