Collecting Crayfish

Crayfish are often nocturnal because they are prey to many organisms that forage during the daylight hours (fish in particular). If you are having trouble finding crayfish during daylight hours, try turning over rocks or other shelter (be sure to return rocks to their original position), or wait until dark. Most crayfish species will forage at night in the open, and can be spotted in shallow water in the beam of a strong flashlight. The following information will direct you on how to properly collect crayfish specimens and what to do after you have samples. 

 GENERAL PROTOCOL FOR CRAYFISH COLLECTIONS

Objectives:

To collect specimens throughout Maine to determine distributions of native and invasive species.

To collect information on crayfish abundance.

Materials:

• • Ziploc bags or Jars

  • Freezer 

  • Specimen labels (rite-on-rain paper if possible) – see provided labels.

  • Pencil (Do not use ink because most inks dissolve in alcohol)

  • Ice (if possible)

  • Small dip nets

Protocol:

A. Collecting Crayfish:

• 1. Several common Maine crayfish do not trap well – traps need to be left soaking for at least 2 nights, and hand or electroshock collection may be needed.

  2. Specimens can be kept alive in the refrigerator for some time; use only enough water to barely cover the crayfish (crayfish can quickly dirty water that does not have filtration so it’s best to maximize air-water oxygen exchange).

  3. If temporarily storing outside, put crayfish aside in a bucket with ½ inch of clean water (just enough to moisten their gills) and place in the shade.

  4. When collecting crayfish in the field, please make note of the following:

     • Any distinguishing behavior (such as aggression or mild tempered), and habitat, where they were found under rocks, burrows, mucky areas, vegetation, and so on).

     • Note abundance (rare, common, and abundant).

Rare: only one or two crayfish seen

Common: not readily visible moving on the substrate

Abundant: readily visible moving on the substrate

Absent: no crayfish seen, no evidence of burrows, etc - the absence of crayfish in an area is just as important to our study.

B. Choosing Specimens (Vouchers):

• • 1.  Examine males to see if they are of all the same species. Pay particular attention to the structure of the first pleopod (otherwise known as the copulatory stylet or gonopod). Shape of the claws and presence or absence of spines on the carapace can be useful.

    2.  Preserve males in alcohol or by freezing. It is more humane to freeze or ice before putting them in alcohol.

    3.  Preserve only 1 individual if all crayfish are the same species. *Please return others to the exact location you found them*

    4.  If you are unsure, preserve more than 1 individual.

    5.  If you only have females, preserve 1 female if they all look the same; preserve more than one if you are unsure of the species.

***IMPORTANT NOTE: Please do not release any live crayfish except where you found it. It is easy to inadvertently introduce non-native crayfish species to new habitat. Even if you think you have a native species, it may not be native to a specific lake or stream. The best way to prevent their spread is to leave them be.

C. Label your specimen (paper and pencil - no pen):

• 1.  Name of water body, town, & GPS (latitude/longitude) coordinates are critical.

  2.  Abundance information is helpful, especially for spotting possible invasive populations.

  3.  Additional information and observations, like behavior and habitat, can be written on the back of the specimen label.

  4.  Fill out Labels to the best of your ability and place in storage container with the crayfish specimen.

D. Ship Labeled Specimens to the following address: (please give us a heads up so we can prepare for their arrival especially if they are frozen!)

    Ship To:

        Dr. Karen A. Wilson, Dept. of Environmental Science and Policy

        University of Southern Maine, 309 Bailey Hall

        37 College Ave, Gorham, ME 04038

Many thanks for your help & interest!

Any questions or interesting observations? Please contact us at anytime:

Dr. Karen Wilson, University of Southern Maine

207-780-5395