Short-term movement and behaviour of black marlin Makaira indica in the Coral Sea as determined through a pop-up satellite archival tagging experiment

Abstract

Pop-up satellite tags were deployed on seven black marlin, Makaira indica,in the north-western Coral Sea, to examine movement, post-capture mortality and habitat preferences. Five of these tags popped up and transmitted positions, and detailed data on diving behaviour, ambient water temperature and daily movement were received via ARGOS transmission from two tags. One tag was later found on a beach, allowing a complete archival data set to be downloaded and geolocation estimates provided by software on-board the pop-up tags and those based on the complete archival tag data sets to be compared. The tags indicated rapid movement away from release sites; three south-easterly displacements (222 km (120 nm), 222 km (120 nm), and 1185.3 km (640 nm) net) appeared to be associated with the East Australian Current, one moved 555.6 km (300 nm) directly east, and the last tag moved offshore and then back towards the coast over a 2-month period for a net displacement of 384 km (207 nm). Based on displacement speeds and diving behaviour, it was concluded that five of the seven fish survived capture and handling for periods ranging from 3 to 64 days. The fate of the other two is unknown. Estimates of longitude made on board the pop-up tag were very similar to the best estimates that could be made using the complete archival data set; however, pop-up tag latitude estimates were significantly more variable than those using the archival data. In the two cases in which pop-up tags were scheduled to stay on the marlin for more than 3 months, the tags detached prematurely, after 39 and 64 days. Temperature and depth data indicated a preference for waters of the mixed layer (20–120 m) and temperatures warmer than 24°C.