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The effect of two hook types (J-style and circle) and two bait types (jumbo squid and juvenile striped mullet) were tested on pelagic longlines in the northwest Pacific Ocean to determine their effect on catch rates of pelagic species.  There were no significant differences in catch rates between hook types but squid bait caught significantly more blue and silky sharks and dolphinfish.

Acoustic harassment devices (AHDs) were tested in association with a marine fin-fish farm off the north-eastern coast of Sardinia, to determine their effectiveness on common bottlenose dolphins.  This was a controlled exposure experiment.  No significant or immediate effects on bottlenose dolphin presence, distance from AHD, group size or time spent in the fish farm area were caused by activation of the AHD. Thus, additional research is needed on their effectiveness in the marine environment before further deployment.

Bycatch of Australian sea lions in rock lobster and shark gillnet fisheries is a key threat to the species. This report outlines and assesses methods for mitigating bycatch in these fisheries in South Australia. Gear modification was considered in the rock lobster fishery and spatial closures in the shark gillnet fishery. Spikes of different heights were tested to deter sea lions from entering rock lobster pots. Entry success significantly decreased with spikes extending high up into the collar (70 mm + from base) compared to other treatment and control pots. 

A parallel haul method was used to determine the effectiveness of a square-mesh escape panel, installed in a bottom trawl, in reducing the bycatch of scup and other finfish bycatch species during the winter.  The square-mesh escape panel reduced the average catches of scup by 78% and 79% and catches of black sea bass by 69% and 75% in weight and numbers respectively.  The square-mesh escape panel was also effective in reducing catches of sublegal-size scup and black sea bass by 17% and 20% in weight and numbers respectively.  However, catches of the target species, longfin squid, were also reduced by 84% and 88% in weight and numbers respectively.  Therefore the square-mesh escape panel is not a reasonable solution for bycatch reduction in this fishery during winter months.

Tests with captive, as well as wild, juvenile sandbar sharks were undertaken to determine the effectiveness of electropositive metals in reducing the interactions with longline gear.  Electropositive metals deterred feeding in groups of captive juvenile sharks, for a short period of time, and altered the swimming patterns of individuals when food motivation was not present.  In the field, electropositive metals placed within 10 cm of the bottom longline hooks reduced the catch of sandbar sharks by around two thirds, compared to the catch on hooks with a placebo.

Tests were conducted on tuna longline fishing vessels in the eastern Pacific Ocean to determine if the use of J (size 4.0 traditional) or circle hooks (sizes 15, 16 and 18) and different bait resulted in differences in the catch rates of target and bycatch species. No significant differences in catch rates of the target species were found between hook types. Significant differences between J and circle hook size 15 and between J and circle hook size 16 were found in the bycatch species group (all species grouped together). The highest catch rates for tunas were found on circle hooks size 15 and for billfishes on J hooks. The largest circle hook (18) had the lowest catch rates. Squid and jack mackerel bait had the highest catch rates for tunas and other fishes, while chub mackerel bait caught the most billfish and sharks.

Bycatch reduction device prototypes ("RS_INP") (industrial and artisanal versions) were tested on vessels targeting shrimp in the Gulf of California to compare bycatch-to-shrimp ratios, catch efficiency, drag resistence indicators, fuel consumption rate and selectivity with traditional versions.  The industrial version of the prototype reduced bycatch-to-shrimp ratios from 20-50% and shrimp production was not reduced.  The artisanal prototype also reduced bycatch-to-shrimp ratios in trawl fishing gear but comparisons were difficult to make between drift gillnets.  Catch efficiency was higher with the prototype (3.6 shrimp kg/hr) compared to the traditional gear (0.9 shrimp kg/hr) and the prototype offered less resistance to drag (871-730 drag force) compared to the traditional gear (1150-1194 drag force).  Fuel consumption was also less with the prototype than with traditional gear.  The taxonomic composition of the catch was very similar for the prototype and traditional fishing gear.

Differences in sink rates of baited hooks attached to mainelines and set under varying degrees of tension, were tested aboard pelagic longlines off eastern Australia.  Three mainline configurations were tested 1. surface set tight with no slackness astern, 2. surface set loose with two seconds of slack astern and 3. deep set loose with seven seconds of slack astern.  Baited hooks on tight mainlines reached depth almost twice as quickly (5.8 s) compared to those on the two loose mainline configurations (9.9 s and 11 s).  The loose configurations therefore allows increased availability of baited hooks to seabirds.  It was hypothesized that the propeller turbulance slowed the sink rates. The authors suggest that unless the mainline can be set to avoid propeller turbulence, mainline deployed with a line shooter (to reduce sea bird interactions) for deep setting should not be accepted as an effective detterent to seabirds.

Experiments were conducted aboard pelagic longline vessels off the east coast of Australia to determine the effects of different bait species (blue mackerel, yellow tail mackerel and squid), live and dead bait, weight of leaded swivels (60 g, 100 g and 160 g) and leader length (2 m, 3 m and 4 m distances between leaded swivel and hook) on the sink rates of hooks.  Live bait sank more slowly than dead bait, increasing the exposure of hooks to seabirds but the sink rates of individual live bait species were very variable.  With respect to dead bait, those on the 160 g leaded swivel with a distance of 2 m leader length had the fastest sink rate, while the 60 g swivel on the 4 m leader length had the slowest.  Overall, small changes to the weight of leaded swivels and the length of the leader are not likely to subtantial reductions in seabird mortality.

Three codends 1. a control, 2. a simplified Nordmore-grid and 3. one with a radial escape section were tested aboard trawl vessels off New South Wales Australia, to determine the effects on the catch of bycatch and target species.  The codend with a radial escape section and the simplified Nordmore-grid retained fewer school prawns by weight 11.5% and 4.6% resepectively, compared to the control net.   The Nordmore-grid codend caught 50% fewer yellowfin bream than the radial escape section net and 55% fewer than the control net.  Both trial codends significantly reduced the predicted mean weight (36% Nordmore-grid and 74.3% radial escape section) and number (17.3% and 49.3%) of bycatch.  The Nordmore-grid codend retained significantly fewer bycatch by weight (59.8%) and number 38.7%) than the radial escape section codend.  In addition, the Nordmore-grid codend retained significantly fewer Ramsey's perchlet than the control (48.3%) and radial escape section (50.7%) and fewer southern herring (69.4% and 57.6% respectively).  Significantly more silver biddy sized 9.5 to 10.5 cm total length were retained inthe control codend compared to the Nordmore-grid and radial escape section codends.