Scomber colias is one of the most important commercial species throughout its habitat. It is fished mainly on the eastern side of the Atlantic (Bay of Biscay to South Africa) as well as in the Mediterranean, mostly in purse seine and pelagic trawl fisheries which target Sardina pilchardus and/or Engraulis engrasicolus. Often being bycatch (and then slipped), it may become the target species when it is highly available whereas sardine and anchovy are not. Another reason contributing to the recent rise in landings is the appearance of new markets (e.g., for tuna feeding). Tuna are among the natural predators together with swordfish, sharks, dolphins, and seals, so these risk becoming bycatch themselves when they are accidentally engulfed by the purse seine – just as other pelagic and semi- pelagic species may be accidentally caught.

The medium-sized pelagic S. colias may already suffer from injuries and stress when the purse seine is hauled close to the ship. Whether slipping of unwanted catch results in delayed mortality requires further research; discarding – once on board – is mostly done when the IND are dead and so should be avoided. Transfer to the storage space via scoop net potentially objects wanted S. colias to further crowding, contact with the gear, lack of oxygen, and experience of its own weight. Storing most likely happens alive and without or with only little ice. And since death occurs most likely through asphyxia, the best would be pumping the IND on board and then immediately stun them followed by slaughter while still unconscious. Further research is needed for such a protocol.

To find the fishes in their habitat, there are different techniques to localise them (e.g., echosound/sonar, chasing).

What is the probability of avoiding a decrease in welfare during the process of searching for the species?

Likelihood

Potential

Certainty

Catching methods differ in the way they are set up and consequently in the time it takes for setting them.

What is the probability of avoiding a decrease in welfare during the process of setting the catching method?

Likelihood

Potential

Certainty

Given the principle of the catching method, the gear (with the fishes caught) may be hauled vertically or horizontally in the water for a certain amount of time and distance.

What is the probability of avoiding a decrease in welfare during catching?

Likelihood

Potential

Certainty

The process of bringing the fishes out of the water also depends on the catching method and may, thus, differ in duration and impact (e.g., netting, brailing, pumping, lifting).

What is the probability of avoiding a decrease in welfare during emersion?

Likelihood

Potential

Certainty

There are different ways to remove the fishes from the gear (e.g., unhooking, disentangling, dropping).

What is the probability of avoiding a decrease in welfare during release from the gear?

Likelihood

Potential

Certainty

Not all specimens of the target species are equally sought after, e.g., when they are undersized, of wrong sex, wrong age, damaged or over quota. Measures to prevent this bycatch still in the water may include slipping in purse seine, window in net, opening in trap, etc.

What is the probability of avoiding a decrease in welfare with the help of bycatch-avoiding measures?

Likelihood

Potential

Certainty

Given the species specificity of the method, sorting might be necessary once the catch arrives on deck.

What is the probability of avoiding a decrease in welfare during sorting?

Likelihood

Potential

Certainty

If bycatch of the target species could not be prevented, the individuals could still be returned from the gear/deck to the water.

What is the probability of avoiding a decrease in welfare during discarding?

Likelihood

Potential

Certainty

Given how long it takes the vessel to return to the harbour, the caught fishes have to be stored for a certain amount of time. This storing happens most frequently with the fishes still being alive, but differing in the type of storage containers and medium (ice, brine, air, etc.).

What is the probability of avoiding a decrease in welfare during storing?

Likelihood

Potential

Certainty

Ideally, slaughter a) immediately follows stunning (i.e., while the individual is unconscious), b) happens according to a clear and reproducible set of instructions verified under catching conditions, and c) avoids pain, suffering, and distress.

What is the probability of avoiding a decrease in welfare during stunning/slaughter?

Likelihood

Potential

Certainty

Sometimes the literature does not specify the welfare hazards and the catching step that lead to hazard consequences.

What are consequences that decrease welfare during uncategorised steps of the catching process?

The focus of this WelfareCheck | catch is the welfare of the target species. There could be improvements to the catching method that are not covered by the criteria and could include prevention of overexploitation, prevention of bycatch of non-target species, e.g., pingers to deter cetaceans, and avoiding damage to the environment, though.

What are these improvements?

• target species: since 2015, management plan (for the fight against illegal, unreported, unregulated fishing) for small pelagics as well as reserve area in Morocco and Senegal 19. Since 2017, annual cap, closure zone, reduced total allowable catch in place in Morocco 19. In 1992-2017, catch off northwest Africa contained 0+ and 1+ age classes (even if lower than natural mortality) which are most likely not mature 19. In 1999-2017, the population off northwest Africa was fully exploited, so increase in catch is not recommended 19. Countries are recommended to collaborate in doing surveys to keep track of populations 19.
  • How to improve: management plan, annual caps, closure zone, reduced total allowable catch, population surveys
• non-target species: given the principle of purse seine to catch whole schools (see here for other small pelagics and/or the same gear that S. colias is often caught with 1), there is the risk to also include co-existing, preyed-on, and predating species 4.
  Usable bycatch: in 2009-2013, other pelagic and semi-pelagic species (Trachurus trachurus, Scomber scombrus, Trachurus picturatus, Engraulis encrasicolus, Boops boops) at <11.1% of the total catch, Diplodus spp., Pagellus acarne, Mugil spp. at <1.2% of the total catch 2. Among reasons for slipping part of or whole catch were catch of non-commercial species, mix with species of less value 2, low size, exceeding quota, low value 3. In 2016-2017, bycatch of Sardina pilchardus, T. picturatus, occasional bycatch of B. boops, Centracanthus cirrus, Sardinella maderensis, Macroramphosus scolopax, Capros aper 3.
  Non-usable bycatch: S. colias is preyed on by tuna, swordfish, sharks, dolphins, seals 20-21 which risk ending up as bycatch. In 2003-2018, Delphinus delphis were accidentally caught in 1.3% of 754 purse seine fishing sets (ending in mortality in 0.8%), Tursiops truncatus and Phocoena phocoena in 0.1% each 13. Numbers may be reduced by assessing the bycatch and put in place conservation plans 13. Welfare hazards including mortality are best avoided by preventing bycatch. Further research needed on gear settings and on other co-existing, preyed-on, and predating species.
  • How to improve: interpreting sonar/echo-sounder, mitigation measures, slipping

How much is this species targeted annually?

As a consequence of welfare hazards, fishes may suffer from physical damage (e.g., barotrauma, abrasions/lacerations/wounds, ecchymosis, desiccation).

Where in the catching process does physical damage occur and how to avoid it?

Physical damage may occur most frequently during decreasing distance to neighbours and contact with the gear or storing containers. To avoid it during catching/hauling and emersion, a) prefer mesh size that avoids catching JUVENILES (given body diameter in season and region), b) decrease bycatch by gentle slipping in an early phase of hauling, c) haul the purse seine slowly, taking especially care to avoid high densities during crowding in last 20% of retrieving the purse seine. To avoid it during release from the gear, sorting, and storing, take more care to increase welfare, but best prefer immediate stunning followed by slaughter while still unconscious. Further research needed.

1.1 Barotrauma

Extruded eyes/guts: no data found yet.

Ruptured swim bladder: no data found yet.

Bleeding: no data found yet.

• Given mesh size of 10 mm (stretched) 5, undersized IND getting stuck in the net is probable 4. Minimum mesh size in Portuguese fisheries for purse seine: 16 mm 3.
  • Catching step:  Catching
  • How to improve: prefer mesh size that avoids catching undersized IND given body diameter in season and region
• Catching depth of mean 41.4-49.3 m 2, range 20-100 m with >80% caught in 20-60 m 6. Given catching during dusk and dawn, attracting IND with artificial light 5 3 and therefore catching at the surface, there is no risk of barotrauma 7 8.
  • Catching step:  Catching

1.2 Damages/abrasions/lacerations/wounds

• Given catching mainly at dusk or dawn 2 3 or between dusk and dawn 5 2, eye damage related to exposure to environmental light or UV light is improbable 4.
  • Catching step:  Emersion

• No difference in survival 4 days after slipping compared to control (94.3% versus 97.6%) 15. Those IND that died had skin damage, fin erosion, lower body condition 15.
  • Catching step:  Bycatch avoidance
  • How to improve: gentle slipping

Scale loss: no data found yet.

Broken spine: no data found yet.

• Given the principle of purse seine to haul the net close to the ship and crowd the IND before lifting them into the storage space of the ship (see here for other small pelagics and/or the same gear that S. colias is often caught with 1), taking 1.4 h/haul 2 or 1.3 h/haul 3, hazard consequences are probable 4. Further research needed on types of hazard consequences and on how to avoid them.
  • Catching steps:  Catching Emersion
• In the related Scomber scombrus, in Norway, below-critical densities to be expected in median-sized catches (270 t) until 80% of seine is hauled in, whereas critical crowding levels reached in large catches (650-985 t) 9. >80% hauling: highly uncertain predictions about seine volume 9 due to complex shapes with large folds that seine may take 10-9; unexpectedly high densities possible as seine is hauled in completely 9. Further research needed for types of hazard consequences and whether this applies to S. colias as well.
  • Catching steps:  Catching Emersion Bycatch avoidance
  • How to improve:
    • take especially care to avoid high densities during crowding in last 20% of retrieving purse seine
    • slipping best before 80% of purse seine is hauled in
• Given that IND school 5, aggression between conspecifics is unlikely 4.
  • Catching step:  Emersion
• IND are lifted out of the purse seine into the storage space of the ship with a scoop net or brailer 3. Given the force with which the net is dipped into the purse seine, exposure to air, and the crowding density, hazard consequences are probable 4. Further research needed on gear settings, on types of hazard consequences, and on how to avoid a decrease in welfare.
  • Catching step:  Emersion
• Given mesh size of 10 mm (stretched) 5, undersized IND getting stuck in the net is probable 4. Minimum mesh size in Portuguese fisheries for purse seine: 16 mm 3.
  • Catching steps:  Emersion Release from gear Bycatch avoidance
  • How to improve: prefer mesh size that avoids catching undersized IND given body diameter in season and region
• After scooping the IND out of the purse seine, the scoop net is released above the storage space of the ship (see here for other small pelagics and/or the same gear that S. colias is often caught with 1). Given dropping from a certain height, landing hard in plastic containers, being catapulted away from the containers, kicked or stood on by fishing folks, and exposure to air, hazard consequences are probable 4. Further research needed on types of hazard consequences and on how to avoid them. 
  • Catching step:  Release from gear
• After being lifted out of the purse seine onto deck, IND were manually sorted by species and size into boxes 3 (see here for other small pelagics and/or the same gear that S. colias is often caught with 1). Given throwing into boxes, landing hard in plastic containers, being catapulted away from the containers, kicked or stood on by fishing folks, pressure by boxes put on top of each others (with the IND inside), and exposure to air, hazard consequences are probable 4. Further research needed on types of hazard consequences and on how to avoid them.
  • Catching step:  Sorting
• Given live storage in boxes with little ice, pressure by boxes put on top of each other (with the IND inside), and exposure to air (see here for other small pelagics and/or the same gear that S. colias is often caught with 1), hazard consequences are probable 4. Further research needed on types of hazard consequences.
  • Catching step:  Storing
• 1-3 sets/trip of range 2.7-18 h, mean 9.4 h before returning to shore 2 or 1 set/trip with mean ca 2.4 h from beginning of catching to returning to shore 3. Given this duration in live storage, hazard consequences are probable 4. Further research needed on types of hazard consequences.
  • Catching step:  Storing
  • How to improve: prefer immediate stunning followed by slaughter while still unconscious

1.3 Ecchymosis

Bruising and discoloration of the skin due to squeezing: no data found yet.

1.4 Desiccation (surface issue)

• Given emersion to air, desiccation is probable 4.
  • Catching step:  Emersion

Stress is a likely consequence of various welfare hazards. It may be measured via physiological parameters (cortisol, glucose, lactate, etc.) or behavioural observations (e.g., opercular movement).

Where in the catching process does stress occur and how to avoid it?

Stress may occur most frequently during decreasing distance to neighbours and contact with the gear. To avoid it during catching/hauling and emersion, a) prefer mesh size that avoids catching JUVENILES (given body diameter in season and region), b) decrease bycatch by interpreting sonar/echo-sounder, sampling or by gentle slipping in an early phase of hauling, c) haul the purse seine slowly, taking especially care to avoid high densities during crowding in last 20% of retrieving the purse seine. To avoid it during release from the gear, sorting, and storing, take more care to increase welfare, but best prefer immediate stunning followed by slaughter while still unconscious. Further research needed.

Cortisol, glucose, lactate, other physiological stress parameters: no data found yet.

Opercular movement: no data found yet.

• Given the principle of purse seine to haul the net close to the ship and crowd the IND before lifting them into the storage space of the ship (see here for other small pelagics and/or the same gear that S. colias is often caught with 1), taking 1.4 h/haul 2 or 1.3 h/haul 3, hazard consequences are probable 4. Further research needed on types of hazard consequences and on how to avoid them.
  • Catching steps:  Catching Emersion
• In the related Scomber scombrus, in Norway, below-critical densities to be expected in median-sized catches (270 t) until 80% of seine is hauled in, whereas critical crowding levels reached in large catches (650-985 t) 9. >80% hauling: highly uncertain predictions about seine volume 9 due to complex shapes with large folds that seine may take 10-9; unexpectedly high densities possible as seine is hauled in completely 9. Further research needed for types of hazard consequences and whether this applies to S. colias as well.
  • Catching steps:  Catching Emersion Bycatch avoidance
  • How to improve:
    • take especially care to avoid high densities during crowding in last 20% of retrieving purse seine
    • slipping best before 80% of purse seine is hauled in
• Given the principle of purse seine to catch IND at the surface and slowly haul the seine close to the ship (see here for other small pelagics and/or the same gear that S. colias is often caught with 1) and thus no way of fleeing predators, there is the risk of stress by predators being present in or close to the net 4. In 2003-2018, Delphinus delphis were present in 10% of 754 purse seine fishing sets, mainly during hauling and transfer on board 13.
  • Catching step:  Emersion
  • How to improve: for ways to avoid predators in the net ➝ 6.7. Other
• IND are lifted out of the purse seine into the storage space of the ship with a scoop net or brailer 3. Given the force with which the net is dipped into the purse seine, exposure to air, and the crowding density, hazard consequences are probable 4. Further research needed on gear settings, on types of hazard consequences, and on how to avoid a decrease in welfare.
  • Catching step:  Emersion
• Given no evolutionary adaptation to experiencing own weight in air 14, hazard consequences following emersion are probable 4. Further research needed on type of hazard consequences.
  • Catching step:  Emersion
• After scooping the IND out of the purse seine, the scoop net is released above the storage space of the ship (see here for other small pelagics and/or the same gear that S. colias is often caught with 1). Given dropping from a certain height, landing hard in plastic containers, being catapulted away from the containers, kicked or stood on by fishing folks, and exposure to air, hazard consequences are probable 4. Further research needed on types of hazard consequences and on how to avoid them. 
  • Catching step:  Release from gear
• Given that IND school 5 and the principle of purse seine is to catch whole schools (see here for other small pelagics and/or the same gear that S. colias is often caught with 1), there is a risk of bycatch (accidental catch of undersized, wrong sex, wrong age, damaged, over quota IND) of the target species 4. After setting the net and in the initial stages of hauling, skippers or captains can get an impression of the catch by looking at a sample of fishes that come to the surface. At that point, they can abort the process if the catch does not include the target species and before the school is crowded 7.
  • Catching step:  Bycatch avoidance
  • How to improve: sampling
• Purse seine was not set in 56 of 179 trips 2, 15 of 72 trips 3 due to, e.g., small schools 2 3 or mixed species schools 2 – effectively avoiding bycatch before it can happen, after interpreting sonar/echo-sounder 3. Yet, slipping part of or whole catch took place throughout observation period (2009-2013) due to, e.g., exceeding daily catching limits or vessel capacity, undersized IND 2. In 2016-2017, 15% of caught IND were slipped, another 28% discarded dead, 6% used at sea due to low market price or small size 3.
  • Catching step:  Bycatch avoidance
  • How to improve: interpreting sonar/echo-sounder, sampling, slipping
• No IND of age 0+ and hardly IND of age 1+ in catch indicate selectivity of purse seine or mesh size (10 mm stretched) large enough for undersized IND to escape or young IND not schooling with older IND 5.
  • Catching step:  Bycatch avoidance
  • How to improve: prefer mesh size that avoids catching undersized IND given body diameter in season and region
• After being lifted out of the purse seine onto deck, IND were manually sorted by species and size into boxes 3 (see here for other small pelagics and/or the same gear that S. colias is often caught with 1). Given throwing into boxes, landing hard in plastic containers, being catapulted away from the containers, kicked or stood on by fishing folks, pressure by boxes put on top of each others (with the IND inside), and exposure to air, hazard consequences are probable 4. Further research needed on types of hazard consequences and on how to avoid them.
  • Catching step:  Sorting
• Given live storage in boxes with little ice, pressure by boxes put on top of each other (with the IND inside), and exposure to air (see here for other small pelagics and/or the same gear that S. colias is often caught with 1), hazard consequences are probable 4. Further research needed on types of hazard consequences.
  • Catching step:  Storing
• 1-3 sets/trip of range 2.7-18 h, mean 9.4 h before returning to shore 2 or 1 set/trip with mean ca 2.4 h from beginning of catching to returning to shore 3. Given this duration in live storage, hazard consequences are probable 4. Further research needed on types of hazard consequences.
  • Catching step:  Storing
  • How to improve: prefer immediate stunning followed by slaughter while still unconscious

The difference between temperature in water and air may induce a thermal shock.

Where in the catching process does temperature shock occur and how to avoid it?

Further research needed to determine whether a temperature shock occurs and how to avoid it respectively.

• Spawning at 15-20 °C could possibly indicate tolerance towards this temperature range 11. In 2014-2015, high catches at 12-24 °C 6. In 2009-2016, higher catches at lower sea surface temperatures (mean 19.8 °C during Jan-June versus 22.8 °C during July-Dec) 12. Further research needed on the rate that S. colias can adapt to temperature changes without decreasing welfare.
  • Catching step:  Catching

The quick transition from one salinity level to another may lead to osmoregulatory distress.

Where in the catching process does osmoregulatory distress occur and how to avoid it?

There is no conclusion yet.

Unspecified: no data found yet.

Removing an individual from its home ground and social group and subjecting it to a potentially stressful catching event may result in disorientation.

Where in the catching process does disorientation occur and how to avoid it?

There is no conclusion yet.

Unspecified: no data found yet.

Lack of oxygen is a likely consequence for aquatic species facing removal from the water.

Where in the catching process does asphyxia occur and how to avoid it?

Asphyxia may occur from emersion on as well as during slaughter. To avoid it, prefer immediate stunning followed by slaughter while still unconscious. Further research needed.

Behaviour indicating lack of oxygen (gulping, tail beating, etc.): no data found yet.

Intolerance towards lower concentrations of oxygen: no data found yet.

• IND are lifted out of the purse seine into the storage space of the ship with a scoop net or brailer 3. Given the force with which the net is dipped into the purse seine, exposure to air, and the crowding density, hazard consequences are probable 4. Further research needed on gear settings, on types of hazard consequences, and on how to avoid a decrease in welfare.
  • Catching step:  Emersion
• After scooping the IND out of the purse seine, the scoop net is released above the storage space of the ship (see here for other small pelagics and/or the same gear that S. colias is often caught with 1). Given dropping from a certain height, landing hard in plastic containers, being catapulted away from the containers, kicked or stood on by fishing folks, and exposure to air, hazard consequences are probable 4. Further research needed on types of hazard consequences and on how to avoid them. 
  • Catching step:  Release from gear
• After being lifted out of the purse seine onto deck, IND were manually sorted by species and size into boxes 3 (see here for other small pelagics and/or the same gear that S. colias is often caught with 1). Given throwing into boxes, landing hard in plastic containers, being catapulted away from the containers, kicked or stood on by fishing folks, pressure by boxes put on top of each others (with the IND inside), and exposure to air, hazard consequences are probable 4. Further research needed on types of hazard consequences and on how to avoid them.
  • Catching step:  Sorting
• Given live storage in boxes with little ice, pressure by boxes put on top of each other (with the IND inside), and exposure to air (see here for other small pelagics and/or the same gear that S. colias is often caught with 1), hazard consequences are probable 4. Further research needed on types of hazard consequences.
  • Catching step:  Storing
• 1-3 sets/trip of range 2.7-18 h, mean 9.4 h before returning to shore 2 or 1 set/trip with mean ca 2.4 h from beginning of catching to returning to shore 3. Given this duration in live storage, hazard consequences are probable 4. Further research needed on types of hazard consequences.
  • Catching step:  Storing
  • How to improve: prefer immediate stunning followed by slaughter while still unconscious
• Given life storage with little ice (see here for other small pelagics and/or the same gear that S. colias is often caught with 1), probably no stunning and slaughter but asphyxia 4.
  • Catching step:  Slaughter
  • How to improve: prefer immediate stunning followed by slaughter while still unconscious

Loss of water is another likely consequence of exposing aquatic species to air.

Where in the catching process does dehydration occur and how to avoid it?

There is no conclusion yet.

Unspecified: no data found yet.

In an attempt to escape the situation of being caught, many individuals struggle and resist until they are exhausted.

Where in the catching process does fatigue/exhaustion occur and how to avoid it?

There is no conclusion yet.

Inactivity/low vitality: no data found yet.

Oxidative stress: no data found yet.

Unspecified: no data found yet.

The process of being caught probably induces states not unlike emotions.

Where in the catching process do emotion-like states occur and how to avoid them?

There is no conclusion yet.

9.1 Fear (continuum up to panic)

Freeze: no data found yet.

Avoidance behaviour: no data found yet.

Escape manoeuvres: no data found yet.

Startling behaviour: no data found yet.

Unspecified: no data found yet.

9.2 Other

Unspecified: no data found yet.

Although killing is the ultimate goal of fisheries, many mortalities happen unwanted - even resulting in discards - and unregulated, without avoiding prolonged suffering.

Where in the catching process does mortality occur and how to avoid it?

Mortality may occur most frequently during decreasing distance to neighbours and contact with the gear. To avoid it during catching/hauling and emersion, a) prefer mesh size that avoids catching JUVENILES (given body diameter in season and region), b) decrease bycatch by interpreting sonar/echo-sounder, sampling or by gentle slipping in an early phase of hauling, c) haul the purse seine slowly, taking especially care to avoid high densities during crowding in last 20% of retrieving the purse seine. To avoid it during release from the gear, sorting, and storing, take more care to increase welfare, but best prefer immediate stunning followed by slaughter while still unconscious. Further research needed.

• Given the principle of purse seine to haul the net close to the ship and crowd the IND before lifting them into the storage space of the ship (see here for other small pelagics and/or the same gear that S. colias is often caught with 1), taking 1.4 h/haul 2 or 1.3 h/haul 3, hazard consequences are probable 4. Further research needed on types of hazard consequences and on how to avoid them.
  • Catching steps:  Catching Emersion
• In the related Scomber scombrus, in Norway, below-critical densities to be expected in median-sized catches (270 t) until 80% of seine is hauled in, whereas critical crowding levels reached in large catches (650-985 t) 9. >80% hauling: highly uncertain predictions about seine volume 9 due to complex shapes with large folds that seine may take 10-9; unexpectedly high densities possible as seine is hauled in completely 9. Further research needed for types of hazard consequences and whether this applies to S. colias as well.
  • Catching steps:  Catching Emersion Bycatch avoidance
  • How to improve:
    • take especially care to avoid high densities during crowding in last 20% of retrieving purse seine
    • slipping best before 80% of purse seine is hauled in
• Given that IND school 5, aggression between conspecifics is unlikely 4.
  • Catching step:  Emersion
• After scooping the IND out of the purse seine, the scoop net is released above the storage space of the ship (see here for other small pelagics and/or the same gear that S. colias is often caught with 1). Given dropping from a certain height, landing hard in plastic containers, being catapulted away from the containers, kicked or stood on by fishing folks, and exposure to air, hazard consequences are probable 4. Further research needed on types of hazard consequences and on how to avoid them. 
  • Catching step:  Release from gear
• No difference in survival 4 days after slipping compared to control (94.3% versus 97.6%) 15. Those IND that died had skin damage, fin erosion, lower body condition 15.
  • Catching step:  Bycatch avoidance
  • How to improve: gentle slipping
• After being lifted out of the purse seine onto deck, IND were manually sorted by species and size into boxes 3 (see here for other small pelagics and/or the same gear that S. colias is often caught with 1). Given throwing into boxes, landing hard in plastic containers, being catapulted away from the containers, kicked or stood on by fishing folks, pressure by boxes put on top of each others (with the IND inside), and exposure to air, hazard consequences are probable 4. Further research needed on types of hazard consequences and on how to avoid them.
  • Catching step:  Sorting
• During manual sorting, undersized IND got discarded dead to sea, used for crew meals or as bait 3, probably without prior stunning or slaughter 4. Further research needed on types of hazard consequences.
  • Catching step:  Discarding
• Discards negligible – IND were rather slipped 16-2 17-2. In 1927-2012, S. colias was chosen to be discarded when Sardina pilchardus was abundant 11. In 1938-2009, S. colias was estimated to represent 18.2% of all unreported species discarded in purse seine fishery due to failed species recognition or size estimation in sonar/echo-sounder 18. In 2016-2017, 15% of caught IND were slipped, another 28% discarded dead, 6% used at sea due to low market price or small size 3.
  • Catching step:  Discarding
  • How to improve: interpreting sonar/echo-sounder, prefer slipping over discarding (getting on board)
• No IND of age 0+ and hardly IND of age 1+ in catch indicate selectivity of purse seine or mesh size (10 mm stretched) large enough for undersized IND to escape or young IND not schooling with older IND 5.
  • Catching step:  Discarding
  • How to improve: prefer mesh size that avoids catching undersized IND given body diameter in season and region
• Given live storage in boxes with little ice, pressure by boxes put on top of each other (with the IND inside), and exposure to air (see here for other small pelagics and/or the same gear that S. colias is often caught with 1), hazard consequences are probable 4. Further research needed on types of hazard consequences.
  • Catching step:  Storing
• 1-3 sets/trip of range 2.7-18 h, mean 9.4 h before returning to shore 2 or 1 set/trip with mean ca 2.4 h from beginning of catching to returning to shore 3. Given this duration in live storage, hazard consequences are probable 4. Further research needed on types of hazard consequences.
  • Catching step:  Storing
  • How to improve: prefer immediate stunning followed by slaughter while still unconscious

When it is difficult to assign an observed behaviour to one of the above categories, we report it here.

Where in the catching process do uncategorised behavioural changes occur and how to avoid them?

There is no conclusion yet.

Unspecified: no data found yet.