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 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: ,000 codfish
Year 3: (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, ,000,000, ,000,000,000,000,000 = 2,000,100,001,800,000 or 2 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-selection In 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-selection In 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
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. R or K ? River Unpredictable flow Unpredictable plankton blooms
Unpredictable water temps
Unpredictable oxygen levels!
R or K ?

21. Coral Reef Stable temperatures Stable water quality Consistent 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 R Stable tropical seas
Large well-developed young Live bearers ? R
Unpredictable conditions for fry
Egg broadcasters- huge numbers

25. Other strategies for 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
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

51. Stingray

53. Torpedo

54. Chevy Stingray

55. Oviporous
Mating Strategies

60. Oviporous
Eggs

61. Skate
Egg
Shark Egg

62. Mermaid’s Purse

69. Port Jackson Shark

73. Oviviparous:
eggs
hatch in
females
and embryos
hang out and grow

75. Smooth Dogfish

78. Porbeagle Shark

80. Another Oviviparous Strategy
Baby sharks swim in the mother and get nutrients by drinking the uterine fluids

81. Viviparous:
Like mammals.
Placenta-like
structure

82. Uterus Like Sac
Shark Embryos
Placenta like structures carrying blood

84. Special (and nasty)
Tiger Shark
Reproduction
(oviparous)

89. Shark embryos in eggs

90. The mother shark feeds
unfertilized eggs to the babies.

91. The mother shark feeds
unfertilized eggs to the babies.

92. Tiger Shark
1 of 5 must survive

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

94. Many Approaches Oviparous: Egg layers
Broadcasters
Parental care
Oviviparous: Eggs hatch inside female
Viviparous: Placenta-like arrangements