Laure Pecquerie Ecology, Evolution and Marine Biology UC Santa Barbara

1. Reconstructing fish life histories from otoliths in the context of the Dynamic Energy Budget (DEB) theory Laure Pecquerie Ecology, Evolution and Marine Biology UC Santa Barbara Pierre Petitgas, Ronan Fablet, Roger Nisbet and Bas Kooijman pecquerie@lifesci.ucsb.edu Santa Cruz, 03/16/2009

2. Fish length (cm) Otolith radius (µm) 1 2 3 Fish otoliths = archives of individual life history • Transect length -> time • Increment widths -> growth 0 0.7 mm 4 years

3. Fish otoliths = archives of individual life history • Opacity pattern -> time • Increment widths -> growth • Isotopic composition -> temperature δ18O (‰) 0 1 2 3 0.7 mm 4 years

4. Fish otoliths = archives of individual life history • Otoliths are used in • Stock assessment • Ecological studies • Paleontological studies • To reconstruct • Growth • Migration pattern • Temperature conditions

5. Fish metabolism (growth + maintenance) Environment Fish otoliths = bio-calcified structures

6. Fish length (cm) Fish length (cm) Fish length (cm) Otolith radius (µm) Otolith radius (µm) Otolith radius (µm) Fish otoliths = bio-calcified structures • Linear otolith radius – fish length (OR-FL) relationship for adults • Slow growing fish have larger otoliths • Non –linear (OR-FL) relationship for larvae  Biais in back-calculation of growth

7. Fish otoliths = bio-calcified structures false annual rings Hake otolith (IFREMER, LASAA)  Opacity pattern can be difficult to interpret

8. Motivations Modeling otolith growth, opacity according to the state of an individual and its environment • We directly compare data and model outputs • Variability among individuals = Testing scenariosCan we disentangle food and temperature effects • Reconstruction of past environment (Paleontology, Ecology) Process-based approach to understand the effect of metabolism on calcified structures  DEB theory

9. Dynamic Energy Budget (DEB) theory Outline Reconstructing food conditions from opacity pattern at the seasonal level Reconstructing food conditions that allow survival up to metamorphosis

10. Dynamic Energy Budget (DEB) theory • Describes the uptake and use of energy and matter by living organisms • Applied to bacteria…but also whales and plants • Classical bioenergetic model: dW / dt = Ingestion – Respiration – Excretion - … = aWb - cWd - eWf • DEB model:biomass = structure + reserve W = WV + WE • dV / dt = f (V, E)dE / dt = g (V, E)

11. DEB theory: mechanistic approach R = 0.0516 L2.437 R = 0.0336 L2 + 0.01845 L3 Respiration rate as a function of length for Daphnia pulex (Kooijman, 2000)

12. food faeces assimilation somatic maintenance  reproduction Reproductionbuffer growth structure Spawning module DEB theory: full life cycle reserve maturity maintenance 1- development maturity

13. Von Bertalanffy growth • In constant environment, the model reproduces a von Bertalanffy growth L = L (1 – e-k(t-t0)) • Physiological interpretation of k and L, with 1 / k = f(L), a well known correlation in fish studies

14. DEB theory: standard model • 3 ordinary differential equations dE / dt = pA – pC dV / dt = (K pC – pM) / [EG] dER / dt = (1 - K ) pC – pJ with pA = f {pAm} V 2/3 pM = [pM] V • 12 parameters for a full life cycle • 2 forcing variables: temperature and food • Outputs : length, number of eggs, energy per egg -- > We need info on growth AND reproduction for the parameter estimation

15. Chl-a 2 - Forcing variables 3 - Numerical integration 4 – Model outputs DEB theory: simulation 1- NPZD simulations

16. Calibration of a DEB model for anchovy Length (cm) Weight (g) Weight (g) Length (cm) Time (months) Time (months) Time (months) Time (months) We calibrated parameters to reproduce the growth pattern of a mean individual in a seasonal environment

17. Length (cm) Development puberty Reproduction metamorphosis first feeding Anchovy life cycle  We can reproduce main features of anchovy life cycle

18. Summary Part I • Dynamic food and temperature conditions can be considered in the context of DEB theory • Reserve buffers variations of food; • Stage transitions can occur at different ages and lengths according to food and temperature history  Features that we could use to reconstruct individual life histories and experienced food conditions

19. Dynamic Energy Budget (DEB) theory Reconstructing food conditions that allow survival up to metamorphosis Outline Reconstructing food conditions from opacity pattern at the seasonal level

20. Otolith as a product • Products in DEB theory: • CO2 respiration • Faeces, nails, hairs • Tree trunk • Weighted sum of the 3 transformations : assimilation,growth and maintenance dP/ dt = αpA + βpG + γ (pM+pJ) • Faeces  β = γ = 0 • Otolith  no contribution from assimilation, α = 0 • Opacity = 0 whithout growth βpG / (βpG + γ (pM+pJ))

21. Otolith growth and opacity Data Length DEB model Simulation Otolith modeling : individual history Environment

22. Slow growing fish have larger otoliths Length DEB model Otolith modeling : individual history Otolith growth and opacity  We can reproduce main observations on otolith growth and opacity with simple mechanisms Environment

23. DEB model Reconstruction of length + Assimilated food Food history reconstruction from otolith We can theoretically reconstruct both growth and assimilated food from temperature and otolith data • extraction of new information from data difficult to obtain • new information = food in natural conditions, at the individual scale

24. Two age-3 individuals ? Individual 1 Individual 2

25. 3 years-old 2 years-old False check

26. Summary Part II • Simple mechanism to reproduce the observations: Otolith formation is tightly coupled to growth but also to maintenance processes • Real potential for extracting new information from otoliths structures: assimilated food in natural conditions; mechanism for false checks • Validation is required  Modeling results can guide experiment design. On going work: test of the method with cod experiments

27. Dynamic Energy Budget (DEB) theory Reconstructing food conditions from opacity pattern at the seasonal level Outline Reconstructing food conditions that allow survival up to metamorphosis

28. Otolith growth rate (m/d) Otolith of a larvae Age (d) P. Grellier, IFREMER Conditions that allow larval survival up to metamorphosis • Recruitment level was higher in 1999 compared to 2003 • Juvenile surveys: 200 individuals in 1999 ; 350 in 2003 ; Otolith growth rate: 125 in 1999; 68 in 2003

29. Age at metamorphosis (d) Otolith radius at metamorphosis (µm) Date at 1st feeding (julian days) Date at 1st feeding (julian days) Age and otolith radius at metamorphosis decrease according to date at first feeding Age and size at metamorphosis Larval period April 1st August 1st How do we explain these patterns ?

30. Simple otolith model + non-isomorphic growth -- > observed Otolith radius – Fish length relationship for larvae Length (mm) Length (mm) Age (days) Otolith radius (µm) • Regner (1996)  Gompertz equation = empirical model • Anchovy DEB model = process-based model Larval stage: growth

31. Lasker et al. (1970) Larval stage : survival to starvation At mouth opening, egg initial reserves allow longer survival under starvation Nb of days before death during starvation Maintenance cost depends on temperature: larvae are more sensitive to mortality at high temperature Scaled reserve density e, -

32. Simulations Temperature (°C) Age at metamorphosis (d) Age at metamorphosis (d) Time (julian days) Date at birth (julian days) Scaled functional response (-) Time (julian days) Time (julian days) Scenario analysis

33. Summary Part III • Larval stage = critical stage that determines recruitment level ; we need more information and food conditions in particular • Anchovy metamorphosis in otoliths: we need validation with experiments in controlled conditions • Otolith change in shape at metamorphosis: need a careful description • New results: Food levels in natural conditions from the analysis of the variability of age and otolith radius at metamorphosis • We could apply this study to other stage transitions

34. Conclusions and Future work • Food conditions in natural environments are highly variable ; DEB theory is a suitable quantitative framework to work on dynamic food conditions • Otolith = one of the few sources of information in natural conditions at the individual level; Development of a new method to obtain food conditions from otolith opacity and growth; • Modeling the full life cycle within the same framework: Promising transfer of the model to the larval stage but shape is an important issue to convert length to volume throughout the different life stages (both body and otolith shapes) • Validation and further development of these methods are required • Numerous potential applications ; other fish species, biogenic carbonates (bivalve shells, coral skeletons)

35. Thanks ! • References • S.A.L.M. Kooijman Dynamic Energy and Mass Budgets in Biological Systems. Cambridge University Press, 2000Third EditionOct 2009 • S.A.L.M. Kooijman,T. Sousa, L. Pecquerie, J. van der Meer and T. Jager, 2008.From food-dependent statistics to metabolic parameters, a practical guide to the use of dynamic energy budget theory. Biological Reviews 83, pp. 533–552 • L. Pecquerie. 2007. Bioenergetic modeling of the growth, development and reproduction of a small pelagic fish: the Bay of Biscay anchovy. http://www.ifremer.fr/docelec/doc/2007/these-3505.pdf.