FISHERIES MODELLING AND MANAGEMENT OR WHAT HAVE I LEARNED FROM 400+ INTERNATIONAL SCIENTIFIC FISHERIES MEETINGS? Doug S Butterworth MARAM (Marine Resource Assessment and Management Group) Department of Mathematics and Applied Mathematics University of Cape Town, Rondebosch 7701, South Africa

OUTLINE Why is sustainable fisheries management so difficult? Local problems International problems “Ecosystem” issues What’s coming next? As a scientist, why bother?

I) WHY IS SUSTAINABLE FISHERIES MANAGEMENT SO DIFFICULT? SUSTAINABLE UTILISATION Pensioner must live off interest What’s my capital? What’s the interest rate? Multiply the two Don’t spend more than that! EASY!! 3

THE SOURCE OF THE DIFFICULTY THE SOURCE OF THE DIFFICULTY . FISHERIES HAVE UNCO-OPERATIVE BANK TELLERS They won’t tell you the interest rate, which in any case is highly variable Recruitment fluctuations They will advise your balance only once a year, with a typically +-50% error, and in the wrong currency Surveys (or abundance indices) are typically available annually only, their results have high variance, and their bias is unknown 4

WHAT NEW DO THEY BRING TO ASSIST SOLVE THE PROBLEM? MANAGEMENT PROCEDURES (MSE – AGREE THE RULES BEFORE YOU PLAY THE GAME) . WHAT NEW DO THEY BRING TO ASSIST SOLVE THE PROBLEM? FEEDBACK CONTROL! Monitor stock changes and adjust management measures (e.g. TACs) accordingly 5

A FINANCIAL ANALOGY $1 000 000 invested at 5% p.a. Each year withdraw $50 000  Investment sustainably maintained at $1 000 000 1 000 000 ton fish stock grows naturally at 5% p.a. Each year catch 50 000 tons  Sustainable exploitation: resource kept at 1 000 000 tons

After 5 years, someone MAY have stolen $300 000 from your investment You keep withdrawing $50 000 per year No theft Theft After 5 years, recruitment failure or IUU fishing MAY have reduced abundance by 30% Catches maintained at 50 000 tons per year If this event did occur, resource is rapidly reduced

WHY’S THERE ANY PROBLEM? Ask the teller for account balance. If this has fallen to $700 000, reduce annual withdrawal to $35 000  Sustainability maintained. BUT The teller will advise balance only once a year with 50% error Resource abundance known only through annual surveys or abundance indicies (e.g. CPUE) which have large associated errors

CAN YOU TELL WHETHER $300 000 WAS STOLEN FROM YOUR ACCOUNT ? (Equivalently, whether fish abundance was reduced by 30%?) In each of the following scenarios shown, the theft occurred in only one of the two cases Can you tell which one?

IMPRESSIONS It wasn’t easy to tell It needed usually about 20 years of new data to be certain By that time, account was almost exhausted (if theft had occurred) By the time the adverse effect of recruitment failure or IUU fishing is detectable, the resource is already heavily depleted

THREE STRATEGIES (MPs) I: Withdraw $ 50 000 every year II: Withdraw 5% of the teller-advised balance each year III: Withdrawal this year = 80% last year’s withdrawal + 1% teller’s (erroneous) balance Strategy must “work” whether or not theft occurred

Annual Withdrawal I II III No theft Theft I II III

Balance in Account I II III No theft Theft I II III

Annual Withdrawal I II III No theft Theft I II III

Balance in Account I II III No theft Theft I II III

“Feedback control” (MP basis) PERFORMANCE I: Going bankrupt if theft occurred II: Stabilises balance in account, but annual withdrawals too variable III: Best of the three – stabilises balance without too much change from year to year Formula III automatically corrects for effect of recruitment failure/IUU fishing if it occurred. “Feedback control” (MP basis)

II) LOCAL PROBLEMS EVEN DATA-RICH IS OFTEN INFORMATION-POOR We’d like to be at an abundance that provides the Maximum Sustainable Yield (US Magnuson-Stevens Act) But how well do we know what that is – implications for rebuilding – will less catch today really deliver more tomorrow? It’s unsurprising that industry can be sceptical. 32

II) LOCAL PROBLEMS ECOLABELLING This has enhanced the attention paid to science by fisheries decision makers But is there undue pressure from some ENGOs for more stringent criteria (fair practice to move goalposts)? Will the system survive this, and consistency problems? Can developing countries hope to achieve these standards (which they view as unfair trade restriction practice)? Losing the plot? – no actual incentive to improve most of the world’s poorer managed fisheries 33

II) LOCAL PROBLEMS THE SCIENTISTS – MANAGERS DIVIDE Managers often fail to master the underlying scientific principles/concepts – frequently because they are too “position-mobile” to have the time to gain experience Scientists are often unable to communicate effectively outside the scientific sphere Scientists should evaluate the implications of alternative action options (e.g. greater catch vs lower resource risk) amongst which managers then choose BUT Managers ask: “Which of these options do the scientists recommend?” 34

III) INTERNATIONAL PROBLEMS POOR CONSERVATION PERFORMANCE OF REGIONAL FISHERIES MANAGEMENT ORGANISATIONS (RFMOs) IOTC – 19 years old and yet to set a TAC The allocation problem (no boss) CITES – Does/Should it have a role? Listings “never” reverse-able The Fisheries vs Environment Ministries clash Industries dominate RFMOs – ENGOs dominate CITES The charismatic megafauna aspect 35

III) INTERNATIONAL PROBLEMS POOR CONSERVATION PERFORMANCE OF REGIONAL FISHERIES MANAGEMENT ORGANISATIONS (RFMOs) Problems of attaining consensus -> Necessary action is delayed International litigation (ITLOS/ICJ) How well are these bodies suited to dealing with essentially scientific issues? But how well suited are scientists to make “objective” decisions in an inexact field with high levels of advocacy/hidden agendas and employment at risk US SSCs – scientists determine policy implementation 36

IV) “ECOSYSTEM” ISSUES POOR RELIABILITY OF MULTI-SPECIES MODELS Will reducing fish catches benefit natural predators? Will culling predators allow for greater fish catches? Precautionary Principle – opportunistic use ECOSYSTEM ASPECTS OF FISHING (EAF) (Ecosystem Based Fisheries Management) Bycatch/Biological interactions/Habitat conservation/Social issues/ …… Many different interpretations in practice/Many words?/ Is this diffusing necessary focus? 37

IV) “ECOSYSTEM” ISSUES MARINE PROTECTED AREAS (MPAs) Widely and strenuously advocated (especialy by ENGOs) They have their value/uses – effort limitation, can benefit recovery of near-sessile species BUT They are NOT a panacea for all fishery ills The primary need is for improved fisheries management 38

V) WHAT’S COMING NEXT? INTERNATIONAL MANAGEMENT (RFMOs) Will the UN step in? RECOVERING DEPLETED STOCKS Will a rising real cost of fuel be the primary determinant? ECOLABELING Will this initiative implode? SCIENTISTS vs MANAGERS Pre-agreed decision rules (MPs) vs Flexibility/negotiation Which will win? A continued risk of “too little too late”? 39

VI) AS A SCIENTIST, WHY BOTHER? INTERACTIONS WITH MANY DISCIPLINES Applied Mathematicians, Botanists, Computer scientists, Microbiologists, Oceanographers, Statisticians, Zoologists Accountants, Economists, Engineers, Social scientists Lawyers, Judges, Criminals (poachers), Industry, ENGOs, Bureaucrats, Journalists, Politicians Add the international dimension A NEW PROBLEM EVERY OTHER DAY CONTROVERSY Can lead to filibustering but promotes better science ANYTHING BUT A BORING LIFE 40

Thank you for your attention And thanks for assistance from the Lowell-Wakefield Symposium to visit Anchorage