A Long‐Term Program for Validation and Verification of Dentaries for Age Estimation in the Yellowstone–Sakakawea Paddlefish Stock

Abstract

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.

Southern and Northern Great Plains (United States) Paddlefish Stocks Within Frameworks of Acipenseriform Life History and the Metabolic Theory of Ecology

“…During these periods, fish brought into the RPC were assigned a unique number, measured to the nearest mm for body length (BL; front of eye to fork of caudal fin; Ruelle and Hudson, 1977), and weighed to the nearest 0.1 kg. Dentaries for age determination (Adams, 1942;Scarnecchia et al 2006) were removed from each fish and placed into manila envelopes to dry. Sex of fish was determined at the beginning of the cleaning process, and one of six maturation stages of females (two immature stages, mature, pre-ovulation [i.e., caviar] stage, ovulated, spawned out, and reabsorbed-developing ["salt and pepper"]) was assigned based on visual observation (Bruch et al, 2001).…”

Riverine and Reservoir Influences on Year Class Strength and Growth of Upper Great Plains Paddlefish

“…A high percentage of harvested paddlefish was processed at these stations (from 65% to 98% of the annual harvest; North Dakota Game and Fish Department and Montana Department of Fish, Wildlife and Parks, Unpublished Data). From each fish, data collected included the date of harvest, harvest location (Rkm), body length (BL; anterior of eye to fork of caudal fin; Ruelle and Hudson, 1977) to the nearest 2.5-cm increment, weight to the nearest 0.5 kg, sex, maturation stage (Scarnecchia et al, 1996c), gonad weight, GFB weight , and dentaries (lower jaw bones) for age determination (Adams, 1942;Scarnecchia et al, 2006).…”

“…Dentaries were removed, cleaned of excess flesh, and stored dry in individual envelopes. The dentaries were later cleaned and sectioned as described in Scarneccchia et al (1996bScarneccchia et al ( , 2006, and ages assessed by counting annuli (Adams, 1942;Meyer, 1960;Scarnecchia et al, 2006) using a Biosonics Optical Pattern Recognition System. From 1999 to 2006, a two-reader, double-blind protocol was used, along with a tolerance for minor disagreement as described in Scarnecchia et al (2006).…”

“…The dentaries were later cleaned and sectioned as described in Scarneccchia et al (1996bScarneccchia et al ( , 2006, and ages assessed by counting annuli (Adams, 1942;Meyer, 1960;Scarnecchia et al, 2006) using a Biosonics Optical Pattern Recognition System. From 1999 to 2006, a two-reader, double-blind protocol was used, along with a tolerance for minor disagreement as described in Scarnecchia et al (2006). The accuracy of age determination using dentaries was validated for young recruits (males ages 9-10) based on recoveries of known-age, coded wire-tagged fish and partially validated for older recruits (females 16-19) based on jaw-tag recoveries .…”

Swimways: Protecting Paddlefish through Movement‐centered Management

“…Paddlefish are not exempt from genetic effects of stocking, and reduced genetic diversity has been reported from hatchery-reared paddlefish (Sloss et al 2009). Moreover, paddlefish are long-lived (>40 years; Scarnecchia et al 2006;Pracheil 2010), creating the potential for longlasting population effects if genetic differences between hatchery-and wild-origin individuals have phenotypic expressions. These reasons and others, such as state-bystate variability in management objectives (e.g., stocking for conservation, stocking to supplement sport harvest), stocking strategies (e.g., no stocking, stocking large numbers of fingerlings), and broodstock selection techniques (i.e., selecting the first several fish collected that meet maturation criteria, selecting broodstock based on genetic …”