Gravel pit ponds as habitat enhancement for juvenile coho salmon.

Abstract

Gravel pits built during road construction in the early 1970's near Yakutat, Alaska, filled with water and were connected to nearby rivers to allow juvenile salmonids to enter. Seasonal changes in population size, length and weight, and length frequencies of the coho salmon population were evaluated over a 2-year period. Numbers of coho salmon fluctuated, but two of the ponds supported high populations, more than 2,000 fish, throughout the study. These ponds appeared to support coho salmon throughout the winter. The range of physical measurements of the ponds did not seem to account for differences in numbers of salmon, but low concentrations of dissolved oxygen were detected in all ponds near the bottom. Aquatic vegetation, water exchange rate, and access may have affected the number of coho salmon in the less productive ponds.