Home - Working Tidal
Leading the investigations on the marine species in the area is UMaine fish ecologist Gayle Zydlewski, who did her Ph.D. research at UMaine on the selective tidal stream transport of eels in the Penobscot River. She studied under one of the foremost experts on the species, Jim McCleave, now a professor emeritus of marine sciences who is assisting in the tidal energy-related research.
In 2009 and 2010 with a portion of the funding received from the Department of Energy, Zydlewski and her research team started collecting data on fish distribution in Western Passage (between Maine and Deer Island, Canada) and Cobscook Bay. Throughout the year at four sites, the researchers use acoustic technology — ultrasonic detection to 50 meters below the surface and high-resolution imaging to 10 meters — to study the distribution of the fish communities in the water column during 24-hour intervals. Every half hour, they also collected information on such factors as water temperature, velocity and salinity.
The researchers had anecdotal information from area fishermen, but most of the commercial harvesting is urchins and scallops, not fish in the water column, where tidal projects capture energy. Available data on fish in the region was more than three decades old.
“We started off wanting to quantify the fish in the water column, no matter the species,” Zydlewski says. “With input from stakeholders, particularly regulators, the questions are becoming more specific: Which species are where in the column?”
Last summer, Zydlewski’s team expanded their work to include netting fish in the mid-water column. Fish biologists know that anadromous species such as salmon and alewife take advantage of tidal energy to move, while some species, like Atlantic herring, disperse to other habitats during peak tidal flows.
Schools of fish that move through the area in June are not the same species moving through in September. Fish communities also change from year to year.
“One of the most interesting things we’ve learned from the data so far is that individual fish and schools move into the water column at different times of the day, and we have documented individuals moving around and through the ORPC test device” Zydlewski says. “The biggest challenge remaining is species-level analysis, especially with species of concern, for example endangered species. These analyses will depend heavily on concurrent netting information.”
The most abundant species netted by the researchers in 2010 were herring and mackerel. Even lumpfish. The groundfish Zydlewski expected to see were not netted in high numbers, substantiating local fishermen’s claim that there’s been no cod for a long time.
“Over the last year, we’ve been focusing on the potential impact of tidal turbines to the entire suite of fish in the Cobscook ecosystem,” Zydlewski says. “The question is, when turbines are in there — particularly multiple turbines — how will the physical dynamics change to ultimately influence the fish there? Our samples are in the high-flow areas where they will put the turbine, but there are also mudflats and smaller parts of the bay.”
Fish netting this summer targeted mudflats and coves. And as the purview widens, questions turn to the dynamics throughout the marine food chain, including how tidal energy projects affect phytoplankton, zooplankton and marine mammals.
For Zydlewski, the next questions also focus on the commercial growth of tidal energy technology — the difference between a single turbine versus an array in the water, and how best to monitor and quantify environmental impact.
From a noncommercial perspective, Zydlewski also wants to understand how to take what researchers learn from Eastport, “where you have the craziest tides,” and help assess smaller proposed tidal energy sites in the most cost-effective way.
“I see the Eastport-Lubec area as having the most potential for commercial development,” Zydlewski says. “Much of the rest of the coast will have smaller projects, where the impacts will be specific and local.”