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Passive Fish Capture

Passive Fish Capture. Collection Methods All 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,

teagan-miller
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Passive Fish Capture

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  1. PassiveFishCapture

  2. Collection Methods All are biased!

  3. Fishery sampling gears generally categorized as active or passive; • Toxicants (poisons) and electrofishing don’t fit these categories well.

  4. 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

  5. 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)

  6. Most common example probably is the gill net

  7. “Experimental” gill net has multiple • panels of various mesh sizes • Example: 6 panels -- 0.5, 0.75, 1.0, 1.5, 2.0, 2.5 in (bar measure)

  8. Experimental Gill Net Catch

  9. 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

  10. 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

  11. Trammel Net • Typically 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.”

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

  13. Passive Entrapment Gear • Entrapment: fish typically retained by some type of “funnel” • Trap (modified fyke) nets and hoop nets most commonly used

  14. Minnow Trap

  15. Fyke Net

  16. 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

  17. Species effectively captured by hoop nets • • Often used in flowing waters; often baited • • Catfishes • • Suckers: buffalo fishes, carpsuckers • • Crappies and sunfishes River Carpsucker Bigmouth Buffalo Fish • Considerations • • Both trap and hoop nets inflict little mortality; most fishes can be released alive

  18. 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

  19. Ghost Fishing

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