Michigan Department of Fish Health Laboratory Natural Resources Laboratory Report Fisheries Division
To: Martha Wolgamood Report date: 9/12/08
Wolf Lake State Fish Hatchery
Necropsy date: 7/21/08 MSU-AAHL No.: 080721-(1-9)
Host: 3 brook stickleback (Culaea inconstans)
28 fathead minnow (Pimephales promelas)
4 northern redbelly dace (Phoxinus eos)
2 brook trout (Salvelinus fontinalis)
19 western blacknose dace (Rhinichthys obtusus)
19 creek chub (Semotilus atromaculatus)
65 white sucker (Catostomus commersonii)
1 brown trout (Salmo trutta)
1 johnny darter (Etheostoma nigrum)
Locality: Pigeon River
Collector: MI-DNR Date collected:
Purpose of examination: recent fish die-off
Condition of fish submitted:
Fish dead for up to 24 hours prior to collection, then frozen. Fish arrived DOA, each species bagged
and frozen together. Majority of fish
were putrified.
Testing results/Diagnosis:
- Q-ELISA for Renibacterium salmoninarum, the causative agent
for bacterial kidney disease in salmonids, was performed for the brown
trout and brook trout. Both
species were found to have medium levels of R. salmoninarum antigen
concentration affecting 100% of the fish from each of these two species submitted (1 of 1 brown trout and 2
of 2 brook trout).
- Kidney and spleen tissues were saved from all species for
virological analyses with tissue culture; results for all species were
negative after two passages.
- Gill and GIT tissues
were removed from fish and picked up by the Water Quality and
Environmental Microbiology Laboratory at Michigan State University for
analysis.
- Pooled kidney and
spleen tissues were submitted to the MSU Toxicology Laboratory for
analysis. Results demonstrated the
presence of extremely high levels of potassium, magnesium, and iron; a
matter that suggests the presence of poor water quality, characteristic of
runoff storm events.
- Due to the poor condition of the tissues, additional analyses were
not performed.
Recommendations:
- Based on all analyses made thus far, the most probable cause of death was anoxia caused by excessive nutrient load and/or unusual sedimentation processes.
Prepared by: Mohamed Faisal, D.V.M., Ph.D
cc: Gary Whelan