STRIPED BASS ASSESSMENT UPDATE: SOME ADVICE, BUT SUBSTANTIAL UNCERTAINTY

 

The 2024 update to the 2018 benchmark striped bass stock assessment has been released.  It offers some guidance on the status and trajectory of the striped bass stock, but is clouded with substantial, if unavoidable, uncertainty.

The clear guidance is presented in the Executive Summary, which states, in part:

“…Total removals from 2022-2023 averaged 6.18 million fish, a 20% increase from 2021, the terminal year of the last assessment.  From 2022-2023, recreational release mortality made up 40% of total removals, with recreational harvest making up 49%, commercial harvest making up 10%, and commercial discards making up 0.5% of the total.  This is a change from 2018-2021, where recreational release mortality made up 50% of total removals and recreational harvest accounted for 37%...

“Because the recruitment trigger in Amendment 7 was tripped based on 2021-2023 data for the New Jersey, Maryland, and Virginia abundance indices, the biological reference points were calculated using the low recruitment regime assumption.  This resulted in a lower F target and F threshold compared to the benchmark assessment.

“In 2023, the Atlantic striped bass stock was overfished.  Fishing mortality was above the F target, but below the F threshold, indicating overfishing was not occurring…Total fishing mortality in 2023 was estimated at 0.18 which is below the updated F threshold of 0.21 per year, but above the updated F target of 0.17 per year.  Although the stock is not experiencing overfishing, these results trip the F target trigger in Amendment 7 since F has exceeded the F target for two consecutive years while [Spawning Stock Biomass] is below the SSB target…

“Projections were run to determine the probability of SSB being at or above the SSB target by 2029, the rebuilding deadline.  If F is reduced to the F target by 2025, and F target is maintained through 2029, there is less than a 5% chance that the stock will be rebuilt by 2029.  [emphasis added]”

So a few things are clear.

With the movement of the 2015s into the slot limit, anglers are taking home more striped bass, and recreational harvest, rather than release mortality, is now the predominant cause of fishing mortality.  In fact, over the past two years, the impact of the two sources of mortality have switched places since the last stock assessment update.  

Recreational release mortality’s contribution to overall fishing mortality has fallen from 50 percent in the 2022 update to 40 percent in the most recent document, while recreational harvest’s contribution has increased from 37 percent in the earlier update to 49 percent in recent years.  

Given such changes in the impact of the two major contributors to fishing mortality, it will be interesting to see whether the Atlantic Striped Bass Management Board’s focus on reducing fishing mortality, as opposed to reducing all sources of striped bass fishing mortality, will abate to any degree.

The various indicators used to gauge the health of the striped bass stock are all pointed in the wrong direction.  The stock remains overfished.  The recruitment trigger, newly added to the management plan by Amendment 7, has been tripped not just by three consecutive years of unusually poor recruitment in a single key region, but by such extremely sub-par recruitment in three of the four major spawning areas. 

And while the striped bass stock is not experiencing overfishing, fishing mortality has risen high enough, for a long enough time, to trip another management trigger, which requires the Management Board to reduce fishing mortality to the target level within one year.

Given that fishing mortality is only marginally above the fishing mortality target, that should be easy to do.  However, even if the Management Board puts such reduction in place, there is no realistic chance that fishing at the target fishing mortality rate will rebuild the stock by the 2029 deadline.  

Further action is needed.

But just what that further action might be isn’t clear.  That’s where the uncertainty comes in.

“The F rate necessary to have a 50% chance of being above the SSB target by 2029 (F_rebuild) depends on the extent of the reductions realized by Addendum II, implemented in 2024.  The [Technical Committee] initially predicted that Add. II measures would result in a 13.7% reduction in total removals relative to 2022, equivalent to 5.86 million fish…In this scenario, F in 2024 is estimated to be 0.20, while F_rebuild=0.11 for 2025 onward.  To achieve F_rebuild in 2025, total removals would have to be reduced to 3.46 million fish, a 46% reduction from the predicted removals in 2024.  However, the preliminary MRIP numbers for 2024 Waves 2-3 are 36% lower than the Waves 2-3 numbers for 2023.  Expanding the preliminary 2024 Waves 2-3 estimates to the full year, based on the proportion of total landings that occurred in those waves in earlier years, and accounting for a 7% decrease in commercial removals relative to 2023 due to the quota reduction, resulted in total removals of 3.89 million fish in 2024.  In this scenario, F in 2024 is estimated to be 0.13, and fishing at this rate each year through 2029 would result in a 50% probability of being above the SSB target in 2029.  In order to maintain this F rate in 2025, a 4% reduction from estimated 2024 removals would be needed.  The [Technical Committee] considers the low 2024 removals scenario based on preliminary MRIP numbers to be more likely than the high 2024 removals scenario.

“However, in 2025, the above-average 2018 year-class will be age-7, the same age the strong 2015 year-class was in 2022, and just entering the 28-31” slot in the ocean fishery.  When the 2015 year-class entered the ocean slot, total removals increased by 32% from 2001 to 2002, and F in 2022 was 39% higher than 2021…F in 2023 under the Emergency Action slot limit was still 17% higher than in 2021.  If F in 2025 increases by the same percentage seen in 2022 or 2023 and remains there, the probability of rebuilding under that F rate is well under 50%.  Historically, an increase in F due to a strong year-class recruiting to the fishery has been followed by a decrease in subsequent years, although the rate of change has been variable.  If F increases only in 2025 and decreases to the level estimated for 2024 as the 2018 year-class moves out of the slot, the probability of rebuilding by 2029 is 43%.

“The level of removals in 2024, 2025, and subsequent years is a major source of uncertainty in these projections.  Although predicted removals for 2024 based on preliminary 2024 MRIP data for Waves 2-3 can support rebuilding by 2029, it is likely that removals will increase in 2025 and the Board should be prepared to respond to this eventuality.  [emphasis added]”

While the assessment update accounted for many sources of significant uncertainty based on hard data, there are additional sources of uncertainty that folks on the water have seen.  For example, one of the big contributors to Wave 2-3 striped bass effort, catch, and landings in recent years has been the spring fishery in Raritan Bay, which borders New York and New Jersey.  That fishery peaked in 2021, when New Jersey anglers caught slightly over 4 million bass during Wave 2.  The New Jersey catch fell to about 1.7 million bass in 2022 and 2023, then dropped again, to just a bit over 1 million bass in 2024.  That’s a 41% drop between 2023 and 2024, and given that New Jersey catch and landings dominate the ocean fishery during Wave 2, was undoubtedly a big contributor to the 36% drop in Wave 2-3 landings mentioned in the assessment update.

The Raritan Bay fishery is largely driven by the abundance of menhaden that typically aggregate there in the spring.  In the spring of 2024, those menhaden, for reasons unknown, were largely absent from Raritan Bay, but if they reappear in 2025, striped bass catch and landings could spike back toward 2022-2023 levels.

In addition, 2024 was a very atypical year in terms of weather.  The late spring—the time when a large body of bass migrates through New York and southern New England waters—was windy and wet, keeping boats off the water and also keeping water temperatures unusually low.  During late June and early July, a dense plankton bloom stretched the length of Long Island, dropping underwater visibility to just a few inches and negatively impacting fishing in the ocean.  And in September, traditionally a time when bass fishing begins to heat up again, incessant east winds, coupled with big swells from offshore storms, again chased boats off the water and severely impacted fishing effort.

Thus, the Technical Committee’s conclusion that “the low 2024 removals scenario based on preliminary MRIP numbers to be more likely than the high 2024 removals scenario” may well prove accurate, but 2024 removals may also prove anomalous, so much so that 2025 landings, propelled by more typical conditions on the water as well as the 2018 year class entering the coastal slot limit, could drive 2025 removals even higher than the assessment update suggests.

Thus, this may be one of those occasions when the Management Board would be well advised to follow the old advice to hope for the best and plan for the worst, the worst not necessarily being the 46% reduction indicated if 2024 landings were assumed to replicate those of 2023, but certainly something far less benign than the 4% reduction based on preliminary MRIP data for the first waves of this year.

At the least, it would probably be wise for the Management Board to assume that there is no better than a 40% probability that the stock will rebuild by 2029 under current management measures, based on both the 2025 fish entering the slot and the assumption that 2025 and subsequent years will see more favorable fishing conditions, and set new management measures accordingly.

Adding a bit of additional precaution to those assumptions certainly wouldn’t hurt, but might be a bit much to ask of the Management Board, which has never shown an institutional appreciation of the need for caution, and has on more than one occasion chosen the riskier road instead of the prudent course.

With the bass facing real problems, including an inevitable decline in the spawning stock once the five failed year classes reach spawning age, we can only hope that on this occasion, prudence will reign.