Resource use, behavior, and ecology of Mysis in Lake Champlain

Many populations of migratory animals exhibit behavioral variability at the individual level. In Lake Champlain, the opossum shrimp Mysis diluviana, undergoes extensive diel vertical migration (DVM), linking offshore benthic and pelagic communities. The general model of Mysis DVM assumes individuals are benthic by day and pelagic by night. Previous benthic investigations, however, have also reported some Mysis remain benthic at night (non-migrants). Non-migrants may or may not feed on benthic resources at night, potentially creating potential for a sub-population solely dependent on benthic rather than pelagic resources. We examined Mysis diel habitat use at two deep sites (60 and 100m) in Lake Champlain to quantify Mysis resource use in the water column and on the lake bottom over 24-hour periods during April-October. Preliminary analysis indicates Mysis gut contents were rarely empty when collected on the lake bottom, regardless of time of day, suggesting non-migrant mysids may continue to feed on benthic resources when foregoing DVM. In total, our results highlight the importance of considering benthic habitat when depicting implications of Mysis migration behavior on their trophic role and availability as prey to fishes in Lake Champlain’s food web.