Grouper species are commonly maintained in large public aquariums. This group of fish can become quite large (>200 kg) and are popular exhibit animals. Although commonly found in captive situations, there is little work published on the captive management and common medical disorders of these animals.
At the Living Seas Pavilion at Epcot (Walt Disney World), attempts are currently underway to perform basic health assessments on the grouper species. Methods have been developed to safely anesthetize and transport these animals. Medical evaluations on both healthy and ill animals are routinely conducted. Medical evaluation has included the following diagnostic tests:
- Ultrasonography; radiography; body weight
- Dermal biopsy for histopathology
- Skin scrapes, gill, and fin biopsies for direct microscopic evaluation; colonic wash for ova and parasite evaluation
- Blood collection for CBC, serum biochemical profile, serum alpha-tocopherol, serum retinol, serum trace minerals, and serum banking
Recently acquired animals from the wild are evaluated and results compared to those from long-term captive animals. This information will lead to a better understanding of the nutritional and environmental requirements of groupers allowing appropriate adjustments to be made to their environment and diet.
A common challenge when working with this species is that they are typically maintained in large multispecies aquariums. The main aquarium at the Living Seas is a marine environment which maintains over 3,000 individuals of 50 species and holds approximately 6 million gallons of man-made seawater. Due to the size of the tank and the numerous coral heads, it is impractical to safely catch these fish without some degree of chemical restraint. An anesthetic delivery system was developed to administer a concentrated bolus (25 g/L) of MS-222 (Tricaine-S, Western Chemical Inc, Ferndale, WA, USA) into the oral cavity. Please note, this dose is 25 times greater than the commonly used euthanasia dose and must be used with extreme caution. Typically, only one to three “blasts” of this solution are needed to induce heavy sedation in these animals. The solution can be placed in a large “Hudson” type spray container similar to those used in horticulture for spraying chemicals on plants. For very large animals (>100 kg), induction may require a larger single bolus. For these animals, a large syringe-like container has been fashioned from PVC. This container has a plunger system which can quickly spray a large volume of the anesthetic solution. Some animals will allow this anesthetic solution to be sprayed directly into the mouth while with other less docile individuals, the solution can be sprayed in the animal’s face.
Using operant conditioning, several animals have been trained to swim into a large plastic container. Once the animal has entered the container, a lid is placed over the top and the grouper can be anesthetized as described above. This method has significant advantage in that the patient is unable to swim away prior to or during the anesthetic induction process.
Once the animal has become recumbent, it is transported to a smaller holding container for medical evaluation. This system contains 75 ppm MS-222 and an oxygen delivery system (air-stone). Respirations as determined by gill movement and response to stimuli are used to determine depth of anesthesia. If respirations become severely depressed or absent, the anesthetic solution can be diluted with unmedicated water. A second container with unmedicated water is kept available in the event of any type anesthetic complication would arise. The grouper is maintained in this system throughout most of the physical exam. For ultrasonography, the animal can be left submerged in water. The grouper’s thick scales may cause significant interference when attempting to acquire a clear ultrasonic image of coelomic structures. In larger animals, the ultrasound probe can be passed orally into the esophagus and high-quality images of the visceral organs can be acquired. If passing the probe down the esophagus is impractical, a high-quality cardiac image can be obtained by lifting the opercular flap and placing the probe just caudal to the gills with the probe directed caudo-ventral. This cardiac imaging technique is very useful for monitoring heart rate and also to locate the sinus venosus for blood collection or catheterization. Blood collection can also be attempted from the tail vein. This is much more difficult in grouper species than other fish. Care must be taken to insert the needle between the thick scales. If blood cannot be collected at this site, we have routinely utilized the sinus venosus. Skin scrapes, gill and fin biopsies are collected as has been described in other species. Samples are placed on microscope slides and directly examined for possible ectoparasitism. Excisional or punch skin biopsies are taken around the head and/or lateral line for histopathology. Histopathologic results have been used to determine possible etiologies and severity of head and lateral line disease (HLLD). That portion of the animal’s body that is being examined is elevated out of the water during sample collection. For radiography, the animal is temporarily lifted out of the water and placed on an x-ray cassette for imaging. X-ray cassettes are sealed in plastic bags for protection from water damage. To facilitate lifting the animal in a non-traumatic manner, a large plastic sheet with numerous perforations for water drainage can be used. This fenestrated plastic sheet of bag is also useful when lifting and transporting the anesthetized patient.
A review of physical exam findings has included the following conditions: exophthalmos, keratitis, HLLD, cachexia, and ectoparasitism (monogenetic trematodes). A review of the necropsy reports in our captive grouper species has shown a large proportion to have systemic granulomatous disease. These granulomas have been fungal (Ichthyophonus sp.), mycobacterial, and parasitic in origin.
The authors are indebted to the following individuals for their help with this project and their assistance with manuscript review and preparation: Don Neiffer, Martha Weber, Michele Miller, Scott Terrell, Conrad Litz, Michael Garner, Howard Krum, Mike Walsh, and Chris Herman.