A Purse Seine for Sampling Juvenile Salmonids

Abstract

to collect live juvenile salmonids in the $5, 000. limnetic zone in numbers sufficient for assessing migratory behavior. The need Description of Equipment for this sampling equipment arose after conventional floating traps—used successPurse Seine fully along the shorelines of the upper and middle reservoir—failed to take fish in The purse seine, 600 feet long by 35 quantity at the lower end of the impoundfeet deep (600 meshes from floatline to ment. Samples also were required from leadline), was constructed principally of offshore areas of the 57.5-mile-long im3/8-inch (bar measure) knotted nylon webpoundment. Trawling was attempted, but bing (thread size, 210-6). To reduce cost, catches were small and fish were often in the lower 10 feet was made of a cheaper poor condition for marking or tagging. synthetic material of the same mesh size. Unsatisfactory results with trawls led to The bunt end of the seine (figure 1) was consideration of the purse seining techmade of 1/4-inch (bar measure) knotiess pique, nylon to retain salmonids as short as Purse seines. are commonly used for 50 millimeters. Sponge): floats, spaced commercial harvesting of marine food fish 15 inches apart on a floatline, supported and have been described and. illustrated the net in water. About 20 percent hang-in by Knake (1950), McNeely (1961), and was made along the floatline and leadline. Dumont and Sundstrom (1961). Craddock' Purse rings, spaced 18 feet apart, were explored the possibility of using a cornsuspended on polypropylene dropper lines mercial bait seine to capture fingerling from the leadline. The purse line consockeye salmon (Oncorhynchus nerka). A sisted of two 325-foot lengths of 1 / 2-thch barge and a small skiff were used, but the nylon rope joined by a 1/4-inch figures attempt was unsuccessful, largely because eight clamp to permit a quick removal. of the lack of auxiliary power equipment from the rings after a set had been cornfor handling the seine. Based in part pleted. on Craddock's experience, a lightweight, small-mesh model of a commercial purse Depressor Weight