on a southern Great Plains stock of paddlefish Polyodon spathula inhabiting the Neosho River, Spring River, and Grand Lake, Oklahoma, is characterized (1) in terms of the Acipenseriform life history framework outlined for the Yellowstone-Sakakawea stock of the Northern Plains and (2) in relation to the framework metabolic theory of ecology and associated latitudinal and environmental correlations with lifespan. In the Grand Lake stock, male fish typically mature at ages 6-7, and females mature at ages 8-9. The five stages of the lifespan (immature, maturing, growth and reproduction, prime reproduction, senescence to death) are compressed into a period of 15-20 years; the prime reproduction period occurs from ages 12 to 16 years for females. This lifespan compares to one of 40-50 years (and occasionally longer), and a prime reproduction period for females from ages 25 to 40 years, for the Yellowstone-Sakakawea stock. The more compressed lifespan of the Grand Lake stock and lower energy storage, as indicated by weights of gonadal fat bodies, are consistent with the framework metabolic theory of ecology. Over the course of a year, fish in Grand Lake are under a much higher metabolic demand than those in Lake Sakakawea. The distinct differences detailed between these two stocks from the southern and northern plains may exist between other paddlefish stocks, other Acipenseriform species, and other fish taxa separated by large latitudinal and climatic differences. The results have specific implications for harvest management and effects of climate change on Acipenseriform life histories and lifespan.
An approach is described to assess the accuracy and precision of age estimates for paddlefish Polyodon spathula of the Yellowstone-Sakakawea stock in Montana and North Dakota. Twenty-five of 30 fish tagged with coded wire tags as age-0 fish in 1995 and recaptured over the period 2002-2005 were independently aged correctly with dentaries (lower jaw bones); estimates for the other five fish deviated from actual ages by 1 year. For fish older than age 10, estimated ages based on dentaries collected from 1991 to 2004 were compared with the estimated minimum expected ages of recovered fish that were jaw-tagged during 1964-2004. Of 323 fish, 300 (93%) had estimated ages that were the minimum expected age or older. The ages for the remaining 23 fish were less than the minimum expected ages, mostly by three or fewer years; these fish spanned a range of ages but tended to be older. Precision estimates (mean coefficient of variation) for age determination ranged from 3.6% for female fish from Montana in 2003 to 7.1% for male fish from North Dakota in 2003. The results indicate that estimating ages from Yellowstone-Sakakawea paddlefish dentaries is generally a repeatable, straightforward process with sufficient accuracy and precision to be useful for stock assessment. Validation studies should be conducted on other paddlefish stocks because the ease of interpreting dentaries varies with locality.
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