Located just below the Merwin Dam, Ariel, WA, the Merwin fish hatchery is one of the newer hatcheries in Washington State. The hatchery produces several species of salmonids and employs a volitional release program.
Fish can swim out of the hatchery in springtime whenever they feel like it. Barometric pressure changes as frontal systems pass through the area appear to influence salmon migration patterns. The hatchery wanted to quantify the number of fish they were raising and releasing. Since it was infeasible to set up human counters 24 hr. a day, a counter was selected for its ability to count high numbers of fish. Now the exact number of fish can be recorded each 24 hour period. Comparisons can be made from one year to another. Return rates will also carry more weight and validity now that the number of fish released will be known.
Hatchery personnel set the flow from the ponds holding the 150 gram fish at 950 gpm. WMT designed and built a de-watering device (below) capable of de-watering the majority of the flow and delivering the fish unharmed to the counter. An 8 inch gate valve allows the flow to be adjusted and a small bulkhead fitting feeds the counter approximately 30-50 gpm.
The de-watering tool is positioned under the outflow of the water flowing out of the pipe. The fish counter sits beside the dewaterer as pictured in the first photo below. The counter stand and dewaterer are adjustable. The units can be raised or lowered. In this application the counter sits in 2 feet of water.
The hatchery also has other applications within the facility where the equipment will be used to count fish.
More information is available on our Fish Counters from WMT.