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

interspecific and intraspecific associations of this amphipod were examined.
The brood chambers of adult female amphipods, collected in the
long-term study area, indicated that reproduction is completed by late
May-early June at depths less than 35 m and beyond 35 m the amphipod
population breeds intermittently throughout our sampling seasons. The
fact that adults die after reproduction simplifies the recognition of year
classes. Size frequency histograms, collected throughout the sampling
seasons, indicated that Pontoporeia living at a depth of 10 m mature in
one year, those inhabiting a depth zone of 20-35 m require two years to
mature, and those living at depths greater than 35 m possibly require 3
years to mature.
Juvenile Pontopdreia approximately 2 mm long conformed to a
normal distribution and juvenile amphipods approximately 7 mm long
were randomly distributed at the short-term study area. The two size
groups appeared to be positively associated with each other. Both size
groups were negatively associated with the oligochaetes, the large size
group was negatively associated with the sphaeriids, and no association
occurred between amphipods and the chironomids.
Total Pontoporeia of the long-term study area were associated in
a positive manner with the oligochaetes, sphaeriids, and chironomids.
This positive association is attributable to larger benthos samplers that
masked the microa s-so Ciations of the benthic organisms.

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