FAO FISHERIES TECHNICAL PAPER 234
Some simple methods for the assessment of tropical fish stocks
International Center for
Living Aquatic Resources Management
Makati, Metro Manila, the Philippines
First printing 1983
Second printing 1984
All rights reserved. No part of this publication may be reproduced. stored in a retrieval system, or transmitted in any form or by any means. electronic, mechanical, photocopying or otherwise, without the prior permission of the copyright owner. Applications for such permission. with a statement of the purpose and extent of the reproduction, should be addressed to the Director, Publications Division, Food and Agriculture Organization of the United Nations, Via delle Terme di Caracalla, 00100 Rome, Italy.
FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS Rome, 1984
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.
|Distribution:||For bibliographic purposes this document should be cited as follows:|
|FAO Fisheries Department|
FAO Regional Fisheries Officers
|Pauly, D., Some simple methods for the
1983 assessment of tropical fish
stocks. FAO Fish.Tech.Pap.,|
This selection of methods is based on lecture notes used at a FAO/DANIDA training course held in Mombasa, Kenya, in May-June 1980. The methods presented are: regression and correlation, estimation of growth parameters from length-frequency data, estimation of mortalities (total, natural, fishing mortality) and analysis of catch and effort data.
Only methods that are inherently simple and applicable in the tropics are discussed in detail while more advanced concepts such as the distinction between different forms of overfishing, stock-recruitment relationships, multispecies interactions are introduced in the form of an essay. A brief annotated bibliography of tropical fish stock assessment is included.
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.
|1.||DECK SAMPLING AND CATCH RECORDING PROCEDURES|
|2.||STATISTICS: REGRESSION AND CORRELATION|
|3.||METHODS FOR OBTAINING GROWTH PARAMETERS FROM LENGTH-FREQUENCY DATA OF TROPICAL FISH|
|4.||METHODS FOR ESTIMATING TOTAL, FISHING AND NATURAL MORTALITIES|
|5.||SOME PROBLEMS IN TROPICAL STOCK ASSESSMENT|
|6.||TWO FORMULAE FOR THE RAPID ESTIMATION OF POTENTIAL YIELDS IN (MORE OR LESS) VIRGIN STOCKS|
|7.||BIOLOGICAL OVERFISHING OF TROPICAL STOCKS|
|APPENDIX 1: Critical values for correlation coefficients|
|APPENDIX 2: Growth parameters of selected Indo-Pacific fish stocks|
|APPENDIX 3: Length-frequency sheet|
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:
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.
|J. F. Caddy|