Composition of Floating Derelict Fishing Gear in the Central Subtropical North Pacific Ocean
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Authors
McWhirter, Andrew Charles
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Marine Science
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Abstract
Floating derelict fishing gear (DFG) has been polluting the marine environment for decades. The Hawaiian archipelago, in the center of the North Pacific Subtropical Gyre, is exposed to high levels of DFG accumulation and the associated environmental damage. The goals of this project were to develop the most effective methods for sampling and analyzing DFG composition, assess DFG composition in the subtropical North Pacific, and build evidence for sourcing DFG back to specific fisheries and manufacturers. Five methods were developed to sample and analyze DFG events with varying levels of resource requirements and data resolution. Three methods used to assess composition of DFG conglomerates were compared, named the Four Corners method, Disentanglement method, and the Hybrid method. The Hybrid method proved to be the most effective sampling option considering time, resources, and data resolution. However, the Hybrid and Disentanglement methods biased event composition, when compared to the more accurate assessment of composition by mass and count of the disentangled and sorted gear piles. The Hybrid method was used to assess DFG conglomerate composition from three central North Pacific regions, Midway (MID), O?ahu (OAH), and the pelagic North Pacific Gyre (NPG). Composition was investigated at the DFG event level, by proportion of gear categories that make up the event, and within the nets and lines categories, by proportion of count and mass. Composition at the event level revealed that conglomerates are primarily composed of nets and lines by count and mass, with no significant variation among regions. The two dominant gear types were then compared where line composition did not show any significant difference among the regions. Net composition was significantly different among regions, and the majority of this variation was explained by Midway having more monofilament gillnets. This study produced the most detailed database on floating DFG in the subtropical North Pacific and has archived information necessary to trace DFG found in Hawaii back to the source fisheries and manufacturers.
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Hawaii Pacific University