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What can parameters about a fish can we measure that relate to feeding? What environmental factors influence fish feeding? What biotic factors influence.

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Presentation on theme: "What can parameters about a fish can we measure that relate to feeding? What environmental factors influence fish feeding? What biotic factors influence."— Presentation transcript:

1 What can parameters about a fish can we measure that relate to feeding? What environmental factors influence fish feeding? What biotic factors influence fish feeding? Group discussion questions

2 Discussion What parameters about a fish can we measure that relate to feeding? Lists:

3 Discussion What parameters about a fish can we measure that relate to feeding? Lists: -At distance react food -measure stomach contents (counts, weight, volumetric -Gape -how long it takes for a fish to swallow prey -rates, number per time - attempts per diet item - angle of attack - are there other fish around

4 Discussion What environmental factors influence fish feeding? Lists:

5 Discussion What environmental factors influence fish feeding? Lists: pH temp Time of day season light level DO Substrate Fishing pressure Lists: pollution reproductive cycle nest guarding Flow velocity turbidity Physical Habitat Salinity

6 Discussion What biotic factors influence fish feeding Lists:

7 Discussion What biotic factors influence fish feeding Lists: Prey abundance Size of prey Size of predator Competition Gill rakers, mouth placement, and other morphology Indirect competition (common predator) Level of production Specialist or generalist or omnivore Experience Maturity Gender Vegetation Lists: Community Composition

8 Distance till fish reacts to prey Example: General factor: Turbidity Assumptions?: For all visual feeders Water Clarity or Turbidity Distance till fish sees prey...huh? I think the darker the water gets the harder it will be to find food, and the relationship should be linear! No way, fish don't care if it gets a little muddy, up to a point, then they can't see anything! You are both crazy, think about when it gets foggy, you can't see crap, little increases in turbidity have a way bigger effect, but then once it gets cloudy fish just use other senses!

9 Electivity: what's the proportion of item an in the environment compared to the proportion in the stomach? If an items is rare in the environment but prevalent in diets, it is selected for. How do we measure that....well for a lot of organisms we take invertebrates samples and then pick them. How does a fish decide what to eat?

10 Holling Processes of predation –Search –Encounter –Pursuit –Capture –Handling

11 C.S. Buzz Holling aka "the man" Functional response was developed based in a 1959 paper These eating These

12 Sometimes called the disk equation cause this is how he taught it to students

13 Review

14 Trichoptera (Caddisfly) Ephemeroptera (Mayfly)

15 Diptera (Flies) Non-biting MidgesBlack FliesCrane Flies

16 Amphipods

17 Isopod

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