1. Age and Growth Growth & age patterns Measurement techniques

2. Growth patterns Determinate Growth –Mammals & birds Indeterminate Growth –Fishes Determinate Indeterminate Age Size

3. Indeterminate growth & fecundity

5. Fish growth – von Bertalanffy equation L t =L max (1-e -kt )

6. Fish growth – von Bertalanffy equation

7. Length – Weight relation (power function) W=a L b

8. Growth patterns Great Plasticity in growth Size at age: High variability –Between species –Between populations –Between individuals

9. Environmental factors influencing growth Temperature Food and Nutrient Availability Light Regime Oxygen Concentration Salinity Pollutants Predator Densities Intraspecific Social Interactions Genetics

10. Example: Species polymorphism Salmonidae Artic Charr Salvelinus alpinus Large benthic feeder Small benthic feeder Piscivorous feeder Planktivorous feeder

11. Annual growth variation

12. Population Age-Size structure

13. Population Size-Age relationship

14. Age measurement methods Scales Otoliths Vertebrae Rays/Spines

15. Age measurement through scales

18. Age measurement through otoliths

19. Otolith uses Age determination –Daily ring counts –Annual ring counts –Radioactive isotopes Species identification Paleoclimate studies (0 18 ) Life history studies (elemental tracers)

20. (Oncorhynchus clarkii)

21. Weakfish (Cynoscion regalis)

22. Otolith age validation

24. Otolith age validation – nuclear fallout

25. Anoplomatidae Sablefish Anoplopoma fimbria Age calculation error case Scales: 3-8 years Otoliths: 4-40 & up to 80

26. Species identification

27. Dolphin stomach contents

28. Climate studies (isotope 0 18 )

29. (6000 year old fossil)

30. Elemental tracers – Life history (Zn, Sr, Ba, Mn, Fe and Pb)

31. Thorrold et al. 2001 Elemental tracers of weakfish

33. Proof of Natal Homing! Thorrold et al. 2001

34. How many fish are there?

35. N t+1 = N t + B – D + I – E  B = births  D = deaths  I = immigration  E = emigration How do populations change? Deaths Population Births Emigration Immigration Stocking Angling

36. Survival Eggs and larvae suffer the largest losses HATCH Recruit! 2 cohorts each produce 10,000,000 eggs 90.5% survivorship/day yields 24,787 survivors at 60 days 95.1% survivorship/day yields 497,871 survivors at 60 days

37. Recruitment Can mean many things! –Number of young-of-year (YOY) fish entering population in a year –Number of fish achieving age/size at which they are vulnerable to fishing gear Somewhat arbitrary, varies among populations Major goal of fish population dynamics: understanding the relationship between stock size and recruitment

38. What determines recruitment? -Stock size (number and size of females)

39. What determines recruitment? spawning stock biomass (SSB) Ricker Beverton-Holt Density-independent From: Wootton (1998). Ecology of teleost fishes.

40. What determines recruitment? spawning stock biomass (SSB) Ricker Beverton-Holt Density-independent From: Wootton (1998). Ecology of teleost fishes.

41. What determines recruitment? spawning stock biomass (SSB) Ricker Beverton-Holt Density-independent From: Wootton (1998). Ecology of teleost fishes.

42. The problem? Stochasticity = variable recruitment!

43. From: Cushing (1996). Towards a science of recruitment in fish populations

44. Highly variable recruitment results in naturally very variable catches From: Jennings, Kaiser and Reynolds (2001). Marine Fisheries Ecology

45. Population Abundance On rare occasions, abundance can be measured directly –Small enclosed systems –Migration

46. Catch per unit effort (CPUE) Very coarse and very common index of abundance Effort= 4 nets for 12 hours each= 48 net hours Catch= 4 fish CPUE=4/48=0.083 Effort= 4 nets for 12 hours each= 48 net hours Catch=8 fish CPUE=8/48=0.167 We conclude population 2 is 2X larger than population 1 1 2

47. Estimates of Population Size Proportional sampling Rp = size of the range of the population (Rp), (uniform distribution) Rs = size of sampling a region Ns/Np = Rs/Rp. Np = (Ns Rp)/Rs = Population Abundance No Accuracy Estimate

48. Population abundance Density estimates (#/area) –Eggs estimated with quadrats –Pelagic larvae sampled with modified plankton nets –Juvenile and adult fish with nets, traps, hook and line, or electrofishing Density is then used as index of abundance, or multiplied by habitat area to get abundance estimate

49. Depletion methods * * * * Number Caught Number previously caught Closed population Vulnerability constant for each pass Collection efficiency constant Often not simple linear regression

50. Estimates of Population Size Mark & Recapture capture – mark – release - recapture Np = population abundance M = number of individuals that are marked n = size of the second sample of organisms R: number of marked organisms in second sample Np = (M*n)/R Accuracy Estimates Available

51. Mark recapture M=5 C=4 R=2 N=population size=????

53. Modified Petersen method Assumptions: –Closed population –Equal catchability in first sample –Marking does NOT influence catchability Marked and unmarked fish mix randomly Mortality rates are equal –Marks are not lost

54. Schnabel method Closed population Equal catchabilty in first sample Marking does NOT influence catchability Multiple recaptures –Easier to pick up on violation of assumptions