Survival of spring chinook salmon captured and released in a selective commercial fishery using gill nets and tangle nets

摘要

We tested the potential for using live capture, selective harvest as an alternative to a conventional gill net fishery to protect depressed wild stocks of spring chinook salmon (Oncorhynchus tschawytscha) while still allowing harvest of fish from abundant stocks. We conclude that using modified fish handling techniques and replacing conventional 8 or 5.5 in. gill nets with smaller meshed tangle nets significantly improves the survival of spring chinook salmon released from the gear. Tangle nets are similar to small meshed gill nets and capture fish by the snout rather than by the gills or body, reducing injury and allowing them to continue respiring while they are in the net, theoretically allowing live capture and improving the likelihood of survival after release. Experienced gill netters used modified fishing techniques to fish nets constructed of tangle nets joined to conventional gill nets. Captured fish from each net type were tagged and released for recovery in subsequent recreational and commercial fisheries, at hatchery racks, and during spawning ground surveys. Control fish that had not been captured in the fishing gears were tagged and released from a trap near the fishing area. More than 95% of the adult chinook salmon survived the initial capture in any net type. Spring chinook released from the 4.5 in. tangle net were recovered at 1.9 times the rate of fish released from the 8 in. gill net, and 1.2 times the rate of fish released from the 5.5 in. gill net. The 4.5 in. tangle net was as effective at capturing spring chinook as the 8 in. gill net, but less effective than the 5.5 in. gill net.