# Start the story of qualitative analysis in the 12th century with a gentle man called Fibonacci. Then move to Malthus, Darwin, Lotka and Volterra then get.

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Start the story of qualitative analysis in the 12th century with a gentle man called Fibonacci. Then move to Malthus, Darwin, Lotka and Volterra then get into the nitty gritty of qualitative modelling Ecopath Beth Fulton 2012

Ecopath Based around trophodynamic links

Cautions Used intelligently = VERY good tool
that’s why its lasted for >25 years (3000+ users)

Cautions No model can capture reality completely (simplifications necessary) some times will work, some times won’t understand what you’re assuming (ignoring)

Cautions No model can capture reality completely (simplifications necessary) some times will work, some times won’t understand what you’re assuming (ignoring) pragmatic realist Realist Non-believer Believer

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

Equations Equation Reorganise to: Zi

Network of B & Q Zi Think in terms of B and Q
Qij is a rate (biomass per year) Total consumption = sum Q Prey mortality Mij = Qij / Bi Fishing Fi = Ci / Bi Catch B5 C5 B4 Q34 Q35 Q24 B3 B2 Q13 Q12 B1 Zi

Dissipation of Energy Respiration, growth and sloppy feeding
Mortality external to model (Q/B) (P/B) (1-G) (1-EE) Let Ecopath estimate EE Should be close to 1 for most groups (“Small pelagics don’t die of old age”) primary producers ~ ok; unexploited top predators ~ 0

Unassimilated food 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)

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

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

Groups - Guide 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 doesn’t mean best) Try multiple

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

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

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

Biomass Sometimes need multiple models Period 2 Biomass Period 3

Production / Biomass Fishing mortality = from catch composition (standard stock assessment method) F = C / B Natural mortality of estimates M = K0.65 · L∞ ·T (Pauly 1980) Final P/B P/B = Z = F + M P/B = K(L∞-Lavg) / (Lavg-L’) (Beverton & Holt 1956)

Consumption / Biomass

Consumption / Biomass Q/B Lab estimates or… Growth (VBGF) Biomass (B)
Wt = W·(1-e-K(t-t0))b Q/B t Food consumption (Q) Mortality t Nt = R·e-M(t-tr) K1 (Gross food conversion) t t t

Fish Consumption The faster swimming fish eats more

Fish Consumption Yellow Aspect ratio: Red AR = 9.8 AR = 1.3
Height2 AR = 1.3 Q/B = 3 · W∞-0.2 · T0.6 · AR0.5 · 3 eFt W∞ = asymptotic weight T = temperature AR = aspect ratio Ft = foodtype

When Not To… Only for symmetrical tails used for propulsion

Ecopath – Diet data 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

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

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

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

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

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

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

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

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

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

Ecopath – Balancing Guide
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 Typical likelihood of change

Mortality Sheet Green cells show “potentially problematic” values

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

Pedigree Rate data quality

Ecopath - Extras Flow chart

Ecopath - Extras 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

Thank you Explain why important - what has climate change shown as already? Fisheries is streets ahead in thinking about co-management, adaptive management and tools to support that.

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