Fish Surveys - Minnow Traps

Revision History

  • Revised on 05/10/26 to address rope type and length, deployment location identification for maintenance and retrieval, and fish handling concerns.

  • Revised on 10/13/26 to clarify trap location marking, lost traps, and set duration.

Background

Fish surveys are a big part of NFC’s Holistic Stream Assessment/Restoration methodology. This includes NFC sponsored trapping and netting, and agency sponsored electro-fishing where NFC assists. These surveys are usually performed under a Scientific Collection permit issued by a state fish and game agency.

Goals 

Minnow traps are a cheap, non-lethal, effective, and efficient method for surveying certain types of fish. While they are not really effective for predator species such as trout, pickerel, bass, etc., they are very effective for scavengers like shiners, sunfish, perch, and various minnow species. Minnow trap effectiveness is also limited in regard to fish size due to legal restrictions in regard to opening size.

Unlike sein and cast nets which have to be actively maintained, minnow traps can be set and left in place for a period of time. They can also be deployed in conditions that are not conducive to sein nets such as deep water, muddy bottoms, and weedy areas, and places where there are safety concerns due to trash, industrial equipment, etc.

Policy

Below are the guidelines pertaining to the use of minnow traps:

  • Administrative

    • Chapters must obtain a scientific collection permit from the appropriate government agency before setting traps

      • Do not operate under the guise of legal bait trapping as that is not what we are doing

    • Where applicable, landowners should be notified in advance of your intent to trap with a request for permission to do so

      • Municipality owned land

      • State-owned land

        • While this is often covered under a state-issued scientific collection permit, notifying state fish and game lets them know what we are doing where and when

      • Organization owned land

      • Business owned land

      • Private land

  • Equipment

    • Standard minnow traps

      • Black traps are recommended as they are harder to detect and less likely to be stolen, vandalized, or removed from the water by curious people or kids

      • Vinyl dipped traps are preferred as they resist rusting and last a bit longer than painted traps

      • Traps must be equipped with ringed versus barbed entry holes to prevent injury to fish

      • Traps must be equipped with a quick-release clip for fast and easy opening and closing

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  • Identification

    • Traps must have an NFC ID tag affixed to them for easy identification

      • National NFC will provide these upon request

  • Deployment

    • Traps should have a 30-foot dull colored, ideally camouflaged, narrow, sinking rope attached to them

      • Ropes should be tied off to a tree, root, bush, or dull colored tent stake before throwing the trap in the water to prevent loss

      • Traps, ropes, and tie-offs should be placed in a discreet manner so as not to draw attetntion to them

        • We have had traps removed from the water by curious people

      • Excess rope should be coiled up and secured with a twist tie, zip tie, or short length of string or cord so that it does not get in the way or pose a hazard to humans or wildlife

      • Trap locations should be marked with a wire flag with “NFC” on it for easy identification and retrieval.

        • Flags should be non-white so as not to be confused with flags placed by other people for other reasons.

        • Flags should be placed within 10-12-feet of the trap, and directly across from it where possible.

        • If a flag can’t be places directly across from the trap, set it 10-12 feet on either side of the trap mark it with a short piece of surveyors tape for easy identification

        • Do not set flags right at the trap so as not to draw attention

        • National NFC will provide marked orange flags upon request.

    • If a trap is accidentally lost or manages to come unsecured, it needs to be retrieved within 24 hours, no exceptions.

      • Ghost traps can kill fish and amphibians due to stress, oxygen depletion, urine, excrement, and tissue buildup, lack of food, and predation

      • If found by someone outside of NFC, this is a poor reflection on the chapter and the organization as a whole and can result in a refusal to allow trap deployment in the future

  • Bait

    • Traps can be baited with bread, pet kibble, perforated cans of cat food or tuna, capsules or nets with worms or other insects, fish flesh, poultry or meat, etc.

      • Bait should be adjusted based on the targeted species, or mixed to attract multiple species

  • Location

    • Traps should be set away from high traffic areas wherever possible

    • Traps should be set near inlets and outlets

    • Traps should be set in shallow and deep water to increase your odds of finding fish, as well as varying species

  • Duration

    • Traps should be set for no more than 24 hours to lessen the chance of stress and mortality

      • Sets of 6-12 hours are preferred and are often equally as affective as 24-hour sets

      • Dead fish in a trap is not a good message for NFC

    • The longer a trap sits the less useful the data is in regard to estimating general abundance. It is very likely that most fish trapped are captured early in the set.

  • Handling

    • Traps containing fish should not be placed on the ground

    • Fish should be removed from the trap by hand and placed in a 5-gallon bucket of fresh water as quickly as possible to lessen stress

      • If fish will be kept in a bucket for more than 5 minutes, a small battery powered aerator should be used

  • Miscellaneous

    • Dead, visibly stressed, and diseased fish should be removed from the trap and disposed of properly

    • Nonnative fish should be disposed of rather than released when doing so would have a positive ecological impact

    • Rare or protected native species should be quickly photographed and measured, released immediately and unharmed, and reported to the proper authorities with capture location within 24 hours

      • GIS location pins are best for supporting subsequent actions

    • Unusual nonnative species and those not known to be present should be contained and presented to the proper authorities within 24 hours

    • All fish trapped should be identified, measured, and cataloged. Some sample pictures should be taken for reference

      • Like sized fish of the same species do not need to be photographed more than a couple of times

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