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Ecopath Beth Fulton 2012. Based around trophodynamic links Ecopath.

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Presentation on theme: "Ecopath Beth Fulton 2012. Based around trophodynamic links Ecopath."— Presentation transcript:

1 Ecopath Beth Fulton 2012

2 Based around trophodynamic links Ecopath

3 Used intelligently = VERY good tool thats why its lasted for >25 years (3000+ users) Cautions

4 No model can capture reality completely (simplifications necessary) some times will work, some times wont understand what youre assuming (ignoring) Cautions

5 No model can capture reality completely (simplifications necessary) some times will work, some times wont understand what youre assuming (ignoring) pragmatic realist Cautions Non-believer Believer Realist

6 Mass balance model (solved as simultaneous equations) balance = over a year Production = Catch + Predation + Accumulation + Net Migration + Other mortality Consumption = Production + Unassimilated food + Respiration ZiZi Equations

7 Equation Reorganise to: ZiZi Equations

8 Think in terms of B and Q Q ij is a rate (biomass per year) Total consumption = sum Q Prey mortality M ij = Q ij / B i Fishing F i = C i / B i ZiZi Network of B & Q B5B5 B5B5 B4B4 B4B4 B3B3 B3B3 B2B2 B2B2 B1B1 B1B1 Q 35 Q 34 Q 24 Q 13 Q 12 Catch C5C5

9 Respiration, growth and sloppy feeding Mortality external to model Dissipation of Energy (1-G) (1-EE) (Q/B) (P/B) Let Ecopath estimate EE Should be close to 1 for most groups (Small pelagics dont die of old age) primary producers ~ ok; unexploited top predators ~ 0

10 Q = P + R + U Q and P are estimated first Respiration (R) is then calculated as R = (Q - P) - U (so changing U only impacts R) Default value = 0.2 generally OK (herbivores and detritivores better at 0.4) Unassimilated food

11 Dead or alive At least one group must be a detritus group Producer or consumer Multi-stanza Groups

12 Log Numbers at age Age (months) Weight at age Each stanza (range of ages) can be assigned distinctive: 1)Total mortality rate Z (varying with stanza-specific predation rates) 2)Prey and habitat preferences (diet composition, distribution) 3)Behavioural tactics (responses to food availability via growth rate and/or activity and associated predation risk) 4)Vulnerability to fishing and bycatch Shift from density dependent mortality to density dependent growth Cascading bottleneck effects Rockfish Multi-stanza Groups

13 Use functional ecological groupings niche overlap rather than taxonomy Try to be even handed across trophic levels Lump to a point and then omit Leaving out important group because of lack of data is worse than using guesstimates No one answer (lots doesnt mean best) Try multiple Groups - Guide

14 Important Constrain parameters of other consumers (primary production does too) Allow for ontogeny (multustanza) improves Ecosim performance Groups – Top Predators

15 Defining groups in model (ecological only) Ecopath Edit Edit Group, Insert give each entry individual name click on whether consumer or producer edit multistanza Ecopath – Define Groups

16 Biomass (t·km -2 ) Production / Biomass(t·km -2 ·year -1 ) Consumption / Biomass(t·km -2 ·year -1 ) Ecotrophic efficiency(proportion) Diets(proportion) Landings (by fleet)(t·km -2 ·year -1 ) Discards (by fleet)(t·km -2 ·year -1 ) Ecopath Data

17 Basic data biomass, mortality, consumption, unassim EE (if missing one of the others) Ecopath – Base Data

18 shows comment or reference included (mouse over to read it, click on remarks tab to edit it) Ecopath - Comments

19 Time Biomass Period 1 Period 2 Period 3 Sometimes need multiple models

20 Fishing mortality = from catch composition (standard stock assessment method) F = C / B Natural mortality of estimates M = K 0.65 · L ·T (Pauly 1980) Final P/B estimates P/B = Z = F + M P/B = K(L -L avg ) / (L avg -L) (Beverton & Holt 1956) Production / Biomass

21 Consumption / Biomass

22 t t Growth (VBGF) t t Mortality t t Biomass (B) t t K 1 (Gross food conversion) t t Food consumption (Q) W t = W ·(1-e -K(t-t 0 ) ) b N t = R·e -M(t-t r ) Q/B Lab estimates or…

23 The faster swimming fish eats more Fish Consumption

24 Q/B = 3 · W -0.2 · T 0.6 · A R 0.5 · 3 e Ft W = asymptotic weight T = temperature A R = aspect ratio F t = foodtype Aspect ratio: Yellow Red A R = 9.8 A R = 1.3 Height 2 Fish Consumption

25 Only for symmetrical tails used for propulsion When Not To…

26 Diet data proportional diet make-up of each predator external food can be included (supplemental) weighted averages of species in functional group often modified as model balanced Ecopath – Diet data

27 Partly digested fish 31.6% Others 19.3% Portunids 15.8% Euphausiids 3.5% Squids 12.3% Anchovies 8.8% Sardines 7% Auxids 1.7% Tuna diet example Using volume or weight:

28 Migration (immigration and emigration) Biomass accumulation if have evidence of ongoing directional change big implications for Ecosim so use with care Ecopath – Other Production

29 1+ detritus necessary (sometimes have different types) Detritus = from excretion, egestion, mortality Must say where it goes Ecopath – Detritus fate

30 Fisheries data Edit Add fleet can put in economic parameters to differentiate fleets but rarely done Ecopath – Define Fleets

31 Fisheries data Edit Add fleet can put in economic parameters to differentiate fleets but more rarely done landings and discards per fleet Ecopath – Landings

32 Landings (by fleet)(t·km -2 ·year -1 ) Discards (by fleet)(t·km -2 ·year -1 ) Variable costs (percentage vs effort) Fixed costs(percentage) Ex-vessel prices(MU ·tonne -1 ) Non-market prices(MU ·tonne -1 ) Fate of discards Ecopath Fisheries Data

33 Landings = what humans remove from the system Discards cycled in the system Ecopath – Landings & Discards

34 Ecopath – Fate of Discards Same principle as fate of detritus Good to have discards as own detritus pool (so can see direct influence)

35 Ecopath – Economics Market prices (simple bioeconomics) default = 1.0 Existence value (e.g. as tourism base) default = 0.0

36 Parameterization Check values make sense EE > 1 means unbalanced Ecopath - Balancing

37 Change uncertain first Diet (keep cannibalism low) P/B Q/B unassimilated portion Rules of thumb P/Q = 0.1 – 0.3 (more for bacteria, less for top preds) Resp/B = 1-10 for fish, for copepods Ecopath – Balancing Guide Typical likelihood of change

38 Green cells show potentially problematic values Mortality Sheet

39 Green cells show potentially problematic values Sheets showing mortality breakdown per predator & fleet Mortality Sheet

40 Rate data quality Pedigree

41 Flow chart Ecopath - Extras

42 Network Analysis Outputs system statistics network indices flows primary production required mixed trophic impacts particle size distributions keystoneness ascendency cycles and pathways ECOPATH, ECOSIM and ECOSPACE Ecopath - Extras

43 Thank you

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