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Early signs of positive changes after herring count 8-1-15

Early signs of positive changes after herring count

Wicked Local Marshfield
By Kristi Funderburk
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Posted Aug. 1, 2015 at 6:00 AM
Updated Aug 1, 2015 at 9:48 AM

The North and South Rivers Watershed Association staff saw some early signs of positive changes after reviewing its data from the latest herring count.
Numbers in Pembroke's Herring Brook, for example, show a steady comeback after two years (2010 and 2011) when the system's fish ladder—a step-like structure designed to help the herring move upstream—broke and prevented passage over the dam.
And though the counts were low this year in Scituate's First Herring Brook, association executive director Samantha Woods deemed it a good sign to see fish at all. It was an extinct run until 2011 when a town agreement brought the first flow of water to the dam's otherwise ineffective fish ladder.
"The good news is there are fish," Woods said. "The question is, at what point does it become a viable population?"
The North and South Rivers Watershed Association (NSRWA) started collecting data four years ago to measure how many herring are crossing four of the watershed's 65 dams.
This year, it relied on about 100 volunteers to take turns visiting four rivers in the watershed to count how many herring are getting passed the dams. Each count takes 10 minutes and there are six to nine counts per day, so the NSRWA can collect about 300 counts per site.
While NSRWA staff needs a decade of these scientific samplings to see trends in herring population, the annual counts could provide local ecologists the best evidence in supports of an on-going effort to remove unused dams.
"What we need is evidence-based decision making to improve the ecological integrity of our waterways," Woods said.
If dams restrict herring access to larger waterways, it can hamper their ability to spawn and overtime, thrive as a species, Woods explained.
The loss of herring has a ripple effect on shore, too.
Herring are a forage fish for striped bass, tuna, and other fish humans like to eat, therefore they sustain other populations of fish on which fishermen can make a living, Woods said. Even the heron, egrets, osprey some birdwatchers enjoy to spot in nature like to dine on herring.
"We have to ask ourselves as a society, what do we want?" Woods said. "We have decisions to make about the repairs of these dams and whether we want to continue that in the future and keep living with the degraded ecosystems that we have, or do something about it."
Some dams, like the one in First Herring Brook in Scituate, have modern-day functions. That dam holds back water for the town's drinking supply.
But many of the 3,000 dams dotting the Commonwealth are leftover from the colonial age and Industrial Revolution, but have little value in the modern world, Woods said.

"A legacy dam isn't serving any purpose other than it's pretty," she said. "People cared about dams until they got electricity. They really are sort of just rotting in place."
Dams may prevent rivers and streams from running freely and can isolate fish like herring and Eastern brook trout, but they also create stagnant waters, which lower water quality and encourage pollution-tolerant species, algae, and invasive species, NSRWA ecologist Sara Grady said.
The likelihood of an infrastructure failure only increases as the dams age, Woods added, making them a liability to the property owner.
The Mill Pond dam behind the South Shore YMCA in Third Herring Brook, which cuts through Norwell and Hanover, was successfully removed last fall, Woods said. The NSRWA is now working with The Cardinal Cushing Centers to take out a dam it owns in the brook by fall 2016 to open access to the estuary, she said.
The Third Herring Brook count showed just 132 fish this year, but Grady said this is likely not an accurate depiction as the numbers are more typically in the thousands, Grady said. Unlike the other count locations, which have fish ladders, volunteers appointed to this brook have to look for herring that swim through a culvert at a road crossing.
As efforts to remove dams continue along Third Herring Brook, the NSRWA plans to watch for a population increase.
Woods is hoping to discuss with the Marshfield officials the dam behind Veterans Memorial Park in the South River, which has caused passage problems and backwatering that may contribute to flooding.
The association's count figures so far show the number of herring to pass the dam is dropping.
NSRWA volunteers reported two fish passed the South River's fish ladder and 1,225 fish were seen below it, Grady said. Previous counts show there were 80 that passed the ladder in 2012, 17 in 2013, and four last year.
"Clearly there's an issue," Woods said, explaining the problem is largely traced to flow management and structure of the fish ladder.
The fish ladders in the South River and Scituate's First Herring Brook are an older style made of concrete and have small pools to allow the herring, which can't jump like other species, to gradually cross a dam, Grady said.
The volunteers reported seeing no herring pass the Scituate dam and four of the fish downstream this year, Grady said.
Water flow dictates if fish cross the water, Woods said.
"It's like Goldilocks," she said. "If it's too much water, they can't go up. If it's too little water, they can't go up. It has to be just right."

Pembroke's fish ladder is a newer model that is made of aluminum and has vanes that create a circulated flow that helps draw the fish, which are attracted to the area of highest flow, Grady said. The town also has a Herring Commission that closely monitors the herring stock, Woods said.
This year's herring count showed 3,725 of the fish passed the ladder and 9,995 were seen below it in Herring Brook in Pembroke, Grady said.
"It is our most prolific run," she said.

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