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,
Curlfin sole Curlfin sole The curlfin sole ("Pleuronichthys decurrens") is a flatfish of the family Pleuronectidae. It is a demersal fish that lives on soft bottoms at depths of between . Its native habitat is the subtropical waters of the eastern Pacific, from Prince William Sound, Alaska in the north to San Quintín, Baja California in the south. It can grow up to in length, and reach weights of up to , with females generally being larger than males. The curlfin sole is a right-eyed flatfish with large, closely set eyes and a small mouth. The upper surface is reddish brown to