Northwest Fisheries Science Center

Glossary

Glossary

Categorical Exclusion
An action that is found not to have a significant effect on the human environment either individually or cumulatively, and which therefore does not require an environmental assessment or an environmental impact statement (for full definition, see U.S. Code of Federal Regulations 40 CFR 1508.4).
Electromagnetic Interference (EMI)
Electrical induction or radiation that interferes with an electronic circuit.  In more permanent PIT–tag monitoring systems, antennas are shielded to prevent EMI.  For instream systems, the lack of shielding means that these systems will be more susceptible to EMI, which can interrupt transmission of the tag signal (code) and degrade tag–reading efficiency.
FDX (Full Duplex)

One of two possible modes of operation for a PIT–tag interrogation system.  In FDX systems, the tag is continuously energized while in the antenna field; it then continuously modulates the electromagnetic field, producing a unique pattern, which is processed by the transceiver to yield a unique tag code. 

We refer mainly to FDX systems, specifically the FDX–B 134.2–kHz system, whose technologies are based on ISO standards 11784 and 11785.  For an overview of how FDX PIT–tag systems function, see Beigel (1999). 

Frequency (kHz)
Frequency refers to the number of occurrences per unit of time.  Wave cycles are usually measured in kilohertz (kHz).  One hertz is equal to one cycle per second; thus 14 kHz means 14,000 cycles per second.
HDX (Half Duplex)
One of two possible modes of operation for a PIT–tag interrogation system.  In HDX systems, a charge cycle and transmit cycle are used, with a small capacitor within the tag being charged during the charge cycle.  Once the charge cycle is complete, the tag telegram (i.e., code) is transmitted. 
ISO (International Organization for Standardization)
Operating frequencies and transceivers for PIT tag detection systems are based on standards published by the ISO (document 11785); these transceivers can read both FDX and HDX tags (ISO 1996). 
Kilohertz (kHz)
A unit of measure for thousands of wave cycles per second, where 1 kHz equals 1000 complete wave cycles per second (see frequency).
NEMA
National Electrical Manufacturers Association.  Provides published standards for enclosures housing electronic components in the U.S. 
PIT Tag (Passive Integrated Transponder Tag)

The passive integrated transponder (PIT) is a type of radio frequency identification (RFID) used extensively in fisheries research.  The PIT tag is relatively inexpensive (~$3 per tag) and can yield high returns of information, with detection rates in the high 90% range for fish that come within reading range of a detection system. 

Encased in glass, the standard 12.5–mm PIT tag is biologically inert and can be injected with a hypodermic needle into salmonids as small as 60 mm. 

PIT Tag Information System
A non–proprietary community data–sharing system, the PIT Tag Information System, or PTAGIS database is a repository for tagging and detection records of fish throughout the Columbia River Basin.  The database and its associated documentation (Marvin and Nighbor 2009) are publicly available to researchers, who contribute and extract data for various studies.  See also the PTAGIS wiki