Age, Growth, and Catch Analysis of the Commercially Exploited Paddlefish Population in Kentucky Lake, Kentucky-Tennessee

Abstract

Paddlefish Polyodon spathula from the 1985‐1986 commercial harvest from Kentucky Lake, Kentucky‐Tennessee, were weighed and their lengths from eye to fork of the tail were measured. During 52 observed trips, commercial fishermen harvested 702 paddlefish (4,002 kg) with 788 gill‐net‐nights of effort. However, the harvest was a disappointment to the fishermen because catch rates were low, and only 15 gravid females were included in the observed catch. The paddlefish that were aged from dentary bones (N = 362) were 2‐16 years old. The age‐length equation was a log10 transformation of a linear relationship, and the weight‐length equation was a log10 transformation of an algebraic relationship. There were no significant differences in backcalculated growth between sexes. Growth was slower than reported for most other populations. The sex ratio was 1:1, and the youngest sexually mature fish were 6 and 8 years old for males and females, respectively. The age of recruitment and annual mortality were 8 years and 61 % for males and 9 years and 60% for females. Overall recruitment age was 9 years, and annual mortality was 69%. The mean length and weight of paddlefish in the commercial catch was 691 mm and 5.7 kg, the mean commercial catch was 57.1 kg and 13.5 fish per night, and mean catch per unit effort (CPUE) was 3.77 kg/91.4‐m net per night. Mean size offish, catch rate, and CPUE were highest during the spawning run. A gill‐net mesh size of 127 mm was most popular and caught larger fish. The Kentucky Lake paddlefish population shows several signs of overexploitation: high mortality for several years, a comparatively young population, and a low number of spawners. Therefore, we recommend the creation of a spawning refuge, implementation of a maximum gill‐net mesh size, and an increase in commercial fishing license fees for paddlefish management.

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

“…Future monitoring of the strong 1999 year class in the next decade will clarify if this conclusion is accurate and how much the near absence of older fish (> 15 years) is a result of harvest. Several studies at midlatitudes of the paddlefish's range have reported what they believed to be truncated age distributions associated with high harvest rates (Watts Bar Reservoir, Tennessee: Alexander et al, 1985;Kentucky Lake: Hoffnagle andTimmons, 1989, Timmons andHughbanks, 2000). Such harvest may exacerbate the natural life history compression of southern stocks such as observed in this study.…”

Stocking Success of Paddlefish in Lake Francis Case, South Dakota: Population Characteristics and Sport Fishery Potential

“…Male paddlefish reached sexual maturity by age 8 in Lake Francis Case and by ages 8-9 in Lake Sakakawea (Scarnecchia et al 2007), but reached maturity by ages 5-6 in Kentucky Lake (Hoffnagle and Timmons 1989;Scholten and Bettoli 2005), age 6 in Louisiana (Reed et al 1992), and age 5 in the Alabama River drainage (Lein and DeVries 1998). Female paddlefish in Lake Francis Case reached sexual maturity at a younger age (age 11) than paddlefish in Lake Sakakawea (age 15, Scarnecchia et al 2007), but reached maturity at an older age than females in Kentucky Lake (ages 8-10, Hoffnagle and Timmons 1989;Scholten and Bettoli 2005), Louisiana (age 9, Reed et al 1992), and the Alabama River drainage (age 6, Lein and DeVries). Paddlefish age at sexual maturity increases with latitude, which may be explained by higher growth rates at southern latitudes (Reed et al 1992).…”

“…caviar (Carlson and Bonislawsky 1981;Timmons and Hughbanks 2000). Hoffnagle and Timmons (1989) reported that the Kentucky Lake, Kentucky-Tennessee, paddlefish population showed signs of commercial overexploitation as roe prices increased to US$110/kg in 1985. Lake Francis Case, South Dakota, supported a paddlefish sport fishery shortly after impoundment, but this fishery closed in 1986 owing to a lack of natural recruitment (Unkenholz 1986;Mestl and Sorensen 2009). Paddlefish have been stocked in Lake Francis Case, primarily with fish reared at Gavins Point National Fish Hatchery (GPNFH), to maintain a broodstock population and potentially reinitiate a sport fishery (Kallemeyn 1974;Graham 1997;Stancill et al 2002).…”

Lack of size selectivity for paddlefish captured in hobbled gillnets

“…Paukert and Fisher (1999) also noted that the smallest paddlefish in their study were collected in the largest mesh (203 mm). Hoffnagle and Timmons (1989) speculated that small paddlefish were caught in large meshes due to entanglement of their rostrums when they turned upon encountering a net. Perhaps a more plausible reason why we did not observe any size selectivity is the way in which paddlefish move through the water column.…”