Reproductive behaviour of the endangered eastern freshwater Cod Maccullochella ikei in the Mann-Nymboida Rivers of NSW
The aim of this study was to quantify breeding behaviour and spawning cues of wild eastern freshwater cod (Maccullochella ikei). Data were collected over three breeding seasons between 2003 and 2005. Three areas were sampled 3-5 kilometers in length within the Mann-Nymboida River, with each area separated by approximately 40 river kilometers. Areas were generally homogenous for all parameters except altitude, with areas one, two and three at 80, 160 and 220MASL respectively. Cod were observed using an underwater camera operated from a canoe and by fixed cameras placed at known spawning sites. To determine spawning cues, water temperature, moon phase, barometric pressure, river flow and day length were all monitored. Eastern freshwater cod have a short, succinct breeding season lasting only 8-10 weeks. Over the three years 30 spawnings were observed at 18 sites across areas one and two; no observations were made in area three. Spawning commenced each year in area one in the first week of September, and one week later in area two. Multiple use of spawning sites was observed both within and between years. Day-length and temperature appear to be the primary spawning cues for M. ikei. Male cod were observed at or near nesting sites up to one week prior to spawning. Site selection was specific, with security appearing to be the key factor driving choice. Nest sites were vigorously cleaned by males up until the day of spawning when females entered the site. A complex courting ritual to facilitate spawning was observed. Post-spawning care of eggs was carried out exclusively by males, with continuous protection and fanning of the eggs undertaken until hatch. Larval care by the male was observed at all sites with vigorous defence offered up until 12-14 days post-hatch when larvae dispersed. Barbless fishing lures passed near nesting sites facilitated aggressive attacks throughout this period. Protection of spawning eastern freshwater cod must be considered a management priority to ensure long-term recovery. The closure of key area to all angling is recommended during the breeding season.