Reproduction

1. Reproduction Part 2

2. The Codfish Strategy

3. Up to 9,000,000 eggs/spawn

5. Cod Math • The volume of the earth's oceans is 1.35 X 109 cubic Km. • A typical 50 cm female cod lays 200,000 eggs/yr • A typical mature cod might weigh...10 kg • Assuming that the fish stack perfectly with no void spaces and that the density of the cod is equal to the density of seawater, then a cubic Km of cod would weigh... • (1 cubic km) X (1,000,000,000 cubic m/cubic km) X (1000 kg/cubic m) X 1.032 to correct for seawater density) = 1.32 X 1012 kg. • If a cod weighs 10 kg, then we can calculate the cod fish per cubic km as (1.32 X 1012 kg) X (1 cod/10 kg) = 1.32 X 1011 cod per cubic km of ocean. • Then the number of cod that it would take to fill the ocean is equal to (1.32 X 1011 cod/cubic km of ocean) X (1.35 X 109 cubic km of ocean) = 1.78 X 1020 codfish.

6. If we assume that the codfish take 5 years to reach their maximum size of 10 kg, that they start spawning at 5 years of age, that each female would lays 200,000 eggs per year once it is 5 years old, and that they live to be at least 25 years old… • Year 1: 2 codfish spawn • Year 2: 2 + 200,000 codfish • Year 3: 2 + 2(200,000) • Year 4: 2 + 3(200,000) • Year 5: 2 + 4(200,000) • Year 6: 2+ 5 (200,000) + (100,000 X 200,000) • Year 7: 2 + 6(200,000) + 2(100,000 X 200,000) • Year 8: 2+ 7(200,000) + 3(100,000 X 200,000) • Year 9: 2 + 8(200,000) + 4(100,000 X 200,000) • Year 10: 2 + 9(200,000) + 5(100,000 X 200,000) +(100,000 X 100,000 X 200,000) • 2 + 1,800,000 + 100,000,000,000 + 2,000,000,000,000,000 = 2,000,100,001,800,000 or2 X 1015 • Year 11:2(100,000 X 100,000 X 200,000) • Year 12: 3(100,000 X 100,000 X 200,000) • Year 13: 4(100,000 X 100,000 X 200,000) • Year 14: 5(100,000 X 100,000 X 200,000) = 1 X 1016 • Year 15: 6(100,000 X X 100,000 X 200,000) + (100,000 X 100,000 X 100,000 X 200,000) = 2 X 1020

7. Just 15 Years !

8. Mola

9. 23,000,000 eggs (300,000,000 max!)

11. Over the entire lifetime of this mola pair, how many of their babies must survive in order to keep the population stable ? 2

12. 20 year lifespan 23,000,000 eggs year/mola =460,000,000 eggs X Need to replace the male and female breeding molas, therefore we need 2 fish out of the 460 million eggs. Mola egg survival to maintain population = 1 per 230,000,000

13. Salmon

14. 10,000 eggs year/salmon 1 year spawning =10,000 eggs X Need to replace the male and female breeding salmon, therefore we need 2 fish out of the 10,000 eggs. Salmon egg survival to maintain population = 1 per 5,000

15. Tiger Shark

16. 1 baby 2 years/shark 20 year lifespan =10 baby sharks X Need to replace the male and female breeding sharks, therefore we need 2 fish out of the 10 babies to survive. Shark baby survival to maintain population = 1 per 5

17. Two strategies • Make bazillions of “low cost” disposable eggs and abandon them. Hardly any survive, but when you start with millions… • Make very few eggs with tons of energy and guard them. There aren’t many eggs, but when most are going to survive… R K

18. R-selectionIn unstable or unpredictable environments the ability to reproduce quickly is crucial, and there is little advantage in adaptations that permit successful competition with other organisms, because the environment is likely to change again. R= high fecundity, small body size, short generation time, and the ability to disperse offspring widely. R- Dandelions, mice, grass carp K-selectionIn stable or predictable environments the ability to compete successfully for limited resources is crucial, and populations of K-selected organisms typically are very constant and close to the maximum that the environment can bear. K= large body size, long life expectancy, and the production of fewer offspring that require extensive parental care until they mature. K-elephants, whales, Arctic Terns, tiger sharks

19. R (many eggs): Unstable environments. Many years things go wrong and the population drops, but in good years fry survival is high and the fish population can explode. K (few eggs): Stable environments. Many animals competing with each other for resources. Difficult to find an opportunity for a big population increase, and they would probably starve anyway.

20. River Unpredictable flow Unpredictable plankton blooms Unpredictable water temps Unpredictable oxygen levels! R or K ?

21. Coral ReefStable temperaturesStable water qualityConsistent plankton populations R or K ?

22. R or K ? Shallow temperate seas Unpredictable plankton blooms Unpredictable water temps

23. R or K ? Deep Sea Constant water temp Constant water quality Stable food supply

24. Intermediate Strategies K Stable tropical seas Large well-developed youngLive bearers ? R Unpredictable conditions for fry Egg broadcasters- huge numbers

25. Other strategiesfor the Kish crowd

27. Kurtus gulliveri the Nursery Fish

28. Kurtus gulliveri the Nursery Fish

29. Males carry eggs in clusters or balls attached to a hook on the head. This may be an adaptation to environments with low oxygen and high turbidity

30. Snailfish

33. Snail Fish Eggs

34. Bitterling

36. Bitterlings At Work

37. Seahorses

41. Sharks, Rays, and Ratfish Truly Special K

42. Internal Fertilization

43. Egg Layers are "oviparous"

44. Ratfish

45. Cownose Ray

49. Eagle Ray

50. Manta