Transcript Slide 1
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 14th in Alex’s mailbox at the CFL • Lecture: Techniques (this is fair game for exam!) • Jeopardy! Two main types of methods: ACTIVE PASSIVE Passive Gear Entanglement – gill nets Considerations: habitat, depth, mesh size, mortality Standard Nordi-mesh Passive Gear Entanglement -Longlining Considerations: Habitat, by-catch, hook size, type of bait, set time, predation, finding the gear Freshwater Equivalent= Pelagic Bottom Passive Gear Considerations: location, mesh size, funnel diameter Entrapment- trap nets, know the parts! Wings Pot or Car Funnel Wings Lead Trap nets, Lots of variety Fyke Net Pound Net River Trap Net PA style trap Net Hoop Net - river Passive Gear – Fish Weirs Block entire stream, catch everything going up or down Considerations: location, high level of effort, non-target effects 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 Glass style Plastic style 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 Active gear – Trawling Considerations: depth, bycatch, habitat destruction Tickler chains Rockhopper Active gear Drag/Tow – larval fish sampling – Bongo nets, Miller sampler Considerations: depth, size of larvae, other stuff in water Reduced Opening Standing Wave Active gear - Seine Purse seine and beach seine Considerations: how to find fish, preventing escape, bycatch Active gear - Electrofishing Stream electrofishingbackpack, tow boat, bank based, electric seine Considerations: safety – fish and researchers, not effective in all habitats Active gear Boat Electrofishing Considerations: depth, safety again Active gear Toxicants – rotenone, lampricides Considerations: Selectivity, ease of application, health concerns Active gear Direct observations (underwater, camera, or viewing windows Considerations: behavioral changes due to your presence, water clarity, can’t measure some things Active gear - hydroacoustics Considerations: expensive, how to determine species composition, difficult to sample fish near the bottom 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 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!