. California fish and game. Fisheries -- California; Game and game-birds -- California; Fishes -- California; Animal Population Groups; Pêches; Gibier; Poissons. 220 CALIFORNIA FISH AND GAME CO - I- o < liJ Z. FIGURE 4. OTOLITH SECTION AGE (YEARS) Differences between otolith section ages and whole otolith ages from another agency for male Sebastes diploproa (N = 246). It is clear from our results that an important part of the populations of both species is significantly underaged using the whole otolith technique, particularly by the other laboratory (Figures 3,4,5). An important point to n
. California fish and game. Fisheries -- California; Game and game-birds -- California; Fishes -- California; Animal Population Groups; Pêches; Gibier; Poissons. 220 CALIFORNIA FISH AND GAME CO - I- o < liJ Z. FIGURE 4. OTOLITH SECTION AGE (YEARS) Differences between otolith section ages and whole otolith ages from another agency for male Sebastes diploproa (N = 246). It is clear from our results that an important part of the populations of both species is significantly underaged using the whole otolith technique, particularly by the other laboratory (Figures 3,4,5). An important point to note from these data is the fact that the deviations for males are generally greater than those for females. Female Sebastes grow faster than males for most species (Boehlert and Kappenman 1980, Westrheim and Marling 1975) and are therefore characterized by otoliths which have broader, clearer annuli on whole otoliths to a greater age. Thus, the age at which the otolith growth occurs only as "caps" on the internal surface will be greater for females. Using whole otoliths for age determination, the females will appear to be older than the males whereas the opposite is actually true based upon section age (Tables 6 and 7). The systematic bias which is introduced by using whole otolith ages is therefore compounded by differ- ences in the error of longevity estimates for males and females. These older fish represent an important part of the population which should not be ignored. Hirschhorn (1974) argued that excluding older, difficult-to-age individuals from growth analysis for the population can have detrimental effects upon estimates of von Bertalanffy parameters. For production modelling or stock analysis purposes, unbiased errors in age determination, particularly for older segments of the population, will have little effect, whereas systematic bias in. Please note that these images are extracted from scanned page images that may have been digitally enhanced for read
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