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Focuses on the non-destructive determination of fat content in frozen and thawed mackerel by near infrared spectroscopy in Japan. Importance of fat content and freshness vis-a-vis fish quality; Analysis of the multiple linear regression based on second derivative spectra and fat content in frozen and thawed fish; Calibration equation with temperature compensation of fish samples.

Investigates the biological indicator for stock identification of sandfish Arctoscopus japonicus in Japan. Role of the copepod Steindachner Acanthochondria priacanthi; Parasitic relationship between the sand fish and the crustacean; Percentage of infected hosts in a sample.

Focuses on the otolith microstructural analysis of reared larvae of the Japanese eel Anguilla japonica in Japan. Validation of the daily deposition of otolith increments; Problems with the rearing techniques used with eel larvae; Estimation of the early growth of artificially fertilized larvae in comparison with wild glass eels.

Examines the effect of increased seawater temperature on Ecklonia cava population in Tosa Bay, southern Japan. Ecophysiology; Seasonal average surface water temperature; Photosynthetic rate of bladelets of Ecklonia cava.

Studies the impact of the water currents, temperature and salinity along the coastal areas of northern Japan on the occurrence of Dinophysis species, the causative plankton of diarrhetic shellfish poisoning. Collection of samples of the species and seawater along Kesennuma Bay; Determination and monitoring of inorganic concentration of nitrogen and phosphorus; Influences of salinity and the different environmental conditions to the appearance of the species.

Studies the potential smolting ability of stream-dwelling Dolly Varden, Salvelinus malma. Collection of samples of the species; Classification of the species into phenotypes according to body coloration characteristics; Observation of the phenotypes on their smolting abilities.

The purpose of the present paper was to reveal the migration pattern of shirauo Salangichthys microdon Bleeker, in the Ishikari River system and its adjacent coastal sea areas. To this end, the strontium–calcium (Sr:Ca) ratios of the otoliths of 98 individuals were examined. Profiles of the Sr:Ca ratios during the life history after hatching in the estuary of the Ishikari River fell into two different patterns. One was characterized by a high (slightly fluctuating) Sr:Ca ratio throughout the life history; the other was characterized by an initial high Sr:Ca ratio followed by a lower value later in life. The former pattern was considered to be that of estuary–sea residents and the latter that of upstream migrants. Most upstream migrants migrated upstream once, although several did it twice. Back-calculated body lengths during the upstream and seaward migrations of the upstream migrants varied widely from 6.4 mm to 39.8 mm and from 13.5 mm to 79.4 mm, respectively. These findings suggest that estuary–sea residents and upstream migrants co-occurred spatiotemporally, and suggest a wide variation in migration patterns in the shirauo's life history. [ABSTRACT FROM AUTHOR]

The purpose of the present paper was to examine the genetic population structure of Buccinum tsubai in the Japan Sea. Mitochondrial 16SrRNA gene sequence analysis was performed with specimens from various stations in the Japan Sea. Mitochondrial lineages were clearly patterned geographically in four separate areas: the Hokkaido area, the Yamagata–Toyama area, the Yamato Bank area, and the San’in area. The main distribution depth range of B. tsubai is between 200 m and 1000 m isodepths, and the horizontal distance between the 200 m and 1000 m isodepth lines represents the specific spatial scale of the habitat (SSSH). These four areas were separated either by the complete discontinuity of the SSSH area or by its narrow spatial extension. Genetic distances between the main haplotypes of each area were calculated as Jukes–Cantor distances, the value of which ranged between 0.012 and 0.017. This value seemed to be unrelated to the geographic distance. There was no tendency for clustering according to depth. In future, the morphological characters of the four lineages of B. tsubai should be compared in detail in order to elucidate significant genetic differences among them. [ABSTRACT FROM AUTHOR]

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]