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Summary:

Pelagic longlines were weighted with lead weights, enabling them to fish deeper in the water column than traditional pelagic longlines.  Weighted longlines caught 31 target species with a slightly higher catch per unit effort (CPUE) of 1.3 fish/100 hooks (49 kg/100 hooks) compared to traditional gear (38 target species and a CPUE of 1.08 fish/100 hooks or 41 kg/100 hooks).  Bigeye tuna CPUE for the weighted gear was higher, 0.95 fish/100 hooks (36 kg/100 hooks), than for traditional gear, 0.56/100 hooks (21 kg/100 hooks).  Swordfish CPUE was very similar for weighted (0.3 fish/100 hooks or 17 kg/100 hooks) and traditional (0.25 fish/100 hooks or 14 kg/100 hooks) gear.  This technique could be used to reduce sea turtle and other bycatch species interactions, however this was not tested during this initial trial study.

Summary:

The number of floats and hanging ratio of trammel nets were altered in two experimental nets and compared to a standard trammel net to determine the impact on reducing the bycatch of purple dye murex, mantis shrimp and crabs.  The first experimental net had more floats than the control net in addition to a guarding net and the second experimental net had the same number of floats as the control net, with the addition of a guarding net.  During the first trial only experimental net 1 and the control net were compared and in the second trial all three nets were compared.  During the first trial, the experimental net caught 17% fewer prawns, the target species, 44% fewer crabs and mantis shrimp and 49% fewer murex than the control net.  During the second trial, experimental net 1 caught 66% fewer crabs, 27% fewer mantis shrimp and 32% fewer murex than the control net.  Experimental net 2 caught slightly fewer prawns (2%), 51% fewer crabs, 17% fewer mantis shrimp and 26% fewer murex than the control net. 

Summary:

Sea otters are caught and drowned in fishing pots and traps.  Live California sea otters were exposed to finfish traps, lobster traps, and mock Dungeness crab traps in captive trials.  Researchers found that the otters attempted to enter the circular and rectangular fyke openings and some became entrapped.  They determined that a 3x9 inch opening, rather than the standard 4x9 inch, would prevent bycatch of free-living otters, while retaining crab catch.  

Summary:

The type (circle 18/0 0 degree offset and J-style 9/0 10 degree offset) and position of hooks in the water column were tested to determine the effects on catch rates and mortality of elasmobranchs.  Tests were conducted aboard pelagic and bottom longline vessels. CPUEs for blue, silky and oceanic whitetip sharks were significantly higher with circle hooks than with J-style hooks. Silky, blue and oceanic whitetip sharks had a significantly higher mortality at haulback with J-style hooks.  Significant differences in hooking location between the two hook types was found for night, blue, silky and oceanic whitetip sharks. These sharks were more commonly hooked externally vs internally.  No significant differences between hook types was found for the CPUE's on bottom longlines.  Significantly more blacknose were alive at haulback when circle hooks were used on bottom longlines. Bottom longlines were also used to test for differences in CPUE by fishing depth.  Demersal hooks had significantly higher CPUE's than those suspended in the water column for blacknose and nurse sharks and southern stingrays.

Summary:

Small cetaceans are by-caught in salmon gillnet fisheries in British Columbia (BC) waters. In Canada, there is currently no generic calculation to identify when management action is necessary to reduce cetacean bycatch below sustainable limits. We estimated potential anthropogenic mortality limits for harbour (Phocoena phocoena) and Dall’s (Phocoenoides dalli) porpoises and Pacific white-sided dolphins (Lagenorhynchus obliquidens) using quantitative objectives from two well-established frameworks for conservation and management (the United States’ Marine Mammal Protection Act and the Agreement on the Conservation of Small Cetaceans of the Baltic and North Seas), which are similar to some management objectives developed for marine mammal stocks elsewhere in Canada. Limits were calculated as functions of (i) a minimum abundance estimate (2004–2005); (ii) maximum rate of population increase; and (iii) uncertainty factors to account for bias in abundance estimates and uncertainty in mortality estimates. Best estimates of bycatch mortality in 2004 and 2005 exceeded only the most precautionary limits and only for porpoise species. Future research priority should be given to determining small cetacean stock structure in BC and refining species-specific entanglement rates in these and other fisheries. The approach offers a quantitative framework for Canada to meet its stated objectives to maintain favourable conservation status of cetacean populations.

Summary:

Tests were conducted aboard deep-set Hawaii tuna longline vessels to determine differences in catches, fish size selectivity and survival on 18/0 circle hooks vs. Japanese style tuna hooks size 3.6 sun and vs. 9/0 "J" hooks.  There were no significant differences in catch, catch rate or mean length between hook types for bigeye tuna (the primary target) but catch rates on circle hooks were lower for 16 other species than on the Japanese style tuna hook and for 8 species on the "J" hook.  Fish length was significantly shorter on Japanese style tuna hooks for four species compared to circle hooks and four 3 species on "J" hooks.  Survival was significantly higher for 6 species, including bigeye tuna, on circle hooks compared to Japanese style hooks and for five species on "J" hooks.

Summary:

Two bycatch reduction devices (BRD), the Florida fisheye (FFE) and large-mesh extended-mesh funnel (EMF) were tested in roller-frame trawls to determine their effectiveness in reducing bycatch.  Tests were conducted at two locations (Tarpon Springs and Biscayne Bay, FL) using a paired trawl design with the BRD equipped net deployed off one side and the control net off the other side.  The FFE did not significantly reduce overall finfish bycatch but did retain shrimp at both locations.  At Tarpon Springs, the EMF reduced bycatch significantly and shrimp loss was low, while at Biscayne Bay, bycatch and shrimp loss were both significantly reduced. A simulator cone was also tested with both BRD's at Tarpon Springs and resulted in significant bycatch reduction but also significant shirmp loss.

Summary:

Tests were conducted in the Hawaii-based tuna longline fishery to determine if removing the shallowest hooks from pelagic longline sets would maximize the catches of target species while minimizing the incidental catch of non-target species.  Catch rates of bigeye tuna were not significantly different between the two set types but catch rates of sickle pomfret were significantly higher in experimental compared to control sets.  Statistically fewer wahoo, dolphinfish, blue marlin, striped marlin and shortbill spearfish were caught on the experimental sets. 

Summary: A semi-flexible exclusion grid with a bar spacing of 15.5 cm reduced dolphin bycatch in the Pilbara trawl fishery by close to 50% and reduced the bycatch of sea turtles, large sharks and rays. However, the fate of the dolphins that encountered the grid and escaped is unknown.

Summary:

Tests were conducted to determine if twin trawl nets containing a Turtle Excluder Device (TED) and a Popeye Fishbox caught less bycatch then nets fitted only with a TED. Nets that had the Popeye Fishbox located 70 meshes from the codend draw strings had a 48% reduction in the weight of small bycatch, an 87% reduction in number of sea snakes and a 35% reduction in the number of sharks and rays caught. When the Popeye Fishbox was placed 100 meshes from the codend draw strings, the weight of small bycatch was reduced by 28% and the number of sharks and rays was reduced by 27%. No analysis of sea snake bycatch at this distance was carried out. There was no significant difference in the catch of targeted prawns between nets with and without the Popeye Fishbox.