Marine Science Faculty Publications

Reproductive Cycle and Fecundity of Euphausia pacifica in Puget Sound, Washington

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The length and timing of the spawning season and the fecundity of Euphausia pacifica in northern Puget Sound, Washington, were investigated by analyzing preserved samples and by observing spawning of euphausiids in the laboratory. Gravid females (stage IV) and ripe females (spawning within 24 h) first appeared in mid‐April. Spawning of the overwintered females was most intense in April and May, but continued at a low level throughout most of June. No ripe females <19 mm were found after mid‐May. Larger females disappeared by the end of summer. Females born in April began to develop ovaries (stage I) in mid‐June, and although a few matured to stage IV and released eggs in late July‐early August, most of the population was stage II (with immature eggs in the ovaries) in the fall, overwintered as stage II, and began to mature again in late winter or early spring. The brood size, brood frequency, and length of the spawning season varied with female size. Small females released a maximum of 11–12 broods (≃1,000 eggs) over a 1‐month period from mid‐April to mid‐May. Over a 2‐month period large females released a maximum of 25–31 broods (≃3,700 eggs). A comparison of laboratory and field data suggested a method which may lead to accurate estimates of fecundity from preserved samples.

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Limnology and Oceanography, v. 27, issue 2, p. 304-314