Understanding sturgeon life history: Enigmas, myths, and insights from scientific studies

摘要

Selected enigmas in sturgeon life history are examined based on analysis of the Gulf sturgeon population in the Suwannee River, Florida, and on scientific literature for other sturgeon species. Population structure data from 14 years of Gulf sturgeon sampling yield new insights into sturgeon life history, revealing general parallels with other sturgeons. The enigma of sturgeon fasting, particularly fasting in freshwater by anadromous species, is considered. Fasting is hypothesized as a mechanism to maintain optimum ecological body size in fishes with enormous growth potential and indeterminate ultimate size. The apparent mystery of juveniles participating in the spawning immigration of adults in anadromous species is resolved in the context of the evolution of sturgeons as fundamentally freshwater fishes. Freshwater habitat is a physiological and predator refuge during fasting intervals. The myth of great age as typical of sturgeon populations is evaluated and found to be contradicted by analysis of Gulf sturgeon length and age data, and by comparative literature data for other well-studied sturgeon species. The myth of population stability is similarly contradicted by long-term length/age frequency data for Gulf sturgeon, and is unsupported by additional long-term population analyses reported for other sturgeon species. Potential sturgeon management and conservation actions should be re-evaluated in the light of revised life history knowledge. In particular, it is important to apply the knowledge that adult females typically do not live as long as anecdote and conventional myth suggest. In fact, relative to age at first maturity, most sturgeon populations appear to be dominated by young adults; very large and very old fish are rare. Consequently, there is a low probability in natural sturgeon populations of many successive spawnings over the lifespan of any given female. It is also important to recognize the dynamic instability of sturgeon populations, rapid population recovery is improbable, even in well protected populations, given that strong year-classes are widely separated periodic phenomena in natural sturgeon populations.