Fish Captured in Weekly Trawls Document Warming of Narragansett Bay
April 24, 2020
On a normal Monday morning, University of Rhode Island graduate student Nina Santos would head to the Wickford Shipyard in North Kingstown, R.I., pull on some waterproof gear, and board the Cap’n Bert.
“My dad was a fisherman, so I grew up around fishing and boats but I had never been out on the water on a fishing boat before,” she said. “I had been on my dad’s fishing boat when it came to port but never out on the water, so now I feel like I’m getting to experience what he did for a living.”
Santos and the boat’s captain, Stephen Barber, would normally set sail around 8:15 a.m., measuring the water temperature, oxygen, and salinity levels, and then casting a net out at various checkpoints. They would pull up the net after 30 minutes of cruising at 2 knots, then identify, group, measure, and weigh the fish they caught before tossing them back. This would continue for about 4 hours, before Barber would turn the Cap’n Bert around at Whale Rock and slip back into the Wickford Shipyard around 12:15 p.m.
But the past month or so of Mondays have been anything but normal. The coronavirus hasn’t only shuttered universities around the world, it’s also shuttered much of researchers’ field work, and for Santos, that means a gap in URI fish-trawl records dating back to 1959.
“It’s kind of sad to have this big data gap in the trawl survey but it’s not the first time it’s happened,” Santos said. “So, I don’t think it will change too much, but it is a little bit sad because now is when we would actually see things moving back into the bay.”
Before the coronavirus derailed the weekly trawl, Santos was continuing a 61-year legacy of scooping fish out of Narragansett Bay to paint a picture of its inhabitants.
The story of the fish trawl starts, appropriately, with a couple by the name of Fish.
Charles Fish and his wife, Marie, were longtime members of the marine biology community with a long list of accomplishments: Marie collected and studied fish and marine sounds; Charles was a pioneer in the study of zooplankton. In 1925, the couple were a part of an expedition to study the Sargasso Sea led by naturalist and explorer William Beebe.
But their lasting legacy lies in the creation of the Narragansett Marine Laboratory, which opened 72 years ago, as a part of the School of Arts and Sciences at Rhode Island State College — what would become URI — and in a fish trawl that has collected an astounding amount of data.
“The goal was to measure the seasonal occurrences and abundance of fish in the bay,” said Jeremy Collie, a professor of oceanography at URI who runs the program today. “Part of it was to catch the fish that were in the bay from week to week and actually be able to identify them, and perhaps link that with the soundscape that Marie Fish was hearing.”
Collie took the helm of the program in 1998, after H. Perry Jeffries retired. Jeffries was one of Fish’s original assistants, who took over the program in 1966 after Fish retired.
“Jeffries was one of the first assistants, and when he got the job here as a professor, he decided he would keep the program going. It was really Perry who started looking at the longer-term trends of the fish populations,” Collie said. “When he retired, I took over and the longer we keep going, the more interesting it becomes. It’s a very rich data center.”
While the program has noticed changes in local marine populations, including a shift from fin fish species to more invertebrates such as crabs and lobsters, one of the biggest differences over time has been the introduction of many more warm-water species.
“Since the year 2000, it’s become more and more obvious that it’s the changing climate that is affecting fish populations,” Collie said. “The community is shifting because the cold-water species are less abundant than the warm-water species, which are way more abundant. That’s the big signal that we are measuring.”
Santos has noticed this shift, especially during her wintertime trawls.
“We’re not really catching much right now; it’s surprising how little we do catch. There’s such a disparity between the winter catch and the summer catch, and I think that part of that is the shift that Narragansett Bay has had towards warm-water species,” she said. “There’s not really anything left once winter hits; all the species that would have been here in the winter in the cold waters are not around anymore. They’ve moved north.”
Some flashy examples of warm-water visitors include orange tilefish, sand tiger sharks, and an errant sailfish. There also are two warm-water residents of Narragansett Bay that are so common you might think they were native species: striped searobin and scup.
“We’ve been studying the striped searobin in particular because we’re interested in the impact they have on the fish community,” Collie said. “Searobins kind of swim around on the bottom, vacuuming up everything that’s in their path, and so we’re trying to estimate their impact on the community, on the invertebrates and the fish they may be eating. So, it’s not only that these species are changing in abundance and increasing, they are also having an effect on the food web.”
As for scup, there is a healthy population of the fish also known as porgy in Rhode Island waters. In 2017, the state landed more than 6 million pounds of the bony fish.
For Collie, the reason for its abundance lies in the warming of Narragansett Bay.
“The easy answer to why there are so many is that they’re a warm-water species, and the water is getting warmer so there are more of them,” he said. “The scup population as a whole, coast-wide, is in good shape. There’s a healthy scup population out there.”
As the bay has warmed, with the surface temperature on Jan. 25, 1959 registering 33 degrees Fahrenheit and on the same day in 2017 registering 40 degrees Fahrenheit, the URI trawlers have been there to document it, and they will continue to do so — once the pandemic is squashed.