 At the juvenile stage , a teleost looks more like its adult form . At this stage , its axial skeleton , internal organs , scales , pigmentation and fins are fully developed . The transition from larvae to juvenile can be short and fairly simple , lasting minutes or hours as in some damselfish , while in other species , like salmon , squirrelfish , gobies and flatfishes , the transition is more complex and takes several weeks to complete . At the adult stage , a teleost is able to produce viable gametes for reproduction . Like many fish , teleosts continue to grow throughout their lives . Longevity depends on the species with some gamefish like European perch and largemouth bass living up to 25 years . Rockfish appear to be the longest living teleosts with some species living over 100 years . 
