Observations of dermal sarcoma
prevalence in wild populations suggested that tumor-positive
fish lost their tumors during the period of spring to summer.
This hypothesis was reached based on the fact that large numbers
of adult walleyes (20-30%) were tumor-positive during the spring
spawning run each April and very few tumor-positive fish could
be found in the summer months. Populations dynamics studies of
walleye populations on Oneida Lake conducted by the Cornell University
Biological Field Station did not indicate that massive die-offs
occurred during this period. In addition, during the spring spawning
run, many walleye dermal sarcomas appeared grossly necrotic and
could be easily dislodged from the fish. To better document this
apparent regression, tumor-positive walleyes collected from Oneida
Lake were identified with individually numbered jaw tags. These
fish were transported to experimental ponds near the Cornell
University campus in Ithaca, NY, in April. When the fish were
inventoried in July of the same year, many of the previously
tumor-positive fish had no tumors. This provided difinitive evidence
that the tumors actually regressed during the period of spring
to summer.
Reference:
Bowser, P.R. and G.A. Wooster. 1991. Regression of dermal
sarcoma in adult walleyes (Stizostedionvitreum).
J. Aquat. Animal Health. 3:147-150.
