Ecology of the Australian mudskipper Periophthalmus minutus, an amphibious fish inhabiting a mudflat in the highest intertidal zone

摘要

A population of Periophthalmus minutus inhabiting a mudflat in the highest intertidal zone in Darwin was investigated for surface activity, feeding and reproduction in relation to environmental conditions in the dry (August) and wet (February) seasons. On days with tidal inundation, the fish were diurnally active on the exposed mudflat surface at low tide, but retreated into burrows during daytime inundation and at night. Temperatures above 40°C and heavy precipitation suppressed the daytime surface activity of the fish. During neap tides, the mudflat remained uncovered by the tide for nine days in both seasons. The fish confined themselves in burrows without ingested food throughout the nine-day period in August, but they remained active on the mudflat surface and kept foraging in February. The salinity of burrow water during the nine-day emersion was extremely high (72±6 psu, mean±s.d.) in August, but lower (46±9), though still higher than the open seawater value (34), in February. The burrows were J-shaped in February, but were straight (with no upturn) in August. Fertilised eggs were collected from the upturned portionof the burrow, and hatched upon submersion. Juveniles occurred in water pools on the mudflat surface in March.