Some samples may be easily examined and all veligers within them easily counted. In such cases, water sample density is determined by using this formula:
Total veliger count in the original water sampled
Total volume of original water sampled (L)
In contrast, however, determining the density of veligers within a sample may be too difficult if the number of veligers is large or the sample contains too much suspended matter. In this case, obtaining a series of subsamples and averaging them together may be a reliable method. To do this, gently shake the preserved sample. Immediately remove 1 milliliter of sample from the center before any settlement has a chance to occur. Analyze this subsample and label it subsample #1 and obtain an accurate count of veliger content. Repeat this process four more times to obtain and count a total of five subsamples, labeling them subsamples #2 through #5. Now, add the total counts from subsamples #1 through #5 and divide the sum by 5. This will give an average number of veligers/ milliliter in the sample. To obtain the total veliger count in the sample, multiply this average number by the total ml in the sample. If 1 milliliter proves to be too small a volume to obtain an adequate number of veligers, the calculations in the above-mentioned procedure must be adjusted.