TMR 4137

FISHING GEAR TECHNOLOGY

AN OVERVIEW

Manu Sistiaga
NORWEGIAN FISHERIES, PUTTING THINGS IN CONTEXT
1977

Photo: Norges sjømatråd

Photo: Tersan shipyard Source: www.kystmagasinet.no

Photo: JK photo Photo: Frode Adolfsen

SOME TYPICAL VESSELS IN THE NORWEGIAN COAST
SOURCES: REGULATIONS, BIOLOGY AND ECONOMY
https://www.fiskeridir.no
/English/Fisheries/Statisti
cs/Economic-and-
biological-key-figures

https://www.hi.no/filarkiv
/2017/06/havforskningsr
apporten_2017.pdf/nb-
no

https://www.seafood.no

https://www.ices.dk
DEVELOPMENT OF FISHERMAN AS OCCUPATION

Source: Norwegian fisheries directorate

DEVELOPMENT OF THE NORWEGIAN FLEET

242 units

219 units

5564 units

Source: Norwegian fisheries directorate

DEVELOPMENT OF ENGINE POWER IN THE NORWEGIAN FLEET

Source: Norwegian fisheries directorate

EXPORT VALUE FOR NORWEGIAN SEAFOOD

Source: Norwegian Seafood council

 WHAT IS FISHING GEAR TECHNOLOGY?
• It includes basically the all technology needed to capture fish/crayfish (and
other organisms living in the water).
PASSIVE/ACTIVE FISHING GEAR?
Pasive fishing gear Active fishing gear
(Team Monkfish) (Team Whale)

In principle, the target seeks the gear In principle, the gear seeks the target

• Longlines • Trawl
• Gillnets and trammel nets • Purse seine
• Pots and traps • Danish/Scottish seine
• Fyke nets • Handline (pole and line)?
• Handline (pole and line)?
FISHING GEAR IN THE WATER COLUMN

Source: www.seafish.org
WHEREABOUTS OF THE FISH SPECIES
PASSIVE FISHING GEAR
 PASSIVE FISHING GEAR
• Well suited when the target species is
not specially concentrated and it is
relatively big in size.

• Applied often for target species that live close to the seabed and the
seabed is not appropriate for the use of towed gear.

• These types of gears can fish over a long period of time.

PASSIVE FISHING GEAR
• There are three main fases when fishing with any passive gear:
• Deployment: It is important to do it correctly so
that the gear fishes as intended.

• Soaking period: Critical fase as based on his

judgment the fisherman needs to consider several
factors as fishing efficiency, fish quality, etc.

• Retrieval: The pace of retrieval is important not

to lose the catch specially in longlining. This will
depend on species caught, weather, etc.
PASSIVE FISHING GEAR
LONGLINES
LONGLINE: DEFINITION AND PARTS
• A collection of hooks attached with shorter line pieces (snoods) to a mainline
every certain distance. Elements: main line, Swivel, snood, hook and bait.

• Mostly used on demersal species in Norway (exception haddock).

• Large variability in materials used, distance between hooks, length, bait, etc.
depending on the target species and fishing area.

• Are especially suitable for lower densities of fish, difficult seabed conditions
and great depths.
 LONGLINES: THE HOOK
• Hook: Size and shape of the hook are very important. Must hold
the bait and later the fish

Source: www.wikiwand.com
 LONGLINES, IMPORTANCE OF BAIT
• Depends on target species, price, season, tenacity, etc.

Source: www.ghostfishing.org

Source: https://mustadautoline.com/ Source: Kanstad, Nordlandsmuseet. Wikipedia.no

ADVANCES IN LONGLINING: AUTOLINERS
• Have dramatically increased the efficiency of longline vessels.
• Largest vessels handle ~60,000 per line.

Source: https://mustadautoline.com/
ADVANCES IN LONGLINING: THE MOONPOOL
PASSIVE FISHING GEAR
GILLNETS

Source: www.seafish.org
GILLNETS: DEFINITION
• Gillnets are based om netting sections/panels/walls that the fish meets
unintendedly at sea and gets masked/entangled/snared.

Source: Anishinabek/Ontario Fisheries Resource Centre Source: www.seafish.org Source: www.pacificherring.org

• No attractants and therefore critical how/where it is placed at sea, and the

size of the gillnet, specially for pelagic netting (e.g. sild).
 GILLNETS, ELEMENTS Cork rope (Korktelne)
Gillnet floating ring

Depth rope
Gillnet

Iron ring
Lead rope (Blytelne)
GILLNET, BASIC CONCEPTS Omfar (amount of bars
in an "alen" (627,5 mm).
Given in mm How many "omfar" is a
Bar length mesh in 150 mm?
lm =1255/O (mm)
lm = mesh size mm
Mesh opening O = number in omfar

Mesh length
What is the hanging ratio here?

Length of line
Hanging ratio =
Length of web
 GILLNETS
• Minimizing noticeability is critical for efficiency (e.g. smell/entangled objects).

• Mesh size in gillnets is important and should correspond to the target size.

• Balance between efficiency /

quality determine optimal
soaking time.

• One of the most used fishing

methods in Norway: controversy
due to potential for ghost
fishing.
Foto: Harald A. Skontorp
PASSIVE FISHING GEAR
POTS

Source: www.fvn.no Source: www.leroysjomatgruppen.no

POTS
• Working principle of pots: Bait, shape, size (from pot fishery in Alaska
to cleaner fish in Norway), single pots vs. lines, etc.

• Importance of target species not accessing the bait.

• Advantages of using pots with respect to soaking time, predators (and

birds), quality and live fish.

• Differences between fish pots (e.g. cod) and crayfish pots (e.g. lobster) .
POTS
• Different types of pots:
 PASSIVE FISHING GEAR
FYKE NETS
AND TRAPS

Source: www.daconet.dk
FYKE NETS/TRAPS (RUSER)
• Working principle: Leading netting to the entrance and a chamber system.
• Similarity with pots, excellent fish quality. Can vary a lot in size and shape.
Deeper traps for cod for example Anadrome fish trap
ACTIVE FISHING GEAR
ACTIVE FISHING GEAR
• Target does not come into contact with the gear by itself (attractant or
not)(handline?) but the gear actively catches the fish.

• The fishing operation is carried out actively with the vessel and/or fishermen
actively involved in the process.

• Characteristics and power in the vessel are determinant.

• The operation for the different active fishing methods is very specific.
ACTIVE FISHING GEAR
TRAWLS
TRAWLS
• FAO: The trawls are cone-shaped net (made from two, or more panels)
which are towed, by one or two boats, on the bottom or in midwater.

• Trawls are probably the most adaptable type of gear and can catch from
microscopic organisms to big fish. Limitations for fast swimming and
widespread fish.

• Trawls can be operated pelagic, semi-pelagic of as bottom trawls.

• Controversial gear with respect to environment.

TRAWLS: DIFFERENT TYPES
Demersal trawl Semi-pelagic trawl Pelagic trawl

Twin-trawl Double beam trawl Scallop dredge (multirig-trawl)

Images from: http://www.seafish.org

 BOTTOM TRAWLS, CONSTRUCTION AND RIGGING

Boopendranath, M.R., 2002. Basic principles of fishing gear design and construction, ICAR WinterSchool Manual: Advances in Harvest Technology (Meenakumari, B., Boopendranath, M.R., Pravin,
P.,Thomas, S.N., Edwin, L., Eds), Central Institute of Fisheries Technology, Cochin: 258-272.
TRAWL DOORS
• Pelagic (left), semi-pelagic (middle) and bottom trawl doors (right).

Source: www.thyboron-trawldoor.dk
ACTIVE FISHING GEAR
PURSE SEINE
 PURSE SEINE
• Working principle: Fish is surrounded by a
netting wall that is later closed from
below. The netting bag created diminishes
as the net is retrieved omboad.

• The fish is normally pumped omboard.

• Capture of pelagic schools down to

approximately 200 m.
PURSE SEINE
• It is characterised as species selective fishery.
• Challenges still today with size of fish captured. Point of no return.
• Hugely effective but challenging method that demands skill from
the skipper. Failing to surround the fish is common, specially in
species like tuna. Swimming speed, wind, current, etc, to consider.
• Landnets: Same
Source: Nasjonalbibliotekets bildesamling

principle but nets set

from lan normally at
fixed places.
RINGNOT; BLUEFIN TUNA (MAKRELLSTØRJE)
ACTIVE FISHING GEAR
DEMERSAL SEINES

Source: http://www.seafish.org
DEMERSAL SEINES: DANISH SEINE/SCOTTISH SEINE
• The fishing principle is a "combination between trawl and purse seine".

• Originally created to catch flatfish in sandy bottoms but has been

developed to catch other species like cod and haddock in rougher seabed
conditions and higher up in the water column.

• The fish in a certain area is surrounded by "sweeps" (like in a purse seine)

that gather the fish when they are retrieved. The gathered fish is finally
collected by an overrunning net (like in a trawl).
DEMERSAL SEINES: DANISH SEINE/SCOTTISH SEINE
• Increasing popularity among small-medium fishing vessels. Excellent fish
quality. Often used for catch-based aquaculture of cod and haddock.

• Danish seine (anchor seining) and Scottish seine.

Images from: http://www.seafish.org Herrmann et al., 2016

DEMERSAL SEINES: IMPORTANCE OF ROPES
Source: Winger et al. 2010. Behavior of marine fishes
Source: www.fao.org

Source: Roger B. Larsen, UiT

3
6

4 1. Vingetamper + børtre

5 2.
3.
Vinger
Lask
4. Belg
5. Forlengelse
6. Sekk og sekkløfte

2
1
ACTIVE (PASSIVE) FISHING GEAR

HANDLINES
HANDLINE
• Questionable whether it is an active or a passive fishing method as it often
required that the gear is moved actively and that the fish chases the gear:
Trolling, handline with artifiscial lure, handline with bait.

• Often important that the lure is relatively close to the target (fishing with
bait can be an exception).
HANDLINE, JIGGING MACHINE
• Handlining and the use of traditional reels has been substituted by a jigging machines. A single man
can operate several of them.

• Little commercial importance but a lot used by "hobby" fishermen.

• Importance of echo sounder and constantly repositioning to adjust to movements of vessel and fish.
Source: Fiskerisystem AS
HANDLINE, TROLLING
• In principle it is in a way a handline towed by the vessel.
• Employed to target fish located higher up in the water column, normally pelagic species
like mackerel. Salmon/trout for hobby fishermen.

• Number of hooks varies 1-X and

sometimes the hooks are baited.

• Many different variants.

• Importance of towing the gear
through fish location (depth).

Source: www.afma.gov.au
SELECTIVITY IN FISHING GEAR

GENERAL VIEW
 https://bryanwallace.files.wordpress.com
BYCATCH, SOME DEFINITIONS
• Target Catch - The catch of a species or species
assemblage which is primarily sought in a
fishery, such as shrimp, flounders, cods, etc.
• Incidental Catch - Retained and kept catch of
non-targeted species.
• Discarded Catch - That portion of the catch
returned to the sea as a result of economic,
legal, or personal considerations.
• Bycatch - Discarded catch plus incidental catch.
SELECTIVITY IN FISHING GEARS (GENERAL)
• The selectivity of a gear is a measure of the difference between the population
structure “available” for the gear and the structure that is actually retained.
GENERAL FACTORS AFFECTING
SIZE SELECTIVITY OF FISH
COMMON SELECTIVITY DEVICES IN THE NE ATLANTIC

Source: Madsen, 2007.

SELECTION DEVICES IN THE SHRIMP TRAWL FISHERIES

Source: Larsen et al., 2018

SELECTIVE GRIDS IN THE NORWEGIAN
GADOID TRAWL FISHERY

Sort-X

Sort-V

Flexigrid
Source: Sistiaga et al., 2010.
 SIZE SELECTIVITY, DATA ANALYSIS
1

L75 = 57 cm

0.75
Retention ( r(l))

L50 = 52.5 cm

0.5
L50 = 52.5 cm
L25 = 48 cm
SR = 9 cm
0.25

0
30 35 40 45 50 55 60 65 70 75 80 85 90 95 100
Length (l) in cm
WHERE DO WE WANT TO BE?

0.75
Released
Retention probability

0.5
Retained

0.25

0
30 35 40 45 50 55 60 65 70 75 80 85 90 95 100
Minimum size = 44 cm
Length (l) in cm
SELECTIVITY IN LONGLINE FISHERIES
• "Length distribution of the fish that is caught", and NOT "The proportion of
available fish for each length class that is caught".
FISHSELECT
1. 2.

Cod Haddock

3. 4. L50 (cm) versus mesh size and mesh opening angle

80
60
oa (degree)

40
20

100 120 140 160 180 200

Mesh size (mm)

THANKS FOR YOU ATTENTION!!!