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Healing, classification and
hematological assessments of sea lamprey
(Petromyzon marinus) wounds on lake trout (Salvelinus namaycush).
Shawn M. Nowicki1 and Jill B. K. Leonard1
1 Northern Michigan
University, Marquette, MI
August 2007
ABSTRACT:
The
Great Lakes parasitic sea lamprey (Petromyzon marinus) population is currently modeled using wounding
statistics, subjectively assessed by experts for each lake. Effects of
parasitic sea lampreys on lake trout (Salvelinus namaycush) in the Great Lakes are monitored based on counts
of stage A1 to A3 wounds subjectively assessed using the King (1980)
classification per 100 lake trout captured in commercial fishing nets. To assess
the time required for wounds to progressively heal to stage A3, wounded lake
trout collected from northern Lake Huron were sampled, photographed, their
wounds were classified, and fish were then tagged and released. Recaptured
wounded fish showed that 45.9% of wounds healed by at least one stage within a
year, 48.6% were unchanged and 5.4% were degraded. Substantial healing occurred
following a lamprey attack, but the rate of healing varied (46 – 704 days) and
was insufficient to characterize healing time progression. King (1980) wound
classifications and two new classification indices (quantitative index and
mixed index) were evaluated and compared by conducting Kmeans
cluster analysis. Cluster analysis grouped quantitative wound measures;
however, these groups did not relate to established classification schemes. The
King classification index did not relate to healing any better or worse than
did the other two indices.ii
However,
the new mixed index, which incorporates the King characteristics and morphometry of the wound would provide better data to the
viewer by using quantitative and minimally subjective qualitative measures to make
a better decision on wound healing. Hematological methods were used to assess
immune response in lake trout after sea lamprey wounding. Both wounded and
unwounded lake trout were sampled to determine if there was a detectible
difference in immune status as indicated by differential leukocyte counts,
hematocrit and leukocrit. There were significant
differences in hematological parameters between wound classes and between gear
type groups. It appeared that wound class, specifically A1, changed
hematological parameters in lamprey-wounded lake trout. Stress caused by gear
or immediate sampling after lamprey removal also appeared to play an integral
role in the changes of white blood cell counts present in the sampled fish. The
King (1980) wound classification system is the current index, but it is not
reliable according to numerous classification workshops. An increased amount of
improved data needs to be collected to construct a new wound index that would
incorporate a multitude of wound characteristics and measurements. I also
suggest that hematological assessments of wounded fish be studied both in the
laboratory and the field to better understand the parameters of wound healing
in lake trout. This additional information could provide a more reliable
classification index and a concurrent parasitic abundance model.