These are eggs from Lake Trout. Lake trout spawn on gravel reefs in lakes about this time of year. This picture is from Lake McDonald in Glacier NP. Of course, Lake Trout is a non-native species in the lakes west of the divide and a threat to the native Bull Trout. Here is an early brochure from the Crown of the Continent Research Center that describes the problem. We’ve been reporting on this problem for awhile, so check out the various stories here.