Growth and reproduction of the tidepool sculpinOligocottus maculosus

Abstract

Growth and reproduction of tidepool sculpins (Oligocottus maculosus) from three sites in Puget Sound, Washington State, USA were characterized. One site was a sandy, gently sloping beach, the second was an exposed rock headland with minimal algal cover, and the third was an exposed rock headland with numerous tidepools containing abundant algal cover. Length-weight relationships for sculpins did not differ significantly between sexes within sites. Population age structure, growth rate and recruitment varied among the three study sites using data pooled across both sexes. Young-of-the-year sculpins comprised 91% of the population at the exposed headland site with minimal algal cover but only 6% at the headland with abundant algal cover. Selective predation by great blue herons (Ardea herodias) upon tidepool sculpins larger than 45 mm total length assisted in the maintainance of these age structures. A maximum gonadosomatic index of 28.5 was calculated; this index correlated poorly with either age, length or somatic weight. Diameters of unshed ova from preserved tidepool sculpins sampled prior to spawning fell into three classes. Comparison of the mean egg size of each mode and the number of modes present in preserved sculpins with similar data from tidepool sculpins that spawned in the laboratory suggested that spawning occurred twice yearly from at least January through August.