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What is Fish Exclusion?

Fish exclusion for projects requiring in-water work is typically defined as safely removing and relocating any fish from the in-water work area and then keeping them out until the work is done.

What kind of work requires Fish Exclusion?

Fish exclusion is almost always required where fish-bearing or potentially fish-bearing waters such as streams or ponds must be de-watered or dried up prior to doing work, such as a culvert replacement or stream realignment. Even if the in-water work area does not need to be completely de-watered, fish exclusion will likely be required if there may be impacts to water quality, such as high turbidity, or if fish may be mechanically injured by the proposed work.

Other kinds of work may include stream channel relocation, sediment pond maintenance (dredging), flow diversion structures, pipeline or other utility crossing of streams, or log structure or gravel placement for habitat enhancement projects.

What is a Fish Exclusion Plan? When is it required?

It’s best to think of the fish exclusion plan as a part of and the first step in the actual fish exclusion - a do-able and often required step to be taken prior to commencing fish removal and the in-water work to follow.

A fish exclusion plan describes the materials, methods, and sequencing surrounding how to safely remove fish from the in-water work area prior to construction and to keep them at bay until the work is done. The fish exclusion plan is often very closely related to, and intertwined with, a flow diversion plan. Often a fish exclusion subcontractor and the general contractor (or another subcontractor) will work closely to formulate a combined flow diversion and fish exclusion plan for submittal. Or the fish exclusion plan can be a section in a broader flow diversion plan.

Note that specifications or permit requirements for individual in-water construction projects may require that a fish exclusion plan be submitted and approved, prior to actually conducting safe fish removal and exclusion.

How are the fish removed?

Scientists use a variety of equipment is used to make sure fish are safely removed and nearby habitat is protected, including electrofishers, seine nets, and dipnets.

Accomplishing fish exclusion in a way that is safe for the fish and does the least damage to habitat requires specialized equipment and a certain amount of expertise and training.

Specialized fish exclusion equipment may commonly include electrofishers, (beach) seine nets, and dipnets (including “sanctuary” dipnets). In addition, various block nets, screening, transport buckets or totes, or even boats may be needed. An electrofisher is an electronic backpack-carried device which sends electric currents of various forms and intensities through the water to temporarily stun fish so that they may dipnetted and moved out of the project area. (Learn more about electrofishing here.)

Since this involves some risk to the fish as well as workers, it is often used where seining is infeasible or as a second-choice or “clean-up” method after several seining passes have been made. Sanctuary dipnets have plastic or rubber at the bottom and so do not fully drain and hold some water during fish transfer. Theoretically, transferred fish are never out-of-water. This equipment may be specified where it is anticipated that fish species listed under the federal Endangered Species Act (ESA) may be encountered. Captured fish are typically released to the nearest stream sections or other water bodies which are largely unaffected by the project.

I am a contractor. What if I don't have a plan prior to conducting work?

Often we’re hired to conduct fish exclusion work before it is fully clear to those involved that a fish exclusion plan submittal and approval is needed. A site meeting may be necessary or helpful for all of those involved to understand site and project constraints. For instance, sometimes fish exclusion methods described in plans or permits are not actually feasible due to too much debris or too many snags for seine-netting to work.

How much does a fish exclusion plan cost?

A fish exclusion plan is a way of establishing the equipment needed and the sequencing of steps to be undertaken to conduct the needed fish exclusion so that the required in-water work can follow. Even if a formal plan is not required, it’s a good investment to have an informal plan for construction sequence, so that fish removal doesn’t unduly delay the later steps.

At The Watershed Company, a written plan for submittal may start at around $1000 or less, and fish exclusion work would typically start at around $3000. Not all projects require a formal fish exclusion plan for submittal. In those cases the plan may be more of an informal discussion and understanding between the fish exclusion subcontractor and the prime or general contractor regarding who will be responsible for what tasks, on what schedule, and in what order. This often requires close coordination. For example, the prime or general contractor may be responsible for coffer dam placement and a pumped bypass system, and it may be important for fish exclusion to be very closely coordinated with the activation of the bypass and the initial isolation and/or dewatering of the in-water work area.