chapter 6 l.
Download
Skip this Video
Download Presentation
Chapter 6

Loading in 2 Seconds...

play fullscreen
1 / 37

Chapter 6 - PowerPoint PPT Presentation


  • 121 Views
  • Uploaded on

Chapter 6. Passive Capture Techniques. Passive Capture Techniques. Fish caught by Entanglement Entrapment Angling gears Gear is not moved through the water. Entangling devices. Fish are snared or tangled in fabric or mesh Examples Gill nets Trammel nets. Entrapment devices.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Chapter 6' - rae


Download Now An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
chapter 6

Chapter 6

Passive Capture Techniques

passive capture techniques
Passive Capture Techniques
  • Fish caught by
    • Entanglement
    • Entrapment
    • Angling gears
  • Gear is not moved through the water
entangling devices
Entangling devices
  • Fish are snared or tangled in fabric or mesh
  • Examples
    • Gill nets
    • Trammel nets
entrapment devices
Entrapment devices
  • Capture fish that go through small openings in gear
  • May be more than one opening
  • Fish can't find their way out
  • Examples
    • Hoop nets
    • Trap Nets
    • Lobster Pots
angling devices
Angling devices
  • Use baited hooks on lines
  • May be unattended
  • Examples
    • Trot lines
    • Long lines
    • Jugs and yo-yos
problems with passive gear
Problems with passive gear
  • Gear selectivity - bias for or against certain species, sizes or sexes of fish.
  • Example - trap nets catch crappie, but usually not largemouth bass

orr

X

problems with passive gear7
Problems with passive gear
  • Gear efficiency - number of target animals collected for a given amount of effort expended
  • Example - gill nets catch fewer crappie per net night than trap nets
advantages of passive gear
Advantages of Passive Gear
  • Simple design and construction
  • No mechanical assistance (except boat)
  • Same gear each year ... CPE ~ = Population Abundance
disadvantages of passive gear
Disadvantages of Passive Gear
  • Gear selectivity influences
    • Encounter
    • Caught
    • Retained
capture efficiency influences
Capture efficiency influences
  • Season
  • Turbidity
  • Current
  • Time of day
  • Water Temperature
other considerations
Other Considerations
  • Animal Behavior
  • Movement
  • Schooling
  • Fish morphology

See Fish Swim

Swim Fish Swim

gill nets construction
Gill Nets - Construction
  • Hanging Ratio
  • Mesh size (Bar or stretch)
  • Wall of Netting
  • Floats, Weights
  • Anchors, Bouys
gill nets materials
Net

Cotton

Linen

Nylon

Monofilament

Floats

Wood

Cork

Plastic

Lead weights on bottom

Gill Nets - Materials
gill nets set procedure
Gill Nets - Set Procedure
  • Deployment
    • Drop anchor, play out untangled net, drop anchor
  • Retrieval
    • Start from downwind, remove fish, into tub in coils
gill nets types of sets
Gill Nets - Types of Sets
  • Standard - anchored on bottom like a fence
  • Midwater - suspended mid-depth by lines
  • Surface - strong floats
  • Vertical - for determining vertical distribution (windowshade)
  • Drift - not anchored
gill nets biases cont
Gill Nets - Biases (cont.)
  • Mesh size, elasticity, hanging ratio, strength, visibility
  • Movement of fish
  • Duration

(soak-time)

gill nets biases
Gill Nets - Biases
  • Optimal girth . . . 1.25 x mesh perimeter
  • Few smaller or larger fish than optimal

=1.25 x

movement of fish
Season

Weather fronts

Currents

Water temperature

Movement of Fish
movement of fish20
Water depth

Thermocline location

Movement of Fish
  • Fluctuations

in water level

  • Turbidity
trammel nets construction cont
Trammel Nets - Construction (cont.)
  • Three panels of netting
    • small mesh sandwiched between two large mesh
  • Float line
  • Lead line
  • Fish in a pocket made of small mesh poked through large
trammel nets material
Trammel Nets - Material
  • Cotton or nylon
  • 2-m deep
  • 250-mm bar
  • 25-mm bar
trammel nets sets
Same as gill nets

Standard sets

Floating sets

Trammel Nets - Sets
  • Common in commercial fisheries
hoop nets construction
Hoop Nets - Construction
  • Cylindrical or conical
  • Frames covered by mesh
  • Square or finger throat
  • Cod end
  • Anchor
  • Bouys
hoop nets material
Hoop Nets - Material
  • Hoops - wood, plastic, fiberglass, steel
  • 0.5 to 3m diameter
  • Cotton or nylon mesh
  • 10 to 100mm bar mesh
hoop nets sets
Hoop Nets - Sets
  • Riverine habitats - good in strong currents
  • Anchor upstream, stretch out, mouth downstream
  • Baits - cheese, soybean cakes, chicken livers
hoop nets biases
Hoop Nets - Biases
  • Hoop size
  • Mesh size
  • Escape rates
  • Season, temperature, current, turbidity, habitat type
fyke and trap nets construction
Fyke and Trap Nets - Construction
  • 1-3 wings or leaders (guide fish)
  • enclosure with throat
  • float
  • anchor
fyke and trap nets materials
Fyke and Trap Nets - Materials
  • Hoops or rectangular frames - metal
  • 0.5 to 2m diameter
  • Cotton or nylon mesh
  • 10 to 100mm bar mesh
fyke and trap nets sets
Fyke and Trap Nets - Sets
  • Lakes and reservoirs
  • Perpendicular to shore
  • Leader onshore, anchor away
  • Floating trap nets
fyke and trap nets biases
Fyke and Trap Nets - Biases
  • Species and size selectivity - good for crappie
  • Live releases - mostly larger sport fish
pot gears construction
Pot Gears - Construction
  • Rigid traps with throats
  • Widely variable for different species
  • Box or cylinder with conical funnel
  • Usually with door for easy removal
pot gears materials
Pot Gears - Materials
  • Plastic
  • Wood
  • Metal
  • Partial mesh
pot gears sets
Pot Gears - Sets
  • Usually over the side of boat, with float attached
  • Suspended in midwater - minnow traps
pot gears biases
Pot Gears - Biases
  • Same as other gear
  • Ghost fishing
  • Overcrowded traps
angling gear
Angling Gear
  • Trot lines
    • Floats, lines, drop hooks, weights
    • Mostly warm water inland fisheries
angling gear37
Angling Gear
  • Long lines
    • Floats, lines drop hooks
    • Mostly oceanic fisheries (miles/longline)