FAO FISHERIES TECHNICAL PAPER 234 Some simple methods for the assessment of tropical fish stocks Table of contents

by
Daniel Pauly
Associate Scientist
International Center for
Living Aquatic Resources Management
Makati, Metro Manila, the Philippines

First printing 1983

Second printing 1984

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M-43
ISBN 92-5-101333-0

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FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS Rome, 1984
© FAO

PREPARATION OF THIS PAPER

This document is a revised version of FAO Fisheries Circular No. 729, issued in English and French. The present version is also available in Spanish.

Hyperlinks to non-FAO Internet sites do not imply any official endorsement of or responsibility for the opinions, ideas, data or products presented at these locations, or guarantee the validity of the information provided. The sole purpose of links to non-FAO sites is to indicate further information available on related topics.

CONTENTS

FOREWORD

The present report provides an introduction to the methods of stock assessment particularly tailored to the needs of fisheries workers concerned with the complex resources of the tropical and subtropical areas of the world. In adapting existing methods (largely developed in the temperate and cold temperate regions of the world) for use in the tropics, the author has attempted to illustrate the main principles in as simple and direct way as possible, drawing upon concrete examples from actual published fishery data.

The text of this paper is taken, largely unchanged, from the notes of the lectures given by the author at the FAO/DANIDA Training Course on “The Methodology of Fisheries Science (Biology)”, held from 19 May to 14 June 1980 in the Kenya Marine Fisheries Research Institute (KMFRI) in Mombasa, specifically aimed at an audience drawn from countries bordering on the Western Indian Ocean. This text is an improved version of FAO Fish. Circ. No. 729.

The course followed the usual FAO format: a brief, stremlined exposition of the main points of the subject-matter was followed by roundtable discussions and worked examples during which the pros and cons of the different methods and pitfalls in their application were explained fully. The worked examples used in the course are given in the text of the lecture, and it only remains to point out to the student reader that the application of any method (especially a `short-cut' method) should not ignore the principles underlying the application of scientific methods in marine science.

These principles may be briefly summarized by four questions which the worker should ask himself or herself before and during the course of the analysis:

1. Were the basic data used in the analysis collected following statistically valid procedures?
2. Are the basic data in accordance or conflict with what else you know about the population or species in this or other areas?
3. In carrying out the anlysis, have you followed statistically valid procedures in either selecting the data to analyse, or in interpreting the data?
4. Once again, are the results in general accord with the known biology of the species?

If all these questions are asked before and during the analysis, then the results of a particular procedure may be viewed with the appropriate degree of confidence, particularly if the assumptions underlying each method are understood and borne in mind at all times.