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Fish Passage

Fish Passageways are man-made waterways that allow fish to swim past an obstruction such as a dam in a river or stream.

Why do Atlantic salmon need fish passageways?

• The Atlantic salmon and many other resident fish species need to move to or from the ocean or within rivers and streams in order to reproduce, feed, and survive. Atlantic salmon migrate to the ocean as juveniles to feed then retrace the migration back to the rivers and streams as adults to reproduce.

• Dams contributed to the extinction of the native Connecticut River stock of Atlantic Salmon because they blocked upstream passage.

Upstream Passageway = Allow fish to migrate upstream towards the headwaters.

Downstream Passageway = Allow fish to migrate downstream towards the ocean.

Imagine yourself running up a skyscraper!

• That’s what fish think when they encounter a dam as they migrate upstream from the ocean.

• Instead of swimming to the top of a dam, fish swim up fish ways or ride up fish elevators.

Types of Upstream Passageways

1. Vertical Slot Fishway

   • Fish weave through the slots on the sides of the chute and rest in the pools.

   • Used by all types of migrating fish.

   
   Bellows Fishway – de-watered.

2. Denil Fishway

   • Fish burst up the middle of the chute in between V-shaped baffles and rest in the pools if the fishway is very long.

   • Used by all types of migrating fish.

   
   Top: DSI, entrance by dam. Bottom: Rainbow fishway.

3. Pool and Weir Fishway

   • Fish leap, plop!, over each weir and rest from pool to pool.

   • Used by Atlantic Salmon and Trout, but not by River Herring, Shad, and Eels because they are not strong enough to jump over the weirs.

   
   Cabot Ladder at the Turners Falls dam in MA

4. Alaska Steeppass Fishway

   • Fish zoom up the middle of the chute through vanes along the sides and bottom, and rest in the pools if the fishway is very long.

   • Used by all types of migrating fish except Atlantic Salmon, because they’re too big for the fishway.

   
   Alaska Mary Steube Fishway in Old Lyme, CT - an Alaska Steeppass.

5. Eel Pass Fishway

   • Eels slither up the wet incline using the bumps and bristles on the chute for leverage.

   • Used only by Eels.

   
   Top: Kineytown eelpass in CT.
   Bottom: Lower Mill Pond Eelpass in
   Old Lyme, CT (on the left ends in the blue trap tank)

6. Culvert

   • A Culvert is a large tube that looks like a drinking straw and goes under a road.

   • Fish swim inside the culvert through baffles to get to the other side of the road.

   • Used by all types of migrating fish.

   • Issues include drop at end of culvert, length of culvert, and water depth within the culvert – all deter fish passage.

   
   Tower Brook culvert in Massachusetts.

7. Fish Lift

   • A fish lift is an elevator just for fish. (Top floor, please.)

   • The elevator only lets fish out at the top of the dam and not at the bottom.

   Here’s how it works:

   
   First, fish swim into a hopper below the dam.
   Then the elevator raises them to the top of the dam,
   and finally opens its doors to release the fish.

Downstream Passageway

What to Do?

A fish has four choices when it approaches a dam as it migrates downstream.

1. Swim over the dam.
2. Stop migrating and get eaten by predators.
3. Swim through the deadly turbines.
4. Swim safely around the dam in a bypass.

Imagine yourself riding down a waterslide.

As fish migrate back to the ocean sometimes they swim through a bypass built alongside a dam to get to the other side.

1. Bypass

   • Fish swim safely around a dam through a man-made canal called a bypass.

   • Used by all types of migrating fish. (Great for River Herring and Shad.)

   
   Leesville

   Dam Removal: Restores both up and downstream access and habitat.

   
   Removal of the McGoldrick Dam on the Ashuelot River in Hinsdale, NH.

U.S. Fish and Wildlife Service