PassiveFishCapture

Collection MethodsAll are biased!

•Fishery sampling gears generally categorized as active or passive;

•Toxicants (poisons) and electrofishing don’t fit these categories well.

Passive entanglement gear

• Passive: gear is relatively stationary,and fish come to gear• Entanglement: they get tangled

General advantages of passive gear:-- simple design and construction-- relatively low cost-- require little specialized training

General disadvantages of passive gear:

-- rely on fish activity: if they are not moving, you won’t catch them

-- may damage bycatch

-- can be selective for species, size,sex... (more on this later)

Most common example probably is the gill net

“Experimental” gill net has multiplepanels of various mesh sizes

Example: 6 panels -- 0.5, 0.75, 1.0, 1.5, 2.0, 2.5 in (bar measure)

Experimental Gill Net Catch

Species effectively captured:• Gill nets most effective on fusiform (torpedo-shaped) fishes such as Northern Pike, Walleye, Yellow Perch, trout and salmon, etc.• Largemouth Bass avoid gill nets

Considerations:

• Gill nets can cause substantial mortality

• Short-term sets can alleviate some of problem

• Most biologists prefer to use most benign gear that is still effective

Trammel NetTypically constructed of three mesh panels:

• two outer panels have large mesh, and the middle panel is small mesh. Thus, thefish get caught in a “bag.”

Trammel nets• Commonly used in commercial fisheries• Target species: catfishes, catostomids, Common Carp.

Passive Entrapment Gear

• Entrapment: fish typically retained by some type of “funnel”

• Trap (modified fyke) nets and hoop nets most commonly used

Minnow Trap

Fyke Net

Species effectively captured by trap nets:

• Most effective on species that seek cover, such as crappies and sunfishes• Often effective for collection of spawning Northern Pike or Walleye• Largemouth Bass avoid trap nets

Species effectively captured by hoop nets• Often used in flowing waters; often baited• Catfishes• Suckers: buffalo fishes, carpsuckers• Crappies and sunfishes

Considerations• Both trap and hoop nets inflict little mortality; most fishes can be released alive

Bigmouth Buffalo Fish River Carpsucker

Pot Gears

-e.g., lobster, eel & crab pots, fish traps

-construction of wood, metal or plastic

-equipped w/funnels to prevent escape

-used for bottom-dwelling or cavity-seeking spp.

-commonly baited

-often fished in large numbers

Ghost Fishing