The temporal nature of sculpin predation on eggs in the
nests of individual females may account for the relatively short
spawning season of sockeye salmon on island beach spawning
locations in Iliamna Lake (Hendry et al. 1995; Fig. 1B). In
1992, peak spawning was observed within 6 days of the first
female spawning, and the majority of females appeared to
spawn over a 6- to 10-day period. This is in contrast with
stream spawners in sockeye salmon where runs are typically
much more extended, including those in Alaska and other parts
of Iliamna Lake, lasting 3–6 weeks and sometimes longer
(e.g., Demory et al. 1964; Wood and Foote 1996). Sweeney
and Vannote (1982) argued that the “predator satiation” hypothesis
accounted for the marked synchrony in adult emergence
patterns in mayflies, and the same argument appears to
apply here. They showed that the percentage of adults succumbing
to predators on a given day was inversely related to
the total number of adults available as prey each day, which
agrees with what we found relative to sculpin predation in
sockeye nests. The interesting conclusion from our study is
that the abundance of predators over time alone does not reveal
the temporal nature of egg predation. In that case, peak sculpin
and sockeye numbers coincide. Rather, it is the independent
temporal measures of the sculpins per nest and the attraction
of sculpins to egg-baited traps that indicate this pattern of selective
predation