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KELP-SEA URCHIN-FISHERMEN DYNAMICS: IMPLICATIONS FOR SMALL-SCALE FISHERIES MANAGEMENT
Nicolas GutierrezSAFS - UW
R Hilborn, AE Punt, LW Botsford, D Armstrong, D Beauchamp
I. A spatially-explicit individual-based model of sea urchin, kelp and fishermen
II. Alternative approaches for sea urchin stock assessment
- Gutiérrez et al. Developing a Bayesian stock assessment framework and decision analysis for the red sea urchin fishery in Baja California, Mexico (Submitted N. Am. J. Fish. Manag.)
III. Exploring dedicated access management strategies for sedentary small-scale fisheries
- Fishing for uni: potential benefits of cooperative harvesting
Thesis Sections
Background & Motivation
• Roe fishery, with marked spatio-temporal patterns in gonad quality/yield (depending on food availability)
• SDWA and the fishing industry concerned about sustainability and economic viability. Optimize harvest flexibility and quality by:
- getting biological information to better manage the fishery (BE program)
- developing a community-based management strategy
• Fishing for uni: Selective harvesting of “well fed urchins”, by fishing those areas where the gonad yield is at its peak
Fishing for uni: potential benefits of cooperative harvesting
Approach
5 areas with same number of urchins (B0 = 20,000)
1. Competitive fishery: each diver go to the area that produced the best return (as total uni production: Y = gonad yield x abundance)
2. Cooperative managed fishery: each diver is directed to fish each area at/around its seasonal peak
a. Constant recruitment (legal/mature):
b. Seasonal/pulse recruitment:
Fishing for uni: potential benefits of cooperative harvesting
Time
Re
cru
itsR
ecru
its
Fishing for uni: potential benefits of cooperative harvesting
DATA: Spatio-temporal variations in gonad yield (%)
4.0
5.0
6.0
7.0
8.0
9.0
Jan-05
Feb-05
Mar-05
Apr-05
May-05
Jul-05 Aug-05
Sep-05
Oct-05
Nov-05
Time (months)
4.00
5.00
6.00
7.00
8.00
9.00
1 2 3 4 5 6 7 8 9 10 11 12
Time (months)
Gonad Y
ield
(%
)
12345
Area 3
a
b
Preliminary results
Fishing for uni: potential benefits of cooperative harvesting
Catch (lbs)
Revenue (US$)
Catch 22,449 25,943 13%
Revenue 18,821 23,272 19%
Catch 20,931 21,355 2%
Revenue 17,370 19,665 12%
Change
Constant
Seasonal
Open Access (Competitive) Dedicated Access (Cooperative)
Management strategyRecruitment Indicator
Competitive Cooperative
Constant recruitment Seasonal recruitment
Competitive Cooperative Competitive Cooperative
Next steps
• Increase spatial resolution of data set on gonad yield, abundance, etc
• Density-dependence recruitment
• Market considerations (e.g. price depending on catches 2 weeks earlier)
• Gonad Quality threshold (e.g. > 5.2 % ~ 0.75 $ per lbs)
• Depletion levels (e.g. B=0.4•B0)
• Include processing costs for “bad” urchins
Fishing for uni: potential benefits of cooperative harvesting