Ecology of the burrowing amphipod, Pontoporeia affinis, in Lake Michigan / by Wayne Paul Alley.

DISCUSSION

REPRODUCTION
The results of the present investigation indicate that at least three
distinct breeding populations of Pontoporeia occur in Lake Michigan.
The data strongly suggest that amphipods living at a depth of about 10m
mature in one year, while those in approximately the 20-35m zone require two years to mature. The reproductive season seems to be completed by late May-early June for these populations. Amphipods living
at depths greater than 35m may require at least three years to mature,
and the population there breeds intermittently throughout the spring,
summer, and fall. Insufficient data were obtained to determine whether
breeding also takes place in winter.
Juday and Birge (1927) found that the breeding season of Pontoporeia extended from December to May in Green Lake, Wis., and there
the population required two years to mature. Bousfield (1958) reported
ovigerous females from November to April in Canadian oligotrophic
lakes, and indicated that the life span was slightly more than two years.
Larkin (1948) found that this amphipod had a life span of 2 and perhaps
3 years in Great Slave Lake. Teter (1960) felt that P. affinis matured
in one year in Lake Huron while Cooper (1962) found a one year life
cycle at a depth of 12 m and a two year life cycle at a depth of 35 m in

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