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PIT Tag Technology Development and Implementation:

In addition to antennas that are integrated into common handheld PIT tag readers, larger custom-built antennas can also be designed. There are two general types of PIT tag antennas: stationary and portable. Since 1999, we have been designing and building custom antennas to monitor fish movements in small streams. As PIT technology has progressed, we have been able to construct larger antennas with increased read distances.

Design:

• Tags: Because we are interested in tagging small fish, we design our antennas to work with 12mm full-duplex PIT tags; the smallest commercially available half-duplex tag is 23mm.



• Readers: We have designed antennas using the Digital Angel FS1001M (Multiplexor), FS1001A(Adult Reader), and FS2001ISO(Cheese Block). We have also designed antennas to work with the TIRIS half-duplex PIT tag reader. [Disclaimer: mention of company names does not imply endorsement by the US Government]



• Stationary: There are two basic types of stationary antennas: flat plates and pass-thru. Flat plates are fixed to stream bottom and detect tagged fish that swim over the antenna. Pass-thru antennas stand vertically in the stream, with tagged fish being detected as they pass through the antenna. Because the electromagnetic field generated by the antenna is strongest in the plane of the antenna, pass-thru antennas are more effective at sampling the whole water column. However, pass-thru antennas are more susceptible to high stream flow and debris loading.



• Portable: Small antennas can be attached to poles to actively search for tagged fish. These antennas are smaller than stationary antennas with smaller read ranges, but because they are portable they can be used to survey the whole study area.

Implementation:

• Stationary: (click on pictures to enlarge)

  West Brook, MA (2002-2007); paired FS 1001 A transceivers	West Brook smolt weir; single FS 1001 A transceiver	West Brook, MA (2008-current); FS 1001 Multiplexor
  Stanley Brook, Maine; Tidal(fresh- & seawater) FS 1001 Multiplexor installation	Mitchell Brook, MA; paired FS 2001 transceivers to monitor culvert passage	Red Brook, MA; Tidal (freshwater) paired FS 2001 transceivers
  Quashnet River, MA; paired FS 2001 ISO transceivers	Bajit Vidis, Norway; paired FS 2001 ISO transceivers	Nash Stream, NH;paired FS 2001 ISO transceivers used to monitor culvert passage before and after culvert replacement

   

• Portable: (click on pictures to enlarge)

• FS 1001 A
• FS 2001 ISO

Analysis:

The stationary antennas provide critical data on movements past fixed locations. In our primary, long-term study areas, we have installed antennas at the confluence of tributaries and at the top and bottom of mainstem study area. Using data from these antennas, we have identified the timing and extent of seasonal spawning movements of tagged salmonids into tributaries and temporary and permanent emigration from the study area. Emigration data are important for separating losses due to mortality and emigration, providing much improved survival estimates.

The portable antennas can be used much like a metal detector to locate tags over large spatial scales. Data from portable antenna surveys can be used to examine small-scale (10-1000m) movements and for short-term survival estimates (daily to weekly). Portable antenna surveys are particularly useful when repeated observations are required but animal handling must be kept to a minimum. In one very interesting study (Nash Stream, NH), collaborators surveyed the stream weekly from July to November. The result is an extremely detailed history of individual movements and fine-scale survival estimates. Because the study area was also bounded by stationary antennas and mortality could be separated from emigration, the survival estimates approached estimates of true survival.

Relevant Publications:

O'Donnell, M. J., G. E. Horton and B. H. Letcher. Submitted. Use of portable antennas to estimate population abundance of PIT tagged fish in small streams: factors affecting detection efficiency.

Horton, G. E., T. L. Dubreuil, and B. H. Letcher. 2007. A model for estimating passive integrated transponder (PIT) tag antenna efficiencies for interval-specific emigration rates. Transactions of the American Fisheries Society 136: 1165-1176.

Zydlewski, G.B., G. Horton, T. Dubreuil, B. Letcher, S. Casey, and J. Zydlewski. 2006. Remote monitoring of fish in small streams: a unified approach using PIT tags. Fisheries 31(10): 492-502.