I studied effects of UV-B radiation on egg and larval golden shiner (Notemigonus crysoleucas) in Castle Lake, California, USA. To compare egg hatching and survival of larval golden shiner, I exposed eggs and larval fish to three different UV-B treatments, low UV-B (4% UV-B), high UV-B (92% UV-B), and ambient (100% UV-B). The egg experiment was conducted in lake and pond water, whereas proto- and mesolarval stage experiments were conducted in lake water only. High and ambient UV-B radiation affected the hatching rate of golden shiner eggs. The mean hatching rate was 13% lower in high UV-B, and 9% lower in ambient UV-B compared to the low UV-B treatments. The hatching rate, however, was not significantly different between lake and pond treatments. The survival of egg to hatched larval stage was reduced under high and ambient UV- 8 radiation compared to low UV-8 treatment in the lake water experiment. In the pond water experiment, however, the survival of newly hatched larvae was not different among UV-8 treatments. During the experimental periods, no survival difference among treatments was observed for larval stages of golden shiners. Mean amount of UV-8 radiation penetrating an oligo-mesotrophic lake differed from that in an adjoining pond during the summer of 1997. UV-8 radiation in pond water was highly absorbed compared to absorbency in lake water. High concentrations of dissolved organic carbon in pond water were likely responsible for the difference in absorbency of UV-8 radiation.

Coldwater Lake and Castle Lake are two new lakes which were formed in the aftermath of the volcanic eruption of Mount St . Helens, WA in May, 1980. This research describes the limnology of these lakes ten years later, and includes physical, chemical, and biological parameters. The two lakes are compared and contrasted. Previous research on the eruption and its aftermath, as well as earlier studies of the lakes are described.