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What Works in Conservation 2021

 | 
William Junior Sutherland
, 
Lynn V. Dicks
, 
Silviu O. Petrovan
, 
et al.

14. Marine and freshwater mammal conservation

14.4 Threat: Biological resource use

Texte intégral

14.4.1 Reduce hunting and persecution

Beneficial

●Prohibit or restrict hunting of marine and freshwater mammal species

1Five studies evaluated the effects of prohibiting hunting of marine mammal species. One study was in each of the Kattegat and Skagerrak seas (Denmark and Sweden), the North Atlantic Ocean, North Pacific Ocean and the Southern Hemisphere, the South Pacific Ocean (Australia), the North Atlantic Ocean (Greenland) and the Southern Ocean (Australia).

2COMMUNITY RESPONSE (0 STUDIES)

3POPULATION RESPONSE (5 STUDIES)

4Abundance (5 studies): Four of five studies (including three before-and-after studies) in the Kattegat and Skagerrak Seas, the South Pacific Ocean, the North Atlantic Ocean and the Southern Ocean found that after hunting was prohibited, the abundance of harbour seals and humpback whales increased over 7–30 years. The other study found that numbers of mature male sperm whales did not differ significantly before or 31 years after hunting was prohibited. One review in the North Atlantic Ocean, North Pacific Ocean and the Southern Hemisphere found significant increase rates for 10 of 12 baleen whale populations during 7–21 years after legislation to prohibit hunting was introduced.

5BEHAVIOUR (0 STUDIES)

6Assessment: beneficial (effectiveness 84 %; certainty 70 %; harms 0 %).

https://www.conservationevidence.com/​actions/​2780

No evidence found (no assessment)

7We have captured no evidence for the following interventions:

  • Educate local communities and fishers on mammal protection laws to reduce killing of marine and freshwater mammals

  • Enforce legislation to prevent the trafficking and trade of marine and freshwater mammal products

  • Inform local communities and fishers about the negative impacts of hunting to reduce the killing of marine and freshwater mammals

  • Introduce alternative food sources to replace marine and freshwater mammal meat

  • Introduce alternative income sources to reduce marine and freshwater mammal exploitation and trade

  • Introduce alternative sources of bait to replace the use of marine and freshwater mammals

  • Introduce alternative treatments to reduce the use of marine and freshwater mammals in traditional medicine

  • Introduce and enforce legislation to prevent intentional killing of mammals at wild fisheries

  • Introduce and enforce regulations for sustainable hunting of marine and freshwater mammals for traditional subsistence and handicrafts

  • Introduce and enforce regulations to prevent the use of harmful deterrents on mammals at wild fisheries

  • Restrict capture of marine and freshwater mammals for research or aquariums and zoos.

14.4.2 Reduce unwanted catch (’bycatch’) of mammals and improve survival of released or escaped mammals

Likely to be beneficial

●Increase visual detectability of fishing gear for mammals

8Two studies evaluated the effects on marine mammals of increasing the visual detectability of fishing gear for mammals. One study was in the Gulf of St. Lawrence (Canada) and one was in Cape Cod Bay (USA).

9COMMUNITY RESPONSE (0 STUDIES)

10POPULATION RESPONSE (0 STUDIES)

11BEHAVIOUR (2 STUDIES)

12Behaviour change (2 studies): One study in the Gulf of St. Lawrence found that minke whales approached white ropes more slowly and changed their bearing more when approaching black ropes compared to ropes of other colours. One study in Cape Cod Bay found that simulated ropes painted red or orange were detected by North Atlantic right whales at greater distances than green but not black ropes, and more whales collided with green ropes than the other three rope colours.

13Assessment: likely to be beneficial (effectiveness 55 %; certainty 45 %; harms 5 %).

https://www.conservationevidence.com/​actions/​2805

●Install exclusion and/or escape devices for mammals on fishing nets

14Seven studies evaluated the effects on marine mammals of installing exclusion and/or escape devices on fishing nets. Four studies were in the Indian Ocean (Australia, Tasmania) and/or Tasman Sea (Tasmania) and three studies were in the South Atlantic Ocean (South Georgia).

15COMMUNITY RESPONSE (0 STUDIES)

16POPULATION RESPONSE (2 STUDIES)

17Survival (2 studies): One study in the Indian Ocean found that less than one third of common bottlenose dolphins exited escape hatches on trawl nets alive. One replicated study in the Tasman Sea and Indian Ocean found that fewer fur seals died in exclusion devices with large escape openings than in those with small openings.

18BEHAVIOUR (0 STUDIES)

19OTHER (5 STUDIES)

20Reduction in entanglements/unwanted catch (5 studies): Three studies (including two controlled studies) in the South Atlantic Ocean and Indian Ocean found that installing exclusion and/or escape devices on trawl nets reduced the number of trapped or entangled Antarctic fur seals and common bottlenose dolphins. One before-and-after study in the Indian Ocean found that installing exclusion and escape devices on trawl nets reduced common bottlenose dolphin entanglements for three of four fishing vessels. One study in the South Atlantic Ocean found that modifying an exclusion and escape device by enlarging and relocating the escape panel resulted in fewer Antarctic fur seal entanglements.

21Assessment: likely to be beneficial (effectiveness 60 %; certainty 60 %; harms 15 %).

http://www.conservationevidence.com/​actions/​2823

●Modify fishing pots and traps to exclude mammals

22Six studies evaluated the effects on marine mammals of modifying fishing pots and traps to exclude mammals. Two studies were in the North Sea (UK, Sweden) and one study was in each of the Indian River Lagoon (USA), the Gulf of Finland (Finland), the Bothnian Sea (Finland), the Indian Ocean (Australia) and the Baltic Sea (Sweden).

23COMMUNITY RESPONSE (0 STUDIES)

24POPULATION RESPONSE (0 STUDIES)

25BEHAVIOUR (0 STUDIES)

26OTHER (6 STUDIES)

27Reduction in entanglements/unwanted catch (2 studies): Two controlled studies (including one replicated study) in the Indian Ocean, and the Baltic Sea and North Sea found that installing steel rods on lobster pots or metal frames on fishing pots reduced the number of Australian sea lion pups or grey seals and harbour seals that entered or became trapped in pots.

28Human wildlife conflict (4 studies): Two controlled studies (including one replicated study) in the Bothnian Sea and the North Sea found that installing wire grids or steel bars on fishing trap-nets or bag-nets, along with strengthened netting or other modifications to prevent seal access, reduced damage to salmon catches by seals. One controlled study in the Indian River Lagoon found that one of two methods of securing crab pot doors with a bungee cord reduced the number of common bottlenose dolphin interactions. One controlled study in the Gulf of Finland found that installing wire grids on trap-nets, along with strengthened netting, resulted in higher catches of undamaged salmon but not whitefish, likely due to reduced seal predation. Assessment: likely to be beneficial (effectiveness 70 %; certainty 56 %; harms 10 %).

https://www.conservationevidence.com/​actions/​2822

●Use acoustically reflective fishing gear materials

29Five studies evaluated the effects on marine mammals of using acoustically reflective fishing gear materials. Two studies were in the Bay of Fundy (Canada) and one study was in each of the Fortune Channel (Canada), the North Sea (Denmark) and the South Atlantic Ocean (Argentina).

30COMMUNITY RESPONSE (0 STUDIES)

31POPULATION RESPONSE (0 STUDIES)

32BEHAVIOUR (2 STUDIES)

33Behaviour change (2 studies): One controlled study in the Fortune Channel found that harbour porpoises approached nets made from acoustically reflective material (barium sulfate) and conventional nets to similar distances and for similar durations, but porpoises used fewer echolocation clicks at barium sulfate nets. One controlled study in the Bay of Fundy found that harbour porpoise echolocation activity was similar at barium sulfate and conventional nets.

34OTHER (3 STUDIES)

35Reduction in entanglements/unwanted catch (3 studies): Two of three controlled studies (including two replicated studies) in the North Sea, the Bay of Fundy and the South Atlantic Ocean found that fishing nets made from acoustically reflective materials (iron-oxide or barium sulfate) had fewer entanglements of harbour porpoises than conventional fishing nets. The other study found that nets made from barium sulfate did not reduce the number of dolphin entanglements.

36Assessment: likely to be beneficial (effectiveness 40 %; certainty 45 %; harms 0 %).

https://www.conservationevidence.com/​actions/​2807

●Use catch and hook protection devices on fishing gear

37Five studies evaluated the effects on marine mammals of using catch and hook protection devices on fishing gear. Two studies were in the South Pacific Ocean (Chile, Australia and Fiji), two were in the Indian Ocean (Seychelles, Madagascar) and one was in the Southwest Atlantic Ocean.

38COMMUNITY RESPONSE (0 STUDIES)

39POPULATION RESPONSE (0 STUDIES)

40BEHAVIOUR (0 STUDIES)

41OTHER (5 STUDIES)

42Reduction in entanglements/unwanted catch (1 study): One study in the South Pacific Ocean found that using cage or chain devices on fishing hooks resulted in fewer unwanted catches of toothed whales.

43Human-wildlife conflict (5 studies): Two of four studies (including three controlled and one before-and-after study) in the South Pacific Ocean, the Southwest Atlantic Ocean and the Indian Ocean found that net sleeves or cage and chain devices on fishing hooks reduced damage to fish catches by sperm whales, killer whales and toothed whales. The two other studies found that attaching ‘umbrella’ or ‘spider’ devices on fishing hooks did not reduce predation and/or damage to fish catches by sperm whales or toothed whales. One controlled study in the Indian Ocean found that attaching catch protection devices made from streamers to fishing lines reduced Indo-Pacific bottlenose and spinner dolphin predation on fish bait, but only during the first two trials.

44Assessment: likely to be beneficial (effectiveness 43 %; certainty 42 %; harms 10 %).

https://www.conservationevidence.com/​actions/​2821

Trade-off between benefit and harms

●Use acoustic devices on fishing gear

45Thirty-three studies evaluated the effects on marine mammals of using acoustic devices on fishing gear. Eight studies were in the North Atlantic Ocean (Canada, USA, UK), four studies were in each of the North Pacific Ocean (USA) and the North Sea (Germany, Denmark, UK), three studies were in the Mediterranean Sea (Spain, Italy), two studies were in each of the Fortune Channel (Canada), the South Atlantic Ocean (Argentina, Brazil) and the Baltic Sea (Denmark, Germany, Sweden), and one study was in each of Moreton Bay (Australia), the Black Sea (Turkey), the Celtic Sea (UK), the South Pacific Ocean (Peru), the Rainbow Channel (Australia), the UK (water body not stated), the Great Belt (Denmark), Omura Bay (Japan), and the Indian Ocean (Australia).

46COMMUNITY RESPONSE (0 STUDIES)

47POPULATION RESPONSE (0 STUDIES)

48BEHAVIOUR (16 STUDIES)

49Behaviour change (16 studies): Twelve of 16 controlled studies (including three replicated studies) in the North Atlantic Ocean, the Fortune Channel, the South Atlantic Ocean, Moreton Bay, the Mediterranean Sea, the Celtic Sea, the Rainbow Channel, a coastal site in the UK, the Great Belt, the North Sea, Omura Bay and the Indian Ocean found that using acoustic devices on fishing nets, float lines or simulated fishing nets resulted in harbour porpoises, common bottlenose dolphins, tuxuci dolphins, finless porpoises and seals approaching nets or lines less closely, having fewer encounters or interactions with nets, or activity and sightings were reduced in the surrounding area. The other four studies found that using acoustic devices on trawl nets, float lines or simulated fishing nets did not have a significant effect on the behaviour of common bottlenose dolphins, harbour porpoises, Indo-Pacific humpback dolphins or dugongs.

50OTHER (19 STUDIES)

51Reduction in entanglements/unwanted catch (14 studies): Nine studies (including seven controlled studies and two before-and after studies) in the North Atlantic Ocean, the North Sea, the South Atlantic Ocean, the North Pacific Ocean, the Black Sea, and the South Pacific Ocean found that using acoustic devices on cod traps or fishing nets resulted in fewer collisions of humpback whales or entanglements of harbour porpoises, Franciscana dolphins, beaked whales and small cetaceans. Three studies (including two controlled studies and one before-and-after study) in the North Pacific Ocean found that using acoustic devices on fishing nets resulted in fewer entanglements of some species but not others. One controlled study in the North Atlantic Ocean found that fishing nets with a ‘complete’ set of acoustic devices had fewer entanglements of harbour porpoises, but those with an ‘incomplete’ set did not. One replicated, controlled study in the North Sea and Baltic Sea found that using acoustic devices on fishing nets reduced harbour porpoise entanglements in one fishing area but not the other.

52Human-wildlife conflict (6 studies): Five of six studies (including six controlled studies, one of which was replicated) in the Baltic Sea, the Mediterranean Sea, the North Pacific Ocean, a coastal site in the UK and the North Sea found that using acoustic devices reduced damage to fish catches and/or fishing nets caused by common bottlenose dolphins and seals. The other study found that acoustic devices did not reduce damage to swordfish catches by California sea lions.

53Assessment: trade-off between benefit and harms (effectiveness 70 %; certainty 65 %; harms 20 %).

https://www.conservationevidence.com/​actions/​2808

●Use acoustic devices on fishing vessels

54Five studies evaluated the effects on marine mammals of using acoustic devices on vessels. One study was in each of the Shannon Estuary (Ireland), the Rainbow Channel (Australia), Keppel Bay (Australia), the North Atlantic Ocean (Azores) and the Indian Ocean (Crozet Islands).

55COMMUNITY RESPONSE (0 STUDIES)

56POPULATION RESPONSE (0 STUDIES)

57BEHAVIOUR (4 STUDIES)

58Behaviour change (4 studies): One controlled study in the Shannon Estuary found that common bottlenose dolphins avoided a boat more frequently when acoustic devices of two types were deployed alongside it. One controlled study in the Indian Ocean found that killer whales were recorded further from a fishing vessel when an acoustic device was used during hauls, but distances decreased after the first exposure to the device. Two before-and-after studies in the Rainbow Channel and Keppel Bay found that an acoustic device deployed alongside a vessel reduced surfacing and echolocation rates and time spent foraging or socializing of Indo-Pacific humpback dolphins and Australian snubfin dolphins but there was no effect on 8–10 other types of behaviour (e.g. vocalizing, diving, travelling etc.).

59OTHER (1 STUDY)

60Human-wildlife conflict (1 study): One randomized, controlled study in the North Atlantic Ocean found that using acoustic devices of two types did not reduce predation of squid catches by Risso’s dolphins.

61Assessment: trade-off between benefit and harms (effectiveness 40 %; certainty 50 %; harms 20 %).

https://www.conservationevidence.com/​actions/​2815

●Use acoustic devices on moorings

62Eight studies evaluated the effects on marine and freshwater mammals of using acoustic devices on moorings. Two studies were in the South Pacific Ocean and one study was in each of the Puntledge River (Canada), the Bay of Fundy (Canada), the Shannon Estuary (Ireland), the Rivers Conon and Esk (UK), the Kyle of Sutherland estuary (UK) and the North Atlantic Ocean (UK). COMMUNITY RESPONSE (0 STUDIES)

63POPULATION RESPONSE (0 STUDIES)

64BEHAVIOUR (7 STUDIES)

65Behaviour change (7 studies): Two of four controlled studies in the South Pacific Ocean, the Kyle of Sutherland estuary and the North Atlantic Ocean found that deploying acoustic devices on moorings reduced numbers of grey and harbour seals, and the activity of harbour porpoises, short-beaked common dolphins and common bottlenose dolphins. The two other studies found that using an acoustic device on a mooring did not have a significant effect on the number, direction of movement, speed, or dive durations of migrating humpback whales. One controlled study in the Bay of Fundy found that using an acoustic device on a mooring reduced harbour porpoise echolocation activity, but the probability of porpoises approaching within 125 m of the device increased over 10–11 days. One controlled study in the Shannon Estuary found that one of two types of acoustic device reduced the activity of common bottlenose dolphins. One replicated, controlled study in the Rivers Conon and Esk found that using acoustic devices reduced the number of grey and harbour seals upstream of the device but did not reduce seal numbers overall.

66OTHER (1 STUDY)

67Human-wildlife conflict (1 study): One randomized controlled study in the Puntledge River found that deploying an acoustic device on a mooring reduced the number of harbour seals feeding on migrating juvenile salmon. Assessment: trade-off between benefit and harms (effectiveness 42 %; certainty 50 %; harms 20 %).

https://www.conservationevidence.com/​actions/​2816

Unknown effectiveness

●Deploy fishing gear at different depths

68One study evaluated the effects on marine mammals of deploying fishing gear at different depths. The study was in the Arafura Sea (Australia).

69COMMUNITY RESPONSE (0 STUDIES)

70POPULATION RESPONSE (0 STUDIES)

71BEHAVIOUR (0 STUDIES)

72OTHER (1 STUDY)

73Reduction in entanglements/unwanted catch (1 study): One controlled study in the Arafura Sea found that fishing nets deployed 4.5 m below the water surface had fewer entanglements of dolphins than surface nets.

74Assessment: unknown effectiveness (effectiveness 50 %; certainty 35 %; harms 15 %).

https://www.conservationevidence.com/​actions/​2793

●Establish handling and release protocols for mammals captured by fisheries

75One study evaluated the effects on marine mammals of establishing handling and release protocols for mammals captured by wild fisheries. The study was in the Great Australian Bight (Australia).

76COMMUNITY RESPONSE (0 STUDIES)

77POPULATION RESPONSE (1 STUDY)

78Survival (1 study): One before-and-after study in the Great Australian Bight found that introducing a code of conduct for releasing dolphins trapped in nets, along with avoiding dolphins during fishing, resulted in lower mortality of short-beaked common dolphins.

79BEHAVIOUR (0 STUDIES)

80Assessment: unknown effectiveness (effectiveness 67 %; certainty 27 %; harms 0 %).

https://www.conservationevidence.com/​actions/​2829

●Establish ‘move-on rules’ for fishing vessels if mammals are encountered

81One study evaluated the effects on marine mammals of establishing move-on rules for fishing vessels if mammals are encountered. The study was in the Great Australian Bight (Australia).

82COMMUNITY RESPONSE (0 STUDIES)

83POPULATION RESPONSE (1 STUDY)

84Survival (1 study): One before-and-after study in the Great Australian Bight found that introducing measures to delay or relocate fishing if dolphins were encountered, along with releasing trapped dolphins, resulted in fewer short-beaked common dolphins being encircled and killed.

85BEHAVIOUR (0 STUDIES)

86Assessment: unknown effectiveness (effectiveness 70 %; certainty 27 %; harms 0 %).

https://www.conservationevidence.com/​actions/​2790

●Install barriers at wild fisheries

87One study evaluated the effects on freshwater mammals of installing a barrier at a wild fishery. The study was in the Puntledge River (Canada).

88COMMUNITY RESPONSE (0 STUDIES)

89POPULATION RESPONSE (0 STUDIES)

90BEHAVIOUR (0 STUDIES)

91OTHER (1 STUDY)

92Human-wildlife conflict (1 study): One randomized, controlled study in the Puntledge River found that installing a ‘cork line’ barrier did not deter harbour seals from feeding on salmon released from a hatchery.

93Assessment: unknown effectiveness (effectiveness 0 %; certainty 20 %; harms 0 %).

https://www.conservationevidence.com/​actions/​2824

●Play predator calls to deter mammals from fishing gear

94One study evaluated the effects of playing predator calls to deter mammals from fishing gear. The study was in the South Atlantic Ocean (Africa).

95COMMUNITY RESPONSE (0 STUDIES)

96POPULATION RESPONSE (0 STUDIES)

97BEHAVIOUR (0 STUDIES)

98OTHER (1 STUDY)

99Human-wildlife conflict (1 study): One study in the South Atlantic Ocean found that playing killer whale vocalisations did not deter Cape fur seals from feeding on fish catches in a purse-seine net or trawl net.

100Assessment: unknown effectiveness (effectiveness 0 %; certainty 20 %; harms 10 %).

https://www.conservationevidence.com/​actions/​2817

●Switch off artificial lighting at wild fisheries

101One study evaluated the effects on freshwater mammals of switching off artificial lights at a wild fishery. The study was in the Puntledge River (Canada). COMMUNITY RESPONSE (0 STUDIES)

102POPULATION RESPONSE (0 STUDIES)

103BEHAVIOUR (0 STUDIES)

104OTHER (1 STUDY)

105Human-wildlife conflict (1 study): One randomized, controlled study in the Puntledge River found that switching off artificial lights on a bridge did not deter harbour seals from feeding on salmon released from a hatchery.

106Assessment: unknown effectiveness (effectiveness 5 %; certainty 25 %; harms 0 %).

https://www.conservationevidence.com/​actions/​2825

●Use a larger mesh size for fishing trap-nets

107One study evaluated the effects on freshwater mammals of using a larger mesh size for fishing trap-nets. The study was in the River Indal (Sweden). COMMUNITY RESPONSE (0 STUDIES)

108POPULATION RESPONSE (0 STUDIES)

109BEHAVIOUR (0 STUDIES)

110OTHER (1 STUDY)

111Human-wildlife conflict (1 study): One controlled study in the River Indal found that a fishing trap-net with a larger mesh size in the first two sections had fewer grey seals feeding around it and less damage caused by seals.

112Assessment: unknown effectiveness (effectiveness 50 %; certainty 30 %; harms 15 %).

https://www.conservationevidence.com/​actions/​2803

●Use acoustic decoys to divert mammals away from fishing gear

113One study evaluated the effects on marine mammals of using acoustic decoys to divert mammals away from fishing gear. The study was in the Gulf of Alaska (USA).

114COMMUNITY RESPONSE (0 STUDIES)

115POPULATION RESPONSE (0 STUDIES)

116BEHAVIOUR (1 STUDY)

117Behaviour change (1 study): One study in the Gulf of Alaska found that increasing the distance between an acoustic decoy device and fishing lines resulted in fewer sperm whales at the lines, but sperm whale presence and time of arrival did not differ.

118Assessment: unknown effectiveness (effectiveness 37 %; certainty 30 %; harms 0 %).

https://www.conservationevidence.com/​actions/​2820

●Use an electric current to deter mammals from fishing gear

119One study evaluated the effects of using an electric current to deter mammals from fishing gear. The study was in the Fraser River (Canada).

120COMMUNITY RESPONSE (0 STUDIES)

121POPULATION RESPONSE (0 STUDIES)

122BEHAVIOUR (0 STUDIES)

123OTHER (1 STUDY)

124Human-wildlife conflict (1 study): One controlled study in the Fraser River found that using an electric current on a fishing net reduced Pacific harbour seal predation on salmon catches.

125Assessment: unknown effectiveness (effectiveness 50 %; certainty 30 %; harms 20 %).

https://www.conservationevidence.com/​actions/​2818

●Use noise aversive conditioning to deter mammals from fishing gear

126One 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).

127COMMUNITY RESPONSE (0 STUDIES)

128POPULATION RESPONSE (0 STUDIES)

129BEHAVIOUR (0 STUDIES)

130OTHER (1 STUDY)

131Human-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.

132Assessment: unknown effectiveness (effectiveness 20 %; certainty 30 %; harms 10 %).

http://www.conservationevidence.com/​actions/​2819

●Use stiffened materials or increase tension of fishing gear

133One 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)

134POPULATION RESPONSE (0 STUDIES)

135BEHAVIOUR (0 STUDIES)

136OTHER (1 STUDY)

137Reduction 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.

138Assessment: unknown effectiveness (effectiveness 0 %; certainty 28 %; harms 10 %).

https://www.conservationevidence.com/​actions/​2801

●Use ‘mammal-safe’ nets to capture and release mammals trapped in fishing structures

139One study evaluated the effects on marine mammals of using ‘mammal-safe’ nets to capture and release mammals trapped in fishing structures. The study was in the Bay of Fundy (Canada).

140COMMUNITY RESPONSE (0 STUDIES)

141POPULATION RESPONSE (1 STUDY)

142Survival (1 study): One controlled study in the Bay of Fundy found that using ‘marine mammal nets’ with a larger mesh size to release harbour porpoises from herring weirs resulted in lower porpoise mortality compared to using conventional herring nets.

143BEHAVIOUR (0 STUDIES)

144Assessment: unknown effectiveness (effectiveness 65 %; certainty 32 %; harms 0 %).

https://www.conservationevidence.com/​actions/​2828

Unlikely to be beneficial

●Attach acoustically reflective objects to fishing gear

145Two studies evaluated the effects on marine mammals of attaching acoustically reflective objects to fishing gear. One study was in the Timor Sea and Arafura Sea (Australia) and one was in the Gulf of Alaska (USA).

146COMMUNITY RESPONSE (0 STUDIES)

147POPULATION RESPONSE (0 STUDIES)

148BEHAVIOUR (0 STUDIES)

149OTHER (2 STUDIES)

150Reduction in entanglements/unwanted catch (1 study): One controlled study in the Timor Sea and Arafura Sea found that attaching metallic bead chains to fishing nets did not reduce the number of dolphin entanglements.

151Human-wildlife conflict (1 study): One controlled study in the Gulf of Alaska found that attaching acrylic beads next to fishing hooks did not reduce predation on fish catches by sperm whales.

152Assessment: unlikely to be beneficial (effectiveness 10 %; certainty 41 %; harms 15 %).

https://www.conservationevidence.com/​actions/​2806

No evidence found (no assessment)

153We have captured no evidence for the following interventions:

  • Deploy fishing gear at times when mammals are less active

  • Educate the public to reduce consumer demand for fisheries that threaten mammals

  • Enforce legislation to control illegal fishing using gear or methods that are harmful to mammals

  • Finance low interest loans to convert to fishing gear that reduces unwanted catch of mammals

  • Introduce fishing gear exchange programmes to encourage fishers to use gear that reduces unwanted catch of mammals

  • Introduce legislation to prohibit or restrict the use of fishing gear types or methods that are harmful to mammals

  • Involve fishers in designing and trialling new fishing gear types to encourage uptake of gear that reduces unwanted catch of mammals

  • Limit size of trawl net openings

  • Limit the length of fishing gear in an area

  • Limit the number of fishing vessels or fishing days in an area

  • Promote fish and seafood certification (e.g. ecolabels) to reduce consumer demand for fisheries that threaten mammals

  • Provide training and tools for safe release of mammals captured by fisheries

  • Reduce duration of time fishing gear is in the water

  • Retain buoys and lines at the sea floor or river bed when not hauling

  • Retain offal on fishing vessels instead of discarding overboard

  • Use a smaller mesh size for fishing nets

  • Use bindings to keep trawl nets closed until they have sunk below the water surface

  • Use different bait species for fishing that are less attractive to mammals

  • Use passive listening devices to detect mammals and prompt fishing vessels to move away

  • Use sinking lines instead of floating lines

  • Use weakened fishing gear.

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