Difference in Sex Ratios of the Anadromous Alewife, Alosa pseudoharengus, Between the Top and Bottom of a Fishway at Damariscotta Lake, Maine
alewife, sex composition, spawning
Journal or Book Title
The Damariscotta River alewife, Alosa pseudoharengus, fishery has been monitored by the Maine Department of Marine Resources every year since 1971 for abundance of fish, length and weight frequencies, age distribution, and sex ratios. From 1977 through 1979, sampling plans were also devised to estimate numbers, size, and sex composition of ripe alewives escaping the fishery and entering the lake to spawn. (Throughout this paper they will be collectively referred to as escapements.) While sampling the 1977 escapement run it became evident that a greater number of males than females were entering the lake to spawn. This male dominance was not unusual as it was reported in other alewife runs, as well. Bigelow and Schroder (1953) stated that as a rule males greatly outnumber females on the spawning grounds. What prompted this investigation was the fact that while the escapement runs had significantly more males than females, the samples from the commercial catch revealed a consistent sex ratio of 1:1. Similar disproportionate ratios were observed in 1978 and 1979 escapement runs, while the commercial catch ratios were 1:1 each year. In this paper I will examine these varying sex ratios and offer considerations for further investigation.