Sunday, November 8, 2015
WHAT'S GOING ON WITH STRIPED BASS?
There has been a lot of chatter about striped bass this fall.
Depending on where you fish, the fall run is either peaking or past, and folks are trying to figure out why they either did or didn’t do as well as they'd hoped.
Some places saw a lot of small fish, some are still seeing some large ones. Everywhere, anglers are trying to figure out what it all means.
On the management side, Maryland young-of-the-year numbers and a stock assessment update provide reason to hope, while maneuvering at last week’s meeting of the Atlantic States Marine Fisheries Commission’s Striped Bass Management Board are making some anglers wonder whether it’s time to prepare to do battle all over again.
There has been chatter, but just what does It mean?
It’s probably best to begin with the numbers, because they provide a reasonably objective place to start.
Over the long term, one of the most reliable indicators of the future health of the striped bass stock has been the Maryland Young-of-the-Year index, which provides an unbroken time series, recording spawning success in Maryland’s waters, dating back to 1957 (actually, to 1954, but the spreadsheet provided on line by the Maryland Department of Natural Resources doesn’t include the first three years).
Recent years have seen a spate of below-average spawns, but the 2015 index, at 24.2, more than double the long-term average of 11.9. That’s reasonably good news, particularly when the 2015 index is coupled with the 2011 index of 34.58, a strong spawn that produced a lot of the roughly five-pound shorts that have been swarming off parts of Long Island and elsewhere.
The best spawn on record occurred in 1996, when the index hit 59.39, five times the long-term average. On the other hand, a bad year can’t fall below zero, which thankfully has never happened, although 2012, at 0.89, came pretty close. Thus, one really good year can make up for a few really bad ones.
To put things in some kind of context, the average for the ten years ending in 2015 was 11.07, a little below the longer-term average and an indication that, despite the strong 2011 and 2015 year classes, striped bass aren’t doing as well as they have at some points in the past. The average young-of-the-year index for the decade ending in 2005 was 22.38, twice the average for the current decade and nearly twice the long-term average.
Thus, no one should expect fishing in 2020 to be as good as it was in 2010—when it was already beginning to slide downhill.
On the other hand, things could be a lot worse. The average young-of-the-year number for the ten years ending in 1985 was just 4.26, less than half of the average for the last ten years. That's reason enough to tell folks who say that we’re on the verge of another collapse to stop overreacting.
From a historic standpoint, we’re more or less in the middle, with bass likely to be somewhat less abundant than normal for the next five or six years, but still far from the low numbers of the 1980s.
Recent stock assessment also seem to provide some reason for optimism, but need to be read closely.
Back in 2013, ASMFC issued the Update of the Striped Bass Stock Assessment Using Final 2012 Data. Using the scenario that most closely resembles what actually happened so far, it predicts that
“If the current fully-recruited [fishing mortality] (0.200) is maintained during 2013-2017, the probability of being below the [spawning stock biomass] reference point increases to 0.86 by 2015. After 2016, the probability is expected to decline slightly.”
An 86% chance that the striped bass stock would become overfished this season could only be seen as bad news.
However, at the recent meeting of ASMFC’s Striped Bass Management Board, the Striped Bass Technical Committee presented the Atlantic Striped Bass Stock Assessment Update 2015, which incorporated data through 2014. The newest update presented better news, projecting that
“If the constant catch of 3,402,641 fish [the estimated 2015 harvest plus the average commercial discards for the period 2010-2014] was maintained during 2015-2017, the probability of being below the [spawning stock biomass] threshold increases to 0.49 by 2015. After 2015, the probability is expected to decline slightly…”
A quick comparison would give the impression that managers are becoming more optimistic, and have reduced the likelihood of the stock becoming overfished this year from 86% to 49%.
However, first impressions can be misleading.
The 2013 update, employing 2012 data, assumed a constant fishing mortality rate of 0.200. The 2015 update, employing 2014 data, assumed a constant catch rate of about 3.4 million fish. Those are two very different approaches, that could yield very different results.
A constant fishing mortality rate assumes that the same percentage of the fish population will be removed in any given year. Thus, if the fish population is declining, a constant fishing mortality rate would result in fewer fish being landed, while if the population is increasing, applying the same rate would result in a larger harvest.
A constant catch rate, on the other hand, would result in a higher fishing mortality rate when the population is declining, and a lower fishing mortality rate when abundance increases.
Thus, it is difficult to compare the two projections. It's probably best to remain skeptical of both and wait for the next benchmark assessment, currently scheduled for 2017, to be performed.
Unfortunately, there are folks trying to jump the gun, and that’s where the real danger lies.
Relying on the 2015 young-of-the-year numbers and the seemingly more optimistic 2015 update, and apparently motivated by the complaints of some stakeholders that they were being adversely affected by the more restrictive regulations that went into effect this year, Striped Bass Management Board members from Maryland and Virginia recently attempted to undo some of the conservation measures mandated by Addendum IV to Addendum 6 to the Striped Bass Interstate Fishery Management Plan.
They made a motion to begin a new addendum to the management plan that would do just that. The motion was tabled until the February ASMFC meeting, not voted down, so there is always the chance that it will be considered again.
As a substitute action, the Management Board agreed that another update to the stock assessment would be prepared after the 2015 season, to determine what the impact of the first year of harvest reductions actually was.
It will be valuable to know whether the new regulations managed to keep landings within the F=0.180 target this year, and whether the spawning stock biomass remained above the overfishing threshold, so such action, standing alone, is not a bad thing.
However, anglers concerned with the long-term future of the striped bass will have to be vigilant, lest representatives from the Chesapeake Bay jurisdictions, perhaps joined by the usual suspects from New Jersey and Delaware who gave them some support at the last meeting, will try to use any such update to expand harvest while striped bass abundance remains a long way below target.
Back in November 2011, the Striped Bass Management Board was on the verge of releasing a proposed addendum that would reduce striped bass harvest in response to the clear decline in the spawning stock biomass. However, because the situation had not yet gotten bad enough to trip triggers built into the management plan, the Management Board decided to take no action on the harvest reductions untilafter the benchmark assessment, scheduled for 2012, was completed.
It would be hypocritical if the Management Board, having made that decision, now took any action to increase harvest prior to the benchmark assessment scheduled for 2017.
If the Management Board can decide that there is no urgency to decrease landings in the face of a clear decline in abundance until a benchmark assessment is completed, it certainly should remain consistent and refuse to increase landings when indicators such as a young-of-the-year index suggests that the female spawning stock biomass may increase at some point in the future—if the recently-spawned bass survive long enough to recruit into the SSB.
So what’s going on with striped bass?
The same thing as always, with some folks trying to conserve them, and others pushing hard to increase their kill.
Right now, the good folks are winning. While bass aren’t abundant, they’re also not overfished. A couple of good year classes hold out hope that there still will be some fish around in the future.
At the same time, striped bass are far from abundant. And there are plenty of people out there who would render them less abundant still, should we fail to keep up our guard.