Tracking Salmon on the Columbia River

Many species of animals have been microchipped with RF-ID tags, including parrots, horses, llamas, sheep, pigs, rabbits, deer, ferrets, snakes, lizards, alligators, turtles, toads, fish, mice, and prairie dogs — even whales and elephants. The U.S. Fish and Wildlife Service uses microchipping in its research of wild bison, black-footed ferrets, grizzly bears, elk, white-tailed deer, giant land tortoises and armadillos.

USGS and USFWS are tracking fish movement in the Columbia River by implanting juveniles with radio tags, which are more effective in shallow water.

Pacific NW National Labs is complementing that effort with acoustic tags (right), which work better in deeper water. PNNL is also contributing its hydrology expertise to measure the Clearwater and Snake rivers’ physical conditions. The University of Washington is providing statistical analysis of the tagging.

At the mouth of the Columbia, NOAA’s Point Adams research station, near Astoria Oregon, gathers additional information by scanning bird droppings at nesting sites.

Grant County PUD, in Washington State, owns and operates two large hydroelectric dams on the Columbia River. They must observe chinook, steelhead, and sockeye salmon as they pass through dams on their way to the ocean. This data also is used to design future fish bypass structures.

Grant County PUD uses several tagging technologies to track fish survival and passage data. No single technology is useful in all situations.

They use three types of tags; Passive Integrated Transponder (PIT), radio tags and acoustic tags. Each has advantages and limitations, says Curtis L. Dotson of Grant County PUD:

  • Passive Integrated Transponders are glass-encapsulated, implantable radio-frequency identification (RFID) devices. They contain no battery. The tag remains functional for the life of the fish and beyond. Each PIT tag contains an individual alphanumeric code, similar to a UPC bar code. They’re injected into an open space in the chest cavity of the anesthetized fish.

    Biomark supplies the tags. It uses both 125 kHz and 134.2 kHz. Cost for an individual PIT tag is about $3, depending on the number of tags purchased.

    Because of their relatively small size (12.5mm long), PIT tags can be implanted into salmon smolts as small as 60 millimeters. The tag detection range is relatively short (measured in feet). This limitation imposed by the receiving antenna size (although there is a 17-foot by 17-foot antenna being used at Bonneville Dam).

  • Radio tags transmit a radio-frequency signal. The tags usually are surgically implanted into a fish and function much like conventional radio transmitters. Radio tags can be used to study all species of adult salmon, adult Pacific lamprey, and juvenile salmonids as small as 90 millimeters. Cost is about $250 per tag, with the price depending on the number of tags purchased. Columbia scientists followed the out-migration of over forty thousand salmon smolts using Lotek tags.

    A radio tag can be tracked from the air as well as a vehicle or boat, allowing surveys of remote or large areas, or tagged fish consumed by predatory birds.

    Typically receiving equipment works similar to a “police scanner,” listening on a variety of frequencies. All radio tags used in the Columbia River Basin require an external trailing antenna, which may affect the swimming performance of juvenile fish or attract predators. The pulse rates of the tags is relatively high, ranging from 1 to 2 seconds. The battery life of the tag is relatively short (9 to 18 days). Slowing the pulse rate limits the tag’s effectiveness in determining route-specific passage at the dam.

    Lotek manufactures most of the radio tags used in the Columbia River Basin. They use one of 25 frequencies ranging from either 149.32 to 149.80 MHz or 150.32 to 150.80 MHz. For each frequency, Lotek features 521 unique codes, for a total of 12,500 unique transmitters. Lotek also makes Archival Tags, which offer data recording capabilities.

  • Acoustic telemetry tags use sound waves through the water to a hydrophone. The tag contains a transducer that intermittently produces signals by inducing high-frequency (416 kHz) vibrations in the water. Fish movements, migration rates, duration of residency, and survival rates can be estimated using acoustic tags. Detection ranges for acoustic-tagged fish can exceed 500 yards and have an efficiency of nearly 100 percent. Acoustic tags cost about $250 each, but the nearly 100 percent detection rate means a much smaller sample size (number) of study fish.

Three types of acoustic telemetry systems are used with Columbia River salmon:

A tagged fish can be heard by an underwater receiver as far as three football fields away. Researchers have placed hundreds of those receivers up and down the Columbia.

As with radio tags, acoustic tags have limitations due to handling and surgical procedures for tag insertion and size and life of the tag. Because there is no external antenna on the acoustic tag transmitter, surgical implantation is less invasive than with PIT tags. Acoustic tags are implanted only in smolts larger than 85 millimeters.

Transmitting life is directly correlated to power and (“ping”) rate. Battery life is 20 to 90 days. The acoustic tag is able to provide accurate location of the fish, not unlike using a global positioning system (GPS) unit, by using multiple receivers.

Grant County PUD has used passive tags, radio tags, and acoustic tags. The most effective strategy may be to use several tag technologies in combination to address all management needs, concludes the Grant County Report.

Posted by Sam Churchill on .

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