Harvesting strategies and tactics II

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 64:613-617

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)

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 325:578-585 Ricard et al. (in press) Fish and Fisheries. doi: 10.1111/j.1467-2979.2011.00435.x Lightly exploited Recovery Biomass (B/BMSY)

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col="gray50",lwd=3,lty=2) abline(h=0.45, col="gray50",lwd=3,lty=2) dev.off() Biomass (B/BMSY) Hilborn & Branch (unpublished)

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 25:777-786

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

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

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

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

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

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”

Consumer incentives for sustainability

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

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

http://www.msc.org/documents/msc-brochures/msc-theory-of-change

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

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

Developing harvest control rules The 40-10 rule The 20% of B0 rule Management strategy evaluations

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

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

Management procedures (Management strategy evaluations)

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 52:359-372

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

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 52:359-372

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 52:359-372

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)?

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 52:359-372

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

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

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: 613-617