Fishing gear

1
Fishing gear methodsChapter 5 in Jennings et
al.

• Traps
• Hooks and Lines
• Stationary nets
• Towed nets and dredges
• Surrounding nets
• Fish aggregation devices
• Destructive effects
• Gear selectivity

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Type of gear and method used

• Dependent on species fishing

3
Type of gear and method used

• Dependent on species fishing
• Gear types
• passive
• inexpensive and less damage to habitat

4
Type of gear and method used

• Dependent on species fishing
• Gear types
• passive
• inexpensive and less damage to habitat
• active
• more expensive, but more efficient

5
Type of gear and method used

• Dependent on species fishing
• Gear types
• Accounting for fish behavior
• tend to be most efficient methods

6
Type of gear and method used

• Dependent on species fishing
• Gear types
• Accounting for fish behavior
• Choice of gear depends on intended market
• presentability of line-caught fish vs.
  gill-netted fish

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Traps

• Encourage entry and prevent escape

8
Traps

• Encourage entry and prevent escape
• baited traps
• carnivorous species
• eels, snappers, breams

Eel trap
9
Traps

• Encourage entry and prevent escape
• baited traps
• control through regulating
• size of mesh
• number and position of openings

Minnow trap
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Traps

• Encourage entry and prevent escape
• baited traps
• unbaited
• resembling a refuge

11
Traps

• Encourage entry and prevent escape
• baited traps
• unbaited
• barrier or fence traps

12
Traps

• Encourage entry and prevent escape
• baited traps
• unbaited
• barrier or fence traps
• especially in estuaries (taking advantage of
  tides)
• sardine, mackerel, eel, squid, yellow tail
• control through regulating ( used)

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Barrier net
14
Hook and line

• Hand-held
• J-hook
• recreational
• circle hook
• commercial
• shark, halibut, deep water snappers

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Hook and line

• Hand-held
• Trolling
• Towed behind boats to catch PELAGIC species
• tuna, mackerel, dolphinfish
• simulating injured prey or use of bait

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• Longlines
• set near surface for pelagic fish (e.g. tuna)
• set near seafloor for demersal fish (e.g. sharks)
• typically in open ocean up to100km long fishing
  to 400 m depth

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Stationary Nets

• Passive gear
• Regulations
• mesh size
• number of vessels deploying

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Stationary Nets

• Gill nets
• used in shallow water for mackerel,mullet, shad
• used in deeper water for demersal fish such as
  sharks

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Stationary Nets

• Gill nets
• very selective fishing gear (see Box 5.4)

European sea bass
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Stationary Nets

• Gill nets
• very selective fishing gear
• but, responsible for bycatches of marine mammals,
  reptiles and birds

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Stationary Nets

• Trammel nets
• small mesh net sandwiched loosely between panels
  of larger-mesh net
• entangling fish of a larger size range
• effective for flatfishes, rays, crustaceans

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Stationary Nets

• Trammel nets

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Stationary Nets

• Tangle nets
• large mesh
• animals get snagged on mesh
• effective for spiny organisms

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Towed nets and dredges

• Active gear

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Towed nets and dredges

• Active gear
• most widely used

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Towed nets and dredges

• Active gear
• most widely used
• incredibly unselective

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Towed nets and dredges

• Otter trawls
• otter boards, floats
• demersal or pelagic species
• fishing speed

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Towed nets and dredges

• Beam trawl
• Horizontal beam
• Any speed
• Shrimp, flatfish

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Towed nets and dredges

• Dredges
• Similar to beam trawls
• Scallops, clams, gastropods

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Towed nets and dredges

• Dredges
• Destroy habitat
• Reduced bycatch

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Surrounding nets

• Take advantage of schooling behavior
• clupeids, tuna, etc.

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Surrounding nets

• Beach seine
• sardine, mackerel, flat fish

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Surrounding nets

• Purse seine
• efficient gear
• over 100 tons captured in single haul
• located with sonar or helicopter then...

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Aggregation devices

• Take advantage of congregation behavior
• Floating rafts anchored offshore to attract
  pelagic fish (depths gt1000m)

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Aggregation devices

• Advantages
• reduce search time
• reducing fuel costs
• increase fish catch

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Aggregation devices

• Disadvantage
• costs (3000/unit in 1990)
• lifespan less than 1 year

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Other techniques

• spears, poles
• diving
• poison
• explosives

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Destructive effects

• Development of gear aimed at reducing catch of
  small and non-target individuals

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Destructive effects

• Exclusion devices (TEDs)
• Trawl Efficiency Devices
• Trash Eradication Devices
• Turtle Exclusion Devices

Fig 5.13
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Destructive effects

• Ecological Effects
• e.g. on food chains (krill fishing on stocks of
  whales)

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Destructive effects

• Physical damage (easy to assess)
• demersal trawl nets and dredges
• prevent settlement of benthos

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Destructive effects

• Effect on escaped individuals?

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Destructive effects

• Effect on escaped individuals?
• assumptions fish escaping are
• not damaged
• minimally stressed
• make a complete recovery

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Destructive effects

• Effect on escaped individuals?
• escaped fish mortality due to
• physical damage
• stress
• decreased ability to escape predators or resist
  disease
• growth reproductive capacity impaired

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Gear mortality estimates Chopin Arimoto.
1995. Fisheries Research. 21 315-327.

• Highly variable depending on fishing method and
  study conducted

48
Gear mortality estimates Chopin Arimoto.
1995. Fisheries Research. 21 315-327.

• Trawl
• 1-32 mortality of cod escaping codend
• 16-17 mortality of fish later released

49
Gear mortality estimates Chopin Arimoto.
1995. Fisheries Research. 21 315-327.

• Seines
• 85 mortality of those released due to forced
  swimming, struggling injury

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Gear mortality estimates Chopin Arimoto.
1995. Fisheries Research. 21 315-327.

• Trolling
• 40-86 and 34-52 of chinook coho

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Gear mortality estimates Chopin Arimoto.
1995. Fisheries Research. 21 315-327.

• Gillnet escapees
• 80-100 mortality
• due to scale damage alone 40
• due to stress 80

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Gear mortality estimates Chopin Arimoto.
1995. Fisheries Research. 21 315-327.

• Catch release
• dependent of species, bait type size, fish
  length and water temperature
• 0 when lure in mouth, 11 when swallowed

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Recruitment vs gear selectivity

• Stage chosen for a recruitment index depends on
  consistent (precise) and verifiable measures

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Recruitment vs gear selectivity

• consistent and verifiable measures depend on
  sampling gear used

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Recruitment vs gear selectivity

• In addition to recruitment ogive, must consider
  selectivity ogive

100
recruitment
Recruited
resultant
selectivity
0
Age or size
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Recruitment vs gear selectivity

• selectivity ogive

Fig 9.7
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Logistic Curve (p. 187)
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Recruitment vs gear selectivity

• Factors to consider when examining gear
  selectivity

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Recruitment vs gear selectivity

• Factors to consider when examining gear
  selectivity
• fish girth

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Recruitment vs gear selectivity

• Factors to consider when examining gear
  selectivity
• mesh size

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Recruitment vs gear selectivity

• Factors to consider when examining gear
  selectivity
• gear avoidance capabilities

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Recruitment vs gear selectivity

• Factors to consider when examining gear
  selectivity
• recruitment size

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Recruitment vs gear selectivity

• Factors to consider when examining gear
  selectivity
• fish behaviour (schooling, diel)

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Recruitment vs gear selectivity

• Factors to consider when examining gear
  selectivity
• day or night deployment

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Recruitment vs gear selectivity

• Factors to consider when examining gear
  selectivity
• is gear sampling random portion

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Recruitment vs gear selectivity

• Factors to consider when examining gear
  selectivity
• gear type

trawl
gill net
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retention of sea bream in gill nets
selection curves
Fig 9.8
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Normal Curve (p. 188)
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Historical trends in landing value by gear type

• Ranking of the 10 gear types with the highest
  landed value for New England from 1950-1997

from Pol Carr 2000 NE Natur.7329