Authors: Jordi Lleonart & Jordi Salat, ICM-CSIC

The program and the models underlying the VIT software are conceived for the analysis of fisheries where the time depth of the information available is limited and where the technical interaction among fishing gears is an important factor to account for. Typically, this programs is addressed to the analysis of Mediterranean fisheries. The program VIT was first published in Spanish (Lleonart and Salat 1992) and later in English as volume 11 of the FAO Computerized Information Series (FAO, 1997).

For this release of the VIT program, the code has been revised and implemented in MS Windows 95/98/NT. The new implementation has striven for compatibility with the original version, while some improvements have been added, specially regarding the data management routines (input), and the tables and graphics output.

The program VIT is designed for the analysis of marine populations, exploited by one or several gears, based on single species' catch data (structured by age or size). The main assumption underlying the model is that of steady state, because the program works with pseudo-cohorts and it is therefore not suitable for historical data series. The program uses the catch data and ancillary parameters for rebuilding the population of the species and the mortality vectors affecting it by means of Virtual Population Analysis (VPA). Once the virtual population has been rebuilt, an analysis of the fishery can be carried out with the aid of several tools: Comprehensive VPA results, Yield-per-Recruit analysis based on the fishing mortality vector, analysis of sensitivity to parameter values and transition analysis. The latter permits non-equilibrium analysis of how a shift in exploitation regime is reflected in the fisheries. All these tools can be applied to specific studies of competition among fishing gears.

The program can be used to carry out the numerical analysis, the edition of data and parameters, to obtain an age-structured data file from a size-structured data file and to visualize results. The results can also be exported to other Windows applications to refine specific details of the analysis or for the final presentation of the results.

Installing and using VIT: You can download a zipped version of the program. You can install the program by unzipping the vit4win.zip file and executing setup.exe. An installer will guide you through the installation process. Additional help can be found under Help in the vit4win.exe executable.

References:

FAO. 1997. VIT: Software for fishery analysis. User's manual. FAO Computerized Information Series, Fisheries. Vol. 11. 107 pp. + diskette.

Lleonart J and Salat J 1992. VIT: Programa de análisis de pesquerías. Informes Técnicos de Scientia Marina. vol. 168-169. 116 p.