Collected Evidence: Collected Evidence: Reduce the duration of exposure to air of captured fish before release Three studies examined the effect of reducing the duration of exposure of fish to air on marine fish populations. One study was in each of the Bay of Biscay (Spain), Gulf of Alaska (Canada) and Coral Sea (Australia).  COMMUNITY RESPONSE (0 STUDIES) POPULATION RESPONSE (2 STUDIES) Survival (1 study): One replicated study in the Bay of Biscay found that reducing air exposure before release did not increase the survival of small-spotted catshark caught during commercial trawling. Condition (1 study): One replicated study in the Gulf of Alaska found that shorter durations of air exposure before release improved the physical condition and reduced the amount of injury to discarded chum salmon caught in purse seine nets.  BEHAVIOUR (1 STUDY) Behaviour change (1 study): One study in the Coral Sea found that minimal exposure to air and handling resulted in improved overall behaviour after release (activity and ability to return to reef) of reef fish, compared to fish exposed to air and handling for longer duration. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2690https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2690Wed, 02 Dec 2020 14:47:25 +0000Collected Evidence: Collected Evidence: Release protected or species of concern alive after capture Six studies examined the effects of releasing protected or species of concern alive after capture on marine fish populations. Two studies were in the Atlantic Ocean (USA and Canada), and one was in each of the Coral Sea (Australia), Tasman Sea (New Zealand), Cantabrian Sea (Spain) and the Pacific Ocean (USA).  COMMUNITY RESPONSE (0 STUDIES) POPULATION RESPONSE (6 STUDIES) Survival (6 studies): Four of six replicated studies in the Atlantic Ocean, Tasman Sea, Cantabrian Sea and the Pacific Ocean found that the majority (76–92%) of unwanted (discarded or protected) small-spotted catshark, thorny skate, pearl perch and Atlantic wolffish, but less than half of smooth skate, survived for at least 1 h–5 days after capture and/or release, and survival was reduced by hooking/capture depth injuries and longer tow durations. One study found that nearly all yelloweye rockfish survived for four days after capture and release, but canary rockfish survival decreased with increasing capture depth. The other study found that all spinetail devilrays brailed aboard from purse seine nets survived but not those brought aboard entangled in the net. BEHAVIOUR (0 STUDIES)Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2691https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2691Wed, 02 Dec 2020 14:55:19 +0000Collected Evidence: Collected Evidence: Establish handling and release protocols in non-recreational fisheries Two studies examined the effects of establishing handling and release protocols in non-recreational fisheries on marine fish populations. One study was in the Atlantic Ocean (West Africa) and one was in the South Pacific Ocean (Australia).  COMMUNITY RESPONSE (0 STUDIES) POPULATION RESPONSE (1 STUDY) Survival (1 study): One study in the Atlantic Ocean reported that tracked whale sharks released from purse seines using an enhanced protocol survived for at least 21 days, and post-release movements appeared normal. BEHAVIOUR (2 STUDIES) Behaviour change (2 studies): One study in the Pacific Ocean found that after release protocols (minimal handling and air exposure), reef fish returned more quickly to a reef or the seabed after release, compared to higher stress handling and longer air exposure. One study in the Atlantic Ocean reported that the post-release movements of tracked whale sharks released from purse seines using an enhanced protocol appeared normal. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2692https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2692Wed, 02 Dec 2020 15:51:06 +0000Collected Evidence: Collected Evidence: Set catch limits or quotas for non-targeted commercial catch Two studies examined the effects of setting catch limits or quotas for non-targeted commercial fish species on marine fish populations. One review was in the North Atlantic and Pacific Oceans and one study was in the Pacific Ocean (Canada).  COMMUNITY RESPONSE (0 STUDIES) POPULATION RESPONSE (0 STUDIES) BEHAVIOUR (0 STUDIES) OTHER (2 STUDIES) Reduction of unwanted catch (2 studies): One review in the Atlantic and Pacific Oceans found that setting catch limits or quotas for non-commercially targeted fish reduced unwanted catch in two of three cases. One before-and-after study in the Pacific Ocean found that catch limits for non-target commercial species reduced the amount of unwanted halibut, but a previous quota system based on the whole catch (individual transferrable quotas) did not. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2693https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2693Wed, 02 Dec 2020 16:15:52 +0000Collected Evidence: Collected Evidence: Legislate to oblige fishers to retain and land all catch of species managed by quotas We found no studies that evaluated the effects of legislating to oblige fishers to retain and land all catch of quota species on marine fish populations. ‘We found no studies’ means that we have not yet found any studies that have directly evaluated this intervention during our systematic journal and report searches. Therefore, we have no evidence to indicate whether or not the intervention has any desirable or harmful effects.Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2694https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2694Wed, 02 Dec 2020 16:24:14 +0000Collected Evidence: Collected Evidence: Use artificial light on fishing gear Two studies examined the effects of using artificial light on fishing gear on marine fish populations. One study was in the Pacific Ocean (USA) and one in the Barents Sea (Norway).  COMMUNITY RESPONSE (0 STUDIES) POPULATION RESPONSE (0 STUDIES) BEHAVIOUR (0 STUDIES) OTHER (2 STUDIES) Reduction of unwanted catch (1 study): One replicated, paired, controlled study in the Pacific Ocean found that shrimp trawl nets with artificial lights caught fewer unwanted fish when they were fitted to the fishing line, but not to a size-sorting grid, compared to a conventional trawl. Improved size-selectivity of fishing gear (1 study): One replicated, controlled study in the Barents Sea found that size-selectivity of long rough dab, Atlantic cod, haddock and redfish was not improved by the presence of LED lights on a size-sorting grid. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2695https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2695Wed, 02 Dec 2020 17:04:07 +0000Collected Evidence: Collected Evidence: Attach an electropositive deterrent to fishing gear Nine studies examined the effect of attaching an electropositive deterrent to fishing gear on marine fish populations. Three studies were in the Atlantic Ocean (USA, Canada, Bahamas). One study was in each of the Gulf of Alaska (USA), the South Pacific Ocean (Australia) and the Tasman Sea (Australia). One study was a global systematic review and two studies were in laboratory facilities (USA).  COMMUNITY RESPONSE (0 STUDIES) POPULATION RESPONSE (0 STUDIES) BEHAVIOUR (4 STUDIES) Behaviour change (4 studies): Three of four replicated studies (one paired and controlled, one randomized and controlled, one randomized, and one controlled) in the Atlantic Ocean, Tasman Sea, and in laboratory conditions, found that the presence of potentially deterrent materials attached near the bait reduced the frequency of feeding attempts and bait consumption of spiny dogfish, great hammerhead and draughtboard sharks compared to the absence of deterrent materials. The other study found that a potentially deterrent material did not reduce bait consumption by bonnethead and young lemon sharks compared to non-deterrents. One of the studies also found that the bait consumption behaviour of commercially valuable Pacific halibut was unaffected by deterrent materials. OTHER (5 STUDIES) Reduction of unwanted catch (5 studies): Two of four replicated, controlled studies (one randomized) in the Gulf of Alaska, the Pacific Ocean and the Atlantic Ocean found that fishing gear (longlines and traps) fitted with electropositive deterrent materials caught fewer unwanted spiny dogfish, longnose skate, sharks and rays, and fewer undersized halibut, compared to standard fishing gear or gears with non-deterrent materials. The other two studies, and a global systematic review found that electropositive deterrents on fishing gear resulted in similar catches of unwanted spiny dogfish, sharks (total catch), blue shark and sharks and rays (total catch), compared to gear with no deterrents. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2696https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2696Thu, 03 Dec 2020 12:05:21 +0000Collected Evidence: Collected Evidence: Use a larger mesh size Forty-two studies examined the effects of using a larger mesh size of fishing net on marine fish populations. Ten studies, and one review, were in the Atlantic Ocean (UK, Portugal, USA). Eight studies were in the Aegean Sea (Greece, Turkey). Five studies were in the North Sea (UK, Netherlands, France, North Europe) and three were in the Tasman Sea (Australia). Two studies were in each of the Mediterranean Sea (Italy, Turkey), the Pacific Ocean (USA, Chile), the Skagerrak and Kattegat (Northern Europe) and the Gulf of Mexico (Mexico). One study was in each of the English Channel (UK), the Bering Sea (USA), the Baltic Sea (Finland), the Caribbean Sea (Barbados), the Persian Gulf (Kuwait), the Bristol Channel (UK), the Barents Sea (Norway) and the Arabian Sea (India).  COMMUNITY RESPONSE (0 STUDIES) POPULATION RESPONSE (3 STUDIES) Survival (3 studies): One of three controlled studies (one replicated and paired, and one replicated) in the Atlantic Ocean, Baltic Sea and Bristol Channel found that larger mesh sizes improved the post-capture survival of skates and rays compared to smaller meshes. The other two found similar post-capture survival in haddock, whiting and small herring between trawl nets with larger mesh and nets of smaller mesh size. Condition (1 study): One replicated, paired, controlled study in the Bristol Channel reported that the condition of skates and rays at capture was better with a larger trawl codend mesh size compared to a smaller mesh. BEHAVIOUR (0 STUDIES) OTHER (41 STUDIES) Reduction of unwanted catch (21 studies): Fifteen of 20 replicated studies (five controlled, two paired, eight paired and controlled, one randomized and one randomized and controlled) in the North Sea, Skagerrak/Kattegat, Aegean Sea, Caribbean Sea, Mediterranean Sea, Atlantic Ocean, Tasman Sea, Gulf of Mexico, Pacific Ocean, Bering Sea and the Bristol Channel found that using a larger mesh size in a fishing net (various trawls, gillnets, seines and trammel nets) reduced the catches of unwanted (small/undersized, non-commercial, discarded) fish or fish and invertebrates combined, compared to nets with standard/smaller mesh sizes. One study found that amounts of unwanted fish were reduced with larger mesh at smaller catch sizes but were similar between large and small meshes at larger catch sizes, and one found that increasing a trawl codend mesh size reduced the unwanted catch of one of two fish species compared to a standard mesh. Three found that larger mesh sized fishing nets did not typically reduce the unwanted fish catch compared to nets of smaller mesh sizes. One study found that increasing both the mesh size and minimum size limit reduced catches of the youngest fish. Improved size-selectivity of fishing gear (23 studies): Nineteen of 21 replicated studies (eight controlled, four paired and controlled, three randomized and controlled, and one paired) and one review, in the North Sea, Aegean Sea, Baltic Sea, Pacific Ocean, Atlantic Ocean, Gulf of Mexico, Tasman Sea, Arabian Sea, Persian Gulf, Barents Sea and the Mediterranean Sea found that larger mesh sizes (both diamond and square) of the netting of various gear types improved the size-selectivity for all fish species assessed and in one, for two of three fish species, compared to smaller mesh sizes. One study found that size-selectivity for fish was not improved with larger mesh size in the netting of fish traps. The other found that increasing the codend mesh size of trawls fitted with size-sorting escape grids resulted in similar size-selectivity of the codend for fish compared to smaller codend mesh sizes. One controlled study in the English Channel found that a trawl net codend with a larger size of square mesh had similar size-selectivity for Atlantic mackerel as a smaller diamond mesh codend. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2697https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2697Thu, 03 Dec 2020 19:56:32 +0000Collected Evidence: Collected Evidence: Use a different hook type Twenty-five studies examined the effect of using a different hook type on marine fish populations. Nine studies were in the Atlantic Ocean (Portugal, South Africa, USA, Brazil, Portugal, Iceland), six studies were in Pacific Ocean (New Zealand, Japan, Costa Rica, Hawaii, Fiji) and two studies were in the Mediterranean Sea (Spain, Italy). One study was in each of the Barents Sea (Norway), the Denmark Strait (Greenland), the Coral Sea (Australia) and the Strait of Gibraltar (Spain/Morocco). Four studies were reviews (worldwide, Atlantic and Pacific Oceans). COMMUNITY RESPONSE (0 STUDIES) POPULATION RESPONSE (10 STUDIES) Survival (10 studies): Four of seven replicated, controlled studies in the Atlantic Ocean, Pacific Ocean and Coral Sea and two of three worldwide systematic reviews, found that using different hook types in longline or recreational fisheries, including sizes, styles and other modifications to hooks, reduced the incidence of fish hook injuries (associated with higher post-release mortality), and reduced the capture mortality of some species of unwanted sharks and rays and non-target billfish species, compared to conventional hooks or other hook types. The other four studies found that using a different hook type did not reduce the post-release mortality of young sea breams, or the capture mortality of sharks species and non-target fish species, but did reduce the incidence of deep-hooking in some cases. BEHAVIOUR (0 STUDIES) OTHER (23 STUDIES) Reduction of unwanted catch (20 studies): Eight of 16 replicated studies (13 controlled, one randomized) in the Atlantic Ocean, Pacific Ocean, Barents Sea, Mediterranean Sea, Denmark Strait and Coral Sea, found that using a different hook type, including different sizes, styles and hook modifications, reduced the unwanted catch in longline and recreational hook fisheries of non-commercially targeted and targeted fish species, small non-target fish species, overall fish catch, overall discarded bony fish catch but not sharks and rays, undersized haddock, two of three unwanted fish species, non-target sharks and rays and non-target rays and sailfish, compared to standard hooks or hooks of other types. Seven studies found that changing hook type did not reduce the unwanted catch of young or non-target fish species, unwanted sharks and rays, unwanted blue shark, unwanted roughhead grenadier or non-target pelagic stingray and silky shark, compared to standard or other hook types. The other study found that catch rates of young groupers, and non-target fish and shark species varied with hook design, and larger hooks caught fewer non-target fish species overall, but more undersized grouper and sharks compared to other hook types. Four global systematic reviews found that hook style did not affect the unwanted catch of billfish species, sharks and rays or sharks, compared to standard styles. Improved size-selectivity of fishing gear (3 studies): Two of three replicated studies in the Atlantic Ocean and Strait of Gibraltar, found that increasing hook sizes improved the size-selectivity (by increasing the average catch length) of hottentot and black spot seabream compared to smaller hook sizes. The other study found that a different hook size improved size selectivity for two of five commercially targeted fish species and was also affected by bait size. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2698https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2698Tue, 08 Dec 2020 15:46:56 +0000Collected Evidence: Collected Evidence: Modify longline configuration Four studies examined the effects of modifying longline configuration on marine fish populations. One study was in each of the Norwegian Sea (Norway) and Atlantic Ocean (Brazil). Two were global reviews.  COMMUNITY RESPONSE (0 STUDIES) POPULATION RESPONSE (2 STUDIES) Survival (2 studies): One global review found that survival of unwanted sharks and rays at retrieval of longline gear was higher on nylon hook attachment lines instead of wire for two of three species and lower for one. One replicated, controlled study in the Atlantic Ocean found that survival of unwanted sharks caught on tuna longlines was reduced with nylon hook lines compared to wire. BEHAVIOUR RESPONSE (0 STUDIES) OTHER (4 STUDIES) Reduction of unwanted catch (4 studies): One of two replicated, controlled studies in the Norwegian Sea and Atlantic Ocean and one of two reviews of worldwide longline fisheries found that modifying longline configuration (increasing the lead weight on mid-water longlines to increase the sinking rate or using nylon instead of wire hook attachments) reduced the catches of unwanted sharks and/or rays compared to standard longlines. One review found that longline modifications reduced unwanted shark/ray catches in one of two cases. The other study found that modified longlines did not reduce catches of undersized haddock compared to standard longlines. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2699https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2699Wed, 09 Dec 2020 16:42:33 +0000Collected Evidence: Collected Evidence: Use a different bait type Eleven studies examined the effects of using different bait on marine fish populations. Two studies were global systematic reviews. Three studies were in the North Atlantic Ocean (USA, Iceland).Two studies were in the South Pacific Ocean (New Zealand). One study was in each of the Norwegian/Barents Seas (Norway), the Barents Sea (Norway), the Denmark Strait (Greenland) and the Mediterranean Sea. COMMUNITY RESPONSE (0 STUDIES) POPULATION RESPONSE (2 STUDIES) Survival (2 studies): One replicated study in the South Pacific Ocean and one global systematic review found that using different bait species did not reduce hooking injuries (associated with higher post-release mortality) of undersized snapper or sharks and rays, and did not increase survival of sharks and rays on gear retrieval. BEHAVIOUR (0 STUDIES) OTHER (10 STUDIES) Reduction of unwanted catch (10 studies): Six of eight replicated studies (three controlled and one randomized) in the Norwegian/Barents Seas, Barents Sea, Denmark Strait, North Atlantic Ocean, Mediterranean Sea and the South Pacific Ocean, found that using a different bait type (including size, species and manufacture method) reduced the unwanted catches of undersized haddock (although in one case in only two of six comparisons), Atlantic cod and other unwanted or non-target fish catch, but unwanted catches of torsk and ling were similar, compared to standard or other bait types. Two other studies found no reduction in unwanted catches of pelagic stingray and overall unwanted fish with different bait types. Two systematic global reviews found that using different bait types did not affect the number of unwanted sharks and rays caught. Improved size-selectivity of fishing gear (1 study): One replicated study in the Denmark Strait found that using a different bait species increased the size-selectivity of commercially targeted Greenland halibut. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2700https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2700Thu, 10 Dec 2020 14:26:24 +0000Collected Evidence: Collected Evidence: Modify gillnet or entangling (trammel/tangle) net configuration Four studies examined the effects of modifying gillnet or entangling (trammel or tangle) net configuration on marine fish populations. One study was in each of the Gulf of Maine (USA), the Atlantic Ocean (USA) and the Adriatic Sea (Italy), and one study was in two estuaries in North Carolina (USA).  COMMUNITY RESPONSE (0 STUDIES) POPULATION RESPONSE (0 STUDIES) BEHAVIOUR (0 STUDIES) OTHER (4 STUDIES) Reduction in unwanted catch (4 studies): Three of four replicated studies (one controlled, two paired and controlled) in the Gulf of Maine, Atlantic Ocean, Adriatic Sea and estuaries in the USA, found that modifications to the configuration of gillnets, including reduced height, increased tension twine diameter and mesh size and orientation, reduced the unwanted catch of cod in one of two net designs, discarded fish of commercial and non-commercial species, and the discards of non-commercial, but not commercial species (fish and invertebrates), compared to conventional configurations. The other study found that gillnet modification did not typically reduce unwanted shark catches compared to unmodified gillnets. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2701https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2701Fri, 11 Dec 2020 11:55:00 +0000Collected Evidence: Collected Evidence: Modify fishing trap/pot configuration Twenty-three studies examined the effects of modifying fishing trap or pot configuration on marine fish populations. Five studies were in the Atlantic Ocean (USA, Brazil, Canary Islands, Canada). Three studies were in each of the Bothnian Sea (Sweden), the Baltic Sea (Poland, Sweden), the Tasman Sea (Australia) and the Indian Ocean (Kenya, South Africa). One study was in each of the Kattegat (Denmark), the Mediterranean Sea (Spain), the Adriatic Sea (Italy), the Southern Ocean (Australia), the Pacific Ocean (Canada) and the Barents Sea (Norway).  COMMUNITY RESPONSE (0 STUDIES) POPULATION RESPONSE (1 STUDY) Survival (1 study): One replicated, controlled study in the Bothnian Sea found that survival of small herring escaped from a pontoon fish trap through a size-sorting grid was similar to trap-caught herring that did not pass through a grid. BEHAVIOUR (0 STUDIES) OTHER (22 STUDIES) Reduction of unwanted catch (20 studies): Sixteen of 20 replicated studies (11 controlled, one randomized, paired and controlled, one randomized and controlled, two paired and controlled and one randomized) and one before-and-after study in the Atlantic Ocean, Baltic Sea, Mediterranean Sea, Southern Ocean, Tasman Sea, Adriatic Sea, Bothnian Sea, Indian Ocean, Pacific Ocean, the Kattegat and the Barents Sea, found that modifications to trap configuration (various, including using a different trap type, increased mesh size and fitting an escape device) reduced the unwanted (undersized, discarded or non-commercial target) catches of fish (overall, or all of multiple study species), brown trout, black sea bass, herring, bluethroat wrasse and leatherjacket, cod, protected rockfishes, whitefish, black sea bass, American eel and winter flounder, sharks/rays and of salmon and rainbow trout in one of two cases, compared to unmodified conventional traps or traps of other designs. One of these also found that the number of unwanted species (fish and invertebrates) was lower in modified traps. Three other studies, found that trap modification or type had no effect on unwanted catches of white croaker, non-commercial fish or undersized Atlantic cod, and non-target haddock catches were increased. However, one of these also reported that traps (creels) did not catch high proportions of immature fish, unlike bottom trawls. Improved size-selectivity of fishing gear (4 studies): Three of four replicated studies (two controlled and one randomized, paired and controlled) in the Baltic Sea, Tasman Sea, Indian Ocean and Atlantic Ocean found that traps or pots modified with a square mesh escape window or larger mesh sizes improved the size-selectivity of Atlantic cod, black sea bass and most fish species compared to smaller mesh and/or standard gear. The other found that increasing mesh size of a trap escape panel had no effect on size-selectivity of panga. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2702https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2702Mon, 14 Dec 2020 10:32:58 +0000Collected Evidence: Collected Evidence: Fit escape devices (panels/grids) to encircling nets Three studies examined the effect of fitting fish escape devices (panels or size-sorting grids) to encircling nets on marine fish populations. One study was in the Tasman Sea (Australia), one was in the North and Norwegian Seas (Norway) and one was in the Atlantic Ocean (Portugal).  COMMUNITY RESPONSE (0 STUDIES) POPULATION RESPONSE (1 STUDY) Survival (1 study): One replicated, controlled study in the North and Norwegian Seas reported no difference in the survival of saithe, but reduced survival of mackerel, between fish that had passed through a rigid size-sorting escape grid in a purse seine net and those that had not, after one month. BEHAVIOUR (0 STUDIES) OTHER (2 STUDIES) Reduction of unwanted catch (2 studies): Two replicated studies (one controlled) in the Tasman Sea and Atlantic Ocean found that transparent panels of net and a large-diamond mesh escape panel fitted to fish seine nets, reduced the catches of unwanted small individuals of one of four commercially targeted fish and unwanted or undersized fish, compared to conventional seine nets. Improved size-selectivity of fishing gear (1 study): One replicated, controlled study in the Tasman Sea found that size-selectivity of one of four commercial fish species was improved in seine nets with transparent netting panels compared to without. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2703https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2703Mon, 14 Dec 2020 14:09:11 +0000Collected Evidence: Collected Evidence: Modify the design or configuration of trawl gear (mixed measures) Nineteen studies examined the effects of modifying the design or configuration of trawl gear on marine fish populations. Seven studies were in the Clarence River estuary (Australia), three studies were in each of the Mediterranean Sea (Turkey) and North Sea (UK), two studies were in the North Pacific Ocean (USA), and one study was in each of the South Pacific Ocean, the Skagerrak and Baltic Sea (Denmark/Sweden), the Atlantic Ocean (USA) and the Coral Sea (Australia).  COMMUNITY RESPONSE (0 STUDIES) POPULATION RESPONSE (0 STUDIES) BEHAVIOUR (0 STUDIES) OTHER (19 STUDIES) Reduce unwanted catch (16 studies): Twelve of 16 replicated studies (seven paired and controlled, five controlled, and two paired) in the Clarence River estuary, South Pacific Ocean, North Pacific Ocean, Mediterranean Sea, Skagerrak and Baltic Sea, Atlantic Ocean, North Sea and the Coral Sea, found that various modifications to trawl gear, including changes to the trawl wires, number of nets, codend number, footrope configuration, front trawl body panels, codend netting layers, spreading mechanism, method of weaving, knot orientation or using a new overall trawl design, resulted in reduced unwanted catches of non-target and/or discarded fish species or sizes, and of all sizes of four of seven commercial species, compared to standard unmodified trawl gear or other trawl designs. One of these also found increased catch rate of one commercial species and for another two species the effect varied with fish size. Two studies found that modified trawl gear reduced the unwanted catch of only a small proportion of the number of individual fish species caught compared to other trawl configurations, and also that unwanted fish catches varied between day/night. One study found that different trawl configurations had mixed effects on the numbers and sizes of non-target fish catch. The other study found no reduction in catches of discarded finfish between a modified and standard trawl codend. Improved size-selectivity of fishing gear (5 studies): Five replicated, controlled studies in the North Sea and Mediterranean Sea found that various modifications to trawl gear, including changes to the length of the extension piece, the codend strengthening bag, the method of weaving, the number of codend layers and overall design improved the size-selectivity for unwanted (non-target/discarded) fish species or sizes, and annular seabream in one of two cases, compared to unmodified standard trawl gear or other design configurations. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2704https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2704Thu, 17 Dec 2020 11:29:15 +0000Collected Evidence: Collected Evidence: Change the size of the main body of a trawl net One study examined the effects of changing the size of the main body of a trawl net to reduce unwanted catch on marine fish populations. The study was in the North Sea (Norway). COMMUNITY RESPONSE (0 STUDIES) POPULATION RESPONSE (0 STUDIES) BEHAVIOUR (0 STUDIES) OTHER (1 STUDY) Improved size-selectivity of fishing gear (1 study): One replicated study in the North Sea found that reducing the size of the main body of a trawl net did not improve the size-selection of cod and haddock. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2705https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2705Thu, 17 Dec 2020 12:05:11 +0000Collected Evidence: Collected Evidence: Decrease the circumference or diameter of the codend of a trawl net Thirteen studies examined the effects of decreasing the circumference or diameter of a trawl codend on marine fish populations. Four studies were in the Tasman Sea (Australia) and three studies were in the North Sea (UK, Norway). Two studies were in the Adriatic Sea (Italy) and two were in the Baltic Sea (Denmark/ Germany). One study and one review were in the Northeast Atlantic Ocean (Northern Europe).  COMMUNITY RESPONSE (0 STUDIES) POPULATION RESPONSE (0 STUDIES) BEHAVIOUR (0 STUDIES) OTHER (13 STUDIES) Reduction of unwanted catch (6 studies): Two of six replicated, controlled studies (three paired, and one randomized and paired) in the Tasman Sea, Adriatic Sea and Northeast Atlantic Ocean found that bottom trawl nets of smaller circumferences reduced discarded catch of fish in three of five cases and of total discarded catch (fish and invertebrates) in one of two areas, but not overall, compared to standard trawls. Two studies found that reduced circumference codends reduced non-target or discarded fish catch in three of 12 cases and for one of four species. The two other studies found that discarded fish catch was not reduced in smaller circumference codends. Improve size-selectivity of fishing gear (8 studies): Four of eight replicated, controlled studies (one paired) in the North Sea, Adriatic Sea and Baltic Sea, and one review in the Northeast Atlantic Ocean, found that decreasing the circumference or diameter of the codend of trawl gear (bottom trawls and seines) improved the size-selectivity of haddock, Atlantic cod, whiting and European hake and red mullet, compared to larger circumferences/diameters. One also found the effect was the same across two codend mesh sizes, and one also found the effect was greater in diamond mesh with the netting orientation turned by 90° compared to standard diamond mesh. Two studies found that a decrease in codend circumference/diameter improved size-selectivity of haddock and saithe in one of two cases, and of one of three fish species. The other study found that a smaller circumference codend reduced size-selectivity of the gear for one of three fish species and was similar for the other two. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2706https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2706Thu, 17 Dec 2020 14:51:11 +0000Collected Evidence: Collected Evidence: Modify the design or configuration of trawl doors Three studies examined the effects of modifying the design or configuration of trawl doors on marine fish populations. One study was in the Tasman Sea, one in the Clarence Estuary and one in Lake Wooloweyah (all in Australia).  COMMUNITY RESPONSE (0 STUDIES) POPULATION RESPONSE (0 STUDIES) BEHAVIOUR (0 STUDIES) OTHER (3 STUDIES) Reduction in unwanted catch (3 studies): Three replicated, controlled studies (one paired) in the Tasman Sea, the Clarence Estuary and Lake Wooloweyah found that modified or different designs of trawl doors caught similar amounts of unwanted fish overall, compared to conventional door types. However, one study found fewer of one of five individual unwanted fish species were caught with modified doors. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2707https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2707Mon, 28 Dec 2020 15:41:41 +0000Collected Evidence: Collected Evidence: Modify a bottom trawl to raise parts of the gear off the seabed during fishing Two studies examined the effects of modifying a bottom trawl to raise parts of the gear off the seabed during fishing on marine fish populations. One study was in the Gulf of Carpentaria (Australia) and one was in the Atlantic Ocean (USA).  COMMUNITY RESPONSE (0 STUDIES) POPULATION RESPONSE (0 STUDIES) BEHAVIOUR (0 STUDIES) OTHER (2 STUDIES) Reduction of unwanted catch (2 studies): Two replicated studies (one randomized and both controlled) in the Gulf of Carpentaria and the Atlantic Ocean found that bottom trawls with parts of the gear raised off the seabed caught fewer unwanted sharks, other elasmobranchs and fish and fewer of three of seven unwanted fish species compared to conventional trawls. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2708https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2708Mon, 28 Dec 2020 15:51:05 +0000Collected Evidence: Collected Evidence: Modify design or arrangement of tickler chains/chain mats in a bottom trawl Two studies examined the effects of modifying the design or arrangement of tickler chains in a bottom trawl on marine fish populations. One was in the North Sea (Netherlands/UK) and one was in the Atlantic Ocean (Scotland).  COMMUNITY RESPONSE (0 STUDIES) POPULATION RESPONSE (0 STUDIES) BEHAVIOUR (0 STUDIES) OTHER (2 STUDIES) Reduction of unwanted catch (2 studies): One of two replicated, paired, controlled studies in the North Sea and Atlantic Ocean found that removing the tickler chain from a trawl reduced catches of non-commercial target skates/rays and sharks, and individuals were larger, compared to trawling with the chain. The study also found that catches of commercial target species were typically unaffected. The other study found that two modified tickler chain arrangements did not reduce discarded fish catch compared to a standard arrangement. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2709https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2709Mon, 28 Dec 2020 15:58:06 +0000Collected Evidence: Collected Evidence: Use a different twine type in a trawl net Five studies examined the effects of using a different twine type in a trawl net on marine fish populations. Two studies were in each of the North Sea (UK) and the Western Baltic Sea (Denmark/Germany), and one study was in the Adriatic Sea (Italy). COMMUNITY RESPONSE (0 STUDIES) POPULATION RESPONSE (0 STUDIES) BEHAVIOUR (0 STUDIES) OTHER (5 STUDIES) Improved size-selectivity of fishing gear (5 studies): Four of five replicated studies (four controlled) in the North Sea, Baltic Sea and Adriatic Sea found that using a different twine type (twine thickness and construction material) improved the size-selectivity of bottom fish, haddock, Atlantic cod, plaice and flounder, compared to thinner or other twine materials. One study found that selectivity of non-target haddock and plaice was similar for three different twine diameters. One of these studies also found that size-selectivity of fish was influenced by twine number and mesh orientation, while another found no effect of twine number and mesh orientation, but cod selectivity increased with a smaller codend circumference. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2710https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2710Tue, 29 Dec 2020 16:07:09 +0000Collected Evidence: Collected Evidence: Use a separator trawl Two studies examined the effect of using a separator trawl on marine fish populations. One study was in the North Sea (UK) and the other in the Atlantic Ocean (Portugal).  COMMUNITY RESPONSE (0 STUDIES) POPULATION RESPONSE (0 STUDIES) BEHAVIOUR (0 STUDIES) OTHER (2 STUDIES) Reduction of unwanted catch (2 studies): One replicated, randomized study in the North Sea found that a separator trawl separated unwanted cod from target fish species into the lower codend, where a larger mesh size allowed more unwanted smaller cod to escape capture. One replicated study in the Atlantic Ocean found that a separator trawl fitted with a square-mesh escape panel caught less of one of two unwanted fish species in a crustacean fishery. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2711https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2711Tue, 29 Dec 2020 16:27:31 +0000Collected Evidence: Collected Evidence: Use a topless (coverless) trawl Four studies examined the effect of using a topless or coverless trawl on marine fish populations. Two studies were in the North Sea (UK, Norway, Sweden), one study was in the Gulf of Maine (USA) and one study was in the North Sea, Skagerrak and the Baltic Sea (Northern Europe).  COMMUNITY RESPONSE (0 STUDIES) POPULATION RESPONSE (0 STUDIES) BEHAVIOUR (0 STUDIES) OTHER (4 STUDIES) Reduction of unwanted catch (4 studies): Two of four replicated, controlled studies (three paired) in the North Sea, Gulf of Maine, and North Sea, Skagerrak and Baltic Sea found that using a topless trawl, in one case in combination with another non-conventional trawl type, reduced the catch of unwanted Atlantic cod and discards of commercial fish species compared to conventional trawl types. One study found that topless trawls reduced unwanted catches of larger but not smaller haddock and larger Atlantic cod only in one of two cases, compared to standard trawl types. The other study found that discarded catches of one of four commercial fish species were reduced in topless trawls. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2712https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2712Tue, 29 Dec 2020 16:31:56 +0000Collected Evidence: Collected Evidence: Use an electric (pulse) trawl Three studies examined the effects of using an electric (pulse) trawl on marine fish populations. The studies were in the North Sea (Belgium, Netherlands and multiple European countries).  COMMUNITY RESPONSE (0 STUDIES) POPULATION RESPONSE (0 STUDIES) BEHAVIOUR RESPONSE (0 STUDIES) OTHER (3 STUDIES) Reduction of unwanted catch (3 studies): Two replicated, paired, controlled studies and one review in the North Sea found that using an electric/pulse trawl reduced the catches of non-target or undersized (discarded) commercial fish in some or all cases, compared to using a standard trawl. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2713https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2713Tue, 29 Dec 2020 16:45:07 +0000Collected Evidence: Collected Evidence: Use a square mesh instead of a diamond mesh codend in a trawl net Twenty-six studies examined the effects of using a square mesh instead of a diamond mesh codend in a trawl net on marine fish populations. Five studies were in the North Atlantic Ocean (Canada, Portugal, USA), four were in the Aegean Sea (Greece, Turkey), three were in the Mediterranean Sea (Spain) and the Tasman Sea (Australia), two studies were in each of the English Channel (UK), the Adriatic Sea (Italy) and the South Pacific Ocean (Australia, Chile), and one study was in each of the Greenland Sea (Iceland), the North Pacific Ocean (USA), the Bristol Channel (UK), the Kattegat and the Skagerrak (Denmark) and the Coral Sea (Australia).  COMMUNITY RESPONSE (0 STUDIES) POPULATION RESPONSE (2 STUDIES) Survival (2 studies): One of two replicated, paired, controlled studies in the Aegean Sea and Bristol Channel found that the short-term survival of two of six fish species was higher after escaping through a square mesh compared to a diamond mesh codend. The other study reported that skate caught in a square mesh codend had a higher overall survival likelihood than those caught in a diamond mesh codend. BEHAVIOUR (0 STUDIES) OTHER (25 STUDIES) Reduction of unwanted catch (16 studies): Ten of 16 replicated, controlled studies (including five paired, three randomized and three randomized and paired) in the Greenland Sea, Aegean Sea, Atlantic Ocean, Tasman Sea, Pacific Ocean, Mediterranean Sea, English Channel, Bristol Channel and Coral Sea, found that square mesh codends reduced the unwanted (non-target or non-marketable/discarded) catches of all fish species monitored, young individuals of half or most commercially targeted fish, total unwanted catch (fish and invertebrates), and discarded fish in deeper but not shallower fishing areas, compared to diamond mesh codends; and two of those studies also found that there was a variable effect on unwanted catch between individual fish species/groups. Four studies found no reduction in catches of unwanted small rockfish and flatfish, three of four commercially important bottom fish species, total unwanted catch (fish and invertebrates), or the total number of unwanted species (fish and invertebrates), compared to diamond mesh codends. One study found that square mesh codends retained more fish overall than diamond mesh but varied for individual species by fish shape and size. One study found that unwanted fish catch depended on codend mesh size as well as configuration (square or diamond). Two of the studies, where square mesh codends had no or a varied effect, also found that size selectivity increased with increases in mesh size for both square and diamond mesh codends. Improved size-selectivity of fishing gear (14 studies): Six of 14 replicated, controlled studies (including three paired, one randomized and one randomized and paired) in the Atlantic Ocean, Mediterranean Sea, Adriatic Sea, Aegean Sea, English Channel, Pacific Ocean, Tasman Sea and the Kattegat and Skagerrak, found that using a square mesh codend in a trawl net (bottom and pelagic) improved size selectivity for silver hake, horse mackerel, European hake, axillary seabream, poor cod, greater forkbeard, blue whiting, discarded fish and three of four commercially targeted fish, compared to diamond mesh codends. Five studies found no difference in size selectivity between square and diamond mesh codends for Atlantic mackerel, long rough dab, yellowtail scad and striped seapike, rockfish and flatfish, and three of four commercially important bottom fish species. The other three studies found that the effect of square mesh instead of diamond mesh codends varied with fish body shape (round or flat), and for three of three and five of five roundfish species size selectivity was improved, but not for one flatfish. Two of the studies, where square mesh codends had either no or a varied effect, also found that size selectivity increased with increases in mesh size for both square and diamond mesh codends. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2714https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F2714Fri, 01 Jan 2021 14:39:22 +0000
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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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