Variation in Reproductive Output of Cultured Female Delta Smelt

Delta smelt are a federally listed species in Northern California that have seen significant population declines over the last decade and the population shows no signs of recovery.  Developing a better understanding of the reproductive potential of the animals and the variables that modulate the reproductive output is important to understanding population outcomes.  We have begun to investigate the effect of age and size on fecundity in captive and cultured delta smelt.  In the wild, delta smelt are primarily an annual fish and most do not survive to spawn in their second year.  However, there is a small proportion of fish that spawn and most of the cultured fish live to spawn as two year olds.  There is a significant relationship between size and fecundity, with the two year old fish producing about three times as many eggs per clutch as one year olds.  Within the one-year old year class, length and weight continue to influence fecundity, but seasonal cues and rearing history may also exert a significant influence on the total number of clutches spawned, the timing of spawns, and the total fecundity of the fish over the season.  Comparisons are drawn between the cultured and the wild delta smelt populations.  The potential role of genetics in accounting for variation in fecundity is being addressed.