Introduction

The INDMED3 program, as it exists in its last version dated from February 1996, has been estimated as no complete : the abundance indices calculations were made only in density by weight or number by square kilometre. It has then been proposed to make available indices in CPUE (weight or number per hour trawling). Furthermore, a bug remained in the previous version : in the output dealing with only the shelf and the slope separately, not sampled strata (or strata with no valid hauls at all) had the value 0 instead of -1 as in the detailed outputs. Although this case occurs only once a year (at present) for the super-stratum 200-800 m in Slovenian waters, it seemed intellectually better to correct the program in that way.

Generally speaking, this program works as the former version INDMED3. Only one new choice is proposed to the user : abundance indices calculation based either on density or on CPUE. This choice is mentioned in the heading of the print out. The above mentioned bug has been corrected.

The calculations of abundance indices based on density have not been changed. Those based on CPUE are very similar : the total trawled surface within a stratum has been replaced by the total trawling time. The calculation of area indices always uses a weighted average of indices by stratum, using the ratio stratum surface / area surface as weighting factor. This is explained below.

Notations :

A total surface of the area

N number of strata in that area

Ai surface of the stratum i

Wi relative weight of the stratum i in the area

ni number of hauls in the stratum i

Ti,j time trawled during the haul j in the stratum i

fi sampling fraction in the stratum i

xi,j measured value in the haul j

with and

The term (1- fi) could be neglected because fi is in general very small.

With this fourth version, the INDMED program can now be considered as complete and is no longer expected to change. It can provide all requested results by country/area to build up the final report. In case of some new requests would be necessary, it is though that a new program should be written.