To calculate the veliger density in the water sampled, use the following formula:
Total veliger count in the original water sampled
Total original volume of water sampled (L)
The total veliger count in the original water sampled can be calculated from the Sedgwick-Rafter cell counts as follows:
Mean number of veligers per ml in sample X Number ml in sample
Keep in mind that each Sedgwick-Rafter cell holds 1 ml of sample. Five replicate Sedgwick-Rafter cells should have been counted for each sample. If samples have been diluted, be sure to account for the dilution factor by multiplying the number of veligers counted per cell by the dilution factor. Average the five Sedgwick-Rafter counts to obtain the mean number of veligers per milliliter in the sample.
Veliger Analysis Techniques