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SUMMARY:This paper proposes a method for estimating stock abundance for a fishery exploiting two stocks, using a model of stock dynamics incorporating effort allocation. We assume that the fishery selects a target stock every hour of operation from the two stocks with a certain probability (α), and that the spatial distribution of stock is either regular or aggregated. The parameters are estimated by the maximum likelihood procedure. Our model is applied to the data of the diving fishery from 1972 to 1976 which catches abalone and top shell along the coast of Toji in Shizuoka Prefecture. The minimum Akaike Information Criterion (AIC) supported the model that the α values were changed between- and within-year. The coefficients of variation of the abundance estimate for abalone ranged from 0.01 to 1.37, and for top shell from 0.01 to 0.03. The abundance estimates were compared with those by the DeLury’s method. The modifications of the model are discussed. [ABSTRACT FROM AUTHOR]

SUMMARY:This paper estimates the age and growth of the alfonsino Beryx splendens in the waters around the Izu Islands off the Pacific side of Japan. The samples consist of 250 fish of the landings of the offshore longliners from December 1995 to November 1996 and 10 fish of the coastal longliners in February of 1995. By the surface method using a microscope, a reader counted the number of hyaline and opaque zones on the sagittal otoliths, judged whether the edge was hyaline, and measured the radii from the focus to the outer edge of each hyaline zone. In order to estimate the parameters of the von Bertalanffy’s growth equation representing the overall ages, the age and fork length data and the mean length at 1 year old. In a previous study were used for the maximum likelihood approach. From the results, the rate of readability of the otolith from the offshore samples was 97.6% and that from the coastal samples was 100%. The monthly changes in the frequency of the opaque edge showed that the hyaline and opaque zones were laid down once a year. The hyaline zone began to form from May to July (peaking in August). The ages of the offshore samples for both the sexes ranged from 2 to 23 years, and those of the coastal samples 2 to 5, respectively. The estimated growth curves were expressed by l(t) = 44.4[1–exp{–0.132(t + 3.45)}] for males and l(t) = 45.0[1–exp{–0.150(t + 2.08)}] for females, where l(t) and t denote the fork length (cm) and the age in years, respectively. The issues to be resolved in the future were discussed. [ABSTRACT FROM AUTHOR]