1. Announcements and Such Limnology Hiring Fair Wednesday April 2 nd at 5pm in the Red Gym (check “today in the union” postins for exact location) Comments on the Midterm Assignment: Peer Review Draft

2. Outline for the Day How to Write a Scientific Paper Lecture (Reminders of Expectations) Reproduction and Early Life History 2 nd Half of Wisconsin Fishes

3. GOALS Background on an important part of fish ecology that is often overlooked Generalizations of early life history of fish Spawning strategies

4. Basic Background

5. What do you mean “larval fish”? Embryo/Egg Larvae Adult

6. Early Life History Stages Embryonic period Larval Period Juvenile Period

7. What do Fish Larvae Look Like?

8. Diversity of Larvae American Eel

9. Diversity of Larvae Lake Sturgeon Yellow Perch Lake Trout

10. Diversity of Larvae Brown Bullhead Northern Pike Largemouth Bass

11. How we sample larvae Bongo Nets

12. Opening Discussion Why are early life histories important to fish ecology?

13. Answers Kornis Came Up With 1.Survivorship of young influence future generation’s abundance (year class strength) a. Majority of mortality occurs early in life 2.Survivorship is affected by spawning strategies a.Time of hatch b.Habitat selection c.Size of larvae at hatch

14. Factors that influence early life survival Temperature -How quickly adult fish mature and spawn -How quickly eggs hatch -Growth rate of larvae and YOY

15. Factors that influence early life survival Food availability -Is the right food available once yolk sac is used up? -As they grow does the food out grow them? Do they outgrow the food?

16. Factors that influence early life survival Spawning Site -Water Level: Eggs can be left high and dry or smothered? -Refugia: Egg survival can depend on size of substrate or degree to which they are hidden -Flow: Too fast and eggs are swept away. Too slow and not enough oxygen

17. Factors that influence early life survival Predation -Do larvae face a predator gauntlet? Brandt et al. 1987

18. Predation Lake trout eat alewives…right? What about larval lake trout? Great lakes LT spawning reefs Must fill swim bladder at surface (physoclistous )

19. Strength of Year Class Match/Mismatch Hypothesis –Food and other conditions are good for survival = strong year class Food is abundant Predators are not abundant Temperature is appropriate –Cues for Spawning –Several factors can disrupt matching and result in weak year classes

20. Match/Mismatch Hypothesis Yellow perch hatch Eat small copepods, then switch to Daphnia Eat small copepods but Daphnia show up too late Conditions match what is needed Conditions don’t match what is needed

21. Timing is everything… Figure from Cargnelli and Gross 1996 Evolution at work!

22. Yolk Size and Larvae Survival Temperature and Development of Fish at Hatch Lake Trout (Coldwater) Pygmy Sunfish (Warm water) Temperature also effects how long egg stage lasts

23. Egg Size (r vs K strategist) Larger eggs more developed at hatching Herring: eggs, newly hatched, and 7-10 months Newly Hatched Steelhead Altricial: Mouths just formed at yolk depletion (Long Larvae) Precocial: Good predators at yolk depletion (Short Larvae)

24. Yolk Size of Various Fishes

25. Fish evolve to spawn in different locations Temiscamie – strain Tributary spawner Assinica- strain Outlet spawner Little Tupper strain Shoal spawner Why...think about the emerged fry!

26. Lentic vs. Lotic Patterns Lentic Fish often have pelagic larvae –Major period of dispersal –Major period of mortality Lotic Fish often have benthic larvae –Avoid being swept away –Exist for short periods, under heavy cover

27. How often: Semelparous = once, Iteroparous = more then once Common Spawning Strategies

28. Life history strategies Multiple strategies: Bluegill – parental care or Cuckolder http://publish.uwo.ca/~bneff/research_beea.htm Female mimic

29. Common Spawning Strategies Non-guarding vs. guarding Pelagic vs. Benthic Fine vs. Coarse substrate Vegetation Livebearers

30. Non-gaurding, Pelagic Alewife - inshore waters, eggs settle Gizzard shad - Often move up rivers, eggs drift down High fecundity High early stage mortality

31. Non-gaurding, Pelagic Freshwater drum eggs float on surface until hatch Paddlefish eggs are sticky when fertilized, adhere to the first thing they touch

32. Non-gaurding, Benthic – fine substrate Spottail shiners spawn on gravel and silt substrates

33. Non-gaurding, Benthic - Crevice Spotfin shiners use rock crevices to hold eggs

34. Non-gaurding, Benthic – stream Pacific salmon and brown trout dig redds – clean gravel where stream water upwells

35. Non-gaurding, Benthic –vegetation Northern pike prefer flooded vegetation in backwaters

36. Sticklebacks make nests of algae and macrophytes and then lay eggs inside the nests Guarding, Nests – nests of plants Guarding means higher survival

37. Gaurding, Benthic – Underside of rocks Both round gobies and Johnny darters spawn under rocks, attaching the eggs to the underside of the rocks Aggressive defense can incur high costs to parents or death

38. Gaurding, Nests – gravel Common in centrachids also lamprey, nests are often fanned to increase water flow and remove sediments Smallmouth bass American brook lamprey

39. Gaurding, Nest – fine sediment Bluegill nests associated with fine sediments

40. Gaurding, Nests – Holes and burrows Catfish and bullheads make burrows or use existing holes

41. Livebearers, (none native) Mosquitofish 60 -100 progeny per brood, born live, male has modified anal fin to impregnate female