robertprice
June 12th, 2013, 01:16 PM
The study of Meristics in fish is the study of things that can be counted to tell species and genera apart. Taxonomists use meristics and mensural data (things that can be measured) to separate cryptic species. Meristics are very important in all lower vertebrate classification. I did my master's thesis on Meristics and I can tell you its not fun putting a live squirming fish on a binocluar microscope to count its dorsal fin rays, or the number of scales in a row. However when 2 species have boundaries that are uncertain and look very similar Meristics may be the only way to tell them apart. Oscars have 12-14 spines and 19-21 rays in their dorsal fin. Astronautus crassipinnis which looks very similar, has 11-13 spines and 19-22 rays. So, if we are looking at a fish that has 11 dorsal spines and 22 rays, we can say for sure that it's a crassipinnis and not an ocellatus. If you have a fish that is of uncertain species, it's a good idea to preserve it in alcohol if it dies so that these measurements can be done at a university or museum more easily.