Finfish Diagnostics

The prioritization of the basic user diagnostic needs are as follows, in descending order of
importance:

• Disease outbreaks or finfish/shellfish mortality
• Broodstock screening for Family Tracking of bacterial kidney disease (BKD) (finfish)
• Broodstock screening for shellfish (oyster) certification and importation of Crassostrea gigas spat
• Screening of broodstock or resident animals to establish a disease history, generally to satisfy a Fish Transport Permit (FTP) for finfish and shellfish
• Required pre-release inspection of apparently healthy fish or shellfish

The major purpose of this section is to clarify to laboratory staff and user groups the proper sampling procedures to be carried out by clients when finfish or shellfish disease problems arise. This is an absolute necessity to insure that samples received by the pathology labs are adequate for allowing a definitive disease diagnosis.

• Disease Recognition and Action – Whenever abnormal behavior patterns, external abnormalities, or high mortality occur at a hatchery, an immediate response from the hatchery staff in charge is imperative. Assistance should be requested from the Fish Pathology Section (FPS) of ADF&G whenever mortality appears excessive and is not related to known handling or mechanical malfunction of the physical plant. An epizootic is occurring when mortality reaches 1.5% per day. This requires immediate attention. A total commitment of the facility staff and appropriate personnel is needed to save the remaining fish. Mortality less than 1.5% down to 0.5% indicates that a fish health problem is present and the FPS should be notified for consultation. Mortality of less than 0.5% per day but greater than 0.3% should be investigated. Hatchery personnel should attempt to remedy the situation by modifications of environment or feeding and notify the FPS. The percentages given above are for total mortality. It is no less a matter of concern, however, if one lot of fish or shellfish is dying at 1.5% per day while the others remain healthy. The sick animals should be isolated as much as possible to prevent transmission of the disease to other lots. In order to reduce the spread of disease, dead fish and shellfish should be incinerated or soaked in a solution of 200 ppm of chlorine or iodine (active ingredient) for 12 hours before disposal.

• Sample Collection and Shipment – Prior to collecting any samples, the FPS must be contacted to discuss whether samples are necessary, and if so, the appropriate type of sample and numbers of fish or shellfish needed. Advance notice of sample submission by at least one week is preferred. Obviously, serious disease outbreaks will merit an exception. If advance notice is not given, samples may not be processed if other samples have priority or if appropriate lab personnel are not alerted and therefore unavailable to process the samples. The following instructions are general guidelines but some samples need special treatment and the pathology personnel will provide details. Samples that are not in an adequate condition (either substandard or improperly packaged) upon arrival may not be processed. All proposals for sampling (Southeast Region, Southcentral Region and AYK-Westward Regions) should be cleared through pathology staff by contacting the appropriate lab personnel.

• Preparing Samples – Different procedures are followed in sampling for bacteriological, virological, parasitological, ELISA, FAT or histological analyses. Further details regarding the procedures below will be provided to hatchery personnel upon initial contact with the FPS.

• In clinical cases of disease ( 0.5% mortality/day) 10 moribund fish or shellfish are generally a sufficient sample size to make a diagnosis. In situations where no excessive mortality or clinical disease is apparent, a larger sample size of 60 animals may be necessary. However, depending upon individual circumstances, sample sizes may vary between 10 and 60. Samples should be examined from each affected lot, incubator, or rearing container. Consult with the FPS for specific sampling requirements in each situation.