The analysis of data in studies of invertebrate reproduction. I. Introduction and statistical analysis of gonad indices and maturity indices

As studies of invertebrate reproduction are expensive in time and money, there is a need to make the maximum use of the resultant data. It is also important to ensure that the conclusions of a study can be legitimately drawn from the data. Both of these factors necessitate the development of appropriate statistical methodology in reproductive biology.

The structure of data in reproductive biology is detailed, and methods of analysing gonad indices and maturity indices are reviewed. Although gonad indices have been widely used, they are only really satisfactory in species with strong seasonality of reproduction. There is, however, considerable scope for extracting more information from gonad indices than is usually obtained. The value of periodic regression as a tool to aid the understanding of reproductive cycles deserves further investigation.

If microscopic preparations of the gonads are being produced to estimate maturity indices, it is definitely worthwhile measuring oocyte sizes in the females, as the amount of information gained is considerable.