Evaluating the proposed MPA designs under California MLPA using fully age and spatially structured models Ray Hilborn University of Washington

Talk layout Brief outline of the model A bit of “reality” about overfishing in general and the California current ecosystem Results of the model

Key elements of model Model coast as an array of nm strips Track numbers at age by area Use usual age structured model including age specific maturity, fecundity, vulnerability and weight Assume annual dispersal that is normally distributed, one s.d. for larvae, another sd for all other ages Post dispersal density dependence Assume total exploitation rate on entire stock and catches taken outside the MPAs Assume fleet distributes itself in relation to catch rates

Limits to the model Runs are deterministic First cut assumed uniform habitat No economics of harvesting – all biology

Summary of model Basically the same model as in Hilborn, Micheli and de Leo except instead of biomass dynamics, each area has full age structure and larvae have different dispersal distances.

Is overfishing the big problem Orange roughy in New Zealand

European Cod

Some Canadian cod stocks

Canadian cod

The ecosystem

History of catch From Little et al

Revenue (constant $) from Little et al

Overfishing is not costing much decrease in potential yield

Maximum biomass of key species in the ecosystem Pacific whiting 7,272,000 Dover sole 596,000 Pacific sardine 4,015,000 Shortbelly rockfish 295,000 Jack mackerel 1,905,000 Widow rockfish 265,000 Northern anchovy 1,598,000 Shortspine thornyhead 230,000 Pacific mackerel 1,394,000 Longspine thornyhead 228,000 Sablefish723,000Yellowtail rockfish 138,000

None of these stocks are overfished – no lost yield These stocks constitute 97% of the biomass! All of the overfished stocks are low abundance stocks, they constitute 1.3% of the unfished stock biomass

Maximum biomass of less abundant species Canary rockfish 93,000Dark blotched 28,000 Pacific Ocean Perch 83,000Petrale sole26,000 Lingcod76,000Vermilion rockfish 21,000 English sole 63,000Blackgill rockfish 21,000 Chilipepper rockfish 58,000Black rockfish 20,000 Bocaccio46,000Bank rockfish 14,000

The overfished stocks

State of the Pacific fisheries What is the problem? It depends on the question –what is the objective

What is the problem? If the objective is yield – the problem is not overfishing, but discarding and regulations imposed to try to keep all stocks above the overfishing threshold – loss of yield from overfishing is very little

What is the problem? If the objective is intact ecosystems – the problem is fishing and the desire to produce yield and jobs – less fishing, less yield, and fewer jobs would provide for more intact ecosystems

What is the problem? If the objective is jobs – the problem is discarding due to the trip limit system and regulations to protect overfished stocks, and the economic inefficiency of a large fleet – the same catch could be caught by a much smaller fleet

What is the problem? If the objective is profit – the problem is the trip-limit system, the regulations to prevent overfishing – the lack of a rational economic management system From a taxpayer perspective the problem is public subsidies

Results From Walters, Hilborn, Parrish … submitted to CJFAS

Model parameters

Abalone

Bocaccio

Lingcod

Conclusions The outcome depends primarily on he fisheries management outside of reserves, ignoring management is ignoring the most important factors Generally these reserves are much too small to allow buildup of abundance inside the reserves except for totally sedentary species

Conclusions re MLPA Science process did not use models – seemed to rely on intuition of biologists. This can easily be improved in subsequent applications since models are available and easy to use. Entire process seems to be predicated on the mis-conception that the “ecosystem” suffers from overfishing The concept of “connectivity” is ill thought out and irrelevant unless there is “scorched earth” management outside of reserves

Conclusions re flow fish We have models that can be used to answer very important social questions

The End