Demographic characteristics of young-of-year freshwater mussel populations in ponds
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PRIMARY RESEARCH PAPER
Demographic characteristics of young-of-year freshwater mussel populations in ponds Wendell R. Haag
. James A. Stoeckel
Received: 26 May 2020 / Revised: 22 September 2020 / Accepted: 8 October 2020 Ó This is a U.S. government work and not under copyright protection in the U.S.; foreign copyright protection may apply 2020
Abstract We describe demographics of young-ofyear (YOY) Pondmussels (Ligumia subrostrata) and Giant Floaters (Pyganodon grandis) in ponds during 2009 and 2011. YOY attained large size by approximately 6 months (Pondmussel, mean = 48.5 mm; Floater = 57.5), most individuals were sexually mature, and most females were gravid. Size and sex ratios varied among ponds. Pondmussel size was negatively related to mussel density, suggesting food competition; Floater size was not related to density. Size was not related to glochidial infestation pressure on fishes, suggesting that acquired immunity did not affect YOY performance. The percentage of gravid female Pondmussels varied between years from 27 to 100%, and 91% of female Floaters were gravid in 2011. Mean fecundity was high (Pondmussel = 34,311; Floater = 38,873). The proportion of gravid females and mean fecundity were not related to male density, showing that fertilization was efficient. Variation in size, sex ratios, and gravidity among ponds suggests that small differences in environmental
Handling editor: Manuel Lopes Lima W. R. Haag (&) US Forest Service, Center for Bottomland Hardwoods Research, Frankfort, KY 40601, USA e-mail: [email protected] J. A. Stoeckel School of Fisheries, Aquaculture, and Aquatic Science, Auburn University, Auburn, AL 36849, USA
conditions or demographic stochasticity can have large effects on populations. Rapid growth, early maturity, efficient fertilization, and high fecundity of YOY are contrary to traditional views of mussel life history, but these traits may allow Pondmussels and Floaters to rapidly colonize disturbed, unstable habitats. Keywords Unionidae Life history Juveniles Recruitment Growth
Introduction Factors affecting animals early in their life can have lasting effects on individual performance and population structure. Competition for food among filterfeeding bivalves can result in reduced growth (Eldridge et al., 1979), which in turn may delay sexual maturity or growth beyond a size vulnerable to predation. Female freshwater mussels (order Unionoida) fertilize eggs by filtering sperm from the water, and low male density or removal of sperm by other filter feeders both are proposed to influence fertilization and fecundity (Downing et al., 1993; Strayer, 1999). Freshwater mussels are unique among bivalves in having larvae (glochidia) that require a period as parasites on fishes, and host-parasite interactions also may influence subsequent juvenile performance. For
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Hydrobiologia
example, fishes exposed to high glochidial burdens can acquire partial immunity to subsequent glochidial infestation, which may influe
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