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4. KNOWLEDGE GAPS

4.1 Biology

Very little information is available on some key aspects of the life history and biology of the western silvery minnow.  Studies have not, for example, been conducted to describe the species’ reproductive strategy or overwintering requirements. Because accurate threats assessments and critical habitat identifications depend upon knowledge of the species’ reproductive strategy and its overwintering requirements, such studies should be a priority.  There is also little or no information available on population structure, movements, or early life stages.

4.2 Habitat

The specific habitat needs of the western silvery minnow, particularly for eggs and fry, remain unknown.  Spawning has not been documented in the Milk River, nor has the presence of larval and early juvenile stages.  Overwintering habitats also have not been documented and the relationship between sediment load, turbidity, and the abundance of minnows remains unresolved.

4.3 Abundance

To date, there are no reliable abundance estimates for the western silvery minnow within the Milk River.  As such, it is not yet possible to set a conservation population target size, or to confirm whether changes in abundance have occurred.  The magnitude of natural variability in population size is also unknown, making it difficult to determine if changes in abundance over the short term are related to normal fluctuations or a real change in population status. However, recent studies suggest that abundance of western silvery minnow may be significantly greater than previously assumed (D. Watkinson, pers. comm.).

4.4 Threats

Some potential threats cannot be fully evaluated because detailed information on the stressors and the mechanisms by which they might affect the minnow are not well understood.  To accurately predict the effects of impoundment, for example, requires better knowledge of how changes in the physical conditions of the river, such as an altered flow regime, may interact with the species given its life history and habitat requirements.  Further study of these relationships is warranted.