Submission of Fish for Diagnostic Evaluation
Ruth Ellen Klinger and Ruth Francis-Floyd  

Determining the cause of a fish's illness and death can be difficult and frustrating for anyone who works with fish. Disease problems are commonly misdiagnosed and fish are often incorrectly treated with over-the-counter medications. A vicious cycle arises when the first treatment doesn't work and another one is tried, then another, and so on. Not only is this method a waste of time and money, but it usually does more harm than good to the fish in question. In addition, over-treatment, and the time lag from problem onset to submission could allow secondary infections (caused by agents that invade fish tissue after the damage by the initial agent has occurred) to take hold. Therefore, it is important to contact a diagnostic laboratory as soon as a disease problem is noticed to prevent misdirection in your fish health management plan.

When fish become sick or die, the first response should be to find out why. The sooner the cause of their demise is determined, the faster a response can be taken to rectify the situation. Whether it is a pond, home aquarium, production farm, or a fish kill observed in the wild, it is imperative to respond quickly and correctly. The following is the proper procedure to submit fish and water samples to a diagnostic facility. Following these steps should result in a correct evaluation and the best recommendation for treatment.

The Importance of History and Records
When a client contacts a diagnostic laboratory, he/she will be asked a routine set of questions. Everyone involved should be knowledgeable about the system and animals that live there. Keeping records of water chemistry parameters, water changes, species in the system, and recent additions can accelerate processing of samples and provide the needed recommendation. The following is a selection of questions a fish health specialist is likely to ask, depending on the individual's situation. The client should be prepared to provide information on the following:

  • What is the size and design of the system involved?
  • How old is the system?
  • What are the species and numbers of each species in that system?
  • What are their sizes and ages?
  • Which species are in trouble? Which are not?
  • Have there been recent additions? Which species and when?
  • When was abnormal behavior or death first noticed?
  • Number of sick fish per day? Number of mortalities per day?
  • What weather changes were observed (important in pond cases)?
  • Have there been problems in this system before?
  • Have there been problems with this/these species before?

Behavioral Changes:
  • What are the fish doing (e.g., are they flashing, is their breathing rate increased, are they lethargic)?
  • What are the positions of the fish in the water column (at surface, vertical, lying on the bottom, near the aerator or pond edge)?
  • Are the fish eating? If not, when did they stop?

Physical Changes:
  • What is the fish's body condition (e.g., thin, bloated)?
  • Are one or both eyes normal, sunken in, or popped out?
  • Are the fins clamped down, frayed, or bloody?
  • Are the gills discolored, bloody, or frayed?
  • Are there lesions or growths on the fish?
  • What else looks abnormal on the fish?

Routine Procedures:
  • What type and size of feed is fed?
  • How much and how often is fed per day?
  • Has there been any change in feeding or system maintenance recently?
  • When was the last water change? How much was changed?

Previous Treatments:
  • When was the last treatment?
  • What was the treatment(s) and dosage(s)?

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