Movement, Dispersal, Home Range

Abstract

To determine movement rates, home range size, and dispersal ability, 49 adult northern snakeheads were implanted with radio tags in October, 2006. Fish were located once per month through March, 2007 and twice per week from April to August, 2007. A subset of fish was also tracked multiple times over a 24 hour period in November, March, and July. Data are currently being analyzed, and results will be reported here and published in a scientific manuscript. One quarter of the fish died by the end of the study period, with few deaths immediately after release, and the majority of deaths at the end of winter. All fish remained in the bay they were re-released into until May, 2007. During May, one third of the surviving fish dispersed from the release area, establishing new home ranges 5 to 35 km from their release point. Several other fish went missing or were found on forays in nearby bays during this period, but all of these quickly returned to their bay of release. During May, snakeheads were in the pre-spawn phase of their life history, and we believe these dispersal and foray movements represented searches for a mate or spawning habitat. The fish that remained in their area of release were shown to have an average home range size of just over 1.5 km2. General movement rates were higher during the pre-spawn period than the spawning period, which lasted from June until the end of the study. Hourly movement rates were higher in summer than winter, and appeared to increase around dawn and dusk.