Hurdles for Herring in Wellfleet's Herring River 11-17-14

Hurdles for Herring in Wellfleet's Herring River
By Rich Eldred
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Posted Nov. 17, 2014 @ 5:58 am

WELLFLEET -- People have been counting herring as they swim upstream to spawn for years but Derrick Alcott is interested in river herring as individuals.
No he's not interested in their feelings, pet peeves or whether they like long walks on the beach (they don't). But the Ph.D student at UMass Amherst is curious about their trials and travails as they navigate the Herring River in Wellfleet.
One reason people haven't paid much attention to individual herring is they're not only hard to tell apart but it's difficult to distinguish one species of river herring from another.
Alewives (Alosa pseudoharengus) and blueback herring (Alosa aestivalis) overlap quite a bit in their physical characteristics but bluebacks are a little more torpedo shaped, have differences in the structure of the eye and should have a bluer cast to their back. They are also a little more southern in their distribution, however both fish swim up the rivers of Cape Cod each spring.
Once they get up to the spawning ponds alewives prefer to lay their eggs in the sand of the pond while bluebacks favor streams flowing into the pond. Alewives are the first to migrate up-river, arriving in April on Cape Cod while bluebacks roll in a little later during May and June. Unlike salmon herring can swim back out to sea and return to spawn again, sometimes three or four times as they live about eight years.
Alcott studies both species and he is particularly interested in how the various impediments in the Herring River valley, five culverts and the tidal gates at the dike on Chequesset Neck Road, affect the herring's ability to migrate. He spoke at the Wellfleet Harbor Conference last Saturday at Wellfleet Elementary School.
Massachusetts has imposed a moratorium on river herring harvest since 2006, as their numbers seemed to be plummeting. While the exact cause of the population drop isn't known, it appears accidental bycatch at sea may have more of an impact than people netting the fish once they enter the rivers. The damming and diking of rivers has also reduced spawning runs. The tidal flow in the Herring River has been reduced since 1909 but there is currently a project to restore flow to much of the 1,000-acre estuary.
Alcott is using passive integrated transponder telemetry to tag and track individual fish through the current restrictions.
"The tide gates are at the mouth of the river and they attempt to control the tidal flow into the estuary," Alcott explained. "When the tide is low on the harborside freshwater pours out through all three gates. When the tide is up two of the three gates close and seal and only one gate lets the saltwater through, and that's like having a thumb on a hose; the water shoots out faster."
That can also shoot a herring through but it makes it difficult to get up stream when the tide is flowing out.
The culverts don't present a barrier of out-rushing water, however.
"Thy are clear and open and the fish are physically able to get through but not all of a sudden," Alcott noted. "Thy are a choke point. They are a lot darker and the fish is swimming along a sunny river and comes up to this and freezes. They don't like the dark."
Herring are schooling fish and once one fish stops they all stop on their way to Herring, Higgins and Gull ponds on the other side of Route 6. That stalling provides an opportunity for predators.
"Everything likes to eat them, they're an important part of the foodweb," Alcott noted. Snapping turtles like to linger at the culverts, he said.
Alcott also tagged 20 bass and didn't observe any swimming upstream. The PIT tags have no battery, they use a copper coil, so the tags last forever. They're inserted into the fish, just under the ribcage into the muscle with a small razor blade, the muscles seals up the wound. Each one has a unique code.
Alcott rigged circular antennae inside a PVC pipe at the entrance and exit of each culvert, which 'pings' when the fish swims through, transmitting the tag data to a recorder. He also put antennae at the approaches and departure areas so he could track how long the fish lingered. What usually happens was the fish would dilly-dally as it neared the culvert then quickly shot through the remaining three antennae once it finally decided to try the culvert.
Alcott also recorded how many actually made it all the way up-river. Out of 53-tagged alewives 80 percent made it through the tide gates and 90 percent of those swam all the way into the ponds but the bluebacks arriving later fared much worse; only 10 percent of 63 tagged got through the tide gates and lass than half of those (just four fish) arrived at the ponds. Only one blueback made it out alive on its way back to the sea.
"What's important? Don't be late to dinner," Alcott theorized. "Or is it don't be a blueback? My hypothesis is that when you show up early the striped bass aren't there yet. So you can take your time waiting at the tide gate. The bluebacks arrive later (May and June) and the striped bass are going after them while they wait for the tide (at the gate) to turn."
The early data suggests the tide gate is having a disproportionate impact on bluebacks.
Next year Alcott wants to take a closer look at how predators (bass and turtles especially) are using the barriers. He'd also like to see if the herring are migrating during the day or might.

From Forum

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