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

Michael L Domeier,Peter Speare,Howard Browman

doi:10.1371/journal.pone.0031629

Michael L Domeier, Peter Speare + Show 1 more

Open Access

https://doi.org/10.1371/journal.pone.0031629

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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.

Highlights

Identifying spawning regions is an important step in defining the spatial distribution of separate stocks of the same fish species
Evidence of Spawning Our findings, which include the presence of hydrated eggs, postovulatory follicles and black marlin larvae, offer the first validation of a black marlin spawning aggregation
Recreational fishing catch rates for black marlin are highest from Cairns north to the Ribbon Reefs, suggesting that this is the focus of spawning activity

Summary

Introduction

Identifying spawning regions is an important step in defining the spatial distribution of separate stocks of the same fish species. Some fish species gather in unusual densities at very specific sites and seasons to spawn. This phenomenon, termed a spawning aggregation [3], is commonly exhibited in certain families of coral reef fish but is far less frequently identified in pelagic species. The fact that spawning aggregations are very predictable in time and space creates a situation where directed fisheries can rapidly deplete a stock to the point of extirpation [4]. Spawning aggregations create a valuable research opportunity since a large sample can be efficiently and economically tagged to study the geographic extent of the spawning stock. Three methods have been proposed to confirm a spawning aggregation: 1) observation of spawning, 2) observation of hydrated eggs and 3) observation of post-ovulatory follicles [5]

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