Investigating a year-round bass population

1 of 4

Researchers and local authorities last week fitted 20 striped bass from Squibnocket Pond in Chilmark with acoustic tags, in an attempt to confirm if there is a year-round population of the typically migratory fish. 

A determination might be available in a matter of weeks, and could confirm the only documented nonmigratory population in Massachusetts. 

The research project is a collaboration of the natural resources department of the Wampanoag Tribe of Gay Head and researchers from the Striped Bass Magic program at the University of Chicago, Marine Biological Laboratory. 

Researchers are interested in the project because striped bass typically leave the Northeast in the fall, migrating to warmer waters in the Southeast.

A year-round bass population would also be a predatory pressure on local herring populations, restoration of which has been a focus of the tribe’s natural resources department for roughly a decade. Menemsha and Squibnocket ponds are connected by Herring Creek, and since as recently as the mid-1990s, herring there have declined significantly.

On the night of Halloween, in preparation for tagging, the natural resources department corralled bass at Squibnocket Pond into a pen. At the tagging on Thursday, department staff fetched a bass from the pen and placed the fish into a cooler with water and anesthetic. When the fish no longer responded to a pinch on the tail — about 10 minutes later — researchers installed an external loop tag behind the dorsal fin, and an internal acoustic tag was installed with a brief surgery on the fish’s underside. The incision was sewn up, and in several minutes, when the fish showed signs of action, it was released.

At the tagging, Brian Prendergast, a University of Chicago psychology professor, said that he has heard anecdotes of atypical, year-round fish on the Cape. This study, however, is an opportunity to prove such a population. 

Bret Stearns, the head of the natural resources department, also noted during the tagging that a year-round striper population has not been documented in Massachusetts.

An answer is likely to come soon, says Prendergast. “Usually, right around this time of year … October to the second week of November, that’s when they leave, and head South. So these fish either will do that, pretty soon, or they’ll be here. And I think we’ll have an answer within a couple of weeks.”

Interest in Squibnocket Pond’s bass came from visual evidence gathered by the natural resources department, which operates a camera in Herring Creek to track sea life. “From camera systems each year, we’re seeing [a] tremendous amount of striped bass in [Squibnocket] Pond,” said Stearns. “We didn’t see them come in, but they’re in the pond … Obviously, there is suitable habitat [here] year-round.” Stearns expects some of the pond’s stripers to migrate, but any year-round population would be significant.

Scott Bennett of Striped Bass Magic says that more intensive research related to the herring will follow in spring or summer if year-round bass are confirmed. 

“The next half of the research program would be establishing a larger acoustic receiver array in Squibnocket, to actually look at the behavior and movements of the [bass] during the year, and how those behaviors and movements correlate to the arrivals and departure of spawning river herring, while they’re here,” says Bennett.

“If there are year-round bass here,” adds Bennett, “then we can start asking questions about how [the bass] move, and where they reside within the pond, what age group and size are we looking at here, are there sexually mature animals, and are they spawning here if they’re year-round.”

Stearns says that if year-round stripers do spawn in the pond complex, that would make the area unique, and be valuable information for the tribe and state.

Prendergast says that much more research is needed on why typically migratory animals form year-round populations, but that he is aware of some clues worth exploring. “I think there are attributes of this that jump out to me. Shelter, maybe some spring-fed water sources that can stay relatively warmer in winter.”

Aside from exploring year-round bass and herring at the pond complex, Prendergast is also interested in what nonmigratory bass could contribute to scientific fields. A particular interest is behavior related to circadian rhythms, which he has studied in mammals. 

“[In] almost every seasonally breeding mammal population, there is a subset of animals that tries to breed year-round,” he says. “And most of the time they don’t succeed. But every once in a while — maybe it’s a mild winter — they do really, really well.”

Prendergast says that the behaviors of striped bass are particularly seasonal. “Here’s a fish that has a dramatic seasonal rhythm … of this long-distance coastal migration. So [if] it’s the exact same species that doesn’t do that … how do those two different seasonal rhythms impact their daily rhythms?”

One hypothesis, says Prendergast, is that many behavior changes observed in typical striped bass occur because of migration specifically. “And a great way to test that hypothesis is to find a fish that isn’t migrating,” says Prendergast.

A specific behavior to compare is how typical striped bass seek food in summer. “[They have] really clear daily rhythms, where they forage in deeper waters and swim around a lot more at night than they do during the day. But as the summer goes on, as they get closer and closer to migrating South, their daily rhythms start to disintegrate, and they essentially become arrhythmic,” said Prendergast. “My hypothesis is that that is in anticipation of long-distance migration. That is, they’re about to go on a trip … If they dismantle the circadian clocks in anticipation of migration, that’s pretty interesting. How do they do that? Why do they do that?”

A year-round Squibnocket population could be influential for these interests. “Data on year-round populations — hard scientific data — is so lacking that those relationships are going to come from more studies like this,” says Prendergast.

Bennett also noted that identifying year-round striped bass populations could inform regulation of the typically migratory fish. “Regulation of the bass population is particularly difficult because [striped bass] are migratory animals, and they cross state lines … every state government has a policy on size and number of fish that you can catch, and commercial quotas and recreational quotas,” he says.

Whether these bass remain in the Squibnocket–Menemsha pond complex or end up migrating along the coast, Stearns is confident that they will be identified: “When we release these fish, and they go back into Squibnocket, our sensors will pick it up. If they leave and they go out in Menemsha, our sensors will pick it up. If they come back and forth, the sensors will pick it up. So we’ll be able to tell [a] story of where they go.”

For Stearns’ department, no matter the study’s outcome, the impact on herring will be a key focus. This is because, despite offshore fishing being the main cause of herring reduction, his department has control over management at the pond complex: “We’re doing what we can at home to make sure [herring] can spawn and be successful.”