1. Return to Marine Protected Areas

2. Background readings Roberts CM et al. (2001) Effects of marine reserves on adjacent fisheries. Science 294:1920-1923 Halpern BS (2003) The impact of marine reserves: do reserves work and does reserve size matter? Ecological Applications 13:S117-S137 Hilborn R et al. (2004) When can marine reserves improve fisheries management? Ocean and Coastal Management 47:197-205 Hilborn R et al. (2006) Integrating marine protected areas with catch regulation. CJFAS 63:642-649

3. One-dimensional logistic-growth model with harvesting Only survivors of harvest will move Movement rate the same in all cells Numbers in area i in time t Exploitation rate Cell on the left Cell on the right Harvest, then movement Density dependence Harvest Immigration Emigration Logistic model

4. Do protected areas increase yield? MPA No MPA Higher yield without MPA Yield maximized at higher harvest rate with MPA At u > r, MPA halts collapse (insurance policy) u = r = 0.2 u MSY = r/2 = 0.1 16 MPA yield.r Harvest rate (u) Equilibrium yield

5. Harvest rate (u) Size of area closed to fishing Lab 7 solutions.r Highest catch Lowest catch Equilibrium yield (lab 7) Small MPAs increase catches here

6. MPA objectives Conservation of diversity and habitat – Depleted, threatened, rare species or populations – Preserve or restore representative habitats – Wilderness experience Fisheries management – Control exploitation – Insurance against regulatory failure or error – Protect critical life stages (spawners) – Reduce secondary impacts of fishing (fragile habitat) – Build up old and large individuals for trophy hunting

7. Broader objectives Science – Unfished control: estimate capacity of the system – Baseline data to estimate MSY Educational opportunities Recreation and tourism

8. Costs and benefits: catches Costs – Likely decrease catches – Closing areas to rebuild some stocks will reduce catches of other stocks Benefits – Stability in resource – Spillover and increased future recruitment

9. Costs and benefits: enforcement Costs – Requires enforcement of boundaries – Extra costs Benefits – Easier to enforce than species, catch, or effort limits – In some regions may be the only fisheries regulations that can be enforced

10. Murawski SA et al. (2005) Effort distribution and catch patterns adjacent to temperate MPAs. ICES Journal of Marine Science 62:1150-1167 Marine protected area (MPA) MPA

11. Costs and benefits: management Costs – New requirements for data collection – Enforcement Benefits – Better estimates of biological parameters due to contrast in abundance – Intrinsic increase rates can be directly measured – Allows spatially explicit management options

12. Costs and benefits: economics Costs – Bigger impacts on communities bordering MPA – Loss of income and profits Benefits – Increased tourism – Reduced conflict with non-consumptive uses – Insurance against stock collapse – Reducegrowth overfishing (catching fish when too small)

13. Costs and benefits: ecosystems Costs – Increased effort outside may deplete species Benefits – Lower bycatch and habitat damage – Maintains high density spawning aggregations needed for broadcast spawners (sea urchins, abalone) – Increased fecundity of big old fish in MPA

14. BOFFFF hypothesis Big old fat fecund female fish hypothesis: maintaining old fish in population is important – They produce many more larvae – Larvae have greater fat reserves – Longer spawning season – Long-lived, can outlive long periods of bad conditions Fishing truncates age distribution, greatly reduces number of old individuals Berkeley SA et al. (2004) Maternal age as a determinant of larval growth and survival in a marine fish, Sebastes melanops. Ecology 85:1258-1264 Berkeley SA et al. (2004) Fisheries sustainability via protection of age structure and spatial distribution of fish populations. Fisheries 29(8):23-32 Steven Berkeley, 1947-2007

15. Survivors at old age (20+ years) Natural survival = 0.8, harvest rate u Proportion alive at age Ages 0+Ages 20+ At u = 0.2, total abundance (0+) reduced 44% (to about B MSY ), but age 20+ abundance reduced by 99.4%!! 19 MPAs.xlsx, sheet Age Structure Age of fish Harvest rate

16. 19 MPAs.xlsx sheet age structure

17. Costs and benefits: displacement Costs – Hardship on local fishers and businesses – Greater effort on open areas – Fishing the line reduces spillover Benefits – Reduces overall exploitation rate (so does conventional management by cutting catches) – Satisfies legal requirements to protect critical habitat

18. Effort concentration model (omitting subscript t for time, no boats in MPA) Hilborn R et al. (2006) Integrating marine protected areas with catch regulation. CJFAS 63:642-649 Efficiency of boats Total number of boats Concentration coefficient (high values = more concentration) Abundance in each area outside the reserve Highest abundance in an area outside MPA Boats in area i Harvest rate in area i

19. Effort concentration model 19 MPAs.xlsx, sheet Effort no MPA No MPAMPA Fish 19 MPAs.xlsx, sheet Effort MPA

20. 19 MPAs.xlsx sheet Effort no MPA sheet Effort MPA

21. Hilborn R et al. (2006) Integrating marine protected areas with catch regulation. CJFAS 63:642-649 Time trends Heading for extinctionFished at MSY Catches Num inside MPA Num outside MPA Catches Num inside MPA Num outside MPA Assumption: total allowable catch (TAC) does not change when MPA is implemented, therefore need to fish harder to catch the same TAC

22. Where MPAs may improve on catch or effort limitation When few individuals are allowed to mature If there is strong depensation Where fishing reduces the abundance of one sex Imperfect control of fishing Where a large proportion of the effective egg production comes from a small area Density dependence based on abundance of all age groups

23. Rotating closed areas Harvested species is sessile (does not move) Combined with high prices for large individuals, and low prices for small individuals If there is “growth overfishing” (heavy harvesting reduces average size of harvested species) Solution: rotate through area openings so that all harvested individuals are large and valuable E.g. forest plantations, geoducks, trochus, scallops

24. Geoducks $20 per lb at the dock Disturbed geoducks die Tracts auctioned each year in Washington state, about 1% of area per year. Auctions raise $22 million per year for Washington http://seattletimes.com/html/localnews/2018041537_geoduck22m.html

25. Trochus niloticus (large topshell) Open-access fisheries, Indonesia, SW Pacific islands, rotational harvests keep fishers out, optimize yield Left picture: www.seashellshack.com/pearled-trochus-niloticus-ss65b-pr-16249.html Right picture: www.gastropods.com/8/Shell_1608.shtml

26. Huge sea scallops Photo by Michael Reiss www.foodandwineaccess.com/events/event343.htm Average Closed areas Open areas Biomass (kg/tow) Source: www.nefsc.noaa.gov/sos/spsyn/iv/scallop/ Years Closed areas on Georges Bank, when re-opened for scallops, yielded enormous and highly valued scallops.

27. Basic MPA theory If MPA is large relative to a species dispersal MPA increases abundance in MPA, and will “lock up” a fraction of resource with resultant loss in potential sustainable harvest If MPA is small relative to species dispersal it has no effect (Polacheck 1990) At some sizes there may be spillover of larvae or adults that compensates for losses due to “locking up” Polacheck T (1990) Year around closed areas as management tool. Natural Resource Modeling 4:327-354

28. More theory MPAs can, at best, produce fisheries yields equivalent to that achievable by other forms of fisheries management (Hastings and Botsford 1999) But almost all models suggest much lower CPUE as a result MPAs will produce fisheries benefits primarily when stocks are recruitment overfished (low spawning biomass producing low recruitment) Hastings A & Botsford LW (1999) Equivalence in yield from marine reserves and traditional fisheries management. Science 284:1537-1538

29. Empirical evidence for MPA effects More than 5000 MPAs have been declared, covering 1.2% of the world’s oceans Gather evidence of effects on size, growth, catches, etc. What does this evidence show? Within MPAs that are enforced, average size and abundance increases, often dramatically Evidence for spillover effect is hard to tease out from environmental factors

30. Halpern and Warner (2002) “112 independent measurements of 80 reserves to show that the higher average values of density, biomass, average organism size, and diversity inside reserves (relative to controls) reach mean levels within a short (1-3 y) period of time and that the values are subsequently consistent across reserves of all ages (up to 40 y)”. Halpern BS & Warner RR (2002) Marine reserves have rapid and lasting effects. Ecology Letters 5:361-366 Ben HalpernRobert Warner

31. Scientific method Using local unprotected areas as “controls” is problematic – Protected areas may be different and more productive before protection – Effort not going into protected areas goes into the unprotected ones Alternative: control areas with no MPAs and compare total abundance in large areas including MPAs to large areas without MPAs Or BACI (before-after control-impact) design, with before and after plus controls and MPA data

32. Limited BACI results 7 studies, 9 MPAs Before MPAs, future unprotected areas similar to future MPA areas After MPAs, increased density and biomass in unprotected areas Small sample size Halpern BS et al. (2004) Confounding effects of the export of production and the displacement of fishing effort from marine reserves. Ecological Applications 14:1248-1256 Ben HalpernRobert WarnerSteve Gaines

33. File-drawer effect Studies are more interesting and publishable when there are significant positive effects Most studies by reserve managers or proponents Studies showing no effects are less scientifically interesting, and possibly politically embarrassing, and may be “shelved” in a “file drawer” instead of being published So meta-analysis of many published studies can experience a “publication bias” towards positive effects Møller AP & Jennions MD (2001) Testing and adjusting for publication bias. Trends in Ecology and Evolution 16:580-586

34. File-drawer effect Probable area of non-significance True relation between estimated effect and sample size Values from published studies Probable area of significance Modified from Møller AP & Jennions MD (2001) Testing and adjusting for publication bias. Trends in Ecology and Evolution 16:580-586 Log (sample size) Estimated effect size Probable area of non-significance Probable area of significance

35. Spillover (Roberts et al. 2001) Roberts CM et al. (2001) Effects of marine reserves on adjacent fisheries. Science 294:1920-1923 Don’t do this! Y-axis should start at 0 Callum Roberts

36. Shortcomings of Roberts’ study Effort was excluded from protected areas and went to unprotected areas In the first year, most fishers had to increase effort to catch the same amount of fish Yet biomass in the unprotected areas still increased in the first year Average age at maturity for key species is 3-4 yr How could spillover occur so quickly? What about joint environmental changes?

37. Conclusions MPAs offer benefits beyond fishery catches – Biodiversity protection – Insurance against management error – Tourism Spillover of effort needs to be taken into account – Unlikely to generate increased overall catches unless heavily overfished at present Assessing benefits is difficult – Controls, environmental changes – File drawer effect