WHAT NOW? ANOTHER POOR STRIPED BASS SPAWN IN THE CHESAPEAKE BAY

 

If you follow striped bass management at all, you probably already know that the Maryland Juvenile Abundance Index for 2024 was announced last Thursday, and that it came in at just 2.0, marking the sixth consecutive year of recruitment failure in the Maryland portion of the Chesapeake Bay.

You might also know that the Virginia JAI was also announced last Thursday, and came in at 3.43.  That marked the fourth consecutive year that the Virginia Juvenile Abundance Index was below the 25^th percentile in the time series used to determine low recruitment, with the 2024 JAI the lowest in recent years.

And if that’s not bad enough, the average of the Maryland JAI for the last six years was the lowest in the history of the Maryland Juvenile Striped Bass Survey, which first sampled juvenile striped bass abundance in 1957.  The previous low, for the period 1980-1985, was 3.36.  The average for the years 2019-2024 was 2.62, about 22 percent lower.

Maryland produces about two-thirds of the striped bass spawned in the Chesapeake Bay, and a recent study confirmed that the Chesapeake Bay produces over 80 percent of the striped bass caught along the East Coast of the United States.  So with Maryland experiencing six consecutive years of failed spawns, and Virginia not doing much better over the past four years, it’s pretty clear that the striped bass stock is in trouble.

What’s not clear is what managers can do about it.

Maryland has stated that

“warm conditions in winter continue to negatively impact the reproductive success of striped bass, whose larvae are very sensitive to water conditions and food availability in their first several weeks after hatching.”

Fishery managers have generally accepted the proposition that cold winters followed by cool, wet springs favor strong striped bass spawns, while warm winters followed by warm, dry springs can lead to spawning failure.  By that measure, 2024 should have produced at least a mediocre juvenile abundance index, for while the winter of 2023-2024 was relatively mild, the spring of 2024 was cool and wet, with water flows and water temperatures similar to those which produced strong year classes in the past.  Based on those conditions, many of us were expecting at least an average spawn, and hoped for something a little bit better than that.

By midsummer, there were some rumors and other indications that the spawn wasn’t as successful as we had initially expected, but would still result in a Maryland JAI in the 6 or 7 range—below the long-term average of 11, but still the strongest since the somewhat above-average year class of 2018.

When we finally heard, last Thursday, that the JAI was just 2.0, we were floored.

So clearly, something else must be going on.

There has recently been thought that favorable temperatures and water flows may not be enough to ensure a successful spawn. In a paper titled “Climate effects on the timing of Maryland’s striped bass spawning runs,” which was written by Angela Giuliano and appeared in the November 20, 2023 issue of the journal, Marine and Coastal Fisheries, the author suggests that

“If temperatures continue to warm quicker in the latter portion of the spawning season, this could result in a reduced time period during which temperature conditions are ideal for Striped Bass survival…these temperature could affect the timing of larval Striped Bass relative to their zooplankton prey, a concept known as match-mismatch.  Large year-classes of striped bass tend to occur after cold and wet winters and [research] showed a potential mechanism for this, with the rate that copepods reach the adult stage over the winter being dependent on water temperatures.

“…With the shifting spawning window and potential changes in zooplankton availability due to rising water temperatures, it has been suggested that having a broad age range of spawning fish will make it more likely that some eggs and larvae will experience these ideal conditions.  Although fisheries managers cannot directly control the water temperature that larval fish will encounter, they can consider how management actions may affect the age range of fish available in the spawning stock in addition to the size of the spawning stock.  If these management goals are considered in tandem, the Striped Bass stock may be better positioned to adapt to the conditions expected under a changing climate.  [citations omitted]”

Perhaps in addition to water temperatures and flows, there is another factor—zooplankton availability, and the timing of that availability with the timing of the striped bass spawn that dictates whether a spawn will be successful.

That’s not good news, because fisheries managers have no control over climate or weather, or the timing of a zooplankton bloom.

At the same time, Ms. Giuliano’s paper provides some guidance on what the Atlantic States Marine Fisheries Commission’s Atlantic Striped Bass Management Board ought to do when it meets next Wednesday, particularly when read in conjunction with Dr. David Secor’s research, presented in “Spawning in the nick of time?  Effect of adult demographics on spawning behavior and recruitment in Chesapeake Bay striped bass,” which appeared in the ICES Journal of Marine Science in 2000. 

In that paper, Dr. Secor noted that

“large, old striped bass may spawn earlier than small and young individuals.  Increased age diversity in the spawning stock may increase the temporal and spatial frequency of spawning (spawning dispersion) and thereby increase the probability that some offspring will encounter favorable conditions…

“…Increased spawning dispersion may compensate for variable temperature conditions on the spawning grounds, which often results in patterns of egg production that are mistimed for optimal larval survival…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 bets against environmental stochasticity…

“…Striped bass epitomize periodic strategists, spreading risk of failed replacement through variability in spawning behavior over many spawning seasons…  [citations omitted]”

Dr. Secor also noted that

“Through a moratorium on Maryland State harvests in the Chesapeake Bay, the 1982  year-class was effectively protected and became a dominant [year-class].  Ironically, most egg production in 1982 was attributable to striped bass >10 years of age.  Old remnant females produced during the 1960s were a hedge against a long period of recruitment overfishing which occurred during the 1970s.  [citation omitted]”

Thus, even though the recent poor Maryland JAIs are driven by environmental factors—water temperature, water flows, perhaps a mismatch in timing between the striped bass spawn and the presence of the abundant zooplankton that the juvenile bass depend on for food—over which the Management Board has no control, the Management Board can still exert significant influence over the future of the striped bass, by 1) assuring that the spawning stock includes as many different age and size classes as possible, to take advantage of transient favorable spawning conditions that might occur over the course of a spawning season, and 2) by preserving the oldest and largest fish in the spawning stock, in order to preserve a pool of what Dr. Secor called “old remnant females” that can produce a strong year class on its own should favorable conditions arise.

The only way to achieve those two goals is to sharply reduce fishing mortality, which can best be done by sharply cutting back on recreational and commercial landings.

Under current conditions, there is little excuse for harvesting large female striped bass.  Recreational size limits in place in both the ocean and the Chesapeake Bay fisheries prohibit such harvest, but a number of states still do not place a maximum size on the bass that may be harvested by commercial fishermen; Massachusetts, for example, imposes a 35-inch minimum size on its commercial fishermen, with no cap on the size of the bass that might be landed. 

A maximum size limit for commercial fishermen was considered as a part of Addendum II to Amendment 7 to the Interstate Fishery Management Plan for Atlantic Striped Bass, but because such measure would be difficult to implement (by imposing a maximum size limit on the commercial fishery, managers would have forced commercial fishermen to harvest more, but smaller, bass to fill their quota, and adjusting quotas to account for the cap would have been a time-consuming process that would have frustrated the Management Board’s intention to put such Addendum in place quickly) such a size limit was not included in the Addendum.  However, if commercial quotas were cut back sharply at the same time the maximum size was imposed, that issue would largely become irrelevant.

Ending the harvest of larger, older bass would increase the chances of such individuals’ survival, and make it more likely that such fish would be available to to spur a recovery of the striped bass stock when spawning conditions improve, even if there were few younger females in the population.

However, protecting the older females is not enough, if the striped bass stock is to be given its best opportunity to rebuild.  Managers must also protect the younger bass, in order to provide the age and size diversity needed if at least some striped bass are to be able to take advantage of more favorable spawning conditions whenever they occur during the spring spawning season.  That can only be done by sharply cutting back both recreational and commercial landings, through extensive recreational season closures and a much-reduced commercial quota.  It might even be necessary to prohibit all commercial and recreational harvest.

The need to protect the younger fish, in order to create a diverse spawning stock, also means that managers should reconsider present policies that allow both recreational and commercial fishermen to target immature striped bass in the Chesapeake Bay.  

Given the extremely small year classes produced in the Bay in every year since 2019, the 2.79 million pound commercial quota in the Chesapeake Bay allows commercial fishermen to remove a substantial share of each such year class before the fish have had a chance to spawn even once.  Similarly, the 19- to 24-inch slot limit for recreational fishermen within the Bay forces anglers to target and, if so inclined, land immature striped bass.  Such removals are contrary to the objective of including as many year classes as possible in the spawning stock.  

The Management Board should consider applying the same 28- to 31-inch slot size limit now in force in the recreational ocean fishery to the Bay fishery as well, in order to lessen the removals of bass from the smallest year classes.

There would certainly be substantial resistance to such proposals.  Recreational and commercial fishermen in the Chesapeake Bay would undoubtedly object if they were no longer able to harvest immature striped bass, commercial fishermen will oppose any reductions in quota, and the for-hire fleet is unlikely to support any additional restrictions on recreational landings.

Yet the bass is in serious trouble.

Adopting extremely restrictive regulations today may be the only way to avert something far worse from occurring tomorrow.