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Kansas Cooperative Fish and Wildlife Research Unit

Judith Patterson (2011)

Judith Patterson (2011)- Can crayfish influence ecosystem function?: exploring crayfish movement using PIT tags and mobile and stationary antennas. (Mentor: Martha Mather)

Crayfish affect ecological interactions at several trophic levels, and therefore, may alter nutrient cycles and energy flow within streams. Studying crayfish movement can provide insights into these stream ecosystem functions. New technologies, including PIT tags and both stationary and mobile antennas, have recently become available as tools to study movement. In this study, we conducted methodological tests of PIT tag technology and used PIT tags to assess crayfish distribution and movement. Specifically, in King's Creek, Konza Prairie Biology Station (Manhattan, Kansas), 181 crayfish were externally tagged with either 23mm long (diameter=3.85mm; mass=0.6g) or 12mm (diameter=2.15mm; mass=0.1g) half duplex PIT tags, and were then released back into the locations where they were trapped. To detect tagged crayfish, mobile backpack antenna surveys of the study area were conducted once per week in the morning for five consecutive weeks. Additionally, four stationary antennas were set up in one pool of the study area to detect tagged crayfish movement 24 hours per day. In the backpack antenna surveys, 137 tagged crayfish were detected at least once, resulting in a 75.7% detection rate. The stationary antennas detected 128 tagged crayfish over the 5-week study period, including crayfish that were originally released into other areas within the study site. GIS maps of tagged crayfish distributions from the backpack survey data showed that although most crayfish used the three pools within the study site, some also used the riffle, run and glide habitats. Trajectories of crayfish detected more than once using both mobile and stationary antenna data illustrated several types of movement including no movement, small movements within a selected habitat, or larger movements across habitats. Our preliminary results showed that our methodology successfully tagged and located crayfish. However, the differences in range and temporal patterns of the stationary and mobile antenna data show that crayfish movement is complicated and additional analysis and research needs to be done. These distribution and movement data can then be synthesized to provide broader ecological insights into the role that crayfish play in ecosystem function.