A linearized version of the Appeldoorn model of the von Bertalanffy growth function is presented for the estimationof parameters of seasonal growth oscillation.
In many developing countries, availability of suitable tags for use in genetics and aquaculture research has been a problem as they are often expensive and have to be imported from other countries. A simple and inexpensive method used by scientists in Ghana that can be tried and improved by others is described in this article.
Details are given of techniques to be used in the handling of large amounts of data in the field of aquaculture. Two examples are given where different types of multivariate data analyses are performed on the compiled datasets to identify and quantify the effects of key variables governing growth and production of fish in manured pond systems cultivating tilapia and carp.
An equation is given for the selection of interval sizes for use in length frequency analysis of fish classes.
Natural resource management is closely linked to conflict management, prevention and resolution. Managing natural resources involves reconciling diverging interests that often lead to conflict, which can undermine management institutions and lead to exploitation, environmental destruction and deteriorating livelihoods. If conflicts turn violent, they can rip apart the entire fabric of society. Thus, managing conflicts in a peaceful manner is decisive not only for successful and sustainable resource management but for societal stability in general.
A method for estimating the instantaneous mortality rate (Z) is presented which was developed from a truncated equation for average length. The model has zero bias at equilibrium, but has no explicit solution for Z so that its solution requires a numerical method.
Comparative methods are presented which allow for quick and relatively reliable growth parameter estimates when growth data are not at hand. One of these methods involves the use of a newly developed "auximetric grid." An empirical equation for the estimation of natural mortality of any fish stock, given a set of growth parameters, is briefly reviewed. The methods are applied to data from the Gulf of Thailand trawl fishery, and the mortality caused by this fishery is estimated.
A method is presented through which the total mortality undergone by several fish stocks of the same species can be compared when growth parameters are poorly known or unknown. Whereas the estimate of Z obtained via the length-converted catch curve is highly sensitive to the input parameters K and L sub( infinity ), the ratio of Z estimates obtained for different stocks with the same combination of parameters is almost independent of these inputs, at least when the fit of the linear regression is good.
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.