Necropsy techniques for fish

Fish medicine has become more mainstream within the veterinary profession over the past two decades. Aquarium hobbyists, public aquariums, and private facilities are relying more and more on veterinary expertise for fish health problems. Most problems in fish health are related to water quality and other husbandry issues; the necropsy is only one important part of a complete work up. As with necropsy of exotic terrestrial animals, an understanding of the basic anatomy and physiology of a few common fish species can help the practitioner gain confidence when working with more exotic fish. However, because species differences do exist, protocols may require modification. Moribund or fresh dead specimens are best. With fish, perhaps more than any other class of animals, wet mount biopsies of external and internal tissues are very informative. Parasites are an important contributor to disease, and most easily identified alive. The delicate structure of the gill and the rapidity with which it can break down also necessitates careful analysis at the outset. Like-wise, other pathology can be identified quickly using wet mounts. Microbiological culture of kidney, brain, liver, spleen, and other affected organs, and histopathology are also important aspects of the fish necropsy. Cultures should be incubated at temperature ranges similar to those for the fish. Certain viruses, including Spring viremia of carp (SVC) and koi herpes virus (KHV-not Herpesvirus cyprini, the causative agent of carp pox) are important pathogens that require confirmatory virus isolation and culture. SVC is a notifiable disease.