WHITHER THE STRIPED BASS?

 

When we hear people talking about striped bass these days, we get a lot of conflicting messages.

Some, citing the recent poor spawns in the Hudson River and the seven years of record low recruitment in the Chesapeake Bay, are filled with despair.

Others, citing the current cold winter and its hoped-for effect on spawning success, are sounding notes of optimism.

Still others choose to deny reality, speak of bass continuing to spawn in unidentified northern rivers, and claim that all is well.

But when we try to take a reasoned look at where the striped bass is headed, we find that the truth is a little more nuanced.

There are things that we know for certain. 

We know that the Maryland Juvenile Abundance Index for the past seven years—2019 through 2025—has never been lower, on average, in any seven-year period dating back to the start of the index in 1957.  We know that the Virginia JAI has also been low in recent years, that New Jersey’s Delaware River JAI was very low in 2022, 2023, and 2024 (I haven’t yet seen the 2025 JAI), and that, for the past three years,  Hudson River spawning success was below the 25^th percentile of all spawns going back to 1985, and probably met the definition of “recruitment failure” (three consecutive spawns in the lower 25% of all spawns between 1985 and 2009).

We also know that the Chesapeake Bay stock (which, from a genetic standpoint, also includes bass spawned in the Delaware River) of striped bass provides at least 80% of all striped bass caught off New England and the mid-Atlantic states, with the Hudson River providing almost all of the rest.  Since 2018 was the last, very modestly above-average spawn in the Chesapeake, and since Age 9 bass will, for the most part, be more than 31 inches long, we know that, beginning in 2027, legal-sized striped bass are going to be very difficult to find in the ocean fishery, and that drought of legal-sized fish is going to last—assuming that the current slot size limit remains in place—until at least 2033, and perhaps a lot longer than that if recruitment doesn’t improve.

What we don’t know is whether recruitment will improve and, if it does, whether it will reach the levels of the late 1990s/early 2000s, or whether, because of changing environmental conditions, it will stall at some level higher than what we’re experiencing today, but lower than what we enjoyed in the past.

Based on those knowns and unknowns, fisheries managers are going to have to figure out how to manage the resource in both the short and intermediate term, and eventually in the long term as well.  That’s essentially what the striped bass “Work Group,” approved last October by the Atlantic States Marine Fisheries Commission’s Atlantic Striped Bass Management Board, was created to consider, although there is still some work to be done before that Work Group is constituted and gets underway.

So, given the recent history of poor recruitment, can things turn around?  Can we reasonably expect a good spawn this year?

Those are difficult questions to answer.

One research team, led by Julie M. Gross of the Virginia Institute of Marine Science, developed an approach that was dubbed “the poor recruitment paradigm,” which

“hypothesizes that it is easier to predict poor recruitment rather than good recruitment because an environmental variable affects recruitment only when its value is extreme (lethal); otherwise, the variable may be benign and not influence recruitment.  Thus, good recruitment necessitates all environmental conditions not be harmful and for some to be especially favorable; poor recruitment, however, requires only one environmental variable to be extreme.”

Taking that approach to heart, we know that we have most likely escaped the bad impacts created by a warm winter, but we still can’t know whether there will be enough favorable conditions to create a good spawn—or whether just one factor might go far enough in the wrong direction to scuttle the prospects.

The same team of researchers found that, in the case of Chesapeake striped bass,

“Low spring river discharge reliably resulted in poor recruitment of striped bass.”

And once again, we can’t know what water flows are going to look like when the spawn is going on.  Hopefully, the cold winter will lead to some snowmelt increasing river flows, particularly toward the beginning of the spawning period, but it’s far from clear that snowmelt will be enough.  Today (February 12), the Drought Monitor map for Maryland shows most of the state experiencing below-normal precipitation, ranging from “Abnormally Dry” to “Severe Drought,” with the land immediately bordering the Chesapeake Bay deemed to be either “Abnormally Dry” or in “Moderate Drought” while much of the land farther west, where some of the Bay’s tributaries originate, fall into the “Severe Drought” category.

Despite the cold winter and some snowpack, water flows could still prove to be a problem.

Other factors also come into play.  For example, there is the “match-mismatch hypothesis,” which links successful recruitment with suitable prey species being available when and where the juvenile fish need them.  In the case of striped bass, the prey are copepods—tiny crustaceans—that, when available in good numbers, can support a large year class of juvenile fish.  Researchers believe it is likely that

“the best conditions for striped bass recruitment could occur when the peak in [copepod] abundance occurs during late spring in upper Chesapeake Bay.”

High water flows are believed to transport the copepods to where the bass can best take advantage of their abundance, while

“cold winters delay the timing and increase the size of peak [copepod] spring abundance.”

In the coldest winters, copepod abundance peaks around the middle of April. 

Thus, the current cold winter holds out hope that there will be enough food available to support a strong striped bass year class, although the need for high water flows to move that food to places where it is available to the juvenile bass suggests that any optimism based on the cold winter needs to be tempered by the real possibility that current drought conditions will limit water flows.

But there is at least one more parameter to consider, and that is water temperature during the spring.

A paper titled “Climate effects on the timing of Maryland Striped Bass spawning runs,” published in the journal Marine and Coastal Fisheries on November 20, 2023, noted that striped bass spawn when water temperatures are between 12 and 20 degrees Celsius (54.5 to 68 degrees Fahrenheit), and that larval survival is highest in water temperatures between 16^oC and 21^oC (61^oF to 70^oF), although most spawning doesn’t begin until water temperatures reach 14^oC (57^oF), and egg survival decreases once water temperatures exceed 20^oC.  It also noted that female striped bass move onto the spawning grounds about 3 days sooner for every 1^oC (1.8^oF) increase in water temperature.

Looking at spring water temperatures over time, the paper’s author revealed that

“Mean water temperatures on the Upper Bay and Potomac River spawning grounds were lower in the late 1980s and 1990s and have increased since 2000.  Although no significant change was detected over time for when the 14^oC temperature milestone was reached to initiate spawning, a significant change was detected through time with the 20^oC milestone at which Striped Bass egg survival is deemed poor.  These changes suggest that the spawning season has shortened.  All of the spawning milestones…are dependent on water temperatures and occur earlier when mean water temperatures are higher.  [emphasis added]”

That might have a negative impact on striped bass spawning success.

“These shifts and reductions in the spawning window could affect Striped Bass in several ways.  First would be from the direct effects of temperature.  Striped bass eggs and larvae are known to be sensitive to water temperatures, with lethal effects documented at temperatures below 12^oC, and ideal survival over the first 25 days after hatching at temperatures between 16^oC and 21^oC.  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.  Second, these temperature changes 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 [scientists] showed a potential mechanism for this, with the rate that copepods reach the adult stage over the winter being dependent on winter temperatures.  Climate projections for the Chesapeake Bay suggest that in the future, winter air temperatures and precipitation amounts will likely be higher.  These novel conditions could make it less likely that large copepod abundances will coincide with Striped Bass spawning, but it will depend on the exact rate that fish spawn earlier and how that overlaps with prey availability changes.  [references omitted]”

So, as we slowly approach the spawning season, we have one positive—it has been a cold winter—which might make it more likely that the copepods that the newly-spawned bass rely on for food will be available.

However, while the winter has been cold, it hasn’t been particularly wet, with much of Maryland experiencing some level of drought.  There is no guarantee that, by the time the spawning season comes around, water flows will be high enough to promote a good spawn, and to push whatever copepods there are around to the places that the young bass need them to be.  And if the spring is warm, it is very possible that the spawning season will be curtailed as waters quickly rise above 20^oC, and that in the end, the peak abundance of larval striped bass and the peak abundance of copepods won’t coincide.

If we go back to the idea of the “poor recruitment paradigm,” we have a number of things—water flows, high water temperatures, and a mismatch in the availability of prey, to name three—that might go seriously wrong, and no hint that anything except for a cold winter might go particularly right. 

A recent article that appeared on the website of On the Water magazine probably put everything in the right perspective:

“This winter has been persistently cold across much of the Mid-Atlantic and Northeast.  Snowpack, frozen ground, and extended cold snaps raise the possibility of elevated spring runoff, especially if temperatures warm gradually rather than all at once.  That’s why biologists will be watching Chesapeake conditions closely in March and April.  River flow, water temperature, and plankton development during that window will give them a more complete picture of the likelihood of striper spawning success.  For a stock that has endured years of poor recruitment, even a setup that looks promising is worth noting.”

So, whither the striped bass?

An old adage probably provides the right advice:  “Hope for the best, but prepare for the worst.”

For even if we get a more successful spawn in 2026, we’ll still be a very long way from a healthy striped bass stock that, in the long term, is likely to thrive.