ELR has extensive experience estimating population and local abundances, behavior, growth, survival and production of fish. We use mark-recapture techniques including using PIT tags, instream and mobile PIT tag antennas. We also have used hydroacoustics, electroshocking, netting, snorkeling, and underwater videography to evaluate these aspects of fish ecology.
ELR uses passive integrated transponder (PIT) tags to uniquely identify fish and evaluate several performance metrics. PIT tags are small (12mm), inert, require no batteries, have no moving parts, and have a life span exceeding that of the fish. As a tagged fish passes the radiating electronic field of the transceiver (antenna and reader), the tag circuitry is energized and sends a signal that corresponds to the unique code of the tag that is recorded by the reader.
We have built and installed several PIT tag antennas in streams of WA and OR. The antennas detect fish as they pass over. This detection provides information about the timing and degree of migration and whether the fish is still alive.
We also use mobile antennas to locate fish. The reader is fitted with a GPS unit, which automatically records the location of detected tagged fish. This allows us to map fish distribution and movement, and the types of habitat the fish are located in. This also provides more information about whether the fish is still alive.
Because we measure fish whenever they are captured and tagged fish have a capture history we can estimate growth rates. In addition, we use various mark-recapture techniques to estimate survival rates and abundance.
We use several types of fish capture techniques depending on the situation, species, and life stage we are interested in. We use electroshocking techniques, but generally where the electriciy is set to "tickle" to chase fish into a seine, thus greatly reducing injury or mortality. We also snorkel herd, or "snerd" fish into seines as another low impact method.
In the winter, salmonids are best capture at night using lights and an aquarium dipnet- yes one fish at a time. We also enumerate fish through snorkel counts.
We also have considerable experience in lake systems using trawls, fyke nets, trap nets, trammel nets, boat electroshocking, gill nets, and hydroacoustics.
We are currently using underwater 3D videography to help us better understand fish behavior and develop foraging models. This techniques has been created by researchers at The University of Alaska, and have been helpful in showing us how to use this technology