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Two devices were designed to prevent odontocetes from depredating caught fish and putting themselves at-risk of becoming bycatch. One device used physical deterrence by shrouding the fish with a barrier and the other used psychological deterrence by utilizing prior negative experiences of temporary entanglement in fishing gear. Both devices fit on a branchline at a distance from the hook and descend towards a caught fish using a line tension trigger mechanism. All interactions occurred on control branchlines that were not fitted with a deterrent device, suggesting the potential of this technology to deter depredating odontocetes. The impact on fish catch rates, size, and survival was negligible. 

Odontocete (i.e. toothed whale) interaction with longline fisheries is a global phenomenon that threatens the status of some populations and the economic viability of longline fisheries. This review paper summarizes the trend and geographical extent of interactions, the potential impact on odontocetes and fisheries, and describes potential acoustic and physical mitigation solutions. 

Artificial lights were attached to each the rigid-grate BRD and fishing lines in trawls for ocean shrimp (Pandalus jordani) off Oregon, United States. Bycatch of eulachon (Thaleichthys pacificus), a threatened anadromous smelt species, was reduced on trawls with lights on the fishing lines as it was for slender sole (Lyopsetta exilis) and darkblotched rockfish (Sebastes crameri), without affecting target catch.

This study aimed to quantify the risks to Australian sea lion (Neophoca cinerea) and New Zealand fur seal (Arctocephalus forsteri) populations from bycatch in a trap (rock lobster, Panulirus cygnus) and demersal gillnet fishery off South Australia. The approach was to: (1) estimate the spatial distribution of foraging effort for different sex and age classes within each species; (2) compare these with the spatial distribution of fishing effort in order to develop spatial estimates of seal-fishery interaction probabilities; (3) undertake population viability analyses to identify the levels of bycatch that would place subpopulations of each species into different risk categories; and (4) examine different bycatch scenarios and identify subpopulations, regions and marine fishing areas with the greatest bycatch risk. Results suggest that the risk of subpopulation extinction, even from low levels of bycatch, was high for sea lions, but very low for fur seals and that the two fisheries lend themselves to different mitigation approaches: gear modification in the lobster fishery, and spatial management of fishing effort in the demersal gillnet fishery.

This study aimed to quantify the risks to Australian sea lion (Neophoca cinerea) and New Zealand fur seal (Arctocephalus forsteri) populations from bycatch in a trap (rock lobster, Panulirus cygnus) and demersal gillnet fishery off South Australia. The approach was to: (1) estimate the spatial distribution of foraging effort for different sex and age classes within each species; (2) compare these with the spatial distribution of fishing effort in order to develop spatial estimates of seal-fishery interaction probabilities; (3) undertake population viability analyses to identify the levels of bycatch that would place subpopulations of each species into different risk categories; and (4) examine different bycatch scenarios and identify subpopulations, regions and marine fishing areas with the greatest bycatch risk. Results suggest that the risk of subpopulation extinction, even from low levels of bycatch, was high for sea lions, but very low for fur seals and that the two fisheries lend themselves to different mitigation approaches: gear modification in the lobster fishery, and spatial management of fishing effort in the demersal gillnet fishery.

Bycatch of Australian sea lions (Neophoca cinerea) in rock lobster (Jasus edwardsii) 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. 

Bycatch of Australian sea lions (Neophoca cinerea) in rock lobster (Jasus edwardsii) 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. 

Crab traps were fitted with a turtle excluder device to reduce the incidental capture of diamondback terrapins (Malaclemys terrapin). No diamondback terrapins were caught during this study but the total catch rate of targeted blue crabs (Callinectes sapidus), compared to the standard traps, increased by 25.7% (14.5% sublegal size, 32.9% legal size). The difference in total catch rates and catch rates of legal sized blue crabs between the two traps were significantly different.

Blue sharks (Prionace glauca) account for most of the bycatch in the Canadian pelagic longline swordfish (Xiphias gladius) fishery. Electropositive metals (e.g. lanthanide) oxidize in seawater and create electric fields, which can alter the behaviors of several species of sharks. Researchers deployed seven sets (6300 hooks) with three hook treatments (standard hooks, hooks with electropositive metals - neodymium/praseodymium - and hooks with lead weights) on the Scotian Shelf in the Northwest Atlantic. Electropositive metals did not reduce the catch of blue sharks or other common shark bycatch species.  

Analyses of the Hawaiian (U.S.) pelagic longline fishery were conducted to determine what factors, including hook type (J or circle) and location (sea mount v open ocean), have impacted the catch of both target and bycatch species. Standardized catch rates for all tuna species as well as for blue (Prionace glauca) and oceanic whitetip sharks (Carcharhinus longimanus) were significantly higher when the wider circle hooks were used. However, shortbill spearfish (Tetrapturus angustirostris) and striped marlin (Kajikia audax) catch were significantly lower when circle hooks were used.  No differences in catch rates between the two hook types were seen for bigeye thresher sharks (Alopias superciliosus) or swordfish (Xiphias gladius).  The average swordfish lengths were significantly larger when circle hooks were used, while average lengths for bigeye (Thunnus obesus) and skipjack tunas (Katsuwonus pelamis) were significantly smaller.  There was no difference in the average length between the two hooks types for yellowfin (Thunnus albacares) or albacore tunas (Thunnus alalunga), spearfish or marlins. In addition, the change from J hooks to circle was likely a factor in declining sea turtle bycatch rates.