1. Harvesting strategies and tactics II

2. References
Grafton RQ, Kompas Q & Hilborn RW (2007) Economics of overexploitation revisited. Science 318:1601
Butterworth DS (2007) Why a management procedure? Some positives and negatives. ICES Journal of Marine Science 64:

3. Reference points Guidelines for management
May be based on exploitation rates or on biomass
FMSY and BMSY based on stock-recruit relationships
BMEY based on economics
Fmax, F0.1, F35%, F40% based on yield-per-recruit analysis (assumes recruitment independent of stock size)

4. Fishery status (stock assessments)
Overfishing
Fishery reduction
166 stocks
63% biomass below BMSY
65% harvest rate is below uMSY
Harvest rate (u/uMSY)
Worm et al. (2009) Science 325:
Ricard et al. (in press) Fish and Fisheries. doi: /j x
Lightly
exploited
Recovery
Biomass (B/BMSY)

5. Biomass trends Harvest rate (u/uMSY) Biomass (B/BMSY) all declining
most declining
stable on average
Harvest rate (u/uMSY)
most increasing
all increasing
Schaefer model isocline
###isocline plot
#data from Ray Hilborn
#each number represents the average direction of biomass in a year, increase = 1
#decrease = -1 and constant =0. Stocks split by 0.2 unit bins of U/Umsy and B/Bmsy
#and the average calculated within each bin
pdf("Isoclines.pdf",width=6,height=6)
par(oma=c(0,0,0,0), mar=c(5,5,1,1))
X <- read.csv("isocline.csv")
bad.good <- colorRampPalette(c("red","white","darkgreen"))
image(as.matrix(t(X[-1,-1])),col=bad.good(100), axes=F)
axis(1,at=seq(0,1.1,0.1)-0.05, labels=c(seq(0,2,0.2),">2"))
axis(2,at=seq(0,1.1,0.1)-0.05, labels=c(seq(0,2,0.2),">2"), las=1)
mtext(side=1,outer=F,line=3,expression(B[current]/B[MSY]),cex=1.3)
mtext(side=2,outer=F,line=3,expression(u/u[MSY]),cex=1.3)
lines(cbind(c(-0.05,0.95),c(0.95,-0.05)), col="black",lwd=3,lty=2)
abline(v=0.45, col="gray50",lwd=3,lty=2)
abline(h=0.45, col="gray50",lwd=3,lty=2)
dev.off()
Biomass (B/BMSY)
Hilborn & Branch (unpublished)

6. Fishery status (stock assessments)
Collapsed (<0.2BMSY)
Overexploited (<0.5BMSY)
Fully exploited (0.5–1.5BMSY)
Percentage of stocks
Developing (> 1.5BMSY)
Year
Branch TA (2011) Contrasting global trends in marine fishery status obtained from catches and from stock assessments. Cons Biology 25:

7. Economics Few fisheries are about maximizing landed catches
In general economic analysis suggests that one should fish less and have higher CPUE and slightly lower total catch than MSY

8. Western and Central Pacific bigeye tuna
Revenue or profit ($000)
Biomass (tons)
Grafton RQ et al. (2007) Economics of overexploitation revisited. Science 318:1601

9. Adding Economics
Grafton RQ et al. (2007) Economics of overexploitation revisited. Science 318:1601

10. What is generally agreed
Maximum economic yield (MEY) is obtained at BMEY, where usually BMEY > BMSY
Australia has adopted BMEY as their management target for fisheries
Proxy for BMEY is 1.2 BMSY
It is better to be at biomasses larger than BMSY for reasons of risk, economics and ecosystems

11. Other reference points: Fmax and F0.1 Yield per recruit
Gradient 10%
F0.1
No Fmax when
Vulnerability > than
age at maturity
Gradient 10%
F0.1

12. F35% F40% F45% Spawning biomass per recruit
SBPR(F = 0)
45% of SBPR(F = 0)
35% of SBPR(F = 0)
F45%
F35%
24 Reference points.xlsx, sheet “YPR by u”

13. Consumer incentives for sustainability

14. Monterey Bay Aquarium Seafood Watch guide (for U.S. west coast)

15. Marine Stewardship Council
Principle 1: No overfishing, where depleted must lead to recovery
Principle 2: Maintenance of ecosystem (habitat, diversity)
Principle 3: Effective management system (laws, enforcement)
April 2012: 147 certified fisheries, 15,000 labeled products

17. Jacquet J et al. (2010) Seafood stewardship in crisis. Nature 467:28-29

18. Principle 1 performance
Certified
(n=45)
Uncertified
(n=179)
Harvest rate (u/uMSY)
Not
recommended
(n=25)
Biomass (B/BMSY)
Gutiérrez NL et al. (2012) Eco-label conveys reliable information on fish stock health to seafood consumers. PLOS ONE 7(8): e43765

19. Developing harvest control rules
The rule
The 20% of B0 rule
Management strategy evaluations

20. The 40:10 rule
Uref = 0.20
0.1
0.4
0.1
0.4
24 Reference points.xlsx, sheet “40-10 rule”

21. 20% virgin biomass rule R.I.C.C. Francis, New Zealand
Accept no policy that allows the stock to drop below 20% of unfished (virgin) biomass more than 10% of the time
Problems: arbitrary, how to specify uncertainty?
R.I.C.C. (Chris) Francis

22. Management procedures (Management strategy evaluations)

23. Operating model “truth” Management procedure
Kurota H et al. (2010) Developing a management procedure robust to uncertainty for southern bluefin tuna: a somewhat frustrating struggle to bridge the gap between ideals and reality. Population Ecology 52:

24. Southern bluefin tuna “the most valuable fish in the world”
A billion dollar industry !
Entomologist
$3,000/month
[As related by Kurota]
(As you know from this slide,) SBT is one of the most valuable fish in the world.
SBT industry is smaller than other tuna industries, but it is very huge, a billion dollar industry.
I’ve been studying SBT for four years, but honestly I’ve never tasted it.
This fish was caught by me (during field research) two years ago.
It was the biggest that I’ve ever seen, and it weighed 200 kg.
(click)
If this fish’s condition was very good, the price (at the fish market) would be 100 dollar per kg, so this fish is worth 20,000 dollars.
I would have to work for seven months to buy it.
----
Southern bluefin
200 kg × $100/kg
= $20,000
Hiroyuki Kurota, Feb 2002
Slide courtesy of Hiroyuki Kurota

25. Southern bluefin tuna
Kurota H et al. (2010) Developing a management procedure robust to uncertainty for southern bluefin tuna: a somewhat frustrating struggle to bridge the gap between ideals and reality. Population Ecology 52:

26. Very complicated management procedures!!
HK5 management procedure
CGF management procedure
Very complicated management procedures!!
But which one is the best one?
Kurota H et al. (2010) Developing a management procedure robust to uncertainty for southern bluefin tuna: a somewhat frustrating struggle to bridge the gap between ideals and reality. Population Ecology 52:

27. Decisions in MPs How fast are TACs allowed to increase? And decrease?
How much to smooth TAC changes? Next year’s TAC could be a function of this year’s TAC and some increase or decrease
Is the rule empirical (data -> TAC) or model-based (data -> model -> biomass estimate -> TAC)?

28. Kurota H et al. (2010) Developing a management procedure robust to uncertainty for southern bluefin tuna: a somewhat frustrating struggle to bridge the gap between ideals and reality. Population Ecology 52:

29. Robustness tests
Comparing 7 performance measures (e.g. mean catch, minimum biomass) between two management procedures (MP1, MP2), for 6 robustness scenarios (e.g. changes in catchability, low recruitment, different way to calculate CPUE, relation between CPUE and biomass)
Branch TA, unpublished

30. Southern bluefin tuna: lessons
If the data are wrong (massive unreported catches), the exercise is worthless
Very difficult to reach consensus with multiple countries
A management procedure was finally adopted in 2011 (after 7 years of attempts)
If adopted, does reduce chance of political interference

31. Management procedures
Advantages
Avoids annual haggling over an assessment model
Pre-agreement on how to reduce catches
Considers long-term trade-offs explicitly
Feedback control: low biomass -> lower catches, mimicking reality
Can test extreme scenarios
Explicit consideration of tradeoffs (higher catch vs. variability in catch vs. lower biomass)
Disadvantages
Long time to develop rules
Inflexibility after adoption
Continued availability of quality data essential
Butterworth DS (2007) Why a management procedure? Some positives and negatives. ICES J. Mar. Sci. 64: