Dispersal of Adult Black Marlin (Istiompax indica) from a Great Barrier Reef Spawning Aggregation

Abstract

The black marlin (Istiompax indica) is one of the largest bony fishes in the world with females capable of reaching a mass of over 700 kg. This highly migratory predator occurs in the tropical regions of the Pacific and Indian Oceans, and is the target of regional recreational and commercial fisheries. Through the sampling of ichthyoplankton and ovaries we provide evidence that the relatively high seasonal abundance of black marlin off the Great Barrier Reef is, in fact, a spawning aggregation. Furthermore, through the tracking of individual black marlin via satellite popup tags, we document the dispersal of adult black marlin away from the spawning aggregation, thereby identifying the catchment area for this spawning stock. Although tag shedding is an issue when studying billfish, we tentatively identify the catchment area for this stock of black marlin to extend throughout the Coral Sea, including the waters of Papua New Guinea, the Solomon Islands, Micronesia, New Caledonia, Kiribati, Vanuatu, Fiji, Tuvalu and Nauru.

Satellite telemetry reveals physical processes driving billfish behavior

“…Sailfish are among the most surface oriented of the billfishes, spending over 80% of their time at surface temperatures during the day and 93% at night in the Atlantic, which is consistent with the behavior reported for sailfish in the Pacific [63,72,73] and for the only two longbill spearfish that have been tagged [50]. Black marlin in the Coral Sea were found to occupy shallow waters warmer than 24°C [60], and their horizontal movements correlated with the spread of 26°C-27°C sea surface temperatures (SST) [61]. Striped marlin are also largely surface oriented, spending 80% of their time in the mixed layer and 72% in the top 5 m [66].…”

“…Thorough larval collections in the Straits of Florida [81] indicate that spawning activity for the dominant istiophorids in the Atlantic (sailfish and blue and white marlin) generally occurs from April to October, while swordfish larvae have been collected year-round [81,82]. Other collections have identified billfish larvae from Hawaii, Gulf of California, and the Great Barrier Reef [61,[83][84][85], most of which encompassed several months of the year.…”

“…However, only conventional tag data indicates extensive transequatorial and trans-Pacific movements [101]; thus, this behavior is still poorly understood. Along these routes, there is evidence of spawning in the South China Sea and Coral Sea, offshore of Taiwan, and near Cairns, Australia [11,61].…”

Population structure of istiophorid billfishes

“…Recent pop-up satellite archival tagging of adult black marlin off the Great Barrier Reef during the spawning season provided insights on movements of individuals for up to six months following G Model No. of Pages 8 the spawning season and demonstrated that the spawning aggregation has a catchment area that extends up to 5000 km from the spawning area (Domeier and Speare, 2012).…”

Refuge-Seeking Impairments Mirror Metabolic Recovery Following Fisheries-Related Stressors in the Spanish Flag Snapper (Lutjanus carponotatus) on the Great Barrier Reef

“…For example, within the northern region of Australia's Great Barrier Reef Marine Park (GBRMP), a number of "buffer" zones (3% of the entire marine park) exist to allow trollfishing for pelagic species, because this activity is deemed low impact (GBRMP Authority 2003). Buffer zones were introduced in 2004 to protect a historically and socioecologically important sport fishery that targets spawning aggregations of black marlin (Istiompax indica; Domeier and Speare 2012). Unfortunately, marlin catch-and-release fishing may be characterized by unrecorded and cryptic mortality, with anglers in the GBRMP black marlin fishery routinely losing hooked fish to sharks, and fish released in weakened condition are likely to be preyed upon (Domeier et al 2003).…”