Oceanic processes and the recruitment of tropical fish at Rottnest Island (Western Australia)

摘要

Transport processes relating to the observed annual "pulse" of tropical fish larvae arriving at Rottnest Island each autumn are examined using historical current measurements in the Leeuwin Current near the Abrolhos Islands and along the continental shelf just north of Perth. Observations of two common damselfish between 1977 and 2002 (with enhanced detail of fish size categories from 1994) show that the bulk of new recruits settle at Pocillopora Reef in March/April, a time when the Leeuwin Current is strengthening and the Capes Current is waning. Very large recruitment pulses in 1999 and 2000 were in La Nina years when the Leeuwin Current was very strong and water temperatures were at record high levels, but a third relatively strong pulse in 1995 was during an El Nina period with a weak Leeuwin Current (albeit with elevated ocean temperatures). Both advection and temperature therefore appear to play significant roles in recruitment at Rottnest Island, while biological factors such as food and predation during the pelagic stage must also be considered. The potential role of algal rafts in enhancing larval transport and survival may be important in the recruitment process and needs further research.