Large Concentrations of Submerged Pulpwood Logs as Fish Attraction Structures in a Reservoir

Beginning in the 1830s, several rivers in Maine were used to transport logs downstream to mills. After 1900, most such logs were pulpwood, approximately 1 m in length. An estimated 3.6 to 7.2 × 10⁶ m³ of logs (one to three million cords) sank and created artificial habitat in the Kennebec River and its principal reservoir, Wyman Lake. The value of these logs as fish attraction structures was studied in Wyman Lake in 1979–1981. Over 1,600 fishes were collected in two collection periods: 1979–1980, using experimental gill nets; and 1981, using vertical gill nets. Five species were found in significantly higher numbers in areas with submerged logs, while yellow perch, Perca flavescens, the most common species, was more abundant in areas without submerged logs (P < 0.05). Data from 1979–1980 and 1981 suggest, however, that P. flavescens are found in equal to higher numbers in log areas in summer months and are found in non-log areas in fall. The limited use of log areas in spring by this species may be a reflection of the unsuitability of the generally non-vegetated log sites as spawning areas at that time of year. Chi square analyses indicate the sex of P. flavescens was not randomly distributed in either year. Higher numbers of males occurred in non-log areas and higher numbers of females and immature fish were found in log areas, though the differences were not as great in 1981. Studies of macroinvertebrates have shown that highest biomasses are found in the surrounding sediments rather than on the logs themselves. Thus, the value of log concentrations to fishes may be more for their protective function than for their value as attachment sites for food items.