Ecosystem Models

Question 1

Primary motivations for Ecosystem models?

Answer 1

single species models missing important and deterministic drivers of biomass and abundance (e.g., environment / habitat, ecological / trophic, fishery / technical, etc.)

Question 2

What are the four alternatives for ecosystem models in fisheries science?

Answer 2

Incorporate the physical environment

Incorporate ecology

Incorporate people

Incorporate everything
(or multiple things)

Question 3

Incorporating the physical environment

Answer 3

Can determine stock abundance

Can affect: recruitment, growth, natural mortality, availability to fishery

Question 4

Why evaluating the physical environment important?

Answer 4

Management targets and threshold values may be a function of environmental conditions

Question 5

What is an example of a physical environment model?

Answer 5

The salmon habitat model

Question 6

Salmon Habitat Model

Answer 6

incorporated characteristics of spawning habitat (e.g., temperature, stream flow, sediment type) into recruitment/survival and age-structured population dynamics

Question 7

Recruitment of many small pelagic species found to be coupled with

Answer 7

environmental conditions

Question 8

What is an example of environmentally driven abundance?

Answer 8

Pacific sardine (Sardinops sagax) eggs most abundant at sea-surface temperatures of 13-15 °C, larvae most abundant 13-16 °C (best in warm ocean conditions)

Question 9

How does the Pacific Fisheries Management Council use environmental conditions models?

Answer 9

sea-surface temperature data to set environmentally-dependent effort targets

Question 10

The productivity of exploited species may be

Answer 10

temperature dependent

Question 11

How is ecological modeling incorporated most frequently?

Answer 11

predator-prey interactions

example - food web modeling

Question 12

How are food web models useful?

Answer 12

characterizing tradeoffs between exploitation and conservation across multiple, interdependent species

Question 13

How are multispecies models that include predation used?

Answer 13

estimate multispecies maximum sustainable yield (MMSY)

Management that targets MMSY may cause several stocks to collapse

Question 14

Incorporating People

Answer 14

Commercial fisheries -> maximize profit
Recreational fisheries -> maximize utility/satisfaction

Question 15

What is driven by economic incentives?

Answer 15

Fishing effort (and mortality)

Question 16

What is this data showing?

Answer 16

Catch rates lower where fishing is easier / less expensive (closer to population centers, sheltered from prevailing winds); suggests species less abundant in these areas

Question 17

Fisheries dependent data depends on…

Answer 17

human behavior

Spatiotemporal decisions non-random
Length/age composition may reflect targeting

Question 18

Non-random observations can

Answer 18

bias assessment model outputs

Question 19

What is a solution to try and get unbiased data?

Answer 19

Standardization procedures of fishery dependent data common

e.g., control for factors influencing behavior → not perfect

Question 20

Incorporating “everything”

Answer 20

Complete ecosystem models can incorporate all relevant aspects (environment, ecology, people/economic sectors)

Typically simulation based (not analytical)

Question 21

What are two ecosystem models that have frequent fisheries applications?

Answer 21

Ecopath with Ecosim (EwE)
Atlantis

Question 22

Ecopath

Answer 22

trophic mass balance food web model

Question 23

Ecosim

Answer 23

uses mass-balance results from Ecopath and simulates temporal dynamics

Question 24

What can an Ecosim model identify?

Answer 24

fishing mortality rates that maximize: fishery profits, social benefits (employment), species rebuilding, ecosystem resilience/structure

Question 25

What does an ecosim model incorporate?

Answer 25

relative abundance indices, catches, fishing effort

Question 26

Ecospace

Answer 26

adds spatial component to dynamic simulations

Question 27

What can Ecospace model accommodate?

Answer 27

habitat preferences, spatially heterogeneous fishing effort

Question 28

How is an Ecospace model useful?

Answer 28

Useful in exploring impacts of spatial management (e.g, MPAs)

Question 29

Atlantis

Answer 29

Biophysical model: three dimensional model tracks nutrient flows through biological groups

Question 30

What are the important ecological process associated with the Atlantis model?

Answer 30

production, consumption, waste, migration, recruitment, mortality

Question 31

What sub-models can the Atlantis model include?

Answer 31

for fishing, coastal development (habitat change), broad-scale environmental change, assessment and management

Question 32

How are ecosystem model used most often?

Answer 32

illustrate relationships and responses rather than explicit integration into management