Seasonal abundance and availability of forage fishes and their utilization by landlocked Atlantic salmon and brook trout in Echo Lake, Mount Desert Island, Maine

Lackey, Robert

From the abstract: "A study was made of landlocked salmon, brook trout, American smelt and landlocked alewives inhabiting Echo Lake. Landlocked alewives were introduced from Cayuga Lake, New York, in 1966, one year before the start of this study. Seasonal depth distribution, feeding habits, age and growth, and abundance were determined. Salmon were found to be wide-ranging fish, but were infrequently captured in very shallow or very deep water. Brook trout were primarily an inshore species and were not often captured in water deeper than 25 feet. The majority of captured alewives were taken from shallow to mid-depths (0-40 feet) in summer and fall, and from deeper waters (maximum lake depth is 63 feet) in winter and spring. Smelts were widely distributed, but the majority were captured in water deeper than 30 feet during every month of this study. The annual salmon diet consisted of several forage fishes (smelts, sticklebacks, alewives, and killifish) and insects. Smelts were used during the entire year, killifish and sticklebacks during summer, and alewives only during spring. Brook trout had roughly similar feeding habits except that sticklebacks were used throughout the year, and insects constituted a higher proportion of their overall diet. Brook trout fed extensively on isopods (Asellus sp.) during winter and early spring. Alewives fed extensively on plankton with insects being important food only during summer months. Smelts utilized a higher proportion of insects and isopods than did alewives, but still fed mainly on plankton. The growth of salmon, trout, and smelt were similar to growth of these species on other Maine lakes. Echo Lake alewives grew rapidly compared to this species in other completely landlocked lakes. It was concluded that landlocked alewives were utilized only to a limited extend by the salmon (12 to 19 inches in total length) in Echo Lake, but would likely be preyed upon more heavily by larger salmon. Similarly, alewife utilization by brook trout likely would be greater with larger trout. Alewives and smelts were thought to compete for food and space during much of the year."