Thursday, October 20, 2016


Maryland released its annual Juvenile Abundance Index for striped bass a few days ago, and the news isn’t good.

To put that in context, the long-term average is 11.7.  When the Atlantic States Marine Fisheries Commission began recovering the collapsed striped bass stock in the 1980s, it determined that a three-year rolling average of 8.0 would signal that the stock had begun to recover.

So 2.2 is pretty bad.

Still, the Maryland Department of Natural Resources correctly notes that a single year’s index provides no reason to worry.  It issued a reassuring statement which said

“While this year’s striped bass index is disappointing, it is not a concern unless we observe poor spawning in multiple, consecutive years.  Very successful spawning years, as recently as 2011 and 2015, should more than compensate for this below-average year class.  Nonetheless, the department and our partners will continue to work to maintain a sustainable fishery for our commercial watermen and recreational anglers.”
That sounds fine.  But if we remove the word “consecutive” from the Maryland Department of Natural Resources’ statement, and take a broader look at striped bass abundance, does the poor 2016 figure give cause for concern?

While there were dominant year classes in 2011 and 2015, the worst spawn ever recorded in the 62-year history of the Maryland young-of-the-year survey, 0.89, occurred just four years ago.  Other than that record-low year, you have to go back to 1990, when the collapsed striped bass stock was still struggling to rebuild, to find a spawn that was worse.

Still, it’s true that some good year classes can make up for the bad ones, so it’s worthwhile to take a look at some recent averages to see where we might stand today.

The 3-year average is now 12.47, a bit above the long-term figure.

That’s good.

One the other hand, the 5-year average, which captures the terrible 2012 spawn but not the dominant 2011 year class, is a mere 8.81. 

An average of the last 10 years captures both the two worst and two best recent year classess, and returns a figure of 10.87, which remains below the long-term average, but not by very much.

Thus, if we look at the averages alone, it would appear that the Maryland DNR is right.  The poor 2016 spawn is largely offset by more successful spawns in other years.

On the other hand, to determine the trajectory of the stock, and figure out whether abundance is increasing or decreasing over time, you need to look at trends

They tell a somewhat different tale.

The long-term average reaches back six decades.  During most of those years, striped bass were hardly regulated at all, and overfishing was tolerated whenever and wherever it occurred.  The long-term average also includes the spawning stock collapse of the 1970s and early 1980s, when rebuilding had not yet begun.

A medium-term average that includes only the modern era of striped bass management, the years after the stock had been declared rebuilt in 1995, would yield a figure of 16.41, significantly higher than the long-term average, and well above the averages for the most recent 3, 5 and 10-year periods.

Even if the starting point for such medium-term average was moved back to 1986, when the ASMFC’s Striped Bass Management Board adopted Amendment 3 to the management plan and began the stock’s rebuilding, such average, at 15.31, would still remain notably  higher than the long-term average and the most recent 3-year, 5-year and 10-year averages.

Thus, despite having the large 2011 and 2015 year classes included in the mix, the last 10 years of striped bass reproduction, when viewed through the lens of the past three decades, have not been particularly good.

In fact, the average for the past 10 years, 10.87, is the third-lowest average for any 10-year period beginning on or after 1986.  The only two 10-year intervals that returned lower averages were 2004-2013, when the juvenile abundance index averaged 10.47, and 2005-2014, when the index averaged 10.55.

It’s probably significant that all three of the worst 10-year intervals in the past thirty years ended within the past four years.

In contrast, the best 10-year intervals since 1986 included 1992-2001, when the juvenile abundance index averaged 23.69, and 1996-2005, when it averaged 22.24, more than twice the current 10-year average and ten times the 2016 level.

Even the average for the rebuilding period following the collapse, 1986-1995, was 11.76, about equal to the long-term average and somewhat higher than the average for 2007-2016. 

Viewed against that background, the current state of striped bass reproduction doesn’t look all that good.

Another factor also comes into play.

Unfortunately, springs seem to be getting warmer.

Unless there is a drastic, and completely unlikely, change in global weather patterns during the last two months of the year, 2016 will be the warmest year ever recorded.  Even taking 2016 out of the equation, the five warmest years on record occurred in 2015, 2014, 2010, 2013 and 2005.

That’s a trend that doesn’t bode well for striped bass spawning success in the long term.

In the short term, things look somewhat better.

The 2011 year class will begin recruiting into the coastal fishery next season, so anglers that have already been catching a lot of undersized 2011s will now be able to take a bass or two home.  In the Chesapeake, the 2015s will also start appearing in fishermen’s catches, although virtually all of them will probably have to be returned to the water.

So long as harvest remains at 2015 levels, it is unlikely that the stock will become overfished in the next few years.

The danger is that the abundance of smaller fish will lead to further calls to relax the regulations imposed last year, pursuant to Addendum IV to Amendment 6 of the Atlantic Striped Bass Interstate Fishery Management Plan

Hopefully, no such calls will be heard, for the 2016 update to the most recent benchmark stock assessment has already stated that, at current harvest levels, there is only the slimmest possibility of the female spawning stock biomass returning to target abundance by 2018.  The small 2016 year class is certain to further slow the recovery of the stock, even if landings remain unchanged.

Increased landings would make recovery even less likely, and increase the possibility that the female spawning stock, already just slightly above the overfishing threshold, would decline enough to fall below that critical reference point.

Thus, all eyes should be on ASMFC’s Striped Bass Management Board when it meets next week, and all anglers concerned with the health of the striped bass stock should stand ready to challenge any rash effort, however unlikely, to increase the kill.

No comments:

Post a Comment