Chapter 6 Passive Capture Techniques. Fish caught by –Entanglement

Entangling devices Fish are snared or tangled in fabric or mesh Examples –Gill nets –Trammel nets
Chapter 6 Passive Capture Techniques
Fish caught by –Entanglement –Entrapment –Angling gears Gear is not moved through the water
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 Use baited hooks on lines May be unattended Examples –Trot lines –Long lines –Jugs and yo-yos
Example - trap nets catch crappie, but usually not largemouth bass orr X.
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
CPE ~ = Population Abundance.
Disadvantages of Passive Gear Gear selectivity influences –Encounter –Caught –Retained
Capture efficiency influences Season Turbidity Current Time of day Water Temperature
Other Considerations Animal Behavior Movement Schooling Fish morphology See Fish Swim Swim Fish Swim
Gill Nets - Fish caught by Wedged Gilled Tangled
Gill Nets - Construction Wall of Netting Floats, Weights Anchors, Bouys Hanging Ratio Mesh size (Bar or stretch)
Gill Nets - Materials Net Cotton –Linen –Nylon –Monofilament Floats –Wood –Cork –Plastic Lead weights on bottom
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 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.) Mesh size, elasticity, hanging ratio, strength, visibility Movement of fish Duration (soak-time)
1.25 x mesh perimeter Few smaller or larger fish than optimal.
Movement of Fish Season Weather fronts Currents Water temperature
Fluctuations in water level Turbidity Movement of Fish Water depth Thermocline location
Trammel Nets - Construction (cont.) Fish in a pocket made of small mesh poked through large Three panels of netting –small mesh sandwiched between two large mesh Float line Lead line
Trammel Nets - Material Cotton or nylon 2-m deep 250-mm bar 25-mm bar
Common in commercial fisheries Trammel Nets - Sets Same as gill nets Standard sets Floating sets
Hoop Nets - Construction Cylindrical or conical Frames covered by mesh Square or finger throat Cod end Anchor Bouys
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 Riverine habitats - good in strong currents Anchor upstream, stretch out, mouth downstream Baits - cheese, soybean cakes, chicken livers
Hoop Nets - Biases Hoop size Mesh size Escape rates Season, temperature, current, turbidity, habitat type
Fyke and Trap Nets - Construction enclosure with throat float anchor 1-3 wings or leaders (guide fish)
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 Lakes and reservoirs Perpendicular to shore Leader onshore, anchor away Floating trap nets
Fyke and Trap Nets - Biases Species and size selectivity - good for crappie Live releases - mostly larger sport fish
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 Plastic Wood Metal Partial mesh
Pot Gears - Sets Usually over the side of boat, with float attached Suspended in midwater - minnow traps
Pot Gears - Biases Same as other gear Ghost fishing Overcrowded traps
Trot lines –Floats, lines, drop hooks, weights –Mostly warm water inland fisheries Angling Gear
Long lines –Floats, lines drop hooks –Mostly oceanic fisheries (miles/longline)

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