Marine Protected Areas Basic MPA theory If MPA

Marine Protected Areas

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 • At some sizes there may be spillover of larvae or adults that compensates for losses due to “locking up”

MPA objectives • Conservation – Threatened rare species or populations – Preserve representative habitats • Tourism – Wilderness experience & pristine habitat • Fisheries management – – – Insurance against regulatory failures Protect spawning aggregations Reduce impacts of fishing on fragile habitat Build up old and large individuals for trophy hunting Unfished control to estimate carrying capacity and MSY

Costs and benefits • Catches: likely decrease, but more stable and trophy fishing better • Enforcement: added costs; easier than enforcing catch or effort; may be only enforceable regulation • Management: collecting data harder, but better estimates of carrying capacity • Ecosystems: reduced habitat damage, high density spawning aggregations (abalone, urchins) • Displaced fishing effort: local fishers affected more, fishing the line, higher effort in open areas

BOFFFF hypothesis • Big old fat fecund female fish hypothesis: Steven Berkeley, 1947 -2007 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 • MPAs greatly increase proportion of old fish 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

Number of eggs per female Number of eggs produced increases more rapidly than biomass Female mass (g) Barneche et al. (2018) Fish reproductive-energy output increases disproportionately with body size. Science 360: 642 -645.

Survivors at old age (20+ years) Ages 20+ Proportion alive at age Natural survival = 0. 8, harvest rate u Ages 0+ Age of fish Harvest rate At u = 0. 2, total abundance (0+) reduced 44% (to about BMSY), but age 20+ abundance reduced by 99. 4%!! 16 MPAs. xlsx, sheet Age structure

How many old fish remain? • Age truncation examined in 63 fished populations • From unfished levels to the most recent year, fish in the oldest categories declined in 97% of populations • Decline of old fish was >90% for 41% of populations examined Barnett LAK et al. (2017) Old-growth fishes become scarce under fishing. Current Biology 27: 2843 -2848

Marine protected areas Slot limits that only allow fishing on a narrow range of ages Rotational harvesting Number of populations Solutions Old fish (end yr: start yr) Old fish (end yr: unfished) Barnett LAK et al. (2017) Old-growth fishes become scarce under fishing. Current Biology 27: 2843 -2848

Reminder: one-D MPA model Numbers in area i in time t Logistic model Density dependence Harvest Exploitation rate Immigration Emigration Cell on the left Only survivors of harvest will move Movement rate the same in all cells Cell on the right Harvest, then movement

Fleet dynamics and behavior • Previous model assumes equal harvest rate in all cells outside the MPA • Fleet dynamics: the study of how and why fishing fleets increase or decrease in size • Fishing behavior: why do boats fish where they fish? Review paper: Branch TA et al. (2006) Fleet dynamics and fishermen behavior: lessons for fisheries managers. CJFAS 63: 1647 -1668

High-liners • Why do some boats catch more fish? • Skipper effect: “high-liners” are more skilled than others • Boat effect: some boats have more technology • Information: knowledge about the best places to fish Source unknown

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

16 Effort concentration model. r

Empirical evidence for MPA effects • Thousands of MPAs have been declared, covering 7. 4% of the world’s oceans, and growing rapidly • What evidence is there of effects on size, growth, catches, etc. ? – Within MPAs that are enforced, average size and abundance increases, often dramatically – Evidence for spillover effect is hard to tease out from environmental factors

Halpern and Warner (2002) Ben Halpern Robert Warner “ 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 yr) period of time and that the values are subsequently consistent across reserves of all ages (up to 40 yr)”. Halpern BS & Warner RR (2002) Marine reserves have rapid and lasting effects. Ecology Letters 5: 361 -366

Scientific method • Using local unprotected areas as “controls” is problematic – Protected areas may be different and more productive before protection – Effort formerly in protected areas is displaced into unprotected areas • Need control regions with no MPAs to compare with regions including MPAs • Or BACI (before-after control-impact) design, with before and after data in control sites and MPA sites

Limited BACI results Ben Halpern Steve Gaines Robert Warner • 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

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

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

MPA conclusions • MPAs offer benefits beyond fishery catches – Biodiversity protection – Insurance – Tourism • Spillover of effort needs to be taken into account – Unlikely to generate increased overall catches unless heavily overfished • Assessing benefits is difficult – Controls, environmental changes – File drawer effect

What do I personally think? • As a member of the public, I support MPAs • We need some “Yellowstones of the Sea” where biodiversity is fully protected • In many places there is far greater value from tourism than from fishing • But selling MPAs as “they will increase catches” or as a “win-win” scenario is poor science • In almost all cases where catches could be improved, it is because there is overfishing • In such cases, a short-term reduction in catches would also rebuild stocks and increase catches in the long term

Alternative: crop rotation • When harvested species is sessile (does not move) • Plus high prices for large individuals and low prices for small individuals • Plus existing “growth overfishing” (heavy harvesting reduces average size of harvested species) • Solution: open a different part of the region to fishing each year, allowing individuals in the closed areas to grow large and become valuable • E. g. forest plantations, geoducks, trochus, scallops

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_geoduck 22 m. html

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-ss 65 b-pr-16249. html Right picture: www. gastropods. com/8/Shell_1608. shtml

Huge sea scallops Biomass (kg/tow) Closed areas Photo by Michael Reiss www. foodandwineaccess. com/events/event 343. htm Average Open areas Years Closed areas on Georges Bank, when re-opened for scallops, yielded enormous and highly valued scallops. Source: www. nefsc. noaa. gov/sos/spsyn/iv/scallop/

Every yr 2 yr 3 yr 5 yr 6 yr Risk: prob(B < 0. 4 B 0) Crop rotation: lower risk Plagányi ÉE et al. (2015) Crop rotations in the sea: Increasing returns and reducing risk of collapse in sea cucumber fisheries. Proceedings of the National Academy of Sciences USA 112: 6760 -6765

Risk: prob(B < 0. 4 B 0) Crop rotation: higher revenue at lower risk to the resource Éva Plagányi No rotation Fish every 3 yr Total revenue (US$ million) Plagányi ÉE et al. (2015) Crop rotations in the sea: Increasing returns and reducing risk of collapse in sea cucumber fisheries. Proceedings of the National Academy of Sciences USA 112: 6760 -6765