Unanswered Forum Topics

Fishery observer data from Japanese longline vessels targeting southern bluefin tuna, was used to determine if there were differences in seabird avoidance between two types ("WCPFC type" and "Light type") of tori-lines.  There was no signficant difference between the two tori-lines for either the nominal catch rates of albatross or the per-capita catch rates.  Therefore both types of tori-line have similar seabird avoidance effects and the "Light type" may be more practical in areas with difficult weather and oceanic conditions.

Four parts of the tori-pole were tested for their effectiveness in reducing the incidental catch of albatross in the Japanese southern bluefin tuna longline fishery.  Observer data were used to test 1. bird line material, 2. streamer material, 3. bird line length and 4. pole height above sea surface.  The effectiveness of tori-poles in reducing albatross interactions increased with a longer bird line, but there was no difference in the effectiveness between the different bird line materials, type of streamer material or pole height above the sea surface.  

The use of blue-dyed bait (both squid and fish) as a means to reduce seabird interactions with pelagic longline fishing gear was tested during Japanese longline fishery survey cruises off South Africa in the Southern Ocean.  The incidental catch of seabirds was lower for both blue-dyed squid and fish baits compared to non-dyed baits. The catch per unit effort (CPUE) of albatrosses decreased when blue-dyed squid and fish baits were used during all years of the study.  The CPUE of petrels was lower during two years when blue-dyed bait was used.

Hybrid streamer lines with weighted and unweighted branch lines were tested for their effectiveness in reducing seabird interactions with longline gear during the 2010 tuna joint venture fishery in the South African EEZ.  Weighted branch lines with hybrid streamer lines dramatically reduced seabird attacks, secondary attacks and mortalities and had a minimal effect on fish catch.  Bird mortalities on weighted branch lines were reduced by 86% compared to unweighted branch lines.  Primary attack rates were four times lower on weighted branch lines.