RELATIONSHIPS BETWEEN OTOLITH SIZE AND FISH SIZE FOR TWELVE PREY FISH SPECIES FROM JIAOZHOU BAY

Based on the bottom trawl surveys in Jiaozhou Bay from November 2008 to August 2009, the relationships between otolith size (including otolith length, width, long radius and short radius) and fish length of 12 prey fish species were studied in order to provide basic information for further research of feeding ecology of higher trophic level fishes and marine trophodynamics. A total of 1063 samples were collected for all the 12 fish species, belonging to 3 orders, 7 families and 11genera. Results showed that there were significant power functional relationships between length and weight for 12 prey fish species (P0.05). The coefficient of regression (b) in the length-weight relationship functions ranged from 2.871 to 3.371, with the mean value of b being 3.1590.110 (95% CL). In all the 12 prey fish species, Amblychaeturichthys hexanema had the lowest value of b and Apogon lineatus had the highest value. T-test showed that Liza haematocheila and Callionymus sagitta presented isometric growth (P0.05), Callionymus richardsonii and A. hexanema presented negative allometric growth (P0.05), and the other 8 species presented positive allometric growth (P0.05). The analysis of variance indicated that the regressions between otolith size and fish standard length were extremely significant (P0.01). In all 48 regression functions, the determination coefficients (R2) were larger than 0.8 in 37 functions, between 0.7 and 0.8 in 9 functions and lower than 0.7 in the rest two functions. Among all the 12 fish species, A. hexanema had the highest value of R2 (close to 1), while Engraulis japonicus had the lowest value of R2 (lower than 0.8). According to the value of R2 in different functions of the same species, the regression functions of otolith length and width to fish standard length fitted better than the functions of otolith radius to fish standard length for most fish species. Therefore, the size of prey fishes could be estimated by means of otolith length and width. On the other hand, because the tip of the otolith may be damaged frequently in the stomachs of fish, which made it uneasy to measure accurate otolith length, so the regression function of otolith width to fish standard length is more suitable in practice.