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Inherent Uncertainties in Nearshore Fisheries: The Biocomplexity of Flow, Fish and Fishing

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Title: PowerPoint Presentation Last modified by: Dave Siegel Created Date: 8/23/2001 8:23:18 PM Document presentation format: On-screen Show Company – PowerPoint PPT presentation

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Title: Inherent Uncertainties in Nearshore Fisheries: The Biocomplexity of Flow, Fish and Fishing


1
Inherent Uncertainties in Nearshore Fisheries
The Biocomplexity of Flow, Fish and Fishing
Dave Siegel1, Satoshi Mitarai1, Crow White1,
Heather Berkley1, Chris Costello1, Steve Gaines1,
Ray Hilborn2, Bruce Kendall1, Steve Polasky3, Bob
Warner1 Kraig Winters4 1 UCSB, 2 UW,
3 UMn 4 SIO/UCSD Flow, Fish
Fishing (F3) Biocomplexity
2
Flow, Fish Fishing
  • Human-natural system biocomplexity project
  • Oceanography, population dynamics, marine
    ecology, fishery management, fisherman behavior
    economics all wrapped up together
  • Focus on California nearshore fisheries role of
    uncertainty in management but in a general way
  • Today environmental uncertainties their role
    on the stocks harvest of a long-lived fish

3
Settlement
Flow
Climate
Recruitment
Habitat
Fish
Harvest
INFO
Market
Fishermen
Regulation
4
Settlement
Flow
Climate
Recruitment
Habitat
Fish
Harvest
INFO
Market
Fishermen
Regulation
5
Stock / Harvest Modeling
  • Next generation stocks
  • survivors - harvest new recruits
  • SURVIVORS are surviving adults from previous time
  • HARVEST are those extracted from the fishery
  • NEW RECRUITS are a function of fecundity of the
    survivors, larval dispersal mortality,
    settlement recruitment to adult stages

6
Model System
  • Long lived, sessile, harvested fish
  • M 0.05 y-1, density dependence parameterized
    using Beverton-Holt on larval settling densities
  • Larval dispersal scales (Gaussian kernel)
  • PLD 60 d, Dd 150 km Tspawn 60 d
  • Virgin carrying capacity set to 100 units
  • Fixes fecundity
  • 1-D coastline domain
  • 2000 km long, Dx 5 km absorbing BC

7
Harvesting
  • Total allowable catch (TAC) f(recruitment)
  • TAC 20 of the measured recruitment
  • Enables TAC to be set dynamically
  • Spatial harvest allocation f(adult density)
  • Fishermen fish where there are the highest fish
    densities harvest up to the set TAC
  • So-called ideal free distribution

8
Base Case
Adults (60)
Recruitment (4)
Settlement (6)
Harvest (0.9)
Diffusive larval kernel, no sources of
uncertainty
9
Settlement
Flow
Climate
Recruitment
Habitat
Variability in Fecundity CV 50
Fish
Harvest
INFO
Market
Fishermen
Regulation
10
Climate Case
Adults
Recruitment
Settlement
Harvest
Diffusive larval kernel - fecundity variability
(CV 50)
11
Regional means are same as the base case
12
Short time scales of the process makes larval
transport stochastic
Settlement
Flow
Climate
Recruitment
Habitat
Fish
Harvest
INFO
Market
Fishermen
Regulation
13
ROMS simulations from Mitarai et al. JMS 2006
14
Larval Connectivity is a Stochastic
Driven by flow scales, short spawning durations
the low probability of survival Model
stochastically which matches Gaussian kernel when
of settlement events is large Siegel et al. in
review Mitarai et al. in prep.
Source Location (km)
Self settlement
Destination Location (km)
15
Patchy Settlement Case
Adults
Recruitment
Settlement
Harvest
Patchy larval kernel - PLD 60 d, Dd 150 km
Tspawn 60 d
16
Adult densities are lower, why?
17
Role of Density Dependence
Climate Case
Patchy Case
  • Settling densities are 2x the base case due to
    the spatial focusing of successful settlement
    events
  • Larval density dependence on post-settlement
    recruitment rates reduces overall adult
    populations

18
Settlement
Flow
Climate
Recruitment
Habitat
Fish
Sample recruitment at only 5 of the sites to set
the TAC
Harvest
INFO
Market
Fishermen
Regulation
19
Uncertainty Case
Adults
Recruitment
Settlement
Harvest
Patchy larval kernel, varying fecundity
assessment area 5
20
Uncertainty Case
  • Regional scale harvest recruitment are weakly
    correlated
  • Times when fishery is closed when TAC 0
  • Increases risk to sustainability of the stock
    fishing profits

21
Stock-Recruitment Harvest- Recruitment Relations
hips for Uncertainty Case
  • Stock-recruitments do not exists for these
    systems
  • No relationship between total harvest and
    recruitment
  • Shows danger of setting TAC based on little data
    (5 sites)

22
Conclusions to Date
  • Created a caricature of a CA nearshore fishery
  • Climate forcing creates temporal variations
    though its effects are linear (time average
    base case)
  • Flow-induced stochastic settlement creates
    spatial-temporal variability to stocks,
    recruitment harvest
  • Larvae/larvae density dependence mitigates
    extreme settlement event densities
  • Information is critical
  • Poor information leads to overfishing profit
    losses

23
Thank You!!Berkley et al. Spatiotemporal
scales of stocks recruitment Poster Today
OS36K-12Mitarai et al. Role of larval
behavior on dispersal scales Talk Tomorrow
OS43I-01 1pm HCC318 www.icess.ucsb.edu/satoshi
/f3
Photo credit Steve Churchill
24
Mathematically...
25
NUMBER OF SETTLEMENT PACKETS
  • Determine of settlement packets
  • N (T/t) (L/l) f

T Larval release duration t Lagrangian
correlation time L domain size l Rossby
radius f survivability of packet
Siegel et al. in rev., Mitarai et al. in prep.
26
DIFFUSION LIMIT
1 season 6 seasons 12 seasons
Diffusion
Diffusion model
Flow simulation
1 season 6 seasons 12 seasons 120 seasons
Packet model
27
MODEL PREDICTIONS
Summer
Winter
Accounts for spatial structures
28
CONNECTIVITY MATRIX
Summer
Winter
29
(No Transcript)
30
Larval Transport Fish Life Cycles
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