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Volume 70 (2004)
- Issue 6 Pages 853-
- Issue 5 Pages 667-
- Issue 4 Pages 496-
- Issue 3 Pages 276-
- Issue 2 Pages 123-
- Issue 1 Pages 1-
Volume 70, Issue 6
Displaying 1-11 of 11 articles from this issue
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Originals
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YONG TANG, MASAHIKO FURUSAWA2004 Volume 70 Issue 6 Pages 853-864
Published: 2004
Released on J-STAGE: July 08, 2005
JOURNAL FREE ACCESSAn error is introduced by the influence of sea surface and bottom reverberations in quantifying surface fish using fisheries scanning sonar. Minimization of the error is the purpose of this study. The sonar equation is derived to measure the surface backscattering strengths (SS) of the sea surface and bottom reverberations. The characteristics of the equivalent beam angle in the equation is investigated, after clarifying the beam directivity relative to the sea surface and bottom. This equation was applied to an experimental quantitative sonar system, and the SS of the sea surface and bottom reverberations were observed in Tateyama Bay, Japan. The signal to reverberation ratio (SRR) for the average volume scattering measurement of fish is investigated using the characteristics of SS. Combining the SRR and the signal to noise ratio (SNR), an appropriate tilt angle and measurement range are introduced. Then the influence of sea surface and bottom reverberations can be minimized in the abundance measurement by the echo integration method using a sonar.View full abstractDownload PDF (849K) -
SEIJI AKIYAMA, SATOSHI KAIHARA, TAKAFUMI ARIMOTO2004 Volume 70 Issue 6 Pages 865-871
Published: 2004
Released on J-STAGE: July 08, 2005
JOURNAL FREE ACCESSIn order to understand the capture characteristics of a trammel net for herded oval squid Sepioteuthis lessoniana, fishing method and catch composition were surveyed in Tateyama Bay, Chiba Prefecture, in 2002 and 2003. A trammel net with an inner mesh size of 85 mm and an outer mesh size of 360 mm was used in the fishing operation. The trammel net was operated for spawning-group of oval squid in an eelgrass bed area at a depth of 4-12 meters. The operation was divided into three stages: setting, herding and hauling. A total of 1,491 oval squid, 933 fish and 63 others were caught in 363 hauls. The discard rate based on the catch in number of the trammel net was estimated as 17 percent. The mean mantle length of oval squid was 28.0 ± 5.8 cm. Oval squid smaller than 17 cm in mantle length were not captured by the trammel net. Oval squid were mostly taken in the central and bottom part of the trammel net, and 95 percent of the oval squid were pocketed by the bag-shaped inner net.View full abstractDownload PDF (534K) -
TETSUYA NISHIKAWA, YUTAKA HORI2004 Volume 70 Issue 6 Pages 872-878
Published: 2004
Released on J-STAGE: July 08, 2005
JOURNAL FREE ACCESSIn order to elucidate the mechanism of Porphyra bleaching by Coscinodiscus wailesii blooming, effects of nitrogen (N), phosphorus (P) and silicon (Si) on C. wailesii growth under the culture were examined. The maximum growth rate (μm) was 1.0-1.3 divisions/d at 20°C and 0.46-0.49 divisions/d at 9°C nutrient saturated conditions respectively. The half-saturation constants for growth (Ks) of nitrate, phosphate, and silicate were estimated as 1.4 μM-N, 0.39 μM-P, 5.7-6.2 μM-Si, respectively. The minimum cell quotas of N, P and Si were calculated as 0.44 nM-N/cell, 0.030-0.040 nM-P/cell and 1.4 nM-Si/cell, respectively. C. wailesii did not grow on a wide variety of amino acid and organic phosphorus compounds of different molecular structure as a sole N or P source. The present study demonstrated that comsumptions of the nutrients per a cell of C. wailesii are significantly larger than the other species causing Porphyra bleaching. Decrease of orthophosphate or silicate concentration in Harima-Nada during the period from February to March is presumed to be the limiting factors of C. wailesii bloom in spring.View full abstractDownload PDF (521K) -
KAZUHIKO HIRAMATSU2004 Volume 70 Issue 6 Pages 879-883
Published: 2004
Released on J-STAGE: July 08, 2005
JOURNAL FREE ACCESSThe ABC Decision Rule 2-2 was examined by simulation using the operating model. The operating model was based on the production model with stochastic variation in population and observation error of abundance index. Results indicated that Rule 2-2 provided a low yield and high risk of management failure. Alternative decision rules which used the trend and level of abundance index were also examined and provided a higher yield and lower risk of failure than Rule 2-2. Urgently needed is development of management decision rules that are robust to key uncertainties by simulation using the operating model which adequately represents actual stock.View full abstractDownload PDF (351K) -
JUN OHTOMI, HIROMASA YOKOMURA, TATSUO HAMANO2004 Volume 70 Issue 6 Pages 884-888
Published: 2004
Released on J-STAGE: July 08, 2005
JOURNAL FREE ACCESSThe spawning season and food habits of the deep-water stomatopod crustacean Squilloides leptosquilla (Squillidae) were examined using samples collected on board the small-scale bottom trawlers in Kagoshima Bay, southern Japan. From the reproductive analyses, the size at sexual maturity of female S. leptosquilla was estimated to be 10 mm in carapace length and the spawning season was estimated to continue from May to September with a peak during July and September. Gut analysis showed that this species is a typical carnivore and mainly ate shrimps, especially the deep-water mud shrimp Solenocera melantho which is one of the most important target species for the small-scale bottom trawlers in Kagoshima Bay.View full abstractDownload PDF (511K) -
MASASHI YOKOTA, SEIICHI WATANABE2004 Volume 70 Issue 6 Pages 889-895
Published: 2004
Released on J-STAGE: July 08, 2005
JOURNAL FREE ACCESSOccurrence of transmission of a fish disease among culture ponds and risk analysis were computed using a simple simulation model of a one-dimensional pond distribution. We assumed three types of fish transportation ((1) directional exchange, (2) directional on-way transportation and (3) random transportation among tanks) and three defense strategies against the invasion of the disease. Numerical simulations suggested that the strategy which avoids the transportation (3) is more effective to inhibit the spread of disease, and disease-induced mortalities were detected even at lower numbers, so transportation among ponds should be stopped as fast as possible.View full abstractDownload PDF (1232K) -
HIDENOBU YAMBE, ARIMUNE MUNAKATA, KATSUMI AIDA, NOBUHIRO FUSETANI, SHO ...2004 Volume 70 Issue 6 Pages 896-901
Published: 2004
Released on J-STAGE: July 08, 2005
JOURNAL FREE ACCESSThe reproductive cycle of smallmouth bass Micropterus dolomieu naturalized in Lake Akimoto at Fukushima Prefecture was investigated to obtain biological information for developing techniques to exterminate this species in Japan. Samples were captured monthly from April to December 2002. In male testes, spermatozoa or spermatids were observed from April to July and from September to December. In August, males showed low gonadosomatic index (GSI) and the testes were occupied by spermatocytes. In females, oocytes with early or late perinucleolus and yolk stages were observed from April to June and from October to December. From July to September, females showed low GSI and a decrease in the number of oocytes with yolk stages. In both males and females, plasma testosterone and 17,20β-dihydroxy-4-pregnen-3-one levels reached peaks in May. In males, 11-ketotestosterone reached a peak in May. In females, estradiol-17β showed high levels in April. From these results, the reproductive period of smallmouth bass can be considered to be from spring to early summer. However, they have gonads keeping a certain degree of maturity from autumn to early winter.View full abstractDownload PDF (1430K) -
OSAMU KATANO, TOMOYUKI NAKAMURA, SHOICHIRO YAMAMOTO, SINICHIRO ABE2004 Volume 70 Issue 6 Pages 902-909
Published: 2004
Released on J-STAGE: July 08, 2005
JOURNAL FREE ACCESSThe species composition, population density, growth rate and food content of fishes in the Urano River, a tributary of the Chikuma River, were investigated. A total of 7,052 fish belonging to 14 species were captured. The pale chub Zacco platypus, an invasive species from western Japan, was most dominant and accounted for more than 40%, followed by Misgurnus anguillicaudatus, Tribolodon hakonensis and Pseudogobio esocinus esocinus. Zacco platypus were abundant in running waters, whereas M. anguillicaudatus and P. esocinus esocinus mainly used pool areas. These dominant fishes grew positively from June to July or August. Most fishes preyed on aquatic insects such as chironomid larvae and ephemeropteran nymphs and only Z. platypus mainly fed on benthic algae. The piscivorous niche in the Urano River is almost vacant due to the extinction of native Japanese fishes such as the Far Eastern catfish Silurus asotus. Therefore, the Urano River is threatened by the invasion of piscivorous alien fishes such as largemouth bass Micropterus salmoides and smallmouth bass M. dolomieu.View full abstractDownload PDF (654K) -
SHIN ATSUCHI, YASUJI MASUDA2004 Volume 70 Issue 6 Pages 910-921
Published: 2004
Released on J-STAGE: July 08, 2005
JOURNAL FREE ACCESSThe Fish stock enhancement program of Japanese flounder Paralichthys olivaceus in Kagoshima Bay started in 1984 and in recent years about 300 thousand juveniles have been released per year. To clarify the effectiveness of the releases in Kagoshima Bay, a continuous survey on the commercial catch in Kagoshima Fish Market was conducted from 1989 to 2002 and revealed that the ratio of released fish in the landings amounted to 18.9-49.2% in number. Using the age-weight-key estimated by sex based on the samples collected from Kagoshima waters, the catches in number for weight classes in Kagoshima Fish Market from 1989 to 2002 were transformed to those for the age classes. Estimates of recapture rate during 7 years after the release ranged from 1.51 to 3.52% and economic efficiencies were estimated to be from 0.97 to 1.17. Cohort analyses showed the recent decrease in recruitment and spawning biomass. Further studies on the stock management of P. olivaceus in Kagoshima Bay are needed.View full abstractDownload PDF (517K) -
KOICHI KUWAHARA, KAZUFUMI OSAKO, KUNIHIKO KONNO2004 Volume 70 Issue 6 Pages 922-927
Published: 2004
Released on J-STAGE: July 08, 2005
JOURNAL FREE ACCESSFor the purpose of utilizing squid meat as textured products, the effects of sodium citrate, sodium tartrate and sodium gluconate on the gel-forming ability was studied considering the effect on myosin degradation by proteases. All of the compounds increased the breaking strength of squid meat gel. Sodium citrate showed the greatest effect among them. The addition of all of the organic salts to the squid meat suspension suppressed myosin degradation when stored at 5°C. This effect was similar to that of EDTA, indicating that organic salts inhibited myosin degradation by metal protease. When studied at 35°C, sodium citrate showed the greatest inhibition on myosin degradation. The effect was almost comparable to the effect achieved by the mixture of EDTA and PMSF. From these results, sodium citrate was concluded to be the most effective additive for increasing the gel strength of squid meat through the inhibition of both serine protease and metal protease.View full abstractDownload PDF (440K) -
MASANORI SASAKI, YUJI KAWAI, MAMORU YOSHIMIZU, HARUO SHINANO2004 Volume 70 Issue 6 Pages 928-937
Published: 2004
Released on J-STAGE: July 08, 2005
JOURNAL FREE ACCESSChanges in the organoleptic, chemical, and microbiological characteristics of the salmon Izushi were investigated during the pre-treatment and ripening process at around 5°C. Organoleptically, Izushi became acceptable to eat by ripening for 35 d and subsequently became most suitable to eat ripening for 44 d because of the emergence of a specific Izushi flavor. Ripening proceeded uniformly in the entire Izushi. During the ripening process, pH values of the fish and sub-material portions of Izushi remained below pH 5.0. Organic acids in Izushi were mostly acetic acid due to pickling and vinegared rice. Microbial counts of Izushi did not significantly increase during the ripening process. As to the microbial flora of Izushi, Bacillus sp. became the dominant aerobic bacteria by ripening periods of longer than 14 d, and Leuconostoc mesenteroides subsp. cremoris and Debaryomyces hansenii were dominant for groups of lactic acid bacteria and yeast, respectively, after ripening for 35 d or longer.View full abstractDownload PDF (470K)
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