In the US Pacific Northwest, different species and stocks of Pacific salmon (Oncorhynchus) commingle as they migrate toward spawning areas. This often results in mixed-stock fisheries in which some stocks are abundant while others require protection.
In fisheries that exploit complex stock mixtures, mass marking and mark-selective fishing emerged as a way to increase the harvest of hatchery fish while protecting natural stocks of concern. Currently, mass marking in this region involves clipping the adipose fin to provide a visual cue that allows differential retention of marked fish while requiring unmarked fish to be released in mark-selective fisheries.
In theory, mark-selective fisheries enable more hatchery fish to be caught while allowing more natural fish to escape to their natal streams and increase the spawning abundance. Mass marking also provides a valuable tool for assessing wild stocks because hatchery origin and natural origin fish can be distinguished as the fish migrate to the ocean, when captured in fisheries, and when they return to hatcheries and spawning grounds.
With about 200 million fish requiring mass marking each year, this program was clearly not feasible with the manual marking and tagging methods that were available in the early 1990s. In response to this need, Northwest Marine Technology (NMT; Shaw Island, WA, USA; www.nmt.us) in cooperation with the Washington Department of Fish and Wildlife, Bonneville Power Administration, and the US Fish and Wildlife Service began developing a revolutionary new series of machines to automatically inject Decimal Coded Wire Tags (CWTs) and excise the adipose fin on salmon and steelhead. Through consistent research and development, these partners created the AutoFish System.
The AutoFish System uses advanced technology to sort and process Pacific salmon and steelhead in a hatchery or fish farm. The AutoFish System is a cost-effective way to handle juvenile fish rapidly without the use of anesthetic or human contact. This system can be customized to perform any combination of sorting (to within 1-mm accuracy), clipping of adipose fins (marks), and injecting CWT in snouts (tagging).
The natural instinct of fish to move in water currents guides them through the AutoFish System with minimal stress and trauma. This has resulted in the AutoFish System changing the way fish are handled at hatcheries throughout the Pacific Northwest.
An integral component of AutoFish System is the AutoFish Sorter. The sorter uses video imaging and fish behavior to accurately measure fish in a stress-free environment. The sorter measures the fish within 1 mm of total length and distributes them into size categories. Touch-screen software allows operators to view and change the system configuration. A screen shot of the AutoFish Sorter touch screen shows a fish being processed and histogram of the current size distribution.
Operators can observe individual fish, their lengths, and destinations. A graph shows the current size distribution, allowing the operator to fine-tune the system. Tabular data compare the current distribution with the previous day's processing and show the number of fish distributed into each size category. Once a fish is measured, the software selects the appropriate size category described by the user. The sorter instructs the diverter to open the appropriate port and the fish is routed to the lines for further processing.
Since its implementation, the AutoFish System has been used at hatcheries in California, Idaho, Oregon, and Washington. By 2005, more than 100 million fish had been coded wire tagged or fin clipped with the AutoFish System.