It's Not Overfishing, It's the Weather

Says a new model that predicts decreased striped bass recruitment for the next 30 or so years...

So, according to the Bay Foundation, the Health of the  Bay is improving (slightly).  And reportedly the favorable weather this year is the reason.  But striped bass recruitment this year was less than half of the long term average. What's going on?

While Martino crunched numbers in his office, a team of biologists from the Maryland Department of Natural Resources waded into the water at 22 locations once a month from July through September. At each site, they did two sweeps through the water with a 100-foot seine net, then counted everything they caught.

When the work was done, the biologists had averaged 5.6 juvenile striped bass per net haul. That was less than half the long-term average of 11.6. After all of their field work, they had reached the same conclusion as Martino.

Well, maybe "good weather" for the bay is not "good weather" for striped bass.

...His model, which was developed with data from the Maryland DNR, confirms what biologists have thought for years: The weather during any given spring plays a huge role in determining how many larval striped bass survive to be "recruited" into the overall population. But his model puts an exclamation point to just how important weather is: In looking back to 1985, he can account for more than 80 percent of the annual variability in striped bass recruitment in Maryland, where the majority of the East Coast population is spawned. ...."The Bay is full of spawners, but we are seeing a real reduction in recent years in reproduction," Martino said. "So I think it's pretty obvious that something else is going on in the environment." ..

A good year here, a bad year there, it all averages out in the long run, right?  I guess that depends on what you mean by long term.  But it looks like the current trend in low recruitment could go on a while:

...The Atlantic Multidecadal Oscillation is an alternating pattern of warming and cooling over large areas of the Atlantic Ocean, similar to the El Nino, La Nina patterns in the Pacific. The shifts, in turn, affect climate over large regions of North America. Various AMO phases, during which different parts of the Atlantic are warmed or cooled, persist for decades.

During certain AMO phases, which promote wetter winters, cool springs and more frequent nor'easters, the prevailing climate pattern seems to promote improved reproductive success for anadromous fish, such as striped bass, which live most of their lives at sea but return to freshwater to spawn.

  But it's OK, because our fisheries management are on top of the problem.

Striped bass crashed because of overfishing in the 1980s, which was also a time when the AMO was in a phase unfavorable for their recruitment, so fish being caught were not being replaced. The ensuing rebound of striped bass stocks is often touted as a major fishery management success as managers took dramatic actions, including a coastwide moratorium, to protect the spawning stock. And it was. But Wood's work strongly suggests that managers also got lucky - their fishing moratorium coincided with an AMO shift that greatly improved striped bass spawning conditions. "Had the weather not turned, we would have been waiting longer for that recovery," he said.

 Well, it's OK to be lucky, but it's better to be right.

Because of concerns about the population, the Atlantic States Marine Fisheries Commission, a multi-state agency that regulates catches of fish that migrate along the coast, recently decided to assess the striped bass stock next year, rather than 2012 as previously scheduled.

A lot of this is a reinforcement of a hypothesis that fisheries people have discussed for years, with new jargon like AMO thrown in to make it sound more official.  But it does suggest that the Bay is likely to change in the next few years to a new mode, which may be friendlier to some facets of the bay, but are unfriendlier to on of the the great fisheries targets.  We can only hope the ASMFC get this one right.  It would be stupid to keep hammering stripers at the current rates if we expect a long term decrease in their success due to climate shifts.