Survival and growth assessment after reintroduction of the pocketbook mussel, Lampsilis cardium Rafinesque, 1820 among three streams in Nebraska (USA)

Abstract

Freshwater mussels are a globally diverse and fundamental group in aquatic ecosystems. However, 65% of freshwater mussel species have become endangered over the past century and 10% of them are already extinct. Natural population preservation and restoration efforts have been expedited, but the complicated life history of this taxon presents many challenges since species-specific ecology involved in restoration projects is often poorly understood. Lampsilis cardium is an imperilled freshwater mussel in Nebraska, USA. A reintroduction project has been carried out to restore L. cardium populations among three streams in Nebraska, during autumn 2016 and summer 2017. A 2-year mark–recapture study was used to determine habitat, timing and size-at-introduction effects on mussel survival and growth following introduction. Water quality and habitat parameters were seasonally recorded from each site to assess potential effects on mussel growth and survival. The highest daily growth rates of L. cardium ranged between 145 and 185 μm d−1, whereas the lowest daily growth rates observed were ∼88–107 μm d−1, with the greater rate of shell growth always recorded for those individuals introduced in spring and lower for those individuals introduced in summer or autumn. Survival models indicated that mussels were most susceptible to mortality immediately following introduction in spring, whereas size at introduction had almost no effect on survival. At each site, habitat parameter measurements recorded during different seasons indicated that calcium availability, water temperatures, water depth and water quality may contribute to differences in growth and survival rates. Survival rate estimation and population growth predictions are essential knowledge to understand population dynamics; this study provides useful information and a framework for management decisions that may influence L. cardium population dynamics, such as identifying more suitable habitats and introduction times not only for this species but also other similar unionids.