Age determination in fish fish. Johannes Reibisch, working for the Commission of Scientific Investigation of German Seas at Kiel, attempted to use Hoffbauer’s techniques to age plaice ("Plueronectes platessa") but found it difficult to accurately discern annuli. He decided to study a different structure and in 1899 he published the first procedures using otoliths as an aging structure. A fellow scientist also with the German Commission at Kiel, Friedriche Heincke, also frustrated with difficult scale annuli, further studied other structures to age fish. He discovered annuli in the vertebrae, opercula, and pectoral girdle and published his findings in Heicke 1905. The works of Hoffbauer,
Anyperodon than the upper jaw. There are no palatine teeth, a fact which distinguishes this species from other groupers. The basic colour is pale reddish-brown liberally dotted with orange spots which are closer together on the head. There are five pale silvery blue longitudinal lines running down either side, the lower 3 reaching the tail but the upper two breaking into irregular streaks. The dorsal fin has 11 spines and 14 to 16 soft rays. The anal fin has 3 spines and 8 to 9 soft rays. Juvenile fish have vivid blue and red longitudinal stripes. The slender grouper has a