The agnathan hagfish is the plesiomorphic sister group of vertebrates. It is eel-liked, cartilaginous, and has only one semicircular canal. As hagfish have no hard structures that age determination remains unsuccessful. In the present work, we examined the statoconia in the inner ear of the hagfish Paramyxine nelsoni intense to explore it as a useful index in hagfish¡¦s age determination. P. nelsoni is quite abundant at some localities in the southwestern coast of Taiwan. Due to its smaller size, P. nelsoni is not a commercial species in this area. Little information on its populations is available in the literature. Consequently P. nelsoni is a potential model species for fisheries study of hagfish. The statoconia of the P. nelsoni were deciphered from 49 specimens with body length ranging from 10.2cm to 29.5cm. The semicircular canals were examined using scanning electron microscope. Histological sections for the semicircular canals were also made for observation of cytological characters. The masses of statoconia were located on the surface of the macular epithelium. The epithelium of macula was psudostratified columnar type, which was composed of hair cells and supporting cells. Diameters of the statoconia were ranged from 1 &#x00B5;m to 26 &#x00B5;m (3.41¡Ó 0.29 &#x00B5;m). Most of them were distributed in a narrow range from 4 &#x00B5;m to 8 &#x00B5;m. Both small (<4£gm) and large (>8£gm) statoconia were observed in all size of Paramyxine nelsoni. The diameter of statoconia was not correlated with body length. Although the numbers of statoconia were increased with body length, it was not separate clearly between each body size. The shape index (short diameter/long diameter) was decreased when the long diameters of statoconia were larger than 6 &#x00B5;m. This result suggests that statoconia are produced to accumulate from round to ellipse throughout hagfish¡¦s life span. In conclusion, both of the diameters and numbers of statoconia may not be appropriate index in age determination of hagfish.

Food, growth, sex ratio and depth distribution of perch (Perca fluviatilis L.) were studied in Milada Lake, Most Lake and Barbora Lake. These lakes were artificialy created after a coal mining. Sex ratio and depth distribution were also compared with data gathered from Vír Reservoir and Římov Reservoir. Fish designed for the research were captured by gillnets. Age analysis was carried out by otolite scanning. Food, growth and depth distribution were analysed with consideration of size and sex of the fish.