Download presentation
Presentation is loading. Please wait.
Published byDebra Lee Modified over 9 years ago
1
The Influence of Spatial Dynamics on Predation Mortality of Bering Sea Walleye Pollock Pat Livingston, Paul Spencer, Troy Buckley, Angie Greig, and Doug Smith Alaska Fisheries Science Center Seattle WA
2
Eastern Bering Sea Yields and Biomass
3
Eastern Bering Sea Food Web
5
Arrowtooth flounder Walleye Pollock Pacific cod Consumption of Walleye Pollock
10
Recruitment Hypotheses 1) The drift of larval pollock spreads evenly across the Bering Sea shelf and the average distribution of adults (and their cannibalism) is sufficient to explain the observed pattern of population abundance. 2) The interannual variability in larval drift locations is the main force separating larvae from cannibalistic adults and is sufficient to explain the observed patterns of population abundance.
11
Migration Spawning Natural Mortality Age Update Consumption Harvest Growth Immigration Maturity Model Processes Within Each Time Step Calculations across all areas Calculations within each area
12
Model Dynamics
13
Eastern Bering Sea Survey Areas
14
Age Ranges of Stock Groups
15
Data Sources EBS Trawl survey - Annually, 1979-present Observer Sampling Program - Annually, 1979-present Echo Integration Trawls (EIT) - Triennially, 1982-present FOCI Trawls -- 1994,1995
16
Data Sources for Each Model Component Migration -- Trawl surveys, EIT cruises Suitabilities -- MSVPA modeling Consumption -- Model parameters tuned to bioenergetic modeling results Catch -- Observer sampling Growth -- Trawl surveys, observer sampling, FOCI cruises, EIT cruises Spawning -- Trawl surveys Maturity -- Trawl surveys Initial population sizes -- MSVPA modeling, OSCURS circulation model Mean lengths at age -- Trawl surveys, simulation modeling
17
Maturity and Growth Functions
18
Where S(l,L) pred,prey = suitability N(l) prey = Prey #’s by size group (l) and species W(l) prey = Prey weights by size group (l) and species N(L) pred = Predator #’s by size group (L) and species C(L) pred = Consumption by predator size group and species Consumption
20
Age 1 Age 2 Age 3 Distribution by age
21
Effects of Migration on the Relative Amount of Predation
22
Conclusions 1) Substantial data needs for a model with this level of detail 2) Model verification is complicated by the number of processes 3) Information on fishery and ecosystem interactions by spatial location is commonly requested of fishery scientists
Similar presentations
© 2025 SlidePlayer.com. Inc.
All rights reserved.