OLD LYME – Submerged in the shallow but robust flow of an outlet between Black Hall Pond and Long Island Sound, the camera takes a picture once a minute, day and night.
The 24/7 automatic photo shoot is designed to track the number and migration pattern of a small, humble-looking type of herring known as an Alewife as they travel downstream after spawning in the pond and while returning to the saltwater habitat where they spend most of their relatively short lives.
Alewives play a critical role in the food chain in water and on land, and their once-abundant population has been in sharp decline in recent years for reasons not yet known. Alewives have been on the state’s protected list of species for about 20 years.
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The GoPro camera is one of six such setups that UConn graduate student and Branford resident Mike Burgess is installing here and in waterways in East Lyme, Old Saybrook and Mystic to try to track what’s behind the population drop and how to address it.
“Alewives get fat and rich in the saltwater systems and then they swim up here to spawn,” Burgess explained Monday as he secured the camera just above a short rocky drop in the brook, which serves as a fish ladder for adult alewives to reach the 16-acre pond not far upstream. “That provides food for the largemouth bass, the turtles, the birds, the raccoons – they eat the young and they eat the eggs.”
Burgess straps on his waders and visits each of the six sites every other day, collecting the camera memory cards and bringing them back to campus, where undergraduate students manually comb through each frame and add up how many fish it captured – base information for an extrapolation of the overall migration.
Burgess is working on the project under the supervision of UConn professor Dr. Eric Schultz and the state Department of Energy and Environmental Protection, which this spring stocked Black Hall Pond with about 1,500 adult alewives as part of the restoration project in conjunction with the town’s Conservation Commission.
Each female can deposit up to 100,000 tiny eggs that stick to the bottom surface of the pond, which decades ago was packed with the fish.
Tracking when the adult fish leave each of the six ponds and streams he is monitoring – which usually happens between June and October – will help researchers determine when and where to focus their yearly conservation efforts.
“We’re trying to figure out the timing when they leave as far as the season and on a daily scale,” said Burgess, who is pursuing a degree in Ecology and Evolutionary Biology. “Are they leaving at dusk, are they leaving at dawn, are they leaving midday? It’s important to see how it varies among systems when we’re looking at conservation methods.”
Burgess witnessed a mass migration back to the Sound earlier this summer at Bride Lake in East Lyme, long used by the state as an alewife breeding area, including for the ones stocked in Black Hall Pond this spring.
“We watched between 15-20,000 thousand leave at about five in the morning two days in a row,” he recalled. “It was just fish as far as you could see.”
Still, the 150,000 or so adult alewives that swam upstream from the ocean to the lake this spring to spawn were about half of last year. Even smaller numbers have been recorded at some of his other sites.
Burgess and state DEEP researchers say there is no firm theory as to why the population has decreased so sharply. But there is widespread speculation that a major factor may simply be that they are being taken at sea by fishermen who use them as bait when other bait species are declared off limits, as happened within the last year.
A survey of the Black Hall Pond population by a team from Yale University estimated that about 7,000 adults were present in mid-June, several weeks after the stocking by state officials.
“We also discovered the pond already has a population of landlocked alewife,” said Yale researcher Andrew MacDonald. “They are the largest landlocked I have ever seen. We also caught largemouth bass, yellow perch, bluegill, and lots of black crappie.”
Town Conservation Commission member Gary Gregory, one of the drivers of the project, observed Burgess’ work on Monday and said he was encouraged by the results so far.
“They’re doing very well in there,” Gregory said, referring to Black Hall Pond. “Alewives are eaten by just about every game fish in the Sound. If you lose the alewife, the gamefish is not going to have anything to eat. So this is really critical for sport fishing.”
Gregory also was encouraged by the relatively strong flow of water through the outlet below the pond on Monday, which produced a persistent babble as it coursed through dense greenery toward the Sound.
“This creek’s running and we’re in a drought. Any other of your creeks running?” he asked Burgess.
“No – they’re all dry,” Burgess replied. “Two of the sites I work at have actually been dry since I believe July 4.”
“That means this one’s got a better chance in a drought year than anything else,” enthused Gregory. “We might have a goldmine here.”