Gill/Drift Netting

Question 1

What is the oldest form of fishing?

Answer 1

Gill netting
Used for thousands of years to catch herring and pilchard

Question 2

What are more efficient methods of fishing compared to gill netting?

Answer 2

Purse seining and pair trawling

Question 3

What is gill netting?

Answer 3

Is sheets of thin netting allowed to drift with the tide or current to catch fish by enmeshing or entangling them

Question 4

Why is gill netting nicknamed ‘walls of death’?

Answer 4

They are often made invisible by monofilament nylon strands

Question 5

Where does gill netting take place the most?

Answer 5

North Adriatic region of the Mediterranean Sea

Question 6

How does gill nets function?

Answer 6

-Long curtain of net suspended from surface by floats
-Upper corners are attached by ropes to these floats
-Net held in vertical plane by ropes fastened at their lower corners to a heavy cable/weight and anchored to sea-bed

Question 7

How long are gill nets?

Answer 7

Up to 80m long

Question 8

How wide are gill nets?

Answer 8

approx. 15m from top to bottom

Question 9

Can gill netting be joined together?

Answer 9

Yes, and form walls of netting as long as 1-2km

Question 10

What are gill nets used to catch in shallow water?

Answer 10

Mullet and mackerel

Question 11

What are gill nets used to catch in deeper water?

Answer 11

Set on sea floor to catch sharks, nearer to surface to catch tuna

Question 12

Is gill netting active or passive?

Answer 12

Yes,
Entangles species that move into them

Question 13

How do fishers improve catches using gill netting?

Answer 13

Placing gear on
-Migration routes
-Across or with tidal currents
-Close proximity to refuges used by target species

Question 14

What is the most selective type of fishing gear?

Answer 14

Gill netting

Question 15

How is gill netting very selective?

Answer 15

-Meshes are uniform in size and shape
-Undersized fish swim through net
-Larger fish don’t get entangled
-Mesh sizes depend on target species

Question 16

What is the mesh size ranges of gill netting?

Answer 16

50mm (smaller pelagics) to 400mm (monks, rays and swordfish)

Question 17

What are the Northeast Atlantic mesh sizes for gill nets tailored for?

Answer 17

-Turbot
-Sole
-Bass
-Hake

Question 18

What mesh size for gill netting is used to catch herring?

Answer 18

50 - 60mm

Question 19

How does gill netting catch fish? (eg. herring)

Answer 19

Just wide enough to allow the herring to go so far into to the net, so that when the fish trys to retreat, the threads of meshes catch under the gill covers and prevent escape

Question 20

What is gilling?

Answer 20

Bony fish swim into it and are caught by their gill covers (opercula)
(sharks)

Question 21

What is snagging?

Answer 21

Parts of mouth, teeth, parts of head stuck in net

Question 22

What is wedging?

Answer 22

Around fishes body as far as the dorsal fin

Question 23

What is entangling?

Answer 23

Fins or other parts of body become entangled in net

Question 24

How are gill nets characterised?

Answer 24

-Size of panels
-Number of panels
-Filament used
-Thickness of twine (visibility to target species)

Question 25

What do fishers need to account for when using gill netting?

Answer 25

-Quality of their catch -Time fish left in gear/water -Risks of depredations by seals and crustacean scavengers -Cost of retrieval vs catch rate vs losses due to decomposition and predation

Question 26

What types of gill netting is there?

Answer 26

-Surface -Mid-water -Bottom-set -Tangle nets -Trammel nets (mainly on seabed)

Question 27

What different types of gill sets are there?

Answer 27

-Drift -Surface set -Mid-water set -Bottom set

Question 28

Describe a drift set.

Answer 28

Not anchored, set or fixed

Question 29

Describe surface sets

Answer 29

-Strong floats -Top of the net is usually 2-3m below the surface

Question 30

Describe mid-water sets?

Answer 30

Suspended mid-depth by lines

Question 31

Describe bottom sets.

Answer 31

Anchored to bottom like a fence -Catch rate will vary depending on the state of the tide

Question 32

What is the deployment procedure of gill nets?

Answer 32

-Drop anchor -Play out untangled net -Drop anchor

Question 33

What is the retrieval procedure for gill nets?

Answer 33

-Star from downwind -Remove fish -Into tub in coils

Question 34

Describe tangle nets

Answer 34

-Single-walled nets -Loose hung net that entangles fish rather than gilling -Shorter nets with less floatations -Flatfish, rays and monkfish

Question 35

Describe trammel nets

Answer 35

-Mainly set on seabed -3-walled net -Inner small meshed net sandwiched between layers of large-meshed net

Question 36

How does trammel nets catch fish?

Answer 36

Fish swims through the larger outer mesh and becomes entrapped within a pocket of netting

Question 37

What species are caught in trammel nets?

Answer 37

Broad selection Flatfish, rays and crustaceans

Question 38

What is the hanging ratio?

Answer 38

Main determinant of the range of lengths of fish caught by gill nets

Question 39

What is the hanging ratio formula?

Answer 39

Length of headline/ length of stretched mesh

Question 40

What happens if the hanging ratio is low?

Answer 40

<50%, the net will hang slack in the water -Net less selective

Question 41

What is soak time?

Answer 41

Length of time that the gear remains in the water

Question 42

What should maximum soaking time not exceed?

Answer 42

Not more than 18 hours

Question 43

What is a disadvantage of long nets?

Answer 43

Longer time period to haul and clean it

Question 44

Why should soak times not exceed 18 hours?

Answer 44

-Catch rates decrease after 12hrs -24 hrs -Significant numbers are spoilt and unfit for human consumption -Depends on water temperature

Question 45

Is there significant advantages to gill netting?

Answer 45

-Not a lot in terms of advantages

Question 46

What regulations govern gill netting?

Answer 46

-In general, there is few restrictions of gill nets -Current ban on driftnetting for salmon at sea since 2006 -SW Ireland spurdog fishery collapsed in 1980s due to excessive gill netting

Question 47

What was banned to 1992?

Answer 47

Global UN moratorium on large-scale drift nets on the high sea exceeding 2.5 km

Question 48

What was banned in 2002?

Answer 48

EU wide ban on drift nets -Fisheries for tuna, shark and swordfish in all EU waters except the Baltic and all EU vessels on the high seas -Ban only applies to pelagic drift netting

Question 49

What are acoustic pingers?

Answer 49

They are devices that emit sounds underwater at various intervals and are currently mandated in certain fisheries (EC Regulation 812/2004)

Question 50

What is the purpose of acoustic pingers?

Answer 50

Alarms that alert dolphins and porpoises to the presence of fishing gear -Decreases chances of entanglement

Question 51

What are the disadvantages of drill netting?

Answer 51

-A single vessel can scoop half a ton of fish per day -Extremely wasteful method of fishing, 40 -50 % fish escape net when hauling and some are injured in net and die later -Evidence of illegal dumping of sheet netting

Question 52

What countries heavily used gill nets in the 1980s?

Answer 52

Japan, South Korea and Taiwan to target tuna

Question 53

What species are caught as by-catch by gill nets?

Answer 53

Green turtles Leatherback turtles Hawksbill turtle Sharks

Question 54

How much estimated fishing gear is lost per trip?

Answer 54

Anecdotal evidence suggests up to 30km of gear are discarded per trip