Science Advisory Report  2010/045

Recovery Potential Assessment of Wavy-rayed Lampmussel (Lampsilis fasciola) in Canada

Summary

• The current distribution of the Wavy-rayed Lampmussel includes the Ausable, Grand, Maitland and Thames rivers as well as the St. Clair River and delta (Figure 1).
• Wavy-rayed Lampmussel is thought to be extirpated from Lake Erie, Lake St. Clair proper (excluding St. Clair River delta) and the Detroit River, as well as the Sydenham River where it has not been recorded since 1971 despite substantial sampling.
• Gills of the appropriate host fish are the required habitat for the glochidial life stage.
• Adult Wavy-rayed Lampmussel are generally found in small to medium, clear, hydrologically stable rivers, around shallow riffle areas, but are also known to inhabit lacustrine areas. It is generally found on sand or gravel substrates, at times stabilized with cobble or boulders usually at depths of up to 1 m. Juvenile habitat requirements are inferred from the adult life stage.
• For the Grand River population, to achieve a 99% probability of persistence over 250 years, given a 15% chance of partial catastrophe per generation, a population with 1500 female adults is required. If the chance of catastrophe was a 15% chance of full catastrophe per generation, a population with 83 000 female adults is needed
• For the Thames River population, to achieve a 99% probability of persistence over 250 years, given a 15% chance of partial catastrophe per generation, a population with 31 adult females is required. If the chance of catastrophe was a 15% chance of full catastrophe per generation, a population with 420 female adults is needed
• Assuming 15% probability of partial catastrophe; and growth rates of 1.08 and 1.18 respectively, population modeling indicates that in the absence of both recovery efforts and additional harm, populations between 2-20% of the recovery target have a 95% chance of reaching the target in 46-85 years (Grand), or 18-30 years (Thames).
• Population dynamics were most sensitive to changes in adult survival. Recovery time is reduced by approximately half with a 10% increase in adult survival.
• The greatest threats to the survival and persistence of extant Wavy-rayed Lampmussel populations are related to increased levels of contaminants and toxic substance, increases in nutrient loading, increases in turbidity and sediment loading, introduction of exotic species and habitat removal and alteration. Due to the obligate nature of the mussel reproductive cycle, any threat leading to the separation of mussel and fish host during reproduction can be detrimental to the mussel population. Secondary threats include predation and harvesting, and recreational activities.
• The growth rate of Wavy-rayed Lampmussel populations is most sensitive to the survival of adults. Harm to vital rates of the Grand River population should be less than 14% for glochidial survival or 14% for adult fecundity or 9% for juvenile survival or 6% for adult survival. Harm to vital rates of the Thames River population should be less than 33% for glochidial survival or 33% for adult fecundity or 22% for juvenile survival or 14% for adult survival.
• There remain numerous sources of uncertainty related to Wavy-rayed Lampmussel life history, juvenile habitat requirements, host distribution and abundance, and host-mussel distribution overlap. A thorough understanding of the threats affecting the decline of Wavy-rayed Lampmussel populations is also lacking. Numerous threats have been identified at the mussel community level, but the threat likelihood and impact at the species level is currently unknown. Numerous modeling parameters specific to Wavy-rayed Lampmussel are currently unknown, such as glochidial survival, glochidial attachment rates, juvenile survival, and population growth rates.

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