Inter- and Intra-Population Variation in the Fecundity of Chinook Salmon (Oncorhynchus tshawytscha) and its Relevance to Life History Theory

Abstract

Healey, M. C., and W. Ra Heard. 1984. Inter-and intra-population variation in the fecundity of chinook salmon (Oneorhynchus tshawytscha) and its relevance to life history theory. Can. ). Fish. Aquat.Sci .4l r 474-483.Chinook salmon (Bwcsrhynehus tshawytscha) varied significantly in fecundity both between years within populations and between populations throughout their range. Generally less than 50% of the variation in fecundity between individuals within populations couid be explained by variation in length. A small additional amount of variation could be attributed to racial differences (e.g. red or white fleshed types) but age, seasonal timing of subpopulations, and stream or ocean type life history pattern did not contribute significantly to variation in fecundity beyond their correlation with length. A great deal of individual variation in fecundity remains to be explained in chinook salmon. The slopes sf the regression of fecundity on length for all populations were low in comparison with other fishes, indicating that fecundity increases slowly with increasing size in chinook. The mean age sf reproducing females varied among populations, and populations that reproduced at an older age were more fecund at a common length than populations that reproduced at a younger age. The increase in fecundity with increasing age of maturity was consistent with theoretical predictions of the trade-off between fecundity and mortality in fish sf reproductive age. The mean age of reproduction within a population, however, was considerably older than the predicted optimum age of reproduction based on the trade-off between increasing fecundity with age and natura! mortality. These observations suggest that chinook have sacrificed fecundity for increased size in the allocation of surplus energy, a life history characteristic that is consistent with the survival value of size in anadromous salmon.

Assessment of factors limiting Klamath River fall Chinook salmon production potential using historical flows and temperatures

“…We used average fecundity from the Lewiston Hatchery on the Trinity River of 3,732 eggs for a 4-kg fish. This is in good agreement with an older mean value from the Klamath River of 3,634 listed by Healey and Heard (1984), who also noted that Klamath stocks appeared to be only half as fecund as Sacramento River fish of the same length.…”

“…One must be forever critical of what has been published. We are rather fond of a statement from Healey and Heard (1984), to wit: "Much of the work that has been done … is tantalizing rather than conclusive. Most of the studies were undertaken to describe consequences rather than to test specific hypotheses ….…”

“…Magneson and others (2000) provide data showing 367 grilse and 1,978 adult spawners in the main stem Klamath River for 1999, resulting in a 45 percent spawning female to 55 percent nonspawner ratio. Mean spawner length was 694 mm (approximately 4 kg) from a historical data set reported by Healey and Heard (1984). However, recent data collected and summarized by the USFWS and USGS (Tom Shaw, U.S.…”

Relating chronic toxicity responses to population-level effects: A comparison of population-level parameters for three salmon species as a function of low-level toxicity

“…Increasing mortality of older fish, through toxicity or harvesting, selects for individuals that mature at a younger age; this has been observed in coho and chinook (Roni and Quinn, 1995;Quinn et al, 2000). Younger fish, being smaller, often have a lower fecundity and produce eggs with a lower hatch rate (Bagenal, 1969;Healey and Heard, 1984;Wootton, 1992;Roni and Quinn, 1995). Without long-term monitoring, changes in individual productivity may not always be obvious because of the sheer abundance of younger spawners.…”

Modeling Chinook Salmon with SALMOD on the Sacramento River, California

“…One must be forever critical of what has been published. I am rather fond of a statement from Healey and Heard (1984), to wit: "Much of the work that has been done ... is tantalizing rather than conclusive. Most of the studies were undertaken to describe consequences rather than to test specific hypotheses.…”