Ecopath parameters BOBLME Training Workshop on applicaon of EwE Phuket, Thailand, 8-12 Sep. 2014 Data requirements for Ecopath models Any number of living and detritus groups, and fisheries: • B Biomass (t·km-2) • P/B Producon / Biomass (year-1) • Q/B Consumpon / Biomass (year-1) • EE Other mortality (proporon) • Diets (proporons) • Catches (t·km-2 ·year-1) Accepts ranges for basic input, diets and catches The known and the unknowns For each group, provide esmates in green, and the program will esmate those in red. Choose one: 1). B, P/B, Q/B, EE, DCs, ... 2). B, P/B, Q/B, EE, DCs, ... 3). B, P/B, Q/B, EE, DCs, ... 4). B, P/B, Q/B, EE, DCs, ... Ranked ease of esmaon: P/B and Q/B > B > DCs >> EE hence EE oen le unknown (Opon 1). Defining the ecosystem Spaal structure from GIS Ecospace can pick up map (various resoluons) depth, primary producon, …, from GIS Defining the ecosystem groups

• Consider what policy quesons you’ll be asking; • Use funconal ecological groupings; • Use ecological similaries (niche overlap) rather than taxonomy to aggregate species; • Groupings must conform with data availability – notably fisheries stascs; • Leaving out a group known to occur because of lack of data is worse than using guessmates! • As a rule for ecosystem models: – include all trophic levels (but go easy on bacteria). • At least one group must be a detritus group • If there’s discarding a ‘dead fish’ detritus group may be worth considering Top predators are special • They are important in models, as they help to constrain the parameters of other consumers – as primary producon does from below; • Ecosim simulaons may benefit if important groups are split in age-specific stanza to capture ontogenec diet shis and exploitaon paerns Time period for model?

• Example Biomass

Time With Ecosim a recommended procedure is: two models

2. Use the ‘present model’ to make a 1. First make a ‘present ‘past model’ representing first year of model’ taking advantage of time series (can pick up food preference) data availability

Biomass 3. Run ‘past model’ over time, evaluate parameters, and use this info with ‘present model’ for predictions

Time Parameterizing two models

• The time period represented by the ‘past model’ will often be data-sparse, – e.g., with regards to diets; • We may assume that a consumer’s preference will be the same in two models of a given ecosystem; – Ecopath can estimate diets (given B’s) so that preference is the same in the two models – Oops, not in EwE6 yet, but you can do this based on electivity or search rates. Biomass (B)

• Biomasses are obtained from standard assessment methodologies • Biomasses don’t travel well, local information is important P/B - Production/biomass

• P/B = Z = F + M • From catch composition data using standard stock assessment methodologies; • Natural mortality of fish from Pauly’s (1980) empirical equation: 0.65 -0.279 0.463 M = K · L∞ ·T • F = catch / biomass

• P/B = K(L∞-Lavg)/(Lavg-Lfc) [B&H57] Z from FishBase’ Tools / Life history Z from FishBase’ Life-history tool Ecopath Master Equation (I) Again

P = Predation + Fishery + BA + Other M+ (Mig)

= Mortality + BA, or

Production = Mortality + Biomass Accumulation

If near equilibrium at Ecopath baseline, then Production = Mortality Ecopath Master Equation (I) Again2

Production = Mortality

As rates

P/B Ÿ B = Z Ÿ B, i.e. P/B = Z Estimate as a weighted average of P/B by age Q/B - Food consumption

• Relatively easy to estimate, with many literature values (www.fishbase.org) • Varies with P/B, so OK to use P/Q-ratio • Don’t enter B, P/B, EE to let Ecopath estimate Q/B Food consumption (Q/B) Growth (VBGF)

-K(t-t ) b W = W ·(1-e 0 ) Biomass (B) t ω Q/B t

Mortality Food consumption (Q)

-M(t-t ) Nt = R·e r t

K1 (Gross food conversion)

t t

t Food consumption from diurnal variation in stomach content: Maxim’s

Tilapia Lake Awasa, Ethiopia L = 23 cm, W = 265 g

12 16 20 24 04 Time of day

Feeding Start End Start

Maxim’s: developed by Astrid Jarre, available from Jacques Moreau, ENSAT Food consumption - The tail story

The faster swimming fish eats more Food consumption - The tail story

Yellow Aspect ratio: Red

AR = 9.8

Height2

AR = 1.3

-0.2 0.6 0.5 Ft Q/B = 3 · Wω · T · AR · 3 e Wω = asymptotic weight T = temperature

AR = aspect ratio = Ft = foodtype (0 f. carn.) Food consumption The tail story: when not to

Only for symmetrical tails used for propulsion Q/B from FishBase’ Life-history tool Production / Consumption

• P/Q typically varies between .05 and .30; • May be lower for baleens and higher for very small organisms; • Smaller individuals of a species are generally more efficient, i.e. have higher P/Q

• ‘Travels well’ • If P/B changes so should Q/B, hence P/Q changes less; • If P/Q is entered then either P/B or Q/B is calculated Ecotrophic efficiency (EE)

• EE is the proportion of the production that we explain the faith (predation or catch) of in the system; • 1-EE corresponds to ‘other mortality’; • Let Ecopath estimate EE; • For most groups EE will be close to 1, except, e.g., phytoplankton in bloom situations where EE may be closer to 0.5, kelps with EE’s ~ 0.1, and unexploited top predators where EE may be (close to) 0; • Small pelagics don’t die of old age. Diet composition e.g., for a tuna

Auxis 1.7% Sardines 7% Partly digested fish Anchovies 8.8% 31.6%

Squids 12.3%

Euphausiids 3.5%

Portunids 15.8% Others 19.3%

Use volume or weight! Estimation of diet compositions

• ‘Import’ is feeding on prey groups that are not explicitly included in the ecosystem; • Example: If marine mammals in a bay model spend part of the time outside the bay, then treat the food taken outside as ‘import’ in the marine mammal diet; • Diet compositions are often species-specific, and may need averaging. Use weighted averages; • It is often necessary to modify the diet compositions to ensure mass-balance • Ecosim will treat import as constant. Biomass accumulation (BA)

• Ecopath is not a steady-state model, biomasses can change over time period modeled; -2 -1 • Bacc is entered as rates (t · km ·year ) or relative to B;

• Use Bacc if you have data showing change in biomass at start and end of the year the model is for (start year for Ecosim);

• If Bacc values are entered, Ecosim will show change over time even without any change in fishing. Migration

• Immigration and emigration are rates (t·km-2 ·year-1); • Net migration enters into the production equation (Master Eq. I); • Migration is picked up by Ecosim and can be modeled in Ecospace Detritus fate

• At least one detritus group is required. It must be entered after the living groups on the Ecopath input form; • All living groups produce detritus, from excretion and egestion, and from ‘other mortality’; • If you have more than one detritus group it is necessary to specify where detritus produced by a living group is directed. Other input for Ecopath models

For living groups: For fleets: • Biomass accumulation rate • Landings by group • Assimilation rate • Discards by group • Net migration rate • Discard fate • Detritus fate • Fixed cost of fishing • Variable cost • Existence value • Market price by group

• The value chain adds detailed accounting for the production, processing, distribution, and marketing part of the fishing sector

Default values are 20% for non-assimilated, 0 for other Non-assimilated food (U)

• Remember the Ecopath Master Equation (II):

Q = P + R + U

• Q and P are estimated first

• Respiration (R) is then calculated as R = (Q - P) - U

i.e.; changing U only impacts R • The default value of 20% for U is generally acceptable, except for herbivores and detritivores where 40% leads to more reasonable R/B ratios. Fisheries data

• Include any number of fleets/gears;

• Parameters for each:

• variable costs;

• fixed costs;

• market prices;

• landings;

• discards;

• fate of discards. • Plus the value chain Landings • The landings (exclusive of discards) should be entered as rates (t·km-2·year-1); • Landings with no values should be treated as landings (set price to 0), not as discards, as the latter are fed back into the system. Discards are entered as rates (t· km-2·year-1) Discard fate

• For models with discards it is advisable to have a detritus group called, e.g., ‘dead fish’; • When so, then direct the discards to this group, and have scavengers feeding on it; • ‘Dead fish’ are of higher nutritional value than most other detritus (such as excreta from zooplankton). Cost of fishing

• Fixed value of operating each gear can be entered; • Variable cost is entered as relative to the effort in the Ecopath model; • Spatial fishing costs may be entered in Ecospace; • Any monetary currency can be used as unit; • Extensive bio-economical analyses are included. Market prices

• Fleet-specific prices for each group that is landed; • Default value is 1 ( no good) for all groups for all fleets • Ex-vessel prices are available from www.seaaroundus.org. • More about this when we discuss value chain Ecoranger: Semi-Bayesian parameter estimation

Input ranges ‘Priors’

Acceptable inputs Mass balance Selection of possible & models physiological Resampling (Sampling Importance Resampling) constraints

Selection of ‘best’ ‘Posteriors’ model Accepted inputs Outputs Data pedigree

• Describes the origin of data used for model • Overall model pedigree index [0,1] • Feeds confidence intervals to Ecosim (and Ecoranger in EwE5) Pedigree: how well rooted is the model in local data? Pedigree: describes uncertainty – picked up by Monte Carlo routines