Fish Population Dynamic and Stock Assessment (2+1)

Computer Packages for Stock Assessment Studies

Computer applications are widely used in fishery science particularly in fish stock assessment and fish taxonomical studies. Fisheries science was slow to adopt computers on a wide scale basis. Since computer made easy all the calculations, it finds wide applications in stock assessment studies. They are not only solving biological problems but also give many simulations for the fishery managers.

Several packages were developed for stock assessment studies in the temperate waters. Packages were also developed exclusively for tropical waters by FAO and ICLARM during the year 1987 and 1988 respectively. Computer packages for tropical waters and mainly based on the length based data.

1. ELEFAN Packages

The ELEFAN system (Electronic length Frequency Analysis) was developed by ICLARM in response to the need for robust methods for analysis of length frequency data and the availability of cheap microcomputers. This system consists of five programmes

ELEFAN O

ELEFAN I

ELEFAN II

ELEFAN III

ELEFAN IV

ELEFAN O

This is the basic system used to create and modify length frequency data files for the use of other four programmes. ELEFAN I to IV will be using length frequency data created by ELEFAN-O.

ELEFAN-I

Developed by Pauly and David (1987). This programme is used to estimate the growth parameters of fish or invertebrates. Growth oscillations of fish can be correlated with selected environmental parameters.

ELEFAN – II

It performs a variety of computation of which the following are the main ones.

1. Estimation of total mortality (Z) and derived quantities from the straight, descending arm of a length converted catch curve.

2. Estimation of probabilities of capture by length and mean length at first capture (Lc) from the ascending left arm of a length converted catch curve.

3. Expressions of seasonal changes in recruitment intensity in the form of graphical recruitment pattern.

It requires no inputs other than growth parameter estimates and length frequency data.

ELEFAN – III

It incorporate 3types of Virtual Population Analysis (VPA).

VPA – I

Estimates standing stock (in numbers) and fishing mortalities by time intervals.

VPA – II

This programme is used to estimate standing stock (in number) and fishing mortabilities by length class in a stock with age distribution.

VPA – III

Provides estimates of standing stock and fishing mortalities by month by length.

It requires monthly catch data in addition to length frequency and growth parameters as input.

ELEFAN IV

This programme provides gear selection parameters (Tc the probability of capture by length class) and can be used to estimate or and probabilities of recruitment by length class from catch samples.

II LFSA Package

This package Length – based Fish Stock Assessment (LFSA) was developed by Sparre during 1987. This is suitable package for ordinary IBM computers. It requires only length frequency data as input. This package was specially designed for tropical waters divided into four subpackages according to the type of input data.

1. LF – Length frequency analysis

2. AL – Age/length data

3. Beverton and Holt Y/R model

4. Ordinary linear regression

This package is provided with 32 subpackages, and are available to calculate various growth parameters, mortality parameters, analysis, Y/R models etc. It requires length frequency, effort, total catch, position interms of latitude and longitude, depth, gear type as inputs.

III – FiSSAT

FiSAT is relatively new package and the acronym stands for FAO-ICKARM Stock Assessment Tools. This software is resulted from the merging of its two predecessors, the complete ELEFAN package developed by ICLARM and LFSA developed by FAO, with addition to new routines found useful for the analysis of length frequency. FiSAT was developed during the year 1995 by Gayanilo, Sparre and Pauly. FiSAT was developed for an IBM or compatible personal computers with a minimum of 512 KB of free disc space and primarily aimed a helping scientists working on tropical fisheries resources to produce scientific advice for fisheries management.

This length assessment tool was developed to analyse L/F data –at age, catch – at – age, selection and other data typically collected for tropical fish stock assessment. It takes advantage of the high resolution graphic capabilities of micro computer.

FiSAT has four main groups or routines.

1. FILE

2. ASSESS

3. SUPPORT

4. UTILITIES

FILE

Deals with the file creation, editing and various data manipulation.

ASSESS

Contains the models and methodologies used in the analysis of the different types of data that FiSAT supports, ranging from growth and mortality parameters estimation to prediction using either the Beverton and Holt Y/R analysis, or the Thompson & Bell yield and stock prediction models.

SUPPORT

This routine facilitate data analysis. It contains routines to simulate length frequencies, display bar diagram, estimate (unsampled) maximum lengths and sample weight and perform regression analysis.

UTILITIES

Contains functions for importing and exporting data files, configurating output options and managing some DOS functions and a simple calculator is also included.

IV. VIT

Software for fishery analysis published in 1998 by FAO, and is created for the analysis of fisheries where the information is limited. The package is designed to analyse exploited marine populations based on catch data, structured by age or size and by type of gear.

V. POPDYN

A population dynamics database allows to user the store stock based information on the characteristic of fisheries system. Developed by FAO in 1994.

VI. SPATIAL

Developed by FAO in 1994. A simulation package developed to model the space/time distribution of fishing intensity using alternative approaches.

VII. ANALEN

Developed by Chevaillier and Laurec, 1990 in French for FAO in 1990. It is a software for analysis of catch at length data for simulation of multi gear fisheries.

This package contains four programmes.

1. ANALEN – based on Jones length based cohort analysis.

2. ANAJON Calculates Y/R and mature biomass per recruit for different levels of exploitation Also provides short term and long term forcasts of catches.

3. SENJON Sensitivity analysis of the principal results.

4. MONOJO To evaluate techniqual interaction between fishing gear.

VIII. ANACO Developed by Mensil, 1989 for FAO. This package containes two programmes related to VPA.

1. SIMUCO

Developed to analyse the selected properties of catch at age data

2. VPBAS-COHORT-VPUTIL

Software for assessment by using time series of catch at age data

IX. NAN-SIS package

FAO package developed by Stromme (1992). This is specially designed to process data generated by surveys of Dr.NANSEN by swept area method. NAN-SIS is a Survey Information System for logging, editing and analysis of scientific trawl survey data (Catch & I/f data).

It provides outputs, such as tables of catches, mean catch rates, and swept area.