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Fisheries Techniques

Fisheries Techniques. Zoo 511. Today’s outline. Announcements: Final Exam next week! Format will be one section with timed stations, and one section with a total time limit for multiple questions. Final Draft of paper due noon May 14 th in Alex’s mailbox at the CFL

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Fisheries Techniques

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  1. Fisheries Techniques Zoo 511

  2. Today’s outline • Announcements: • Final Exam next week! • Format will be one section with timed stations, and one section with a total time limit for multiple questions. • Final Draft of paper due noon May 14th in Alex’s mailbox at the CFL • Lecture: Techniques (this is fair game for exam!) • Jeopardy!

  3. Two main types of methods: ACTIVE PASSIVE

  4. Passive Gear Standard Nordi-mesh Entanglement – gill nets Considerations: habitat, depth, mesh size, mortality

  5. Freshwater Equivalent= Passive Gear Entanglement -Longlining Considerations: Habitat, by-catch, hook size, type of bait, set time, predation, finding the gear Pelagic Bottom

  6. Passive Gear Considerations: location, mesh size, funnel diameter Entrapment- trap nets, know the parts! Wings Pot or Car Funnel Wings Lead

  7. Trap nets, Lots of variety Fyke Net Pound Net River Trap Net PA style trap Net Hoop Net - river

  8. Passive Gear – Fish Weirs Block entire stream, catch everything going up or down Considerations: location, high level of effort, non-target effects

  9. Passive Gear Minnow trap – can mean anything Considerations: location, mesh size, funnel diameter, trap fullness = more or less caught, predation Gee style B style square Plastic style Glass style

  10. Passive Gear Angling – sort of a weird mix between active/passive Considerations: time and place, what lure, certain types of fish more vulnerable, behavioral effects

  11. Active gear – Trawling Considerations: depth, bycatch, habitat destruction Tickler chains Rockhopper

  12. Active gear Standing Wave Drag/Tow – larval fish sampling – Bongo nets, Miller sampler Considerations: depth, size of larvae, other stuff in water Reduced Opening

  13. Active gear - Seine Purse seine and beach seine Considerations: how to find fish, preventing escape, bycatch

  14. Active gear - Electrofishing Stream electrofishing- backpack, tow boat, bank based, electric seine Considerations: safety – fish and researchers, not effective in all habitats

  15. Active gear - Boat Electrofishing Considerations: depth, safety again

  16. Active gear - Toxicants – rotenone, lampricides Considerations: Selectivity, ease of application, health concerns

  17. Active gear - Direct observations (underwater, camera, or viewing windows Considerations: behavioral changes due to your presence, water clarity, can’t measure some things

  18. Active gear - hydroacoustics Considerations: expensive, how to determine species composition, difficult to sample fish near the bottom

  19. Gear Bias • Why certain species, sizes, or habitats are caught more or less often than their frequency in the population. • Every gear has bias! A B C D 5 6 5 7 25 A 25 B 25 C 25 D A B C D 20 4 1 15

  20. Gear Bias • Gear can also be biased for size • You sample and catch only one size of fish: 2 possible reasons. • The population is all one size • Your gear is biased towards one size • Goal is to get least biased sample possible • USE MULTIPLE GEARS!

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