Ahh, good question. If you know typical growth and mortality rates, then you can develop a good picture of what you might expect for a length frequency at any particular location. If you then sample a population, and it differs from that expected pattern, you can ask the right questions. If there are primarily small fish in a population sample, then you ask where are the big fish? Typical answers are 1) the anglers harveted them and we need protection (regulation), or 2) the population density is too high, growth is slow, and the fish never reach those larger sizes (need to reduce population abundance). The correct management action will then vary depending on the suspected (or preferably "known"
) interpretation of the population sample.
