FISH PATHOLOGIST REPORT

LocationDate

Trinity HatcheryFebruary 23, 2010

SpeciesPonds

Coho yearlings, March releaseG, H and I

Fish Health Assessment

Sixty fish were randomly selected for individual direct fluorescent antibody test (DFAT) for bacterial kidney disease (BKD). The first 20 of these fish were also assessed for over-all health condition. The first 30 fish were sampled from the ponds with the lowest amount of losses (H series), and the second 30 fish were sampled from the ponds with the highest amount of losses (I series. See Path Report Feb 23, 2010 for mortality data). Fish from both groups were sampled from mid-pond. The first 10 fish from each group were utilized for the health assessment.

Health assessment: The average weight of fish in the health assessment was 82.9grams and the average length was 188.7 mm. The average length-weight condition factor was 1.3, indicating a good amount of fat reserves (see raw data on accompanying Excel spreadsheet). Seven fish had a slightly eroded fin, one fish had a “cloudy” eye, and nine fish had spleens with a nodular appearance, but no obvious inflammation. One fish had a white, nodular lesion in the kidney consistent with clinical sign of BKD. All fish had seemingly perfect skin, gills, pseudobranchs, thymus, gastrointestinal tracts (all had food in tract)and livers. The average hematocrit (packed blood cell volume) was 49.7% (in acceptable range) and the average plasma protein concentration was 5.9 g/dL (also in acceptable range).The average mesenteric fat score was “1.9”indicating a proper amount of fat reserves. The average smolt index score was 0.5indicating that all fish are very much readying for outmigration. The overall score was 0.9 (a perfect score is 0.0).

Of the 60 fish examined and prepared for DFATs, a total of two had kidney lesions consistent with clinical sign of BKD, but these observations must be confirmed with the DFATs. It is possible that some fish have sub-clinical BKD infections, but still high amounts of the bacterium. The results of the DFATs for BKD will be available next week.

Comments

Submitted By: Mark Clifford, Ph.D., Associate Fish Pathologist, CDFG