Top photo by Capt. Dave Monti
The Chesapeake Bay produces most of the migratory striped bass on the Atlantic Coast, and about two-thirds of those Chesapeake bass are spawned in Maryland’s waters. Maryland spawning success is so important to the overall health of the striped bass stock that, at the November 2022 meeting of the Atlantic States Marine Fisheries Commission’s (ASMFC) Atlantic Striped Bass Management Board (Management Board), Emilie Franke, the ASMFC’s Fishery Management Plan Coordinator for striped bass, noted that “the Maryland [juvenile abundance index] is a good predictor of Age 1 recruits” into the entire coastal striped bass population.
Right now, Maryland’s striped bass are experiencing a spawning failure. On October 12, 2023, the Maryland Department of Natural Resources announced that Maryland’s 2023 juvenile abundance index (JAI) was 1.02, “well below the long-term average of 11.1.” In fact, the 2023 juvenile abundance index was the second-lowest ever recorded in a time series dating back to 1957; only an index of 0.89, recorded in 2012, was lower.
The most recent addendum to the ASMFC’s striped bass management plan, Addendum 7, contains a so-called “management trigger” that sets a minimum standard for juvenile production, and requires managers to take specific actions if such management trigger is tripped. The relevant section reads,
If any of the four JAIs used in the stock assessment model to estimate recruitment (NY, NJ, MD, VA) shows an index value that is below 75% of all values (i.e., below the 25th percentile) in the respective JAI from 1992-2006 (which represents a period of high recruitment…) for three consecutive years, then the interim [fishing mortality] target and interim [fishing mortality] threshold calculated using the low recruitment assumption will be implemented, and the [fishing mortality]-based triggers…will be reevaluated using those interim reference points. If [a fishing mortality]-based trigger is tripped upon reevaluation, the striped bass management program must be adjusted to reduce [fishing mortality] to the interim [fishing mortality] target within one year.
The lower [fishing mortality] reference points will remain in place at least until the next stock assessment update or benchmark assessment is approved for management use. Upon reviewing the results of that next assessment, the Board will determine which [fishing morality] rate (target or interim target) to manage towards moving forward by considering factors such as current stock status, recent JAI data, and [Technical Committee] input.
With the release of this year’s Maryland JAI, that index has now been below the 25th percentile for five, and not merely three, consecutive years. The management trigger has already been tripped, and the low recruitment assumption has already been implemented; an interim fishing mortality target has been put in place. The management plan specifies no additional remedies to combat cratering recruitment.
Worse, the poor JAIs aren’t limited to Maryland. On the same day that Maryland announced the results of its juvenile abundance survey, the Virginia Institute of Marine Science announced that “a poor year class of young-of-year striped bass was produced in Virginia tributaries of the Chesapeake Bay in 2023.”
Neither the 2023 data for New York’s juvenile abundance survey of Hudson River-spawned fish nor for New Jersey’s survey of juvenile abundance in the Delaware River estuary have yet been released, so there is still some hope that good production could have occurred in at least one of those waters. However, recent trends in most spawning areas have not been good. Each year, the ASMFC reviews the performance of its striped bass management plan. The 2022 review advised that
For the 2023 review of JAIs, the analysis evaluates the 2020, 2021, and 2022 JAI values… One state (Maryland) met the criteria of the Amendment 7 recruitment trigger. Maryland’s JAI values for 2020 (1.12), 2021 (1.65), and 2022 (1.78) were below the Maryland JAI trigger level of 4.16. This trips the recruitment trigger in 2023…
New York’s JAI (Hudson River) was above its trigger level (11.70) from 2020-2022, with values ranging from 15.89 to 35.39. New Jersey’s JAI (Delaware River) was below its trigger level (1.07) in 2021 and 2022 with values of 0.67 and 0.77, respectively. A 2020 JAI value for New Jersey is not available due to COVID-19 restrictions. Virginia’s JAI was above its trigger level (8.22) in 2020 with a value of 13.89, but fell below its trigger level in 2021 and 2022 with values of 6.3 and 7.95, respectively.
Maine’s JAI (Kennebec River) and North Carolina’s JAI (Albemarle-Roanoke) are not part of the recruitment trigger, but are still required monitoring for those states. Maine’s JAI was below the level of recruitment failure in both 2020 and 2021 with values of 0.02 and 0.0, respectively. North Carolina’s JAI value in 2022 was 0.5, the fifth consecutive year below the value of recruitment failure.
Except for the Hudson River, striped bass recruitment has been poor everywhere. This year’s low JAI in Virginia will trip the recruitment trigger for that spawning area, and unless the New Jersey 2023 JAI is substantially higher than it was in recent years, it will also trip the trigger for management action.
But there aren’t too many things that managers can do.
The size of the striped bass stock does not dictate spawning success; there is no direct relationship between the size of the spawning population and the resultant JAI. The most recent benchmark stock assessment assumed a “steepness” value at 1.0, meaning that a striped bass stock reduced to just 20% of its spawning potential can produce the same level of recruitment as a completely unfished stock.
Instead, striped bass recruitment is highly dependent upon environmental conditions in the spawning reaches of coastal rivers. As the Maryland Department of Natural Resources notes,
Striped bass spawning activity is temperature-driven and historically adult fish migrated to the Chesapeake Bay to spawn in April and May, which aligned with the seasonal arrival of zooplankton and other microscopic food sources that larval striped bass eat. However, recent winters have produced less-than-average snowfalls in the region and therefore less snowmelt to cool the rivers and stream where striped bass spawn…
Previously, favorable environmental conditions for striped bass such as heavy winter snowfalls or higher spring rainfalls have helped produce stronger juvenile year classes.
Fishery managers can’t do anything about the weather, but they can try to maintain a striped bass stock that is best able to take advantage of favorable environmental conditions when they occur.
In 2000, Dr. David H. Secor published an article in the ICES Journal of Marine Science, titled “Spawning in the nick of time? Effect of adult demographics on spawning behavior and recruitment in Chesapeake Bay striped bass.” In that article, Dr. Secor noted that
The observation that larger striped bass tend to spawn early in the season suggests that spawning behaviours that vary with size or age might be an effective means to hedge against environmental stochasticity…If minority spawning behaviours—for instance, spawning during early or late parts of the season—in some years resulted in successful offspring, a diverse age composition should contribute to sustained annual recruitment and accumulation of spawning stock biomass…reduction in year-class diversity renders a population more vulnerable to recruitment failures [and] is consistent with the time series of year-class strengths observed for Chesapeake Bay striped bass. Lowest year-class strengths were observed during periods when age structure was severely truncated.
Thus, to best conserve the existing striped bass population, and to maximize the likelihood of improved recruitment, the Management Board should strive to maintain a spawning stock in which as many different ages and sizes are represented, so that some portion of that spawning stock will be present and actively spawning should conditions in the spawning rivers provide more favorable conditions in an otherwise unfavorable spawning year.
Right now, meteorologists are predicting a strong El Nino for the winter of 2023-24. Such El Nino conditions might well bring cold and snow to the northeastern United States, and perhaps provide the conditions that striped bass will need to produce a strong year class.
But weather predictions don’t always prove true. Until the Maryland JAI, and the JAIs from the other major striped bass spawning areas, demonstrate that strong recruitment has occurred, the Management Board must set a very low fishing mortality target, to assure that larger, older fish remain in the spawning stock, and that younger, but still mature females also remain, in order to give the striped bass its best possible chance to overcome its current recruitment problems.