Marine reserve spacing and fishery yield: practical designs offer optimal solutions. Crow White, Bruce Kendall, Dave Siegel, and Chris Costello University of California – Santa Barbara

2 = # reserves at a given site

Larval export No Fishing

Research Question: To maximize larval export (and fishery yield) should reserves be… …few and large, When is larval export maximized? …or many and small? SLOSS debate

Reaction Diffusion model  Adults move and reproduce simultaneously  Larvae mature into adults instantaneously

Real coastal fish & invert population dynamics  Adults are sessile, reproducing seasonally (e.g. Brouwer et al. 2003, Lowe et al. 2003, Parsons et al. 2003)  Larvae disperse, mature after 1+ yrs (e.g. Dethier et al. 2003, Grantham et al. 2003)  Larva settlement success inversely proportional to adult density at settlement location (post-dispersal density dependence) (e.g. Lorenzen and Enberg 2002, Steele and Forrester 2002)

An integro-difference model describing coastal fish population dynamics: Adult abundance at location x during time-step t+1 Number of adults harvested Natural mortality of adults that escaped being harvested Fecundity Larval survival Larval dispersal (Gaussian) (Siegel et al. 2003) Larval recruitment at x Number of larvae that successfully recruit to location x

Incorporating Density Dependence Post-dispersal:

FEW LARGE RESERVES SEVERAL SMALL RESERVES

FEW LARGE RESERVES SEVERAL SMALL RESERVES

Scale bar = 100 km

CHANNEL ISLANDS MARINE PROTECTED AREAS  ~20% coastline into 10 no-take reserves  All < 15 km wide

Summary 1.Post-dispersal density dependence generates larval export.

Summary 1.Post-dispersal density dependence generates larval export. 2.Larval export varies with reserve size and spacing.

Summary 1.Post-dispersal density dependence generates larval export. 2.Larval export varies with reserve size and spacing. 3.Yield maximized via…

Summary 1.Post-dispersal density dependence generates larval export. 2.Larval export varies with reserve size and spacing. 3.Yield maximized via…  Less than ~15% coastline in reserves …Any reserve spacing option.

Summary 1.Post-dispersal density dependence generates larval export. 2.Larval export varies with reserve size and spacing. 3.Yield maximized via…  Less than ~15% coastline in reserves …Any reserve spacing option. SLOSS

Summary 1.Post-dispersal density dependence generates larval export. 2.Larval export varies with reserve size and spacing. 3.Yield maximized via…  Less than ~15% coastline in reserves …Any reserve spacing option. SLOSS

Summary 1.Post-dispersal density dependence generates larval export. 2.Larval export varies with reserve size and spacing. 3.Yield maximized via…  Less than ~15% coastline in reserves …Any reserve spacing option.  More than ~15% coastline in reserves …Several small or few medium-sized reserves. SLOSS

Summary 1.Post-dispersal density dependence generates larval export. 2.Larval export varies with reserve size and spacing. 3.Yield maximized via…  Less than ~15% coastline in reserves …Any reserve spacing option.  More than ~15% coastline in reserves …Several small or few medium-sized reserves. SLOSS

Summary 1.Post-dispersal density dependence generates larval export. 2.Larval export varies with reserve size and spacing. 3.Yield maximized via…  Less than ~15% coastline in reserves …Any reserve spacing option.  More than ~15% coastline in reserves …Several small or few medium-sized reserves. SLOSS SLOFMOSSSLOSS

Summary 1.Post-dispersal density dependence generates larval export. 2.Larval export varies with reserve size and spacing. 3.Yield maximized via…  Less than ~15% coastline in reserves …Any reserve spacing option.  More than ~15% coastline in reserves …Several small or few medium-sized reserves. SLOSS SLOFMOSSSLOSS

Summary 1.Post-dispersal density dependence generates larval export. 2.Larval export varies with reserve size and spacing. 3.Yield maximized via…  Less than ~15% coastline in reserves …Any reserve spacing option.  More than ~15% coastline in reserves …Several small or few medium-sized reserves. SLOSS SLOFMOSSSLOSS 4. Yield may be maximized when reserves constitute a large fraction of the coastline, and fishing elsewhere is intensive.

University of California – Santa Barbara National Science Foundation THANK YOU!