Shellfish health & herring migration are hot topics at Wellfleet harbor conference
Wicked Local Provincetown
By Marilyn Miller
Posted Nov. 14, 2014 @ 8:12 am
WELLFLEET — It was a full house Saturday at the 12th annual State of Wellfleet Harbor Conference held in the elementary school cafeteria. Every year it seems more people turn out to get the latest news on what is going on in the harbor.
Selectman John Morrissey, who opened the conference, recalled how he got a passing high school grade in science, when he had sharper eyes, by sitting near others who knew their science. As then, the room on Saturday was filled with people who knew a lot more about science than he did, and were going to share it with all.
The speakers included John Brawley, senior marine systems ecologist and SPAT aquaculture specialist, who talked about vibrio risk management and research.
Brawley was hired by SPAT “to help reduce the risk of shellfish bed closures in Wellfleet,” he said. A shellfisherman in Duxbury, he recounted the time when he and other shellfishers were closed down for five weeks last year. “We lost over $400,000,” he said. “It shocked us, made a lot of people think that we’ve got to get serious around protecting our industry to improve seafood safety.”
Brawley was pleased to hear that a grant of $450,000 has been awarded to do vibrio research in Wellfleet and Duxbury next year.
Other speakers talked about the results of the horseshoe crab survey in Wellfleet Harbor, sea level rise and vegetation change modeling, findings on ocean sunfish strandings and the result of eel restoration at Wellfleet Bay.
Derrick Alcott, who is working on a Ph.D in organismic and evolutionary biology at UMASS Amherst, talked about his investigation into the impacts of tide gate structures on Chequessett Neck Road and several road-crossing culverts along the Herring River on the spawning migration of adult river herring. He explained how he used a combination of passive integrative transponders and acoustic telemetry to determine how many herring made it through these structures.
During the season, Alcott tagged each herring through two tagging events. Each tag had a unique code that enabled him to track its progression and the date and time when it progressed through the system. His research focused on how many made it through the tidal gates, how many made it to the spawning ground and how many survived to start the process again.
Fifty-three alewives were tagged in April. Later in the season, they tagged 53 bluebacks.
“Over 80 percent of the alewives made it through the tidal gate, which was not 100 percent, but it was good, ” Alcott said.
“But with the bluebacks, it was not so hot. Barely 10 percent of those herring even made it to the tidal gate at all, and out of that very few, less than half of them made it up to the spawning ground,” he reported. “Even more dismal than that, of the few that made it in only one made it out alive.”
Of the 136 herring tagged, 39 percent successfully entered the river by passing through the tide gates, 81 percent were detected at the spawning ponds upstream, and 49 percent of the entrants migrated back out of the river past the tide gates, he said.
“Do [the alewives] do a better job [than the blueback herring] making it up? I don’t think so,” he said. The alewives showed up early at a time when striped bass were not waiting to quickly consume them. The bluebacks got there late in the season and had to deal not only with striped bass, but snapping turtles, otters and birds that prey on them.
“Is it an alewife-blueback thing? Is it the time of the season when they get there? Do herring prefer the daylight or do they wait for nighttime?” he asked. “We need to find that out so we can get more accurate estimates on the number of herring coming in, and that’s what I’m working on now,” he said.
Alcott’s display was a big attraction during a break, drawing a crowd to look at his laptop as it beeped while showing the path of a tagged herring.