Passive Fish Capture. Collection Methods All are biased! - ppt download
By A Mystery Man Writer
Fishery sampling gears generally categorized as active or passive; Toxicants (poisons) and electrofishing don’t fit these categories well.
Collection Methods All are biased!
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
Thus, CPUE is an INDEX to abundance. Catch per day Population size of fish.
Most common example probably is the gill net
Experimental gill net has multiple panels of various mesh sizes Example: 6 panels , 0.75, 1.0, 1.5, 2.0, 2.5 in (bar measure)
multifilament Monofilament gill nets typically catch more fish Size structure similar between net types for most species Monofilament nets easier to run.
Experimental Gill Net Catch
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
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
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
-commonly baited -often fished in large numbers.
Passive Fish Capture. Collection Methods All are biased! - ppt download
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