Radio tracking the endangered eastern freshwater cod, Maccullochella ikei, in the Mann River, Australia
The movement patterns of the endangered eastern freshwater cod were studied over a 12 month period in 2005 and early 2006. Radio tags were implanted in 25 adult cod captured from three consecutive pools within the Mann River, northern New South Wales. Tagged cod were released in March 2005 with 18 monitored for 40 weeks and 13 for 50 weeks. Cod were located once per week by boat, with flow and water temperature recorded using data-loggers. Automated tracking stations located at the intersection of pools recorded movements between weekly observations. Cod moved both upstream and downstream, and within pools as well as between pools. Total stream length occupied varied considerably (between 211 metres to 34.5 kilometres) with no significant relationship between size of fish and home range. Average weekly movements of the tagged population varied significantly for both males and females (range of 36 – 1334 m for males and 3 – 2417 m for females). Inter-pool movement was facilitated primarily by flow, but was independent of water temperature. Increased activity during the breeding season was observed for males, but not for females. The maintenance of flows is paramount for the ongoing conservation of eastern freshwater cod, particularly during the breeding season.