Determination of larvae development stages in rainbow trout (oncorhynchusmykiss walbaum, 1792) based upon morphologic observations, pigment distribution patterns, and fin development patterns

Abstract

Our knowledge aboutfish biology couldn't be completed without our awareness of bio- history oflarvae. The study of fish's bio- history can provide information about fishlarvae actions and reactions in its first life stages. This general descriptioncan represent the anatomical, physiological, behavioral and ecological changesin development stages of fishes. In this research, we study the larvaedevelopment stages on 30 larvae of rainbow trout based on morphologicalobservation, pigment scattering pattern and fins development pattern. From theviewpoint of pigments pattern, in general, the highest pigments wereconcentrated on the rear of head and between eyes and the lowest was on finsbud and their abdomen. The morphological observations in larvae stage indicatedthat larvae in first stage has different shape than its puberty and itsappearance will change in parallel to its development during the time, so thatat the end of stage, it is so like an adult fish. In same researches on larvaeof other salmon species, there are relative similarities due to pigmentscattering pattern but there are significant differences in morphologicalobservation and also the pattern of fins development.