7841 - Laserfiche WebLink

Home Browse Search

6sh species, particularly with internally implanted trans- mitters. Researchers intending to use radsotelemetry on fish spe- cies should consider the following guidelines and com- ments: a. Force-jed and Implanted Transmitters: Force-fed packages should be small enough to pass through the gut without obstructing the passage of food. Force-fed or implanted packages should be coated with an impervious, biologically inert coating. Residence time of up to several days in the gut is generally long enough to provide useful information on movement and body temperature. Implanted hansmitters should not interfere with the function of the organs surrounding them or with the fish's normat behavior. For intraccelomic or subcutaneous im- plants, the transmitter package may have to be sutured in place to prevent its movement or interference with vital organs. b. Externally Attached Transmitters: Consideration must be given to the effect of an externally attached transmitter package on behavioral interactions between tagged fishes and other individuals. For example, the transmitter should neither conceal nor enhance the appearance of dorsal fins or opercular flaps. Transmitters should be shaped and at- tached so as to eliminate or minimize the risk of entangle- ment with underwater vegetation or other obstructions. Most fishes continue to grow throughout life. External transmitters should be removed or designed to be lost after a time, or they may constrict or irritate the animals. Special consideration must be given to soft-skinned species to pre- vent abrasion. Radioisotopes The use of radioisotopes as markers in natural systems is very valuable, and may be the only means of adequately gathering data on movements of very small species; the technique, however, should be undertaken with caution. Special training and precautions are required of researchers by federal, and frequently state law (8). A license, which specifies safety procedures for laboratory use, is required for release of isotopes into natural systems and for disposal of waste material. The pros and cons of using strong emit- tersmust be assessed in terms of possible deleterious effects on the animal, to predators that might ingest isotope-la- belled animals, and potential hazard to the public. When marking with radioisotopes, the animal does not have to be handled for identification, several individuals can be monitored rather quickly, the label is easy to apply, and it can be useful for a limited time if desired. Strong emitters, however, cause extensive tissue neaosis at the implant site, and even weaker ones carry the chance for induction of mutations that may compromise future genetic studies of these populations. Housing and Maintenance at Field Sites Because the biological needs of each species and the na- ture of individual projects vary widely, only the most gen- eral recommendations on housing wild vertebrates in the Field can be made. When dealing with unfamiliar species, testing and comparing several methods of housing to find the method most appropriate for the.needs of the animal and the purposes of the study may be necessary. Restraint and case of maintenance by animal keepers should rTOt be the prirnc determinants of housing conditions, though these arc certainly important considerations. Normal field maintenance should incorporate, as Ear as possible, those aspects of the natural habitat deemed im- portant to the survival and well-being of the animal. Ad- equacy of maintenance can be judged, relative to the natural environment, by monitoring a combination of factors such as changes in growth and weight, survival rates, breeding success, activity levels, general behavior, and appearance (29). Nutritionally balanced diets should be provided or natural foods should be duplicated as closely as possible. Natural light and temperature conditions should be fol- lowed unless alteration of these are factors under investi- gation. Frequency of aquarium cleaning should represent a com- promise between the level of cleanliness necessary to pre- ventdisease (30,31,32), and the amount of distress imposed by frequent handling and exposure to unfamiliar surround- ings. Applied ~Cnowledge of animal ethology can assist the investigator in providing optimum care and housing. Disposition Following Studies Upon completion of studies, researchers should release wild-caught specimens whenever this is practical and eco- logically appropriate. Exceptions are: if national, state, or local laws prohibit release, or if release might be detrimental to the well-being of the existing gene pools of native fishes in a specific geographic area. As a general rule, field captured fishes should be released only: a. At the site of the original capture, unless conservation efforts or safety considerations dictate otherwise. Release should never be made beyond the native range of distribution of a fish without prior approval of the appropriate state and/or federal agencies, and approved relocations should be noted in subsequent publication of research results. b. If theirability to survive in nature has not been irreversibly impaired. c. Where it can be reasonably expected that the released animal will function normally within the population. d. When local and seasonal conditions are conducive to survival. e. When release is not likely to spread pathogens. Captured animals that cannot be released or are not native to the site of intended release should be properly disposed of, either by distribution to colleagues for further study, or if possible by preservation and deposition as teaching or voucher specimens in research collections. In both the Field and laboratory, the investigator must be careful to ensure that animals subjected to an euthanasia procedure are dead before disposal. In those rare instances where specimens are unacceptable for deposition as vouch- ers or teaching purposes, disposal of carcasses must be in accordance with acceptable practices as required by appli- March -April 1988 21