The Role and Importance of Recruitment Variability to a Guild of Tide Pool Fishes

In a guild of tide pool fishes on the outer coast of Washington State, USA, recruitment varied both temporally (seasonally and interannually) and spatially (over intervals of 4—5 km, across a maximum of 30 km of shoreline). Using census data and mark—recapture data, I studied the demography of four species of tide pool sculpins with the goal of understanding how variability in recruitment affected adult population patterns. I found that, although adult populations reflected well the most recent recruitment pulse for the two most common species, adult population growth rate was the most sensitive to changes in survivorship rates. Similarly, analyses of the effect that variance in each demographic parameter had on variability in subsequent adult population size also showed a disproportionate effect of adult survivorship on adult population sizes. In other words, high variability in a demographic estimate did not always result in high variability in population size. Negative density dependence was documented for all species, suggesting that recruitment effects are dampened by postrecruitment events. Thus, although recruitment events could be detected in the adult population for short time periods, postrecruitment events appeared to dampen the effects of seasonal recruitment pulses in these nearshore fishes.