Collected Evidence: Collected Evidence: Use streamer lines to reduce seabird bycatch on longlines A total of eight studies and two literature reviews from coastal and pelagic fisheries across the world found strong evidence for reduced seabird bycatch on longlines when streamer lines were used. A replicated, controlled trial from the sub-Antarctic Indian Ocean found no reduction in bycatch rates when using streamer lines, whilst five studies were inconclusive, uncontrolled or had weak evidence for reductions. The effect of streamer lines appears to vary between seabird species: northern fulmars Fulmarus glacialis were consistently caught at lower rates when streamers were used but shearwaters Puffinus spp. and white-chinned petrels Procellaria aequinoctialis were caught at similar rates with and without streamers in one study each. The three studies that investigated the use of multiple streamer lines all found that fewer birds were caught when two streamer lines were used, compared to one, with even fewer caught when three were used.  Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F285https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F285Tue, 24 Jul 2012 14:37:19 +0100Collected Evidence: Collected Evidence: Weight baits or lines to reduce longline bycatch of seabirds Three replicated and controlled studies found evidence for reduced bycatch in some species when using weighted lines. One study found low bycatch rates, but was uncontrolled. In Hawaii and New Zealand, rates of bait loss and bycatch of albatrosses Phoebastria spp., white-chinned petrels Procellaria aequinoctialis and sooty shearwaters Puffinus griseus were much lower with weighted baits or integrated weight lines than with control lines. In the North Pacific, two trials found that bycatch rates of some species was reduced when using weights, but that shearwaters Puffinus spp. attacked weighted lines more often. A study off New Zealand found that attaching weights to lines had only localised effects on sink-rate.  Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F296https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F296Tue, 24 Jul 2012 17:07:29 +0100Collected Evidence: Collected Evidence: Use shark liver oil to reduce seabird bycatch Two replicated and controlled trials found reductions in the number of seabirds following boats, or diving for baits, when shark liver oil was dripped behind the boats. Other oils had no effect. A third replicated and controlled trial in found no differences in the number of seabirds following a bait-laying boat with shark liver oil.  Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F297https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F297Tue, 24 Jul 2012 17:16:47 +0100Collected Evidence: Collected Evidence: Use high-visibility mesh on gillnets to reduce seabird bycatch A repeated, randomised and controlled trial in the USA found that having gillnets made partially from high-visibility mesh was effective in reducing seabird bycatch. Having a greater percentage (25% vs. 10%) of the net made from high-visibility mesh was more effective, but also reduced catch of the target species.  Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F303https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F303Tue, 24 Jul 2012 18:10:09 +0100Collected Evidence: Collected Evidence: Use visual and acoustic ‘scarers’ to deter birds from landing on pools polluted by mining or sewage Two studies found lower bird mortality or fewer birds rescued from toxic ponds when deterrent systems were used. Four of five studies found that fewer birds landed on pools with deterrents than controls, although one of these found that the effect was weaker for grebes compared to wildfowl and absent for waders. One study that used regular broadcasts of different sounds found that it had no impact on bird behaviour. Two studies investigated different systems and found that radar-operated systems were more effective than systems that worked at random intervals. One of these studies also found that loud noises were more effective than moving peregrine falcons Falco peregrinus models.  Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F452https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F452Wed, 29 Aug 2012 13:32:11 +0100Collected Evidence: Collected Evidence: Use lights low in spectral red to reduce mortality from artificial lightsTwo studies from the North Sea and the Netherlands found that fewer birds were attracted to low-red lights (including green and blue lights), compared with the number expected, or the number attracted to white or red lights.  Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F471https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F471Wed, 29 Aug 2012 16:40:31 +0100Collected Evidence: Collected Evidence: Use of probiotics and immunostimulants One replicated study in Scotland found increased survival in salmon fed a probiotic before exposure to four different disease-causing bacteria over a 28 day period compared with controls. A replicated, controlled study in Norway found the number of salmon infected with lice was reduced by 28% when fed a diet composed of fish meal and 28% plant-based protein. Adding beta-glucans to the diet decreased lice infection levels by a further 28% compared with controls. The same study found the addition of mannan oligosaccharides improved gut function by preventing the development of soybean-induced enteritis compared with controls. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F732https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F732Mon, 03 Jun 2013 11:14:24 +0100Collected Evidence: Collected Evidence: Use vaccinations Two controlled studies from Iceland and Norway found higher survival rates in vaccinated salmon compared to unvaccinated control groups. This was post exposure to the disease-causing bacteria, Aeromonas salmonicida spp.achromogenes and Yersinia ruckeri, respectively. Two controlled studies in Australia and Canadia reported higher survival in salmon infected with marine flexibacteriosis and bacterial kidney disease, post vaccination. Two controlled studies in Norway reported similar results for salmon vaccinated against infectious salmon anaemia. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F733https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F733Mon, 03 Jun 2013 14:33:01 +0100Collected Evidence: Collected Evidence: Use natural control agents: cleaner wrasse Two studies in Ireland found mixed effects of cleaner wrasse on sea lice numbers infesting salmon. One controlled study found corkwing and goldskinny cleaner wrasse were as effective at controlling lice infestation as chemical treatments. One replicated, controlled study found rockcook cleaner wrasse were ineffective at preventing lice outbreaks. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F738https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F738Mon, 03 Jun 2013 15:28:00 +0100Collected Evidence: Collected Evidence: Use genetically modified alternatives Three controlled, replicated (two randomised) studies in Norway found no difference in growth rate of Atlantic salmon that were fed diets containing either GM or non-GM soybeans. One randomised, replicated, controlled study in Norway found no differences in fish fed diets containing either GM or non- GM soybeans on the histology of the fish.  Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F928https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F928Fri, 25 Oct 2013 13:50:59 +0100Collected Evidence: Collected Evidence: Use supplements A controlled, replicated study in Australia found no difference in weight gain of Atlantic salmon with and without dietary supplementation of phytase and phosphate. One controlled, replicated study in Australia fish fed diets supplemented with phytase had greater final weights than those given no supplement. A controlled, replicated study in Norway found no difference in weight gain of salmon that were fed diets with or without taurine supplementation.  Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F930https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F930Fri, 25 Oct 2013 13:54:06 +0100Collected Evidence: Collected Evidence: Use traps instead of fishing nets One study examined the effects of using traps instead of fishing nets on subtidal benthic invertebrates. The study took place in the Mediterranean Sea (Spain).   COMMUNITY RESPONSE (0 STUDIES) POPULATION RESPONSE (1 STUDY) Unwanted catch abundance (1 study): One replicated, controlled study in the Mediterranean Sea found that the combined amount of unwanted catch of invertebrates and fish appeared lower using plastic traps than trammel nets, but higher using collapsible traps. OTHER (1 STUDY) Commercial catch abundance (1 study): One replicated, controlled study in the Mediterranean Sea found that the catch of commercially targeted lobsters was lower using traps than in trammel nets. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2142https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2142Tue, 22 Oct 2019 11:08:46 +0100Collected Evidence: Collected Evidence: Use holding pens at release site prior to release of translocated mammals Thirty-five studies evaluated the effects of using holding pens at the release site prior to release of translocated mammals. Ten studies were in the USA, seven were in South Africa, four were in the UK, three studies were in France, two studies were in each of Canada, Australia and Spain and one was in each of Kenya, Zimbabwe, Italy, Ireland and India. COMMUNITY RESPONSE (0 STUDIES) POPULATION RESPONSE (31 STUDIES) Abundance (4 studies): Three of four studies (two replicated, one before-and-after study) in South Africa, Canada, France and Spain found that following release from holding pens at release sites (in some cases with other associated actions), populations of roe deer, European rabbits and lions increased in size. The other study found that elk numbers increased at two of four sites. Reproductive success (10 studies): A replicated study in the USA found that translocated gray wolves had similar breeding success in the first two years after release when adult family groups were released together from holding pens or when young adults were released directly into the wild. Seven of nine studies (including two replicated and one controlled study) in Kenya, South Africa, the USA, Italy, Ireland, Australia and the UK found that following release from holding pens at release sites (in some cases with other associated actions), translocated populations of roan, California ground squirrels, black-tailed prairie dogs, lions, four of four mammal populations, most female red squirrels and some pine martens reproduced successfully. Two studies found that one of two groups of Cape buffalo and one pair out of 18 Eurasian badgers reproduced. Survival (26 studies): Two of seven studies (five controlled, three replicated studies) in Canada, the USA, France, the UK found that releasing animals from holding pens at release sites (in some cases with associated actions) resulted in higher survival for water voles and female European rabbits compared to those released directly into the wild. Four studies found that translocated swift foxes, gray wolves, Eurasian lynx and Gunnison's prairie dogs released from holding pens had similar survival rates to those released directly into the wild. One study found that translocated American martens released from holding pens had lower survival than those released directly into the wild. Two of four studies (three controlled) in South Africa, Spain, and the USA found that translocated African wild dogs and European rabbits that spent longer in holding pens at release sites had a higher survival rate after release. One study found mixed effects for swift foxes and one found no effect of time in holding pens for San Joaquin kit foxes. Eleven studies (one replicated) in Kenya, South Africa, the USA, France, Italy, Ireland, India, Australia and the UK found that after release from holding pens at release sites (in some cases with other associated actions), translocated populations or individuals survived between one month and six years, and four of four mammal populations survived. Two studies in the UK and South Africa found that no released red squirrels or rock hyraxes survived over five months or 18 days respectively. One of two controlled studies (one replicated, one before-and-after) in South Africa and the USA found that following release from holding pens, survival of translocated lions was higher than that of resident animals, whilst that of translocated San Joaquin kit foxes was lower than that of resident animals. A study in Australia found that translocated bridled nailtail wallabies kept in holding pens prior to release into areas where predators had been controlled had similar annual survival to that of captive-bred animals. Condition (1 study): A controlled study in the UK found that translocated common dormice held in pens before release gained weight after release whereas those released directly lost weight. BEHAVIOUR (5 STUDIES) Behaviour change (5 studies): Three studies (one replicated) in the USA and Canada found that following release from holding pens, fewer translocated sea otters and gray wolves returned to the capture site compared to those released immediately after translocation, and elk remained at all release sites. Two studies in Zimbabwe and South Africa found that following release from holding pens, translocated lions formed new prides. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2434https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2434Tue, 02 Jun 2020 08:44:51 +0100Collected Evidence: Collected Evidence: Use netting of contrasting colour in a trawl net One study examined the effect of using netting of contrasting colour in a trawl net on marine fish populations. The study was in the Baltic Sea (Denmark).  COMMUNITY RESPONSE (0 STUDIES) POPULATION RESPONSE (0 STUDIES) BEHAVIOUR (0 STUDIES) OTHER (1 STUDY) Reduction of unwanted catch (1 study): One replicated, paired, controlled study in the Baltic Sea found that a trawl codend with contrasting black netting used in conjunction with a square mesh escape panel caught a similar amount of undersized cod as a conventional codend. Improved size-selectivity of fishing gear (1 study): One replicated, paired, controlled study in the Baltic Sea found that two designs of contrasting netting colour in trawl codends with square mesh escape windows did not improve the size-selectivity of cod compared to conventional codend netting colour. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2718https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2718Tue, 05 Jan 2021 15:46:48 +0000Collected Evidence: Collected Evidence: Use hook and line fishing instead of other commercial fishing methods Three studies examined the effects of using hook and line fishing instead of other commercial fishing methods on marine fish populations. One study was in each of the Tasman Sea (Australia), the Atlantic Ocean (Canada) and the Gulf of St. Lawrence (Canada).  COMMUNITY RESPONSE (0 STUDIES) POPULATION RESPONSE (1 STUDY) Survival (1 study): One replicated, controlled study in the Gulf of St. Lawrence found that fish caught by hook and line methods had greater vitality (an indicator of post-release survival) than fish caught by other gear types. BEHAVIOUR (0 STUDIES) OTHER (2 STUDIES) Reduction of unwanted catch (1 study): One replicated, controlled study in the Tasman Sea found that using longlines reduced the capture of unwanted small snapper, compared to trawling. Improved size-selectivity of fishing gear (1 study): One replicated, paired, controlled study in the Atlantic Ocean found that longlining compared to trawling, increased the size selectivity of cod and haddock at larger hook sizes only. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2732https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2732Thu, 28 Jan 2021 11:49:50 +0000Collected Evidence: Collected Evidence: Use stiffened materials or increase tension of fishing gear One study evaluated the effects on marine mammals of using stiffened materials in fishing nets. The study was in the South Atlantic Ocean (Argentina). COMMUNITY RESPONSE (0 STUDIES) POPULATION RESPONSE (0 STUDIES) BEHAVIOUR (0 STUDIES) OTHER (1 STUDY) Reduction in entanglements/unwanted catch (1 study): One controlled study in the South Atlantic Ocean found that using stiffened fishing nets did not reduce the number of Franciscana dolphin entanglements. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2801https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2801Thu, 04 Feb 2021 17:10:46 +0000Collected Evidence: Collected Evidence: Use noise aversive conditioning to deter mammals from fishing gear One study evaluated the effects on marine mammals of using noise aversive conditioning to deter mammals from fishing gear. The study was in the North Pacific Ocean (USA). COMMUNITY RESPONSE (0 STUDIES) POPULATION RESPONSE (0 STUDIES) BEHAVIOUR (0 STUDIES) OTHER (1 STUDY) Human-wildlife conflict (1 study): One study in the North Pacific Ocean found that noise aversive conditioning did not reduce bait foraging behaviour by California sea lions. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2819https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2819Fri, 05 Feb 2021 15:12:55 +0000Collected Evidence: Collected Evidence: Use visual deterrents on fishing gear Two studies evaluated the effects of using visual deterrents on fishing gear on reptile populations. One study was off the coast of Mexico and one was in the USA. COMMUNITY RESPONSE (0 STUDIES) POPULATION RESPONSE (0 STUDIES) BEHAVIOUR (1 STUDY) Behaviour change (1 study): One replicated, controlled study in the USA found that shark-shaped and spherical deterrents had mixed effects on a range of captive loggerhead turtle behaviours. OTHER (1 STUDY) Unwanted catch: (1 study): One replicated, controlled study off the coast of Mexico found that gillnets with floating shark shapes attached to them caught fewer green turtles than unmodified nets. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3553https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3553Wed, 08 Dec 2021 12:30:30 +0000Collected Evidence: Collected Evidence: Use non-offset hooks Two studies evaluated the effects of using non-offset hooks on reptile populations. One study was off the Pacific coast of Costa Rica and one was in the north-east Atlantic. COMMUNITY RESPONSE (0 STUDIES) POPULATION RESPONSE (1 STUDY) Survival (1 study): One replicated, controlled, paired study in the north-east Atlantic Ocean found that mortality of leatherback turtles was similar when caught with non-offset hooks or offset hooks. BEHAVIOUR (0 STUDIES) OTHER (2 STUDIES) Unwanted catch (2 studies): One of two replicated, paired studies (including one controlled study) off the Pacific coast of Costa Rica and in the north-east Atlantic found that non-offset circle hooks caught a similar number of olive ridley and green turtles compared to offset circle hooks in a shallow-set longline fishery. The other study found that non-offset G-style circle hooks caught fewer leatherback and hard-shell turtles compared to offset Gt-style circle hooks or offset J-hooks in a longline swordfish fishery. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3571https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3571Wed, 08 Dec 2021 15:13:12 +0000Collected Evidence: Collected Evidence: Use non-ringed hooks One study evaluated the effects of using non-ringed hooks on reptile populations. This study was in the Mediterranean. COMMUNITY RESPONSE (0 STUDIES) POPULATION RESPONSE (0 STUDIES) BEHAVIOUR (0 STUDIES) OTHER (1 STUDY) Unwanted catch (1 study): One replicated, paired study in the Mediterranean found that when non-ringed circle hooks were used in a swordfish longline fishery fewer loggerhead turtles were caught compared to when ringed hooks were used. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3576https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3576Wed, 08 Dec 2021 15:18:56 +0000Collected Evidence: Collected Evidence: Use larger hooks Two studies evaluated the effects of using larger hooks on reptile populations. One study was in the USA and one was in the Eastern Pacific Ocean. COMMUNITY RESPONSE (0 STUDIES) POPULATION RESPONSE (0 STUDIES) BEHAVIOUR (1 STUDY) Use (1 study): One study in the USA of captive loggerhead turtles found that turtles were less likely to attempt to swallow larger circle hooks than smaller ones. OTHER (1 STUDY) Unwanted catch (1 study): One replicated study in the Eastern Pacific Ocean found that olive ridley turtles were less likely to be caught by swallowing larger hooks than smaller ones. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3578https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3578Wed, 08 Dec 2021 15:21:29 +0000Collected Evidence: Collected Evidence: Use technology to communicate near real-time catch information to fishers to enable avoidance of unwanted catchicate near real-time catch information to fishers to enable avoidance of unwanted catch One study examined the effects of using technology to communicate near real-time catch information to fishers to enable avoidance of unwanted catch on marine fish populations. The study was in the North Pacific and North Atlantic Oceans.   COMMUNITY RESPONSE (0 STUDIES) POPULATION RESPONSE (0 STUDIES) BEHAVIOUR (0 STUDIES) OTHER (1 STUDY) Reduction of unwanted catch (1 study): A review in the North Pacific and North Atlantic Oceans reported that where technology was used to provide near real-time catch information to fishers there were reductions of unwanted catch or discards in two of three cases. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3826https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F3826Fri, 27 May 2022 09:38:00 +0100
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What Works in Conservation

What Works in Conservation provides expert assessments of the effectiveness of actions, based on summarised evidence, in synopses. Subjects covered so far include amphibians, birds, mammals, forests, peatland and control of freshwater invasive species. More are in progress.

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