Using surplus production models to study predation in age-structured populations

Transcription

1 Using surplus production models to study predation in age-structured populations Kiva Oken, Timothy E. Essington Quantitative Ecology & Resource Management University of Washington October 15, 2013

2 Why predation? Variable but important in marine ecosystems

3 Why predation? Variable but important in marine ecosystems Part of ecosystem-based management

4 Why predation? Variable but important in marine ecosystems Part of ecosystem-based management Trade-offs

5 Why predation? Variable but important in marine ecosystems Part of ecosystem-based management Trade-offs Natural mortality

6 Why predation? Variable but important in marine ecosystems Part of ecosystem-based management Trade-offs Natural mortality Challenging to estimate precisely

7 Quantifying predation: the correlative approach Shrimp biomass (Gg) Worm & Myers, Ecology, 2003

8 Is surplus production better? Biomass y+1 = Biomass y + Surplus production y Catch y

9 Is surplus production better? Biomass y+1 = Biomass y + Surplus production y Catch y

10 Is surplus production better? Biomass y+1 = Biomass y + Surplus production y Catch y Surplus production Total biomass

11 Surplus production of age-structured populations

12 Surplus production of age-structured populations Low spawning potential High spawning potential

13 Surplus production of age-structured populations Low spawning potential Vulnerable to predators High spawning potential Less vulnerable to predators

14 Surplus production of age-structured populations Low spawning potential Vulnerable to predators Low catchability High spawning potential Less vulnerable to predators High catchability

15 Surplus production of age-structured populations Low spawning potential Vulnerable to predators Low catchability Large growth increment High spawning potential Less vulnerable to predators High catchability Small growth increment

16 Surplus production of age-structured populations Low spawning potential Vulnerable to predators Low catchability Large growth increment High spawning potential Less vulnerable to predators High catchability Small growth increment

17 Questions What can we glean from surplus production models that account for predation? Quantify top-down predation effects Estimates of management reference points

18 Questions What can we glean from surplus production models that account for predation? Quantify top-down predation effects Estimates of management reference points Approach Operating model used to simulate data Statistical model fit to simulated data Results and conclusions

19 Operating model

20 Operating model Predation 0 20 Years

21 Operating model Predation 0 20 Years

22 Operating model Predation 0 20 Years

23 Operating model Predation 0 20 Years

24 Simulated data Surplus production Total biomass

25 Four different prey life histories Pacific sardine Age at 50% maturity: 1.2 Adult natural mortality: 0.4 Silver hake Age at 50% maturity: 1.6 Adult natural mortality: 0.15 Atlantic menhaden Age at 50% maturity: 2.5 Adult natural mortality: 0.47 English sole Age at 50% maturity: 3.5 Adult natural mortality: 0.26

26 Deterministic dynamics Surplus production Time (years)

27 Deterministic dynamics Surplus production Atlantic Menhaden Biomass

28 Deterministic dynamics Surplus production Atlantic Menhaden Juv Adu Rec Biomass

29 Deterministic dynamics Pacific Sardine Silver Hake Surplus production Atlantic Menhaden Juv English Sole Adu Rec Biomass

30 Stochastic dynamics Pacific Sardine Surplus production 0 2MSY 0.5B MSY B MSY 1.5B MSY Biomass

31 Stochastic dynamics Pacific Sardine Silver Hake Surplus production 0 2MSY 0.5B MSY B MSY 1.5B MSY 0 2MSY 0.5B MSY B MSY 1.5B MSY Biomass

32 Stochastic dynamics Pacific Sardine Silver Hake Surplus production 0 2MSY 0.5B MSY B MSY 1.5B MSY Atlantic Menhaden 0 2MSY 0 2MSY 0.5B MSY B MSY 1.5B MSY English Sole 0 2MSY 0.5B MSY B MSY 1.5B MSY 0.5B MSY B MSY 1.5B MSY Biomass

33 Stochastic dynamics Pacific Sardine Silver Hake Surplus production 0 2MSY 0.5B MSY B MSY 1.5B MSY Atlantic Menhaden 0 2MSY 0 2MSY 0.5B MSY B MSY 1.5B MSY English Sole 0 2MSY 0.5B MSY B MSY 1.5B MSY 0.5B MSY B MSY 1.5B MSY Biomass

34 Top-down effects Recruits Predation t value Recruitment CV = Pacific Sardine No Obs. Error Obs. CV = 0.2

35 Top-down effects Recruits Predation t value Recruitment CV = Pacific Sardine Silver Hake Atlantic Menhaden No Obs. Error Obs. CV = 0.2 English Sole

36 Top-down effects Recruits Predation t value Recruitment CV = Recruitment CV = Pacific Sardine Silver Hake Atlantic Menhaden No Obs. Error Obs. CV = 0.2 English Sole

37 Top-down effects Juveniles Predation t value Recruitment CV = Recruitment CV = Pacific Sardine Silver Hake Atlantic Menhaden No Obs. Error Obs. CV = 0.2 English Sole

38 Top-down effects Adults Predation t value Recruitment CV = Recruitment CV = Pacific Sardine Silver Hake Atlantic Menhaden No Obs. Error Obs. CV = 0.2 English Sole

39 What if we add a second predator?

40 Multiple predators further degrades signal 1.0 Recruit Juvenile Proportion of predators detected Pacific Sardine Silver Hake Atlantic Menhaden

41 Multiple predators further degrades signal 1.0 Recruit Juvenile Proportion of predators detected Pacific Sardine Silver Hake Atlantic Menhaden

42 Reference point estimates unreliable

43 Reference point estimates unreliable Single species With predation B MSY Relative error Pacific Sardine Silver Hake Atlantic Menhaden English Sole

44 Reference point estimates unreliable Single species Relative error With predation B MSY MSY Pacific Sardine Silver Hake Atlantic Menhaden English Sole

45 Conclusions What can we glean from surplus production models that account for predation? Quantify top-down predation effects: Estimates of management reference points:

46 Conclusions What can we glean from surplus production models that account for predation? Quantify top-down predation effects: Easily masked by variability Depends on life history Estimates of management reference points:

47 Conclusions What can we glean from surplus production models that account for predation? Quantify top-down predation effects: Easily masked by variability Depends on life history Estimates of management reference points: Predation can improve estimates Surplus production models unreliable

48 Thanks! Trevor Branch, Jason Link, Andre Punt Essington lab