Retention of food safe PIT tags in native fish of the Murray-Darling Basin
Doyle, J., Baumgartner, L. and Mudford, E., 2011. Retention of food safe PIT tags in native fish of the Murray-Darling Basin. Presentation given at the 2011 Annual Australian Society for Fish Biology Conference and 5th Australian Technical Workshop on Fishways. 22 – 24 July 2011, Townsville, North Queensland, Australia.
Scientists frequently use Passive Integrated Transponder (PIT) tagging and dart tagging as a method to quantify fish migrations. However, there is a limited understanding of the retention/shedding rates of tags and thus the reliability of the tag data is uncertain. We evaluated the effectiveness of five different tagging treatments in captive populations of golden perch, silver perch and Murray cod. The treatments were; PIT tags in either the shoulder, gut or chest, a double T-bar tag in the shoulder or no tag (control). Each treatment was applied to 50 individuals per species. Each species was housed in five separate 3000L tanks, each containing ten tagged fish from each of the five different treatments. Five operators were randomly selected for the tagging process as it was deemed useful to understand the influence of operator proficiency on tagging success. Each operator applied two of each tag treatment per tank. Fish were checked daily for mortalities and tag rejections over a period of one year. Results indicated that the gut tagging was the most reliable method across all three species with the highest level of tag retention and the lowest mortality rate. Chest and double T-bar tags were unreliable in all three species, while shoulder tagging was equally as successful as gut tagging in Murray cod. There was no difference in the tag rejection rate or mortalities across different operators.