VIT: software for fishery analysis
User's manual

Institut de Ci�ncies del Mar (CSIC)

Barcelona, Spain

VIT is a program created for the analysis of fisheries where information is limited. The source program is written in FORTRAN for IBM PCs and compatibles that use the MS-DOS operating system. Initially the program was designed and made with the objective of analyzing the data generated by the project "The fishery of Catalunya and Valencia, global description and bases for its monitoring", financed by the XIV General Directorate (Fisheries) of the European Community Commission, and conducted between 1986 and 1990 (Lleonart, 1990). VIT was originally designed to solve the two problems of that project: a population analysis based on a limited time series of size frequencies, and the study of the interaction between gears.

Although the origin of this program is linked to a particular problem, having showed it to other colleagues, it has become obvious that VIT may be of more general use. That is why we have decided to divulge it to the scientific community and develop this manual. The manual deals with program usage, limitations (illustrated with examples) and the theoretical background behind the program.

A first version of this software was published in spanish (Lleonart & Salat, 1992).

The first version of this program was developed in 1988. Since then, and thanks to the number of colleagues that have worked with previous versions, it has been improved and new options have been added to it. The comments and recommendations of these colleagues have definitely contributed to the version of the program that appears in this publication. The authors want to thank all of them and specially, the participants of the project "The fishery of Catalunya and Valencia, global description and bases for its monitoring": Llu�s del Cerro, Montserrat Demestre, Manuel Marhuenda, Paloma Mart�n, Balbina Mol�, Charo Obarti, Juan Pablo Pertierra, Laura Recasens, Pere Rubi�s y Pilar S�nchez.

The authors owe Emilio Garcia and Bego�a Campos for their mathematical and statistical assistance. The authors also want to acknowledge the valuable comments to an earlier draft provided by Jorge Csirke and Jos� Antonio Pereiro.

Lleonart, J.; Salat, J.

VIT: software for fishery analysis. User's manual.

FAO Computerized Information Series (Fisheries). No. 11. Rome, FAO. 1997. 105p.

ABSTRACT

The program VIT was designed to analyse exploited marine populations based on catch data, structured by ages or sizes, from one or several gears. The main assumption is that of steady state because the program works with pseudo-cohorts, therefore it is not suitable for historic series. From the catch data with some auxiliary parameters and using Virtual Population Analysis (VPA) the program rebuilds the population and mortality vectors. After this first step the user has several analysis tools and reporting options available: obtaining comprehensive VPA results, Yield-per-Recruit analyses based on the fishing mortality (F) vector, analyses of sensitivity to parameter inputs, and transition analyses - outside the equilibrium - due to changes in the pattern of exploitation or recruitment. All these analyses are applicable to studies of competition between different kinds of gears.

The program also includes several interactive options in the sense that partial results can be visualised, parameters may be changed and primary data can be converted from size to age structure. The outputs of the analyses are included in an ASCII file ready to be entered onto a worksheet. The present paper includes a complete description of the program, its utilities and limitations, with a complete operator's manual and examples. It also includes a chapter on theoretical fundamentals of each one of the analyses. The source code has been written in FORTRAN and the executables under MS-DOS Operating System.

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