| Remarks |
Seasonal changes in distributions of catch rates, reflecting concentrations of fish, do take place but individuals do not follow clear migration routes (Ref. 30358). Such seasonal concentrations are known to occur in the north-west Coral Sea, off the North West Shelf of Australia, in the Banda Sea and the east China Sea (Ref. 6390). There have been suggestions that the distributions and migrations of black marlin are sex-dependent (Ref. 30359). Knowledge of seasonal changes in distribution and migration patterns of this highly mobile species is largely based on catch data collected by the Japanese longline fleet (Ref. 6390). Tagging has also assisted greatly in interpretation of movement patterns (Ref. 30358, 30360).
In Australian waters, aggregation in the Coral Sea during September-December, presumed 1-2-year-old fish and 1 or 2 older groups move south parallel to the eastern Australian coastline from north Queensland to central New South Wales, apparently in association with the southward movement of the East Australian Current (Ref. 30358). By April, however, the fish have probably dispersed eastwards (catch rates in eastern Australia between April and August are generally very low). Fish can move large distances (up to 7200 km in 359 days) and recaptures from tagging studies over several years strongly suggest annual homing of at least part of the (western Coral Sea) population (Ref. 30358). It appears that fish also migrate from northwestern Australia to Indian Ocean waters south of Indonesia in late March-April, and fish migrate back to north-western Australia during October (Ref. 30354). High catch rates occur in the Banda Sea north of Australia between January and April (Ref. 6390).
Black marlin larvae have been found only in the north-west Coral Sea off Queensland and off northwestern Australia, south of 10°S (where they were misidentified as sailfish larvaeIstiophorus platypterus (Ref. 30361, 30362). Off Lizard Island in north Queensland, concentrations of black marlin larvae have been found in close proximity (within half a mile) to the outer slopes of coral reefs on the edge of the continental shelf (Ref. 30362). |