Demography of a population of freshwater bivalve (Anodonta kennerlyi) and their annual filtration capacity of Marion Lake, British Columbia Roberts, Mikayla Paige
The recent colonization by Anodonta kennerlyi (Bivalvia: Unionoida: Unionidae) of Marion Lake, BC has had unknown effects on the ecosystem. The lake was systematically sampled to determine the distribution of mussels in the lake and individuals brought back to the lab enabled the construction of an age-volume regression. It was found that the mussel distribution did not vary with depth, proximity to inlet or outlet, or side of lake-basin (P > 0.05) and possible explanations include the shallow morphology of the lake and their dependence on currents and fish hosts for dispersal. Of the individuals sampled, 57% were in the seven to ten year age classes indicating a pulsed recruitment. The average age was 8.16 ± 0.36 (SE) years. Age was a good indicator of volume (r² = 0.72) and AFDM (r² = 0.67) and there was also a strong relationship between the volume of the individual and the AFDM of the soft tissues (r² = 0.81). The average biomass per square meter was 0.29 ± 0.04 g/m² and the approximate total biomass was 39000 g. The mean number of mussels per square meter was 1.55 ± 0.27 mussels/m² and the maximum density that was sampled was 8.89 mussels/m². Literature values were used to approximate the daily filtration capacity of the population and create regressions of filtration rate and temperature. Four separate temperature-dependent filtration rate scenarios were made to estimate the proportion of the lake filtered each year by the population. The ‘high’ scenario yielded an estimate of 107% annually while the ‘low’ scenario estimate was 15%. Two other scenarios based on the literature and the literature average predicted 45% and 41%, respectively. The largest daily proportion of the lake filtered was 0.5% which is not considerable, however the effects on primary production are unknown and could be greater than expected. The population of Anodonta kennerlyi likely filter a significant volume of water annually (approximately 40%) and could be experiencing density-dependant effects due to space or food competition. Less than 10% of the population is in the one to three years age classes and this indicates that the population is currently not recruiting new individuals. Further studies should be executed to determine the extent of the mussel population’s effect on primary productivity in Marion Lake and if density-dependent effects are influencing the population dynamics.
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