First‐Year Growth, Condition, and Size‐Selective Winter Mortality of Freshwater Drum in the Lower Missouri River

Abstract

We compared first‐year growth and relative condition (Kn) of the 1997 and 1998 year‐classes of freshwater drum Aplodinotus grunniens among three sites in a 235‐km reach of the channelized Missouri River and tested for the occurrence of size‐selective overwinter mortality during the first winter. Prewinter mean length was 15 mm greater, mean weight was 8 g greater, and mean Kn was 5% greater at the upstream site than at the downstream site. The prewinter mean length of age‐0 freshwater drum was significantly greater in 1997 (115 mm) than in 1998 (109 mm), but Kn was significantly greater in 1998 (107) than in 1997 (102). There was no evidence that density‐dependent interactions influenced prewinter growth and Kn. Size‐selective overwinter mortality of the smallest size‐classes of freshwater drum occurred at two of three sites during the 1997–1998 winter, and Kn decreased 9–15%. Size‐selective overwinter mortality of the 1998 cohort of freshwater drum did not occur during the 1998–1999 winter, and Kn declined 0–10%. A prolonged growing season (through early December 1998), in conjunction with less severe winter water temperature conditions, apparently minimized the incidence of size‐selective overwinter mortality for the 1998 cohort of freshwater drum. We conclude that size‐selective overwinter mortality of age‐0 freshwater drum occurs in the lower channelized Missouri River but depends on the length of the prewinter growing season, winter duration, and the severity of winter water temperatures.

Effects of river discharge on abundance and instantaneous growth of age‐0 carpsuckers in the Oconee River, Georgia, USA

“…Similarly, Archer et al (2000) observed that growth of larval fishes was negatively related to abnormally high summer river discharges. Some studies (Toneys and Coble, 1979;Archer et al, 2000;Braaten and Guy, 2004) have suggested that smaller larval fishes in the fall might increase first-year winter mortality.…”

Latitudinal trends in Freshwater Drum population dynamics: Facing a changing climate

“…In fact, the projected change in climate could be beneficial by potentially allowing these fish to have more stable recruitment, grow faster, reach maturity more quickly, and reach larger maximum lengths. From a population standpoint, these findings suggest that Freshwater Drum populations along the Upper Mississippi River could increase in size due to having more stable recruitment and quicker growth rates, which increases chances of survival through their first winter of life (Braaten & Guy, ). Although these are simply predictions, they could become reality if future temperatures increase at the expected rates.…”

Overwinter Mortality of Sympatric Juvenile Bluegill and Yellow Perch in Mid-Temperate Sandhill lakes, Nebraska, U.S.A

“…To partition the effects of potential growth and sizeselective mortality across the winter, we employed empirical quantile-quantile (QQ) and increment plots [15,40], a combined approach that has been applied to a variety of species [41][42][43][44][45]. For the QQ plots, total length at quantiles 1, 5, 10, 25, 50, 75, 90, 95, and 99 of the size distribution was determined from the length-frequency histograms (i.e., when n > 50; [46]) for the fall and subsequent spring samples, and were plotted against each other.…”