Reviewers: N/A
Editor: Jenny Volstorf

• Initial release: 2026-03-03
• Appearance version: 2026-03-03
• Major version: 2026-03-03

Cite as: »Volstorf, Jenny, and Vighnesh Samel. 2026. Set nets (Dossier). In: fair-fish database, ed. fair-fish international association. World Wide Web electronic publication. Version A | 1.0. CC BY 4.0. https://fair-fish-database.net/db/methods/catch/set-nets/dossier/«

• Catch in the global ocean (for gillnets): 2,790.7 t/year 2019 or 2.6% 1.

• Observations Merluccius merluccius: 28 mm mesh size: 0.017 g/m (0.017 kg/km), 30 mm mesh size: 0.25 g/m (0.25 kg/km), 32 mm mesh size: 0.015 g/m (0.015 kg/km) 2, 53 mm mesh size: 5.3 kg/1,300 m (~4 kg/km), 62.5 mm mesh size: 7.4 kg/1,300 m (5.6 kg/km), 80 mm mesh size: 7.7 kg/1,300 m (~5.9 kg/km), 70 mm mesh size: 8.2 kg/1,300 m (~6.3 kg/km) 3, 81 mm mesh size: 95.6 kg/10,000 m (~9.56 kg/km) 4, 90 mm mesh size: 8.9 ± 7.9 kg/750 m (~11.87 kg/km), 80 mm mesh size: 14.3 ± 8.2 kg/750 m (~19 kg/km), 70 mm mesh size: 24 ± 15.4 kg/750 m (~32 kg/km) 5, 28 mm, 30 mm, and 32 mm mesh size: 11.6 kg/600 m (~19.4 kg/km) 6, 40 mm mesh size: 0.27 kg/set, 60 mm mesh size: 1.15 kg/set, 70 mm mesh size: 1.7 kg/set, 80 mm mesh size: 1.22 kg/set, 90 mm mesh size: 0.65 kg/set 7.
• Observations Mullus surmuletus: B-type nets: 0.013 kg/km, S-type nets: 5.3 kg/km 8, 62.5 mm mesh size: 0.6 kg/1,300 m (~0.46 kg/km), 53 mm mesh size: 1.5 kg/1,300 m (~1.15 kg/km) 3, for 3 m net height: 87 mm mesh size: 0.17 kg/100 m (~1.70 kg/km), 75 mm mesh size: 0.69 kg/100 m (~6.9 kg/km), 53 mm mesh size: 1.3 kg/100 m (13 kg/km), 60 mm mesh size: 1.6 kg/100 m (16 kg/km), for 5 m net height: 87 mm mesh size: 0.12 kg/100 m (~1.2 kg/km), 75 mm mesh size: 0.55 kg/100 m (~5.5 kg/km), 60 mm mesh size: 1.07 kg/100 m (~10.7 kg/km), 53 mm mesh size: 1.1 kg/100 m (11 kg/km) 9, in mesh 40 mm out mesh 240 mm: 0.15 kg/trial, in mesh 40 mm with selvedge out mesh 240 mm: 0.17 kg/trial, in mesh 36 mm out mesh 240 mm: 0.2 kg/trial, in mesh 36 mm with selvedge out mesh 240 mm: 2.8 kg/trial 10, 36 mm: 0.65 kg/survey 11.

• Species covered in the fair-fish database:
  • Merluccius merluccius
  • Mullus surmuletus

• Catch at or near the bottom of the sea with variable soaking times:
  • Observations: Mullus surmuletus: 12 13 14 15.
  • Weighted leadline to set it near the bottom of the sea 16 5 17 7 18 19 3 6.
  • A float line with floats of variable materials and dimensions on the top to provide buoyancy so that the net remains open 16 5 17 7 18 19 3 6.
• Catch IND by different forms of entanglement (snagging, gilling, wedging, etc. →D1):
  • Observations: Merluccius merluccius: 5 18 19 3 6, Mullus surmuletus: 20 21 22 2314 24.
• Haul the net to the vessel:
  • Observations: Merluccius merluccius: 4 7 19 25 26 27 28 29, Mullus surmuletus: 20 21 22 23.
• Manually disentangle the IND from the net:
  • Observations: Merluccius merluccius: 25 26 27 28 29, Mullus surmuletus: 20 21 22 23 14 24.

• Gillnet dimensions (single wall of netting): 107-5,000 m length × 1.5-6.3 m height, trammel net dimensions (one net with smaller mesh sizes sandwiched between two outer nets): 183-5,000 m length × 0.8-1.7 m height:
  • Observations Merluccius merluccius: gillnets: 107 m length × 5.5 m height 19, 200 m length × 3.4 m height 6, 750 m length × 6.3 m height 5, 1,300 m length × 3.3 m height 18, 1,300 m length × 4 m height 3, 1,600 m length × 5 m height 16, 3,000 m length × ~5.4 m height 4, 5,000 m length × 3 m height 7.
  • Observations Mullus surmuletus: gillnets: ~183 m length × 2.4 m height 14 24, 300 m length × 1.8 m height 11, ~493-914 m length 12, 1,000 m length × 3-5 m height 9, 4,600-5,000 m length × 1.5-3 m height 30; trammel nets: ~183 m length × 0.8-1.7 m height 31, 500 m length 10, B-type nets: 823 m length × 1.6 m height, S-type nets: 919 m length × 1.6 m height 8, <2,000 m length per fisher or <5,000 m length per vessel 32.
• Mesh sizes for gillnets (single wall of netting): 17-150 mm; mesh sizes for trammel nets (one net with smaller mesh sizes sandwiched between two outer nets): inner mesh sizes: 22-50+ mm, outer mesh sizes: 120-240 mm:
  
  • Observations Merluccius merluccius: gillnets: 26 mm nylon monofilament, hanging ratio of 0.5 18, 53 mm, 62.5 mm, 70 mm, and 82 mm monofilament, hanging ratio of 0.5 3, 28 mm, 30 mm, and 32 mm 2, 40 mm, 60 mm, 70 mm, and 80 mm monofilament polyamide, hanging ratio of 0.5 7, 52-80 mm 33, 70 mm, 80 mm, 90 mm, 100 mm, hanging ratio of ~0.5 5, 81 mm 17, 80 mm, 100 mm, 120 mm, 140 mm monofilament nylon, hanging ratio of 0.6 19, 100-150 mm 16.
  • Observations Mullus surmuletus: gillnets: 17 mm, 19 mm, 21 mm, and 23 mm, hanging ratio of 0.6 12, 36 mm nylon 11, 53 mm, 60 mm, 75 mm, and 87 mm 9, 50-59 mm, 60-69 mm, and >90 mm 34, 60-100 mm 30, 108 mm 14 24; trammel nets: in mesh 22 mm or 28 mm, out mesh 140 mm 13, in mesh 26 mm, out mesh 120 mm 31, B-type nets: in mesh 32-72 mm, S-type nets: in mesh 27 mm 8, in mesh 36-40 mm, out mesh 240 mm 10, in mesh 40-52 mm 33, in mesh >50 mm 32.

• Observations Merluccius merluccius: 7-10.6 m long 30, 10 m long, 85 HP engine 18, 17.5 m long, 195 kW engine 19, ~20 m long 2 16, 27 m long stern trawler 7.
• Observations Mullus surmuletus: 4.8-12.6 m long, 13.5-230 HP engine 8, 6 m long, 9 HP engine 10, 6-12 m long 32, 8 m long, 43 HP engine 11, 9.5 m long, 68 HP engine 9, 12.7 m long, two engines of 74 HP each 12, 30.3-42 m long 35.

• Mullus surmuletus: fishers use fish finder devices to determine the depth 30, which helps determine the presence of IND 36.

• Mullus surmuletus: with shore netting (Oct-Apr), fishers deploy net in dropping tide in bay and trap IND when they want to leave the bay just at a foot of water 14 24.

• Mullus surmuletus: given that setting does not include active chasing or passive ways to direct IND (noise, light, FADs, etc.), hazard consequences during setting are unlikely 0.

• Observations: Merluccius merluccius: 24-250 m, mostly <100 m 7, 38-327 m 16, 50-70 m 2 6, 65-78 m 5, 68-405 m 18, 95-256 m 3, 150-300 m 5, 500-700 m 4, Mullus surmuletus: 2-68 m 37, 10-65 m 8, 12-70 m 9, 15-21 m 10, 16-86 m 30, 18-60 m 12, 20-80 m 13, 15-30 fathoms (~27.4-54.9 m) 31.

• Merluccius merluccius: catching depth and unknown speed of hauling in nets results in barotrauma 27 38 28 29 39. Further research needed on how to avoid this.
• Mullus surmuletus: given catching depth and unknown speed of hauling, barotrauma is possible 0.

• Observations Merluccius merluccius: soak time of 1.5-3 h (end of lowering to end of picking up: 4.9-6.3 h), sometimes >12 h (end of lowering to end of picking up: 15-16.3 h) 18, 3-24+ h, mean 13-18 h 7, 5 h 3, 7-12 h 4, 10 h 28, average 17.2-22.1 h 16, or 20-22 h 2 6.
• Observations Mullus surmuletus: soak time 60-75 min and hauling of 150 min 30, soaking ~1.5 h 11, soaking 2 h from just before dusk 10, average 172 min soaking from before dawn, average 42 min hauling at sunrise 8, soaking 3-5 h from before sunrise 9, soaking from 2 h prior to 2 h after sunset 12, soaking from sunset to sunrise 31, average 5.8-9.4 h 40.

• Merluccius merluccius: in gillnets in 500-700 m depth, condition of IND decreased with increasing soak time: from 77% IND in good condition after 7 h soak time to 35% in good condition after 12 h, probably due to scavenging crustaceans 4. Further research needed on types of hazard consequences.
• Mullus surmuletus: with bottom-set gillnets, after soak time of 60-75 min and hauling of 150 min, almost 50% IND arrived on board inactive, another ca 25% were lethargic with maximum duration of activity 4 min 30.
  During soaking, interactions with 1-12 bottlenose dolphins Tursiops truncatus 12/88 times (13.6%), during hauling 17/88 times (19.3%), spending average 20 min and reducing catch of M. surmuletus. Negative correlation between catch volume and duration of soaking time and interactions with dolphins 8.

• Snagging, gilling, wedging, or entangling – not avoidable:
  • Merluccius merluccius: given the principle of set nets to catch IND 25 26 27 28 29 by the head region (called "snagging") 5, by the gills (called "gilling") 5 19 3 6, by the mid body (called “wedging”) 5 3 6, or by wrapping the whole body or attaching protruding body parts like teeth (called “entangling”) 5 19 3, hazard consequences are probable 0. Further research needed on types of hazard consequences.
  • Mullus surmuletus: given the principle of set nets to catch IND 20 21 22 23 14 by the head region (called “snagging”) 41, by the gills (called "gilling") 14, by the mid body (called “wedging”) 41, or by wrapping the whole body or attaching protruding body parts like teeth (called “entangling”) 41, hazard consequences are probable 0. During catching, substantial scale loss (26-50% of body surface) in IND, indicating a high risk of external injuries 30.
    Catching SPAWNERS with gillnets and transportation caused skin damage resulting in mortality within 2-3 weeks; more IND dead without external injuries 42.
• Inappropriate mesh sizes resulting in catching undersized IND (or for Merluccius merluccius: large sexually productive females) – prefer mesh size that assures good size selectivity given body ∅ in season and region:
• Merluccius merluccius: the following mesh sizes assure good size selectivity, i.e., the listed sizes of IND will have contact with the gear:
  gillnets in 500-700 m depth after 7-12 h soak time: 81 mm mesh size (commercially used) caught IND of 30-65 cm TOTAL LENGTH and avoided catch of IND <27 cm minimum landing size, avoiding bycatch 4.
  Commercial gillnets in 150-300 m depth: decreasing number of IND and increasing catching length with increasing mesh size (69.5, 81, 88.5 mm), no difference between 88.5 mm commercial and 96.3 mm experimental mesh size. Decreasing number of males, increasing number of females with increasing length. Of 17-65 cm TOTAL LENGTH caught, increasing frequency of IND <27 cm minimal catch size with increasing mesh size (0.6-2.1%), but also lower number of IND <45.3 cm size at maturity 43↶5, prompting recommendation to increase minimum mesh size to 81 mm even though minimum mesh size cannot avoid entangling of small IND by teeth 5.
  Experimental gillnets in mostly <100 m depth: highest number and weight of IND at mesh size 60, 70, 80 mm with best combination at 70 mm; largest IND but lower number at 90 mm. Of 19-67 cm TOTAL LENGTH caught, 5% IND <27 cm (minimal landing size) at 60-80 mm mesh size 7. Corresponds with legally enforced mesh size ≥80 mm given maturity in females at 45.3 cm 43↶7.
  In experimental bottom-set gillnets after average 23.3 h soak time, tendency of increasing size of caught IND with increasing mesh size (80, 100, 120 mm) when caught by gills (majority of cases); no effect when caught by teeth. Lower catch rate at 140 mm mesh size. At 120 mm mesh size (commercial size), small frequency of IND <60 cm and majority of IND 70-85 cm, indicating good size selectivity of currently used mesh size 19.
  Experimental gillnets in 95-256 m depth: tendency of increasing weight and length and decreasing number of IND with increasing mesh size (53, 62.5, 70, 82 mm). Best combination and lowest risk for catching large sexually productive females at 62.5 mm – larger than the commercially used 53 mm mesh size 3.
  Bottom-set gillnets with 28, 30, 32 mm mesh size in 50-70 m depth after 22 h soak time: highest weight and number of IND caught and of 23.5-41.0 cm TOTAL LENGTH, tendency of lowest percentage (2.7%) of IND <25 cm minimal landing size 44↶2 at 30 mm mesh size (commercially used), indicating good size selectivity of currently used mesh size 2.
  With bottom gillnets in 50-70 m depth at soak time 20-22 h, no difference in catching size between mesh sizes 28, 30, 33 mm: 23.5-41 cm TOTAL LENGTH, indicating that commercial mesh size 30 mm assures exceeding minimal landing size 6 of 20 cm TOTAL LENGTH in Turkey 45↶6.
  The following mesh sizes potentially cause bycatch, i.e., they should be avoided to prevent those IND from having contact with the gear:
  70 mm commercial mesh size with highest number of IND caught, but also high number of IND <45.3 cm size at maturity 43↶5 and high discard and scavenging rate in gillnets in 150-300 m depth, prompting recommendation to cease using 70 mm mesh size commercially 5.
  Of 19-67 cm TOTAL LENGTH caught, IND <27 cm (minimal landing size) mainly at 40 mm mesh size in experimental gillnets in mostly <100 m depth, decreasing percentage with increasing mesh size 7.
  At 80 mm mesh size, IND <60 cm caught in experimental bottom-set gillnets after average 23.3 h soak time, increasing size of caught IND with increasing mesh size 19.
  No IND <20 cm minimal landing size and no males below size at maturity (19 cm TOTAL LENGTH 46↶3), but 32.5% immature females (<35.1 cm TOTAL LENGTH 46↶3) caught at 53 mm mesh size (commercially used). Higher number of larger (potentially very sexually productive) females than males at mesh sizes 70 and 82 mm mean potentially big risk to overexploitation of population in experimental gillnets in 95-256 m depth 3.
  Lowest number of IND and weight caught and tendency of highest percentage (4.4%) of IND <25 cm minimal landing size 44↶2 at 32 mm mesh size in bottom-set gillnets in 50-70 m depth after 22 h soak time 2.
  Assuming maturity in females at 21.5 cm, in males at 25.7-27.7 cm 47↶6 48↶6, females were caught above length at maturity, but males were caught below length at maturity in 4.5-8% at mesh sizes 28, 30, 32 mm with bottom gillnets in 50-70 m depth at soak time 20-22 h 6.
• Mullus surmuletus: the following mesh sizes assure good size selectivity, i.e., the listed sizes of IND will have contact with the gear:
  bottom-set gillnets at 18-60 m depth, after soaking from 2 h prior to 2 h after sunset: decreasing number of IND and increasing catching length with increasing mesh size (17, 19, 21, 23 mm). Of 10-21 cm FORK LENGTH caught, all IND were >10 cm FORK LENGTH minimal landing size 49↶12, indicating good size selectivity of currently used mesh sizes and better size selectivity than bottom trawls 12.
  Gillnets at 20 m isobath with mesh size 36 mm, after soaking for 1.5 h, caught IND of 9.4-23.1 cm TOTAL LENGTH, mostly above minimum conservation reference size (11 cm 50↶11) and partly below 50% size at maturity (15.5 cm 50↶11) 11. Recommended mesh size for Mediterranean (38.5 mm 50↶11) might eliminate these issues 0.
  Gillnets at 12-70 m, after soaking 3-5 h from before sunrise: decreasing number of IND with increasing mesh size (53, 60, 75, 87 mm); highest weight at 60 mm. Of 18-39 cm TOTAL LENGTH caught, all IND were >15 cm minimal landing size, prompting recommendation to increase allowed mesh size from 50 to 60 mm. No difference in number of IND and weight with 5 m high net instead which is not allowed and cannot be recommended 9.
  Trammel nets at 15-21 m depth with 36-40 mm in mesh and 240 mm out mesh, after soaking for 2 h caught IND of 14.1-21.7 cm TOTAL LENGTH, all >11 cm minimal landing size 10.
  Trammel nets with 40-52 mm mesh size caught IND of 11-27 cm TOTAL LENGTH, mostly above size at maturity (15-16 cm 51↶33) and with better size selectivity than bottom trawls (5-23 cm TOTAL LENGTH) 33.
  The following mesh sizes potentially cause bycatch, i.e., they should be avoided to prevent those IND from having contact with the gear:
  With bottom-set gillnets, mesh size 50-90+ mm, during 2009-2015: <5% bycatch of IND >40 g (ca 18 cm TOTAL LENGTH) minimal commercial landing weight, for trammel nets >15%, probably indicating a risk for overexploitation of the population 34.
  Trammel nets with minimum mesh size 50 mm, during 2000-2012 caught IND of 9-29 cm TOTAL LENGTH, partly <14 cm size at 50% first maturity, probably indicating a risk for overexploitation of the population 32.

• Merluccius merluccius: no crowding step before hauling the net on board, but IND remained caught and with the same distance to other con-specifics under and above water when net was continuously hauled 25 26 27 28 29, probably not resulting in decreasing distance to neighbour 0.
• Mullus surmuletus: no crowding step before hauling the net on board, but IND remained caught and with the same distance to other con-specifics under and above water when net was continuously hauled 20 21 22 23 or when IND were collected lying on the shore 14 24, probably not resulting in decreasing distance to neighbour 0.

• Merluccius merluccius: in ca 25 m depth, low salinity (ca 18 ppt) water from Black Sea meets high salinity (ca 38 ppt) water from Mediterranean 6.

• Merluccius merluccius: by fishing depth of 50-70 m 6, IND are hauled from low salinity to high salinity layer, and hazard consequences are probable 0. Further research needed on the rate M. merluccius adapts to osmotic changes without decreasing welfare and on reports of osmoregulatory distress after gillnetting.

• Merluccius merluccius: probably scavenging crustaceans during soaking 4.
  Depredation rate by Tursiops truncatus 25%/haul 40.
• Mullus surmuletus: probably scavenging crustaceans 14 or depradation by cetaceans 11 during soaking.
  Depredation rate by Tursiops truncatus ~21-25%/haul 40.
  Interactions with Tursiops truncatus reduced catch of M. surmuletus 8. Bite injuries 8, probably by cuttlefishes Sepia spp., common octopus Octopus vulgaris, European conger Conger conger, Mediterranean moray Murena helena 53↶8.

• Merluccius merluccius: during soaking, depredation rate by Tursiops truncatus 25%/haul 40. Given that scavenged IND are discarded after manual disentangling 26, scavenging should be avoided or at least decreased 0.
  In gillnets in 500-700 m depth, condition of IND decreased with increasing soak time: from 77% IND in good condition after 7 h soak time to 35% in good condition after 12 h, probably due to scavenging crustaceans 4. Further research needed on types of hazard consequences.
• Mullus surmuletus: during soaking, IND may be damaged 21 11, probably by scavenging crustaceans 14 or predating cetaceans 11. Depredation rate by Tursiops truncatus ~21-25%/haul 40. Given that scavenged IND are most likely discarded after manual disentangling, scavenging should be avoided or at least decreased 0.
  During soaking, interactions with 1-12 bottlenose dolphins Tursiops truncatus 12/88 times (13.6%), during hauling 17/88 times (19.3%), spending average 20 min and reducing catch of M. surmuletus. Negative correlation between catch volume and duration of soak time and interactions with dolphins 8 indicates probable reduction of lost catch through lower soak time 0. Of those IND still caught in the net when hauled on board, without interaction with dolphins, mainly bite injuries 8, probably by cuttlefishes Sepia spp, common octopus Octopus vulgaris, European conger Conger conger, Mediterranean moray Murena helena 53↶8; with interaction with dolphins, roughly equal amount of bite injuries, only head remaining, only tail remaining, and fragments remaining 8. As dolphins are probably lured by sounds that the gear make, recommended to amend or switch up gear; dolphins could also hear if vessels leave for the sea at night, so recommended to close fishing for certain times or areas or switch up areas 8 or apply "stealth fishing" 54↶8.
  Using dolphin deterrent devices reduced depradation by T. truncatus by 48%, using dolphin interactive devices reduced depradation by 50%, but their efficiency gradually reduces over time 55.

• Merluccius merluccius: the net is hauled on board 25 26 27 28 29.
• Mullus surmuletus: the net is hauled on board 20 21 22 23 or the IND are collected lying on the shore 14 24.

• Emerge snagged, gilled, wedged, or entangled:
  • Merluccius merluccius: given the principle of set nets to catch IND 25 26 27 28 29 by the head region (called "snagging") 5, by the gills (called "gilling") 5 19 3 6, by the mid body (called “wedging”) 5 3 6, or by wrapping the whole body or attaching protruding body parts like teeth (called “entangling”) 5 19 3, hazard consequences are probable 0. Further research needed on types of hazard consequences.
  • Mullus surmuletus: given the principle of set nets to catch IND 20 21 22 23 14 by the head region (called “snagging”) 41, by the gills (called "gilling") 14, by the mid body (called “wedging”) 41, or by wrapping the whole body or attaching protruding body parts like teeth (called “entangling”) 41, hazard consequences are probable 0. During catching, substantial scale loss (26-50% of body surface) in IND, indicating a high risk of external injuries 30.
    Catching SPAWNERS with gillnets and transportation caused skin damage resulting in mortality within 2-3 weeks; more IND dead without external injuries 42.
• Gear contact during emersion – further research needed on mitigation measures:
  • Merluccius merluccius: when the net is hauled on board, IND may be catapulted on deck, and given how the effect of gravity interacts with the type of catching (snagging, gilling, wedging, entangling) and therefore how the net affects the skin and given contact with several reels along which the net is guided 25 26 27 28 29, hazard consequences are probable 0. Further research needed on types of hazard consequences and on how to avoid or decrease them.
  • Mullus surmuletus: when the net is hauled onboard, IND may be catapulted on deck, and given how the effect of gravity interacts with the type of catching (snagging, gilling, wedging, entangling) and therefore how the net affects the skin and given contact with several reels along which the net is guided 20 21 22 23 and assuming IND are not already dead, hazard consequences are probable 0. Further research needed on types of hazard consequences and on how to avoid or decrease them.
    Catching SPAWNERS with gillnets and transportation caused skin damage resulting in mortality within 2-3 weeks; more IND dead without external injuries 42.

• Merluccius merluccius: no crowding step before hauling the net on board, but IND remained caught and with the same distance to other con-specifics under and above water when net was continuously hauled 25 26 27 28 29, probably not resulting in decreasing distance to neighbour 0.
• Mullus surmuletus: no crowding step before hauling the net on board, but IND remained caught and with the same distance to other con-specifics under and above water when net was continuously hauled 20 21 22 23 or when IND were collected lying on the shore 14 24, probably not resulting in decreasing distance to neighbour 0.

• Merluccius merluccius: predation pressure during emersion is probably low 0.
• Mullus surmuletus: predation pressure during emersion is probably low 0.

• Merluccius merluccius: given short distance between water surface and aboard vessel and thus hardly any occasion 25 26 27 28 29, predation pressure during emersion is probably low 0. More time and more convenient occasion during soak time or hauling → D2.
• Mullus surmuletus: given short distance between water surface and aboard vessel and thus hardly any occasion 20 22 23, predation pressure during emersion is probably low 0. More time and more convenient occasion during soak time or hauling → D2.

• Air exposure:
  • Merluccius merluccius: IND are exposed to air when the net is hauled on board 25 26 27 28 29.
  • Mullus surmuletus: IND are exposed to air when the net is hauled on board 20 21 22 23 or when they are collected lying on the shore 14 24.
• Gravity exposure:
  • Merluccius merluccius: IND are exposed to gravity when hauled on board 25 26 27 28 29.
  • Mullus surmuletus: IND are exposed to gravity when the net is hauled on board 20 21 22 23 or when they are collected lying on the shore 14 24.

• Air exposure – further research needed on mitigation measures:
  • Merluccius merluccius: given that when the net is hauled on board, IND are exposed to air 25 26 27 28 29, hazard consequences are probable 0. Further research needed on types of hazard consequences and on how to avoid or decrease them.
  • Mullus surmuletus: given that when the net is hauled on board 20 21 22 23 or the IND are collected lying on the shore 14 24, IND are exposed to air and assuming IND are not already dead, hazard consequences are probable 0. Further research needed on types of hazard consequences and on how to avoid them.
• Gravity exposure/experience own weight – further research needed on mitigation measures:
  • Merluccius merluccius: given that when the net is hauled on board 25 26 27 28 29, IND are exposed to gravity and given no evolutionary adaptation to experiencing own weight in air 56, hazard consequences following emersion are probable 0. Further research needed on types of hazard consequences and on how to avoid or decrease them.
  • Mullus surmuletus: given that when the net is hauled on board 20 21 22 23 or the IND are collected lying on the shore 14 24, IND are exposed to gravity and given no evolutionary adaptation to experiencing own weight in air 56, hazard consequences are probable 0. Further research needed on types of hazard consequences and on how to avoid or decrease them.

• Merluccius merluccius: manual disentangling 25 26 27 28 29.
• Mullus surmuletus: manual disentangling 20 21 22 30 23 14 24.

• Rough handling – further research needed on mitigation measures; to prevent handling for undersized IND, prefer mesh size that avoids catching undersized IND given body ∅ in season and region (→ D1):
  • Merluccius merluccius: given that manual disentangling happens fast and rough 25 26 27 28 29, hazard consequences are probable 0. Further research needed on types of hazard consequences and on how to avoid or decrease them.
    Given that undersized IND are discarded after manual disentangling 25 27 29, hazard consequences are probable 0. Further research needed on types of hazard consequences.
  • Mullus surmuletus: given that manual disentangling happens fast and rough 20 21 22 23 30 and assuming IND are not already dead, hazard consequences are probable 30 0. Further research needed on types of hazard consequences and on how to avoid or decrease them.
    Given that undersized IND are discarded after manual disentangling 23 and assuming IND are not already dead, hazard consequences are probable 0. Further research needed on types of hazard consequences.
• Dropping – further research needed on mitigation measures:
  • Merluccius merluccius: given that during manual disentangling, IND may fall to the floor 29 and that after disentangling, IND are thrown into trays 25 27 29, hazard consequences are probable 0. Further research needed on types of hazard consequences and on how to avoid or decrease them.
  • Mullus surmuletus: given that during manual disentangling, IND may fall to the floor 20 22 23 and that after disentangling, IND are thrown into buckets 20 21 22 30 14 24 and assuming IND are not already dead, hazard consequences are probable 30 0. Further research needed on types of hazard consequences and on how to avoid or decrease them.
• Air exposure – further research needed on mitigation measures:
  • Merluccius merluccius: given that during manual disentangling, IND are exposed to air 25 26 27 28 29, hazard consequences are probable 0. Further research needed on types of hazard consequences and on how to avoid or decrease them.
  • Mullus surmuletus: given that during manual disentangling, IND are exposed to air 20 21 22 23 30 14 24 and assuming IND are not already dead, hazard consequences are probable 30 0. Further research needed on types of hazard consequences and on how to avoid or decrease them.

• Merluccius merluccius: manual sorting 25 26 27 29.
• Mullus surmuletus: manual sorting 23.

• Rough handling – further research needed on mitigation measures; to prevent handling for undersized IND, prefer mesh size that avoids catching undersized IND given body ∅ in season and region (→ D1):
  • Merluccius merluccius: given that manual disentangling happens fast and rough 25 26 27 28 29, hazard consequences are probable 0. Further research needed on types of hazard consequences and on how to avoid or decrease them.
    Given that undersized IND are discarded after manual disentangling 25 27 29, hazard consequences are probable 0. Further research needed on types of hazard consequences.
  • Mullus surmuletus: given that manual disentangling happens fast and rough 20 21 22 23 30 and assuming IND are not already dead, hazard consequences are probable 30 0. Further research needed on types of hazard consequences and on how to avoid or decrease them.
    Given that undersized IND are discarded after manual disentangling 23 and assuming IND are not already dead, hazard consequences are probable 0. Further research needed on types of hazard consequences.
• Dropping – further research needed on mitigation measures:
  • Merluccius merluccius: given that during manual disentangling, IND may fall to the floor 29 and that after disentangling, IND are thrown into trays 25 27 29, hazard consequences are probable 0. Further research needed on types of hazard consequences and on how to avoid or decrease them.
  • Mullus surmuletus: given that during manual disentangling, IND may fall to the floor 20 22 23 and that after disentangling, IND are thrown into buckets 20 21 22 30 14 24 and assuming IND are not already dead, hazard consequences are probable 30 0. Further research needed on types of hazard consequences and on how to avoid or decrease them.
• Air exposure – further research needed on mitigation measures:
  • Merluccius merluccius: given that during manual disentangling, IND are exposed to air 25 26 27 28 29, hazard consequences are probable 0. Further research needed on types of hazard consequences and on how to avoid or decrease them.
  • Mullus surmuletus: given that during manual disentangling, IND are exposed to air 20 21 22 23 30 14 24 and assuming IND are not already dead, hazard consequences are probable 30 0. Further research needed on types of hazard consequences and on how to avoid or decrease them.

• Live storage (further research needed):
  • Mullus surmuletus: IND were thrown into buckets 20 21 22 30 14 24 with water 22, later placed on and under ice 14 24.
• Storage after death (further research needed):
  • Merluccius merluccius: IND were immediately gutted alive and placed in cleaning bath after disentangling and sorting, then transferred to storing containers initially without ice 25 26 27, eventually with ice 28.

• Merluccius merluccius: IND were immediately gutted alive and placed in cleaning bath after disentangling and sorting 25 26 27. Given that in busy times with a full net, gutting might take place only after a waiting time in a holding container, hazard consequences are probable 0. Further research needed on types of hazard consequences and on how to avoid or decrease them.
• Mullus surmuletus: given that IND were thrown into buckets 20 21 22 30 14 24 with water 22, later placed on and under ice 14 24, and assuming IND are not already dead, hazard consequences are probable 0. Further research needed on types of hazard consequences and on how to avoid or decrease them.

• Merluccius merluccius: IND were immediately gutted alive and placed in cleaning bath after disentangling and sorting 25 26 27. Given that in busy times with a full net, gutting might take place only after a waiting time in a holding container, hazard consequences are probable 0. Further research needed on types of hazard consequences and on how to avoid or decrease them.
  The IND were then transferred to storing containers initially without ice 25 26 27, eventually with ice 28. Given that IND are already dead when stored in containers, hazard consequences are improbable 0.
• Mullus surmuletus: given that IND were thrown into buckets 20 21 22 30 14 24 with water 22, later placed on and under ice 14 24, and assuming IND are not already dead, hazard consequences are probable 0. Further research needed on types of hazard consequences and on how to avoid or decrease them.

• Merluccius merluccius: given that IND were immediately gutted alive after disentangling and sorting without prior stunning 25 26 27, hazard consequences are probable 0. Further research needed on types of hazard consequences and on quick and painless stunning methods.
• Mullus surmuletus: given that IND were thrown into buckets 20 21 22 30 14 24 with water 22, later placed on and under ice 14 24, probably resulting in asphyxia 30 0 or hypothermia 0. Recommended to percussively stun with a fishing priest or captive bolt pistol, followed by cutting gill, immersing in ice water, or storing on ice 57.

• Merluccius merluccius: IND were immediately gutted alive after disentangling and sorting without prior stunning 25 26 27 and placed in ice 28, which prevents live storage and prolonged suffering. Given that stunning is lacking, hazard consequences are probable 0. Further research needed on types of hazard consequences and on quick and painless stunning methods.
• Mullus surmuletus: given that IND were thrown into buckets 20 21 22 30 14 24 with water 22, later placed on and under ice 14 24, probably resulting in asphyxia 30 0 or hypothermia 0. Recommended to percussively stun with a fishing priest or captive bolt pistol, followed by cutting gill, immersing in ice water, or storing on ice 57.

• Merluccius merluccius: gillnets in 500-700 m depth: 42% biomass of caught IND were discarded due to being partially or completely deteriorated by scavenging crustaceans. Condition decreased with increasing soak time: from 77% IND in good condition after 7 h soak time to 35% in good condition after 12 h 4.
  Higher discard rate from gillnetting than longline (42% versus 7% biomass) in 500-700 m depth, together with lower catch and yield and lower quality, led to ban of gillnets in favour of longlines 4.
• Mullus surmuletus: discarding probability is assumed to be low due to high commercial value of M. surmuletus 58↶59 60↶59.
  Gillnets at 12-70 m, after soaking 3-5 h from before sunrise: at commercial mesh size 53 mm, 1.4% discarded due to damage 9.

• Merluccius merluccius: given the principle of set nets to be passive gear floating or standing in habitat that other species use or traverse, there is a risk to also catch co-existing, preyed-on, and predating species 0.
  • Usable bycatch: bottom gillnets in northern Atlantic off south-west of England and Ireland in 38-327 m depth with 100-150 mm, mostly 120 mm mesh sizes, caught Pollachius pollachius, Pollachius virens, Molva molva, Gadus morhua besides target M. merluccius 16.
    Gillnets off the southern Portuguese coast (the Algarve) in 500-700 m depth with 81 mm mesh size (commercially used): 14% of biomass commercially valuable of which very commonly Micromesistius poutassou, commonly Galeus melastomus, uncommonly Brama brama, Phycis blennoides, Ruvettus pretiosus, Scyliorhinus canicula, rarely Auxis rochei, Beryx decadactylus, Helicolenus dactylopterus, Lepidopus caudatus, Lophius piscatorius, Raja clavata, Nephrops norvegicus 4.
    Multispecies fisheries off western Portuguese coast, experimental gillnets in mostly <100 m depth: commercial species Pagellus acarne, Mullus surmuletus, Trisopterus luscus, Trachurus trachurus, almost no bycatch at 90 mm 7.
    In experimental gillnets in northern Tyrrhenian sea in 95-256 m depth with mesh sizes 53, 62.5, 70, 82 mm: decreasing biomass of Trachurus trachurus (72.5% → 36.1%), increasing biomass of Chelidonichthys lucerna (2.4-9.8%), small biomass of 16-20 other species 3.
    Bottom-set gillnets in south-eastern Sea of Marmara in 50-70 m depth with mesh size 28, 30, 32 mm contained commercial species Solea solea (39.4%) 2.
  • Non-usable bycatch: bottom gillnets in northern Atlantic off south-west of England and Ireland in 38-327 m depth with 100-150 mm, mostly 120 mm mesh sizes, caught Phocoena phocoena (0.4-0.7 IND/trip or 15 IND/1,000 km net set), which were already dead or dying, detangled themselves or got detangled, and Delphinus delphis. Per year, estimated 2,200 Phocoena phocoena in vessels ≥15 m or 6.2% of porpoise population in Celtic sea 16 exceeds proposed 1% rate 61↶16.
    Gillnets off the southern Portuguese coast (the Algarve) in 500-700 m depth and 81 mm mesh size (commercially used): 1% of biomass non-commercial species of which commonly Todaropsis eblanae, rarely Benthodesmus elongatus, Centrolophus niger, Chimaera monstrosa, Dalatias licha, Etmopterus pusillus, Etmopterus spinax, Hoplostethus mediterraneus, Hymenocephalus italicus, Naucrates ductor, Illex coindetii 4.
    Multispecies fisheries off western Portuguese coast, experimental gillnets in mostly <100 m depth: at mesh size 40 mm mainly (84%) low (Dicologlossa cuneata, Scyliorhinus canicula) or non-commercial species (Citharus linguatula) 7.
    Bottom-set gillnets in south-eastern Sea of Marmara in 50-70 m depth with mesh size 28, 30, 32 mm contained non-commercial species Raja clavata (0.1%), Buglossidium luteum (0.1%) which were discarded and Trachurus mediterraneus (8.2%), Chelidonichthys lucerna (2.5%), Lophius piscatorius (0.2%) which fed the crew 2.
    Some bycatch (mackerel) fed the crew 26, large bycatch was disentangled and discarded 27 29.
• Mullus surmuletus: given the principle of set nets to be passive gear floating or standing in habitat that other species use or traverse, there is a risk to also catch co-existing, preyed-on, and predating species 0.
  • Usable bycatch: with gillnets of 300 m length × 1.8 m height, 36 mm mesh size, in northern Aegean Sea, Greece: 20.7% biomass catch of (mostly) JUVENILES of Pagellus acarne, Diplodus annularis, and Pagellus erythrinus threatened these species' populations 11.
    With gillnets of 1,000 m length × 3 m height and commercial mesh size 53 mm, in Asturias, northwest Spain: M. surmuletus caught together with other species of high economic value representing 33.5% IND of catch (mostly Merluccius merluccius, some Serranus cabrilla, Pagellus acarne, rarely Trisopterus luscus, Pagellus erythrinus, Sepia officinalis, Pagellus bogaraveo, Belone belone, Octopus vulgaris, Trachurus trachurus, Auxis rochei, Chelidonichthys lucerna, Coris julis, Oblada melanura, Pollachius pollachius, Sarda sarda, Scorpaena porcus, Symphodus melops, Zeus faber), another 53.3% IND for use as bait (Trachurus trachurus, Boops boops) 9.
    With gillnets, in Northern Atlantic, at 68 mm mesh size: pollocks, streaked gurnards, cuckoo wrasses, lesser spotted dogfishes 22 23, scads, poutings, lings, one octopus, horse mackerels 22, one sea cucumber 23.
    With shore netting, in Northern Atlantic, at 108 mm mesh size: bycatch of bass, Gilthead seabream (Sparus aurata), mullet 14 24, jellyfish 14.
    With trammel nets of 500 m length and mesh sizes in 36-40 mm, out 240 mm, in Izmir Bay, Aegean Sea, Turkey: bycatch of commercial species (mostly Diplodus annularis, some Boops boops, Spicara flexuosa, Diplodus vulgaris, Pagellus erythrinus, rarely Sepia officinalis, Octopus vulgaris, Trachurus trachurus, Trigla lucerna, Pagellus acarne) 10.
  • Non-usable bycatch: with gillnets with 60-75 mm mesh size, off the southern Portuguese coast (the Algarve): ~0.9% bycatch of Tursiops truncatus 40.
    With gillnets of 1,000 m length × 3 m height and commercial mesh size 53 mm, in Asturias, northwest Spain: 13.2% IND discarded due to commercial species being damaged (36.3% IND) or being undersized (21.1% IND) or of too little numbers (12.7% IND) or exceeding total allowable catch (4.6% IND) or due to non-commercial species (25.3% IND) (mostly Polybius henslowi, Sardina pilchardus, Boops boops, Trachurus trachurus, some Trachinus draco, Chelidonichthys cululus, Scorpaena scrofa, Trisopterus luscus, rarely Scomber colias, Scorpaena notata, Callionymus lyra, Serranus cabrilla, Chelidonichthys obscurus, Scomber scombrus, Arnoglossus imperialis, Pagellus acarne, Trisopterus minutus, Chelidonichthys gurnadus, Corystes cassivelaunus, Diplodus vulgaris, Echinaster sepositus, Engraulis encrasicolus, Holothuria forskali, Labrus bergylta, Labrus mixtus, Octopus vulgaris, Pagellus bogaraveo, Sarda sarda, Scyliorhynus canicula, Symphodus bailloni) 9.
    With trammel nets of 500 m length and mesh sizes in 36-40 mm, out 240 mm, in Izmir Bay, Aegean Sea, Turkey: 77.4-81.4% IND discarded (Anomura spp., Maja squinado, Hexaplex trunculus, Serranus scriba, Symphodus tinca, Arnoglossus materna, Coris julis, Bolinus brandaris, Aporrhais pespelecani, Serranus cabrilla, Eledone moschata, Sardina pilchardus, Symphodus ocellanus, Serranus hepatus, Blennius ocellaris, Gobius niger, Chromis chromis) 10.
  • General bycatch: with bottom-set trammel nets of 500-2,000 m length × 1.6 m height, 27 mm mesh size, off Sardinia: the following other non-target species caught of which unclear whether they are used (commercially or at sea) or discarded: mostly Diplodus vulgaris, Scorpaena porcus, Diplodus annularis, Scorpaena scrofa, Serranus cabrilla, Pagellus erythrinus, Sepia officinalis, some Symphodus tinca, Phycis phycis, Sciena umbra, Spodyliosoma cantharus, Spicara maena, Sepia orbignyana, Symphodus roissali, Dentex dentex, rarely Octopus vulgaris, Labrus merula, Diplodus puntazzo, Trigloporus lastoviza, Uranoscopus scaber, Zeus faber, Boops boops, Labrus viridis, Sarpa salpa, Palinurus elephas, Diplodus sargus, Scyliorhinus canicula, Trachinus draco, Trisopterus minutus capelanus, Loligo vulgaris, Pagellus acarne, Conger conger, Symphodus mediterraneus, Dasyatis pastinaca, Labrus micaculatus, Sepia elegans, Sphyraena sphyraena, Seriola dumerili, Trachinus radiatus, Trachinus araneus, Scomberesox saurus, Raja clavata, Raja brachyura, Maja squinado 8.

• Probable hazards as a combined effect of depth and hauling speed → D3.
• Long soak time → D4.
• Snagging, gilling, wedging, or entangling → D1.
• Inappropriate mesh sizes resulting in catching undersized IND (or for Merluccius merluccius: large sexually productive females) → D1.
• Abrupt salinity change possible → D5.
• Probably scavengers and predators during soaking → D6.
• Gear contact during emersion → D7.
• Exposure to air and gravity → D8.
• Rough handling, dropping, air exposure → D9.
• Displacement:
  • Merluccius merluccius: given that surviving discarded IND will have to return to their natural living depth, vertical displacement is probable 56. Further research needed on types of hazard consequences.
  • Mullus surmuletus: given that surviving discarded IND will have to return to their natural living depth, vertical displacement is probable 56. Further research needed on types of hazard consequences.
• Predation pressure:
  • Merluccius merluccius: given that surviving discarded IND are probably disoriented, stressed, and weakened after the catching process and release, and given that seabirds and other predators might gather near fishing boats, predation pressure is probable 56. Further research needed on how to avoid or decrease this.
  • Mullus surmuletus: given that surviving discarded IND are probably disoriented, stressed, and weakened after the catching process and release 56, and given that seabirds 20 21 23 and other predators might gather near fishing boats, predation pressure is probable 56. Predation on several FISHES 62, including M. surmuletus 63, by seabirds like Morus bassanus and by Larus spp. 62. Further research needed on types of hazard consequences.

• risk of overexploitation:
  • Mullus surmuletus: usable bycatch: given that in northern Aegean Sea, Greece, fishing season (spring-autumn) fell in reproductive season for these species, risk for overexploitation of the population due to extraction of SPAWNERS of Diplodus annularis, Mullus barbatus, Sphyraena sphyraena, and Trachurus trachurus is probable 11.
    With gillnets of 1,000 m length × 3 m height and commercial mesh size 53 mm, in Asturias, northwest Spain: M. surmuletus caught together with other species of high economic value representing 33.5% IND of catch, another 53.3% IND for use as bait (Trachurus trachurus, Boops boops). Higher number of IND and weight of catch used for bait with 5 m high net instead which is not allowed and cannot be recommended 9.
  • Mullus surmuletus: non-usable bycatch: with gillnets of 1,000 m length × 3 m height and commercial mesh size 53 mm, in Asturias, northwest Spain: 13.2% IND discarded due to commercial species being damaged (36.3% IND) or being undersized (21.1% IND) or of too little numbers (12.7% IND) or exceeding total allowable catch (4.6% IND) or due to non-commercial species (25.3% IND). Higher number of IND damaged and higher number of non-commercial species with 5 m high net instead which is not allowed and cannot be recommended 9.
    Highest discards in May-Oct, probably due to more FISHES inhabiting seagrass 10.
• injuries/mortality:
  • Merluccius merluccius: non-usable bycatch: some bycatch (mackerel) fed the crew 26, large bycatch was disentangled and discarded 27 29, sometimes after being heavily tossed to the floor 26 (probable makeshift stunning 0) or half-eaten by predator 26 which makes survival improbable 0.
  • Mullus surmuletus: non-usable bycatch: FISHES used as bait (Trachurus trachurus, Boops boops) are not treated carefully during disentangling due to their low appreciation 9.

• Probably scavengers and predators during soaking – from Mullus surmuletus: close fishing for certain times or areas or switch up areas → D6.
• High discard rate – from Mullus surmuletus: potentially prefer longlines over gillnets (further research needed):
  • Merluccius merluccius: higher discard rate from gillnetting than longline (42% versus 7% biomass) in 500-700 m depth, together with lower catch and yield and lower quality, led to ban of gillnets in favour of longlines 4.
• Risk of overexploitation – from Mullus surmuletus: prefer set nets over bottom trawl and possibly gillnets over trammel nets:
  • Mullus surmuletus: with bottom-set gillnets, mesh size 50-90+ mm, off France, during 2009-2015: <5% bycatch of IND >40 g (ca 18 cm TOTAL LENGTH) minimal commercial landing weight; for trammel nets >15%, probably indicating a risk for overexploitation of the population 34
    In Mediterranean, bottom trawl was more detrimental for population of M. surmuletus than gillnets 12 or trammel nets 33 due to worse size selectivity 12 including JUVENILES 33.
• Risk of overexploitation – total allowable catch, regulate fishing days per year, closure areas or seasons, from Merluccius merluccius: regulate net length, from Mullus surmuletus: limit fishing depth (<50 m):
  • Merluccius merluccius: total allowable catch, closure of areas to prevent catch of JUVENILES because minimum mesh size cannot avoid entangling of small IND by teeth 5.
    Fishing season off the southern Portuguese coast (the Algarve): first semester 5, in Sea of Marmara: April-May 2, March-May 6. To avoid overexploitation, recommended to regulate length of nets, fishing days per year, close areas or seasons, especially during catching season winter-spring which corresponds with reproductive period in northern Tyrrhenian sea 3.
    In simulation of management strategies for Mediterranean coast off Spain, only 83% reduction in fishing days for multispecies and multigear fisheries (set nets, longline, bottom trawl) during 5 years of simulation achieved maximum sustainable yield, which the authors consider an unrealistic decrease in fishery activity throughout the year 64.
  • Mullus surmuletus: in another DEMERSAL species caught with set nets in the Northern Atlantic and Mediterranean, Merluccius merluccius, total allowable catch is recommended and closure of areas to prevent catch of JUVENILES because minimum mesh size cannot avoid entangling of small IND by teeth 5 which M. surmuletus loses in the upper jaw only from >9 cm TOTAL LENGTH on 65. Further research needed to determine whether this applies to M. surmuletus as well.
    Fishing season: Mar-Aug 33, spring-autumn 11, May-July up to year round 37, July-Dec 32, Sep-Dec 8, Oct-Apr 14 24, year round 10 34 31. In M. merluccius, to avoid overexploitation, recommended to regulate fishing days per year, close areas or seasons, especially during the spawning season 3. Further research needed to determine whether this applies to M. surmuletus as well.
    Trammel nets off Egypt, Mediterranean, caught IND of 9.1-30 cm TOTAL LENGTH which is partly <15.4 cm age at maturity and thus a risk for overexploitation, since the JUVENILES cannot reproduce before being caught. Possible mitigation measures need to be researched: larger mesh size, closure of fishing areas 66.
    Management regulations for trammel nets, off Mallorca: limitation to 6 fishing days per week, forbidden to catch >50 m depth 32

• Risk of overexploitation – from Mullus surmuletus: adjust minimum conservation reference size, encourage consumption of non-commercial species, landing obligation:
  • Mullus surmuletus: usable bycatch: recommended to specify lengths at maturity and adjust minimum conservation reference size 11.
    Encouraging consumption of species (so far) used as bait and implementing a landing obligation could reduce the amount of bycatch 9.
• Injuries/mortality – encourage consumption of non-commercial species:
  • Mullus surmuletus: non-usable bycatch: implementing a landing obligation and encouraging consumption of (so far) non-commercial species could reduce the amount of discards – also because FISHES used as bait (Trachurus trachurus, Boops boops) are not treated carefully during disentangling due to their low appreciation 9.

• Probable hazards as a combined effect of depth and hauling speed – further research needed on mitigation measures → D3
• Long soak time – prefer shorter soak time (further research needed), from Merluccius merluccius: prefer 7 h soak time over 12 h → D4.
• Snagging, gilling, wedging, or entangling – not avoidable → D1.
• Inappropriate mesh sizes resulting in catching undersized IND (or for Merluccius merluccius: large sexually productive females) – prefer mesh size that assures good size selectivity given body ∅ in season and region → D1.
• Abrupt salinity change possible – further research needed on mitigation measures → D5.
• Probably scavengers and predators during soaking – prefer shorter soak time, from Merluccius merluccius: prefer 7 h soak time over 12 h (further research needed), from Mullus surmuletus: amend or switch gear to avoid recognisable sounds, apply "stealth fishing", attach dolphin deterrent devices or, favourably, dolphin interactive devices to the gear → D6.
• Gear contact during emersion – further research needed on mitigation measures → D7.
• Exposure to air and gravity – further research needed on mitigation measures → D8.
• Rough handling, dropping, air exposure – further research needed on mitigation measures → D9.
  • Displacement – further research needed on mitigation measures:
    Merluccius merluccius: given that surviving discarded IND will have to return to their natural living depth, vertical displacement is probable 56. Further research needed on types of hazard consequences and on how to avoid or decrease them.
• Predation pressure – from Mullus surmuletus: use visual scarybird device as deterrent against predatory seabirds:
  • Merluccius merluccius: given that surviving discarded IND are probably disoriented, stressed, and weakened after the catching process and release, and given that seabirds and other predators might gather near fishing boats, predation pressure is probable 56. Further research needed on how to avoid or decrease this.
  • Mullus surmuletus: given that surviving discarded IND are probably disoriented, stressed, and weakened after the catching process and release 56, and given that seabirds 20 21 23 and other predators might gather near fishing boats, predation pressure is probable 56. Predation on several FISHES 62, including M. surmuletus 63, by seabirds like Morus bassanus – which was reduced through use of a visual deterrent in the form of a bird of prey ("scarybird") – and by Larus spp. – which was reduced through retaining to-be-discarded IND in buckets until after hauling the net 62. Given the use of small buckets resulting in crowded conditions, hazard consequences are probable 0. Further research needed on types of hazard consequences.

• Merluccius merluccius: non-usable bycatch: hazard consequences including mortality are best avoided by preventing bycatch 0. Further research needed on gear settings and on other co-existing, preyed-on, and predating species.
• Mullus surmuletus: non-usable bycatch: highest discards in May-Oct, probably due to more FISHES inhabiting seagrass. Attaching guarding nets (selvedge) decreased discards to 18.6-22.6%, especially of decapod crustaceans Anomoura spp. and Maja squinado and gastropods Hexaplex trunculus, Bolinus brandaris, Aporrhais pespelecani 10.

• Merluccius merluccius: catching takes place at the bottom 16 19 2 6 40. The net is usually not dragged along the seafloor 67, though, so seabed damage or huge impact on benthos is relatively low 0.
• Mullus surmuletus: given that M. surmuletus is a BENTHIC carnivore 68, catching takes place at the bottom 31 12 8 34 40 14 62 13 55 30 24. The net is not dragged along the seafloor 14 24, though, so seabed damage or huge impact on benthos is relatively low 0. Recommended to monitor the benthic habitat before deploying the net 36.

Estimate of gillnets abandoned, lost, or discarded globally: average 2,963 km²/year, range 1,153.1-4,772.7 km²/year, average 3,153 m² gillnets/vessel, corresponding to 0.8% of gillnets 69.

• Merluccius merluccius: when gillnets get dragged by a trawl, they may get lost and become "ghost nets". Deliberately "lost" gillnets off the southern Portuguese coast (the Algarve) in 65-78 m depth with mesh size 81 mm (commercially used) started getting holes after 3 months, torn lines after 75 days when set in September or after 248 days when set in spring. May be dragged along the bottom. Catch of number of M. merluccius IND decreased by 5% after 30 days compared to normally fishing gillnets with 24 h soak time, 35% after 90 days, probably due to biofouling on net, amount of hake remains, or strong currents. No more catches after 248 days when set in May, after 75 days when set in autumn. Per year, estimated 7,139 IND or 2,437 t M. merluccius ghost fished off Algarve 17.
  Prominent decrease in number of IND after 30 days, gradual decrease until after 230 days, residual bycatch after 12 months when study stopped. 18 species of which most frequently by number Citharus linguatula (34.2-38.7%), Scorpaena notata (23.7%) in spring, Scomber scombrus (30.7%) in autumn, most frequently by weight Lophius piscatorius, Microchirus azevia, Scorpaena notata (in sum 58.1%) in spring, Scomber scombrus, Auxis rochei, Scyliorhinus canicula (in sum 68.1%) in autumn. After 8 months, almost exclusively BENTHIC species. Per year, estimated 20,367 IND or 5.2 t ghost fished off the southern Portuguese coast (the Algarve), equalling 17,213 Euro. Estimated ghost fishing impact of ~25 FISHES or 64.4 kg/100 m of net in ~430 days of active fishing life of the ghost net. To reduce ghost fishing and the loss of nets, the following measures are recommended: implementing a Code of Good Practice, closure of areas where active and passive gear interact for one gear at a time, biodegradable nets, lower number of nets, soak time, and vessels, making reporting of lost gear mandatory, regular gear recovery attempts, gear retrieval during DEMERSAL trawl surveys 70.
• Mullus surmuletus: in ghost-net experiments (gillnet: 60 mm mesh size, trammel net: in mesh 60 mm and out mesh 100) off the southern Portuguese coast (the Algarve), that catch several FISHES including M. surmuletus, 15-20 weeks effective fishing lifetime of the net. The nets caught 39 species belonging to 4 main groups (crustaceans: Galathea strigosa, Maja squinado, Macropipus puber, Scyllarus arctus; gastropods: Charonia lampas; molluscs: Cybiun olla, Sepia officinalis; FISHES: Alistes carolinensis, Parablennius gattorugine, Callionymus lyra, Caranx rhonchus, Trachurus trachurus, Conger conger, Phycis phycis, Trisopterus luscus, Pomadasys incisus, Labrus merula, Symphodus bailloni, Symphodus spp., Merluccius merluccius, Mugil spp., Mullus surmuletus, Scomber spp., Scomber japonicus, Scorpaena notata, Serranus spp., Serranus cabrilla, Buglossidium luteum, Dentex gibbosus, Diplodus annularis, Diplodus bellottii, Diplodus cervinus, Diplodus puntazzo, Diplodus sargus, Diplodus spp., Diplodus vulgaris). Estimated 344 FISHES/100 m length caught in 120 days. Probable scavenging and predation by Conger spp., Muraeinadae, and Coris julis on the ghost netted FISHES, especially soft bodied species like M. sumuletus 71.