Line Shooter
WHAT ARE LINE SHOOTERS?
Seabirds are at greatest risk of becoming hooked and drowned when foraging during the short period between when hooks leave the vessel, and when they sink beyond seabirds’ diving ranges. Line shooters are designed to mitigate against seabird bycatch in pelagic longline fisheries, by increasing the sink rate of baited hooks. This hydraulically operated device deploys lines off the back of the boat at a faster speed than that of the boat’s forward motion. The effect of this is that, over time, as the boat travels forwards, a greater length of line is deployed off the back than the distance over which the boat has travelled.
This process removes tension from the line and aims to increase the speed at which the hooks sink, as there are reduced forces keeping the line taught and the baited hooks at the surface. Additionally, due to the increased casting speed of the line, the gear can enter the water directly astern of the vessel, rather than some 30m behind.
CURRENT RESEARCH & USE
Research in an Australian tuna longline fishery reported that use of a line shooter actually decreased the sinking rate of baited hooks, contrary to predictions. Although the experiment did not technically measure the effect on seabird bycatch, this slower sinking rate would mean that seabirds could access baited hooks before they sink underwater, increasing the bycatch risk.
The most likely reason for this delayed sinking was suggested to be propeller turbulence. This churns up the water directly behind the boat, interfering with the longline gear placed here and preventing it from sinking. This evidence stresses that until the line shooters can be adapted and directed to avoid propeller turbulence, they should not be accepted as an effective tool for reducing bycatch. However, if being used to improve the efficiency of fishing operations, it is recommended that line shooters are used in conjunction with bird-scaring lines, weighted lines, and / or night-setting measures, to reduce the chance of seabird bycatch.
This page was last updated on 12.02.21.
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