Changes in water quality within anglers' keepnets during the confinement of fish

The influence of mesh size and loading density on conditions within keepnets during the confinement of fish was examined. The performance of a mixed-mesh net was also evaluated. Confinement of fish within nets of a standard diameter and length and of three different mesh sizes for 5 hours resulted in no deleterious changes in levels of dissolved oxygen, unionized ammonia, carbon dioxide, or pH at any of three sample points within each net. Transfer of fish to similar nets at a similar, and a higher, loading for 5 hours resulted in a depletion of oxygen, and accumulation of ammonia, in the high-load nets. No changes in carbon dioxide levels or pH were observed in nets containing either moderate or high loads. Confinement of fish in mixed-mesh nets for 5 hours resulted in a depletion of dissolved oxygen in the lower section of the net and an accumulation of unionized ammonia. There were no changes in carbon dioxide, or pH. These results are discussed with reference to the water quality requirements of freshwater fish. It is concluded that changes in water quality within anglers keepnets during the confinement of fish are not of sufficient magnitude to adversely affect the confined fish.