Influence of Coating Type on Retention of Dummy Transmitters Implanted in Rainbow Trout

The retention of surgically implanted dummy transmitters in tests with rainbow trout Oncorhynchus mykiss was influenced by outside coatings. Transmitters with a beeswax coating were rarely expelled (3%), whereas those with paraffin coatings were more often expelled (13%), and those with silicone coatings were commonly expelled (40%). Gross tissue response to the different types of transmitter coatings varied, but beeswax-coated transmitters usually were encapsulated, whereas others often were free in the body cavity. We were unable to detect a relationship between dummy transmitter size and expulsion rate.