No, that is completely impossible. The reasoning behind it is because if its a large group of fish they're swimming back and forth ect, ect, it would be like counting a bowl of rice, but not being able to take any out. To get around these counting problems, scientists take data from just a small portion of the population called a sample. They take several samples and then use the average size of those samples to calculate an estimate of the entire population size.
If you need help feel free to ask!
Yes because if you have the right circulations and you figure out how many surtain species their are of each merin animal then you take the total average of each species and add it up then you have your population
