SCIENTISTS TAKE A SECOND LOOK AT STRIPED BASS

 

As the Atlantic States Marine Fisheries Commission’s Summer Meeting approaches, a lot of anglers are thinking about the declining striped bass stock, and wondering whether the Commission’s Atlantic Striped Bass Management Board will take any meaningful action to improve the fish’s prospects in the medium and long term.

The debate among anglers has, at times, been hot and heavy, and has not always been fully informed by the facts.  Thus, as the Summer Meeting draws near, we would all probably do well to look at some updated information recently provided by the scientists of the Striped Bass Technical Committee, which will be germane to the upcoming debate.

What happened in 2024?

When the Technical Committee finally had an opportunity to review final 2024 Marine Recreational Information Program data in May, they discovered that 2024 recreational effort was greater than previously thought.  That doesn’t mean that overall effort was high.  In fact, the number of directed striped bass trips taken in 2024 declined by 14 percent compared to the previous year, which is exactly what one would expect to see in a declining fishery that is providing fewer opportunities for anglers to encounter striped bass, since effort in the recreational striped bass fishery has always been driven by abundance.

Most of the increase in the effort estimate came from a revision of the Wave 6 (November/December) estimate for private boat trips in New York.  The preliminary estimate suggested that New York anglers took 442,911 directed striped bass trips during the last two months of 2024, an estimate that seemed surprisingly low, particularly given the good fishing that occurred off western Long Island and New York City during those months.  

The revised MRIP data indicates that the actual number of trips during November and December by New York anglers was closer to 845,711, a figure that seems in accord with observed fishing activity, and also in line with New York’s Wave 6 effort estimates for 2022 and 2023—1,090,000 trips and 867,384 trips, respectively.

The increase in New York’s Wave 6 private boat trips resulted in the landings estimate increasing by 29 percent, or 88,771 fish, and the release estiomate to increase by 34 percent, or 916,579 fish, out of which 82,492—9 percent—would be expected to succumb to release mortality

Despite their continuing complaints about the 1-fish bag limit in the Chesapeake Bay, and their alleged inability to book charters as a result, Maryland’s charter boats also saw an upward revision in their final effort, catch, and landings estimates for 2024. 

The revised effort numbers reveal that Maryland anglers took 48,645 directed for hire striped bass trips during Wave 3 (May/June), 28.4 percent more than originally believed.  That revised Wave 3 figure falls just slightly below the 2019-2023 range of 50,887-72,948 trips.  The final estimate of Maryland’s Wave 4 (July/August) 2024 for-hire trips increased by 64.1 percent over the preliminary number; at 56,560 directed striped bass trips, the revised Wave 4 effort fell well within the range of 47,356-69,316 trips taken during the years 2019-2023.  The same held true for Wave 5 (September/October), which saw the final estimate of directed for-hire striped bass trips increase by 43.3 percent, to 31,564, a number which fell neatly within the 20,900-50,845 trips taken between 2019 and 2023.

Thus, it appears that the charter boat operators’ claim that the 1-fish bag limit is leading to a marked decline in business is not supported by the effort numbers, and seems to be patently untrue.

But what is true is that the Maryland charter boats caught considerably more fish than previously believed, with the final landings estimate higher by 8,288 bass in Wave 3, 10,479 in Wave 4, and 9,480 in Wave 5—a total of 28,247 more dead bass than previously believed, while the final estimate of releases increased by 3,537 in Wave 3, 6,080 in Wave 4, and 11,168 in Wave 5, a total increase of 20,785 striped bass, of which about 1,870 would theoretically be lost to release mortality.

The increase in the New York and Maryland estimates, when combined with smaller (generally, less than 3 percent) revisions to the preliminary estimates in other states, resulted in 2024 striped bass removals being 7 percent greater than originally believed.  That increase in removals had a decided impact on the proposed Addendum III to Amendment 7 to the Interstate Fishery Management Plan for Atlantic Striped Bass, which will now have to include measures that will reduce fishing mortality by 12 percent, rather than 7 percent, in order to achieve a 50 percent probability of rebuilding the striped bass stock by 2029, as required by the management plan, or reduce fishing mortality by 18 percent, in order to achieve a 60 percent probability that timely rebuilding takes place.

Less-optimistic scenarios

The analysis which determined the reductions needed to timely rebuild the stock, at both the 50 percent and 60 percent probability levels, relied on assumptions that might or might not reflect future conditions, and ended with the stock probably being rebuilt in 2029, but with little thought to what happens after that.

However, the Management Board also asked the Technical Committee to consider a few other scenarios, even though they aren’t directly reflected in the proposed Addendum III.  Such scenarios include

·        1)  Analyzing what will happen after the 2029 rebuilding deadline, by constructing a stock trajectory going out to 2025;

·        2)  Assuming that future recruitment will resemble the last six years, when recruitment was the lowest on record, rather than merely the “low-recruitment scenario” that employs 2008-2023 recruitment values; and

·        3)  Assuming that fishing mortality for the period 2026-2029 will be somewhat higher than the low mortality of 2024.

The Technical Committee went out of its way to note that the last two scenarios slanted to the pessimistic side, saying that

“The [Technical Committee-Stock Assessment Subcommittee] noted that these Board-requested sensitivity runs are more pessimistic scenarios compared to the base run and do not encompass the possibility of more optimistic future scenarios.”

But that is as it should be.

There is always uncertainty in any stock assessment, rebuilding plan, or similar document, and the greatest risk is always on the downside.  That is, if an already overfished stock’s biomass is smaller than scientists believe, if recruitment is lower, or if fishing (or natural) mortality is higher, and managers set fishery management measures assuming that such factors are more favorable than they actually are, the overly liberal measures can push a depleted stock into future decline. 

It’s easy to argue that is what happened in 2014, when the explicit language of Amendment 6 to the Interstate Fishery Management Plan for Atlantic Striped Bass required the Management Board to initiate a 10-year rebuilding plan, yet Michael Waine, then the ASMFC’s Fishery Management Plan coordinator for the species, advised that

“The Board is acting to reduce [fishing mortality].  Through that action we see the projection showing that [spawning stock biomass] will start increasing towards its target, but we’re uncomfortable about projecting out far enough to tell you when it will reach its target because the further on the projections we go the more uncertainty that is involved.  Therefore, I think the trend is to get back towards the target, but we can’t tell you exactly how quickly that will happen.”

Even with the acknowledged uncertainty, the Management Board moved forward with Addendum IV to Amendment 6 to the Atlantic Striped Bass Interstate Fishery Management Plan, a document with slightly less than a 50 percent probability of reducing fishing mortality to target within one year, as required by the management plan.  Even with all of the future uncertainty surrounding rebuilding, the Board seemed comfortable that such less-than-bare-minimum measure would be sufficient to rebuild the spawning stock biomass to target, and so made it unnecessary to develop the required 10-year rebuilding plan.

Of course, we now know to our sorrow that the assumptions underlying Addendum VI were far too optimistic, and that the stock not only failed to rebuild, but declined farther.  

Thus, the argument can be made that inserting a strong dose of pessimism into the assumptions underlying management is a wise thing to do.  At worst, should such pessimism prove unjustified, the bass population should recover more quickly or become more abundant than it technically needs be, which are hardly dire problems.

Some might argue that undue pessimism, leading to unnecessarily strict regulations, might cause unnecessary economic distress to fishing-related businesses, but given the relative economic harm caused by each of the two possible alternatives—a brief decline in earnings caused by unnecessarily harsh regulations that lead to a healthy stock, or the long-term decline in profits caused by an overfished stock, depressed angler satisfaction, and perhaps even a stock collapse—taking a somewhat pessimistic stance would seem the wiser management approach.

At any rate, when the Technical Committee considered the three alternate scenarios, it recognized that they were all intimately interconnected, and so provided its analysis in a paragraph that included all three:

“The general findings of these sensitivity runs remain the same.  In the base run, [spawning stock biomass] continues to increase after 2029.  In the scenarios where recruitment is drawn from the very low recruitment regime, spawning stock biomass (SSB) will begin to decline after 2030 as the 2015 and 2018 year-classes continue to die off due to natural and fishing mortality and are replaced by the weak 2019-2024 year-classes.  In the moderate [fishing mortality] scenario (i.e., slightly increased [fishing mortality] from the base run), the probability of being at or above the SSB target in 2029 decreases, and the trajectory of SSB after 2029 depends on the recruitment scenario, with SSB continuing to increase after 2029 under the 2008-2023 recruitment regime and SSB declining after 2029 in the very low recruitment scenario.”

Thus, it quickly becomes clear that recruitment is the key to the striped bass’ future.  If recruitment improves a little bit, to 2008-2023 levels, the striped bass stock will probably remain at healthy biomass levels for a while.  On the other hand, should recruitment remain at current levels—and even a somewhat higher blip now and then such as, say, a Maryland juvenile abundance index of 6 or 8 every half-dozen years—we can expect the striped bass stock to decline, very possibly to the levels that we last experienced in the early 1980s.

Fishing mortality will probably only be a minor player in the outcome, perhaps delaying rebuilding if fishing mortality sees a modest increase over current levels.  Yet even if that happens, should recruitment improve, the stock will continue to rebuild.  But if very low recruitment remains chronic, higher fishing mortality will only accelerate the eventual crash.

So what should managers make of such advice?

The wisest course would be to embrace caution, and a big dose of pessimism.  The Board shouldn’t assume 2008-2023 recruitment levels until they see recruitment improve to such a “low recruitment” scenario.  Instead, the Board would be well advised to assume that current, very low recruitment levels will continue well into the future, and to change that assumption only after recruitment improves.

To assume anything else, particularly given the revised estimates of 2024 fishing mortality, can only put the bass’ future at risk.