Author: Kristina Sorensen, Florida Cooperative Fish and Wildlife Research Unit, P.O. Box 110485, University of Florida, Gainesville, FL 32611-0485, kristina_sorensen@usgs.gov, 352-846-0639

Species list
Description of technique
       Field time components
       Office time
       Equipment
Things that could bias your counts
       Mesh size/funnel diameter
       Baiting
       Water level
       Trap period
       Age and sex
       Weather
       Time of year
       Habitat
Advantages and disadvantages
Existing protocols and programs using this technique
Studies that have used this technique
Literature cited
Send a comment on this technique (this takes you to another page)
See existing comments (this takes you to another page)

Salamanders: Amphiuma means, Two-Toed Amphiuma; Pseudobranchus axanthus, Narrow-Striped Dwarf Siren; Siren intermedi, Lesser Siren; Siren lacertina, Greater Siren

Snakes: Farancia abacura, Eastern Mud Snake; Nerodia fasciata, Banded Water Snake; Nerodia floridana, Florida Green Water Snake; Nerodia taxispilota, Brown Water Snake; Regina alleni, Striped Crayfish Snake; Seminatrix pygaea, Black Swamp Snake; Thamnophis sauritus, Ribbon Snake

Turtles: Sternotherus odoratus, Stinkpot; Kinosternon bauri, Striped Mud Turtle; Pseudemys floridana, Florida Cooter; Chelydra serpentina, Common Snapping Turtle; Apalone ferox, Florida Softshell

Frogs (adults and tadpoles): Acris gryllus, Southern Cricket Frog; Rana clamitans, Bronze Frog; Rana grylio, Pig Frog; Rana sphenocephala, Southern Leopard Frog

Fish: Ameriurus spp., Bullhead Catfish; Amia calva, Bowfin; Centrarchus macropterus, Flier; Elassoma sp., Pygmy Sunfish; Enneacanthus gloriosus, Bluespotted Sunfish; Enneacanthus obesus, Banded Sunfish; Erimyzon sucetta, Bluegill; Esox americanus, Redfin Pickerel; Esox niger, Chain Pickerel; Etheostoma fusiforme, Swamp Darter; Fundulus spp., Topminnows; Gambusia holbrooki, Mosquitofish; Hoplosternum littorale, Armored Catfish; Jordanella floridae, Flagfish; Lepisosteus platyrhincus, Florida Gar; Lepomis spp., Sunfish; Leptolucania ommata, Pygmy Killifish; Micropterus salmoides, Largemouth Bass; Notemigonus crysoleucas, Golden Shiner; Poecilia formosa, Sailfin Molly; Pterygoplicththys sp., Sailfin Catfish

Crayfish traps are large, bell-shaped funnel traps with three funnels located near the bottom. Funnels are conical with an outside openings of ca. 20 cm, and an inside diameter of ca. 4.5 cm. Traps are 80 cm in height. A vertical column (ca. 14 cm tall) located on top of the trap allows captured animals to breather air when the trap is fully submerged. The traps are constructed from 2.5 cm nylon-coated chicken wire. Traps are handmade, and available commercially from a fishing supply company in Tampa, FL (Lee Fisher International, Inc., 813-875-6296).

These traps were first used to catch apple snails (Pomacea paludosa) in the Florida Everglades (Darby et al., 2001). In addition to capturing apple snails, a large number of two-toed amphiuma (Amphiuma means), green water snakes (Nerodia floridana), frogs and small turtles were recorded as by-catch. However, Darby reported high rates of mortality for aquatic snakes, as a result of animals becoming lodged in the large mesh while trying to escape.

Sorensen (2003) conducted a study that examined the effectiveness of these crayfish traps in catching large aquatic salamanders (Siren lacertina and Amphiuma means). In this study, crayfish traps were lined with 5 mm plastic Vexar™ mesh to prevent adult mortality and increase juvenile capture rates. Crayfish traps were compared with minnow traps to determine relative capture success of each method. Crayfish traps were significantly more successful in capturing both siren and amphiuma. Average capture success (# captures/ # trap nights) was 15%, compared with less than 1% success using minnow traps. It should be noted that no mortality occured during the one-year trapping period, indicating that the modification of the trap was successful. In addition to successfully capturing salamanders, crayfish traps captured many additional species of snakes, amphibians, and fish.

Siren and amphiuma are often neglected in amphibian monitoring programs because of their cryptic nature. These species live in bottom debris and heavily vegetated areas that are difficult to sample. Until now, no clear method was available for easily and reliably capturing these species. Modified crayfish traps have emerged as an excellent method for monitoring populations of large aquatic salamanders, as well as a method for inventorying aquatic fauna in lentic systems. To date, these traps have only been tested in the Southeastern U.S., but may prove useful for capturing similar species in other parts of the country.

Techniques for capture of siren and amphiuma

Crayfish traps are placed on the bottom substrate in mucky or heavily vegetated areas. PVC pipes are staked into the ground next to traps and secured to the trap using plastic zip-ties. The PVC pipe is optional, but serves two purposes. First, it prevents traps from tipping over. Secondly, the pipe acts as a visual aid to locate traps from afar.

Traps will often accumulate muck in the bottom of the trap that may disguise captured salamanders. Therefore, traps must be shaken vigorously in the water to dissolve debris and locate any captures. To remove animals, open the top throat and turn the trap upside down, dumping any caught animals in plastic buckets. Buckets must be tall enough so that snakes and large salamanders cannot jump out.

Aquatic salamanders are very slimy and cannot be held with bare hands. To measure and/or mark salamanders, a squeezebox works well and avoids the use of anesthesia. Anesthesia greatly increases time spent in the field while waiting for animals to recover, and may have associated health risks. A squeezebox consists of a plastic storage box lined with upholstery foam and a piece of clear acrylic (such as Plexiglas™) cut to fit the inside of the squeezebox. The salamander is immobilized when sandwiched between the foam and the Plexiglas™. Using a grease pencil, body measurements such as total length can be traced. A small hole (ca. 4 cm) is drilled in the plexiglass that allows access to the body of the animal for marking. The squeezebox works quickly, with less than 3 minutes needed to measure and mark a salamander.

Initial setup:

• Designing your trap array (location and quantity of traps, dependant upon goals of sampling)
• Travel time to and from sampling locations
• Time needed to set out traps

Survey:

• Travel time to and from site (may involve use of boat)
• 1 or 2 people to check traps (time dependant upon number and location of traps)
• Time to record data on captured animals (3-5 minutes per animal)
• Time to return salamanders to original capture location when done

• Data entry
• Data proofing
• Data analysis
• Report writing

• Crayfish traps ($25 each for lined trap)
• PVC pipe (optional)
• Zip-ties (optional - to anchor traps to PVC pipe)
• Waders (if desired)
• Plastic buckets (to hold salamanders after captured)
• Gallon-size resealable bags (to weigh animals)
• Flexible measure tape (to measure length)
• Materials needed to construct squeezebox: Plastic container, upholstery foam (at least 2 inches thick) cut to fit container, clear acrylic (such as Plexiglas), at least .25 inches thick, cut to fit container

Things that could bias your counts

As with all types of funnel traps, species captures are limited by mesh size and funnel diameter. Mesh size will determine the smallest individuals that can be caught. Funnel diameter will determine the largest animals capable of being captured. Therefore, before beginning a trapping experiment, one must evaluate the size of the target species and modify trap dimensions accordingly.

Baiting traps may affect the species composition of captures. Baiting can act to artificially increase captures of certain species, thus over-representing them in your sampling efforts. Sorensen found that baiting does not increases capture rates of either siren or amphiuma (2003) and thus baiting should be avoided to eliminate this potential bias.

Crayfish traps must be placed in water deep enough to completely cover funnels (ca. 25 cm). In times of drought, or in ephemeral wetlands, crayfish traps are not an effective method for capturing aquatic salamanders. Siren and amphiuma aestivate when water levels drop and are thus very difficult to capture using any sampling methods during such periods. Salamander captures were postively correlated with water level (Sorensen 2003), thus it is recommended to sample during periods of high water.

It is best advised to check traps daily. This lowers the risk of mortality and/or predation events occurring in traps. The number of S. lacertina and A. means captures are not affected by the number of trap days (Sorensen 2003). Therefore, trapping can be conducted over several consecutive days without a significant decrease in capture yield.

It is not possible to sex siren or amphiuma in the field. Therefore, it is not known whether sex biases occur. Modified crayfish traps are successful at capturing adults and juveniles, with no apparent bias in number of captures (Sorensen 2003).

Evidence suggests that A. means are captured most often after periods of rainfall, indicating that they may be most active during these times (Machovina 1994, Sorensen 2003). No such relationship has been found with S. lacertina. Other environmental variables, such as percent cloud cover, have not been examined in relation to capture success in these species.

Siren and amphiuma are more active during certain periods of the year. These seasonal activity patterns appear to be correlated with water temperature (Hanlin and Mount 1978, Machovina 1994, Sorensen 2003). In Florida, Siren lacertina are more active in late winter/early spring, when water temperature is coldest (Ultsch 1973, Sorensen 2003). Amphiuma means are most active in summer months when water temperatures are highest (Machovina 1994, Sorensen 2003). These seasonal activity patterns should be incorporated into the design of monitoring programs to maximize trapping effort and avoid trapping when animals are less active.

Both S. lacertina and A. means are found in lentic habitats with dense aquatic vegetation and/or a deep layer of peat or muck (Petranka 1998). Thus, trapping efforts should be focused in these types of habitats. Unfortunately, very little is known about habitat usage or habitat preference in these species, so any possible habitat bias that may exist is unknown.

Advantages:

• Crayfish traps are non-destructive, causing little disturbance to the habitat. Other popular methods for capturing large aquatic salamanders (dipnetting, dredging) can destroy habitat while sampling and therefore cannot be used for continual monitoring.
• Little physical labor involved in checking traps.
• Trapping does not have associated observer biases, i.e. highly skilled workers are not needed to check traps.
• Traps have high capture success of siren and amphiuma (10-20%; Sorensen 2003).

Disadvantages:

• Costly ($25/trap)
• Traps must be checked often to prevent mortality.
• Traps are cumbersome and can be difficult to transport in large numbers.
• Traps do not work well during low water conditions or in ephemeral wetlands.
• Prey concentration in traps is artificially high and may attract predators.

• D.O.I. Amphibian Research and Monitoring Initiative, Southeastern Region
• Ann Marie Muench, University of Florida
• Joseph Mitchell, University of Richmond
• Paul Moler, Florida Fish and Wildlife Conservation Commission

See Literature cited section below for details on these references.

• Croop, 1996
• Darby et al., 2001
• Sorensen, 2003

Croop, J.D. 1996. A quantitative comparison of sampling techniques and habitat use for the apple snail (Pomacea paludosa) in the Florida Everglades. Unpublished masters thesis, University of Florida.

Darby, P.C., P.L. Valentine-Darby, H.F. Percival, and W.M. Kitchens. 2001. Collecting Florida applesnails (Pomacea paludosa) from wetland habitats using funnel traps. Wetlands 21: 308-311.

Hanlin, H.G., and R.H. Mount. 1978. Reproduction and activity of the greater siren, Siren lacertina (Amphibia: Sirenidae), in Alabama.

Machovina, B.L. 1994. Ecology and life history of the salamander Amphiuma means in Everglades National Park. Unpublished M.S. Thesis, Florida International University.

Petranka, J.W. 1998. Salamanders of the United States and Canada. Smithsonian Institution Press, Washington, D.C.

Sorensen, K. 2003. Trapping success and population analysis of Siren lacertina and Amphiuma means. Unpublished M.S. Thesis, University of Florida.