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Volume 69, Issue 4
Displaying 1-19 of 19 articles from this issue
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TETSUYA TAKATSU2003 Volume 69 Issue 4 Pages 543-546
Published: July 15, 2003
Released on J-STAGE: February 01, 2008
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REIJI MASUDA2003 Volume 69 Issue 4 Pages 547-549
Published: July 15, 2003
Released on J-STAGE: February 01, 2008
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KIMINORI MATSUBARA2003 Volume 69 Issue 4 Pages 550-553
Published: July 15, 2003
Released on J-STAGE: February 01, 2008
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TAKESHI YOSHIKAWA2003 Volume 69 Issue 4 Pages 554-557
Published: July 15, 2003
Released on J-STAGE: February 01, 2008
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SATOSHI HONDA, CHIHIRO SUZUKI, TOHRU MUKAI, KOHJI IIDA2003 Volume 69 Issue 4 Pages 558-567
Published: July 15, 2003
Released on J-STAGE: February 01, 2008
JOURNAL FREE ACCESSThe attenuation of acoustic energy due to the effects of sailing were measured on the RV Kaiyo-maru No.3 by integrating the area backscattering strength (Sa) of the sea bottom. The attenuation of the bottom Sa appeared with the increase of the ship speed. In particular, the attenuation was apparent under the head sea condition of sailing ; maximum attenuation of 1.3 dB was attained at 38 kHz, and 0.7 dB at 12 kHz. On the other hand no clear attenuation occurred under the conditions of a following sea. Under the head sea condition of sailing, the attenuation by sailing occurred at a slower sailing speed than the appearance of a missing echo or apparent attenuation shown on the echogram. That is, the attenuation by sailing exerted an influence upon the acoustic data without the operator being aware of it. When planning an acoustic survey by the RV Kaiyo-maru No.3, or even in a survey field, setting the sailing direction in a following sea will prevent underestimation of the acoustic biomass index caused by the acoustic attenuation due to the effects of sailing.View full abstractDownload PDF (1395K) -
TAKASHI KOIKE, HIROKI YAMAZAKI, MAKOTO UCHIDA2003 Volume 69 Issue 4 Pages 568-574
Published: July 15, 2003
Released on J-STAGE: February 01, 2008
JOURNAL FREE ACCESSFeeding activity and daily feed intake of three male Japanese spiny lobsters Panulirus japonicus, 74-81 mm in carapace length, were continuously monitored from February 1998 to December 1998. Lobsters were fed on mussels Mytilus galloprovincialis during a period of 284 days. The activities of the lobsters fluctuated markedly throughout the present study, reflected their molting cycles as well as changes in water temperature. Molting occurred in summer and autumn. Lobsters showed low feed intake for about one month prior to molting, did not feed for 5-17 days just before molting, and resumed feeding 2-26 days after ecdysis. The feed intake of the lobsters increased rapidly in summer following ecdysis. When water temperature was lower than 11.8°C, lobsters did not ingest prey. Feed intake increased as water temperature increased, and decreased when water temperature reached 28°C or higher.View full abstractDownload PDF (961K) -
KAZUO AMAKASU, MASAHIKO FURUSAWA, CHUMING FAN2003 Volume 69 Issue 4 Pages 575-583
Published: July 15, 2003
Released on J-STAGE: February 01, 2008
JOURNAL FREE ACCESSWe developed a precise method for target strength (TS) measurement of small-size animals such as krill in a water tank. The measurement system consists of a 70 kHz split-beam system and a video camera system to observe the orientation of animals. The transducer was set pointing downward on the top of the small tank with a window on one of the side walls for observing orientation. TS measurement and orientation observation are performed simultaneously. This system can avoid external disturbances such as wind and waves and be set up easily for measurements including measurement on board a ship. TS measurement for a physical model (copper cylinder) was conducted and the measured TS was in good agreement with the theoretical result, showing the accuracy of our method. Next, TS measurements of live shrimps were conducted to get detailed TS patterns. We compared the measured results with the theoretical TS patterns and confirmed a reasonable agreement.View full abstractDownload PDF (1107K) -
SOKIJIN CHOI, YOSHIHIKO NAKAMURA2003 Volume 69 Issue 4 Pages 584-590
Published: July 15, 2003
Released on J-STAGE: February 01, 2008
JOURNAL FREE ACCESSThe spatial distribution of squid jigging boats and the shortest distance between boats were abserved by a radar, at major fishing grounds of the Japan Sea in the summer season in order to investigate the actual condition of fishing boat group operation. The Area occupied by squid jigging boats and shortest distance between boats showed the minimum value in the Tsugaru Channel sea area and the maximum value in the Northern Sado offshorearea. Optimum distance and light source output for jigging operation were then estimated for each fishing ground. Furthermore, the proportion of fishing light interference was obtained by cumulative frequency distribution of the shortest distance between boats and calculation of fishing lamp luminous range. As a result, the Tsugaru channel sea area, Yamatotai, Kanazawa offshore, Okushiri channel sea area and Northern Sado offshore aeras showed 100% and 99%, 62%, 40% and 34% of the probabilities of light interference by other boats in group operation respectively, when 180 kW, the upper limit of light source output for small squid jigging boats, was employed.View full abstractDownload PDF (1044K) -
KAZUHIRO TASHIRO, KAZUO IWATA, MAKOTO ENDO, TAKESHI TABARU, MASAKO SAT ...2003 Volume 69 Issue 4 Pages 591-595
Published: July 15, 2003
Released on J-STAGE: February 01, 2008
JOURNAL FREE ACCESSThe spawning season of the female black sole Paraplagusia japonica was examined in the Miyazaki coastal area, Kyushu, Japan. A total of 456 fish (226 males and 230 females) were collected from a muddy sand area of less than 30 m in depth during 1991, 1992, 1996 and 1997 using a small trawl net. Histological examination was mode of the ovaries. The development form of oocytes in the ovaries was thought to belong to the "asynchronous oocyte development" type. From the seasonal changes in oocyte development and the gonad indes, the spawning season in this region was assumed to occur multiple times during May and October, with the peak from June to August. The minimum size for maturation was 214 mm (SL) and the size of fully matured fish was 240 mm in length. The sex ratio was nearly 1: 1 throughout the year.View full abstractDownload PDF (1569K) -
MASASHI NATSUME, TAKASHI MATSUISHI2003 Volume 69 Issue 4 Pages 596-601
Published: July 15, 2003
Released on J-STAGE: February 01, 2008
JOURNAL FREE ACCESSFor a fish to pass through the mesh of a net, the mesh perimeter must be at least equal to the fish's maximum girth. Assuming the maximum girth as the circumference of an ellipse calculated from the maximum body depth (Dm) and maximum body width (Wm), We assessed the necessary conditions of the mesh size (Ln) for a fish passing through the mesh without entanglement and the sufficient conditions of the mesh size (Ls) for the cross-sectional shape of the fish body encountering the four sides of the mesh at four tangential points. For mesh size in a sufficient condition, the hang-in ratio (Si) and hang-out ratio (So) were assessed. The necessary conditions of the mesh size can be expressed as, Ln=(π/4)(1.5(Dm+Wm)-√(D<SUB)mWm>), that is as half the circumference of the ellipse. Sufficient condition of the mesh size can be expressed as Ls=Dm+Wm, that is as the total of the maximum body depth and maximum body width. The hang-in ratio and hang-out ratio were obtained as Si=1-√(W<SUB)m/(Dm+Wm)>, So=√((D<SUB)m+Wm)/Wm>-1. Based on measurements of the maximum body depth and maximum body width of Arabesque greenling, Pleurogrammus azonus, of about 30 cm standard length, the average values of the approximation were : Ln=94.7 mm, Ls=119.0 mm, Si=0.376, So=0.604.View full abstractDownload PDF (1070K) -
MASATO ARITAKI, MASARU TANAKA2003 Volume 69 Issue 4 Pages 602-610
Published: July 15, 2003
Released on J-STAGE: February 01, 2008
JOURNAL FREE ACCESSThe morphological development and growth of slime flounder, Microstomus achne, from newly hatched larva to early juvenile were described for laboratory-reared specimens. The duration of the pelagic larval period was about 85 days after hatching, and that of the metamorphic phase was 40 days under mean water temperature 13.9 (9.2-21.1) °C. The maximum size of metamorphic larvae was about 25 mm TL, having deep-body form, protruded eyes and otic spines. There diagnostic characteristics appeared early at the metamorphic phase and disappeared at settlement and / or completion of metamorphosis, indicating that these morphological characters are adaptive to pelagiclife. The larvae hatched at a much larger size, and in a more advanced developmental stage, than those of other coastal flatfish species. They had long metamorphic phase, and the eye migration was not synchronized with the habitat shift from planktonic to benthic. These observations revealed that slime flounder has a unique early ontogeny characterized by specialized morpho-ecological features for the long duration of its pelagic life stages.View full abstractDownload PDF (1219K) -
KOJI SAIURA, TADASHI TOKAI2003 Volume 69 Issue 4 Pages 611-619
Published: July 15, 2003
Released on J-STAGE: February 01, 2008
JOURNAL FREE ACCESSThe main target of boat seine fisheries in the western sea area of the Kii Channel is anchovy larvae, Engraulis japonica. The fishing gear consists of wings, body net, and codend. The gear is made of various minnow netting, and the mesh size of the codend is 260 kei : the number of twines in webbing 50 cm wide. Five experimental hauls were carried out with small-mesh pocket-nets attached to several positions on the body net and the codend. The selectivity curve for anchovy larvae was estimated with an extended SELECT model for analyzing body size (total length) distributions of the pockets catch and sample from the codend catch. Selectivity parameters were varied in the five hauls, that is, l50 (the length of 50% retention) was 8.7-12.3 mm and SR (selection range=l75-l25) ranged from 3.0 mm to 4.7 mm. Higher catch volumes were likely to prevent small fish from escaping. In this fishery, the codend catch weight usually exceeds 20 kg, which means that the l50 is smaller than 10 mm, and few anchovy larvae smaller than 15 mm are distributed in this fishing ground. Therefore, the current codend mesh size, 269 kei is too fine, and consequently enlargement of the mesh size should be examined for fisheries management and product management.View full abstractDownload PDF (1152K) -
TOSHIHIRO WATANABE, KAZUTOSHI WATANABE, DAIJI KITAGAWA2003 Volume 69 Issue 4 Pages 620-623
Published: July 15, 2003
Released on J-STAGE: February 01, 2008
JOURNAL FREE ACCESSA deep-sea video monitoring system on a towed sledge (DVMSTS) was used in Tohoku waters (Pacific coastal of northern Japan) at depths ranging from 440 to 700 meters to estimate the population density of kichiji rockfish Sebastolobus macrochir. Thirty observations were completed at 24 survey sites in daytime during May and July in 2001. A seafloor area of 86, 160m2 was surveyed, and 253 kichiji rockfish were observed. These fish stayed on the seafloor as solitary individuals. Most fish showed no behavioral response to the DVMSTS. Population densities ranged from 0 to 11 fish/1, 0002 (mean 2.9 fish/1, 000m2). The method of estimating the population density of kichiji rockfish using DVMSTS is effective for stock assessment.View full abstractDownload PDF (788K) -
TEI KISHINO, AKIHIKO SHINOMIYA2003 Volume 69 Issue 4 Pages 624-631
Published: July 15, 2003
Released on J-STAGE: February 01, 2008
JOURNAL FREE ACCESSThe Ryukyu-ayu Plecoglossus altivelis ryukyuensis, whose population is steadily declining, inhabits only limited areas of the Ryukyu Islands in southern Japan. The period, body size, age and developmental stage at upstream migration of larvae and juveniles of Ryukyu-ayu were investigated in the Yakugachi River in Amami-oshima Island in 1994 and 1996. The upstream migration lasted for four months from late January to late May. The range of standard length was 24.4-46.7 mm (average±SD=35.2±3.36), and the range of ages 54-128 days (83.7±15.4). Developmental stages were composed of seven steps from the "whitebait" larvae stage to juvenile stage having comb-like teeth in the jaws. Usptream migrating Ryukyu-ayu were characterized by a smaller size, a younger age and an earlier developmental stage, compared with ayu Plecoglossus altivelis altivelis. Those charactersistics seemd attributable to a shorter period of coastal life befor upstream migration.View full abstractDownload PDF (1064K) -
YASUSHI SHIOBARA, TAKAFUMI ARIMOTO2003 Volume 69 Issue 4 Pages 632-636
Published: July 15, 2003
Released on J-STAGE: February 01, 2008
JOURNAL FREE ACCESSThe change in visual acuity and retinal adaptation according to light intensity was investigated for red sea bream Pagrus major. Visual acuity was estimated by a behavioral training method as 0.24 in 500 lx, 0.19 in 100 lx, 0.15 in 10 lx and 0.10 in 1-0.1 lx. Retinal adaptation was examined by a histological method in fish exposed to the same light condition as a behavioral experiment. The pigment index was 72.8-65.8% in 500-1 lx and 42.0% in 0.1 lx. From the results of behavioral experiments and histological experiments, it was suggested that the visual cells of red sea bream shift to rods from cones between an illumination strength of 1 lx and 0.1 lx.View full abstractDownload PDF (937K) -
KOICHI KUWAHARA, KAZUFUMI OSAKO2003 Volume 69 Issue 4 Pages 637-642
Published: July 15, 2003
Released on J-STAGE: February 01, 2008
JOURNAL FREE ACCESSIn order to improve the thermal gel forming ability of squid, sodium gluconate (Na-gluconate) was added to salted meat paste. Its effect on the gel properties was compared with those of sodium chloride or sorbitol. Breaking strength for the gel with Na-gluconate showed high breaking force when heated at 90°C for 30 min directly. Its effect was also detected with two-step thermal gel. No cross-linking of myosin heavy chain (HC) was detected, and autolysis was obvious during the preheating. Na-gluconate strongly suppressed the autolysis. There was a positive correlation between HC content and breaking strength. It is therefore inferred that high gel strength with Na-gluconate-added gel was caused by the inhibitory effect of Na-gluconate on autolysis.View full abstractDownload PDF (808K) -
TETSUMI TAKAHASHI, KATSUKI NAKAI, KAYOKO KAMEDA2003 Volume 69 Issue 4 Pages 643-645
Published: July 15, 2003
Released on J-STAGE: February 01, 2008
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HIDEKI KISHIMURA, KENJI HAYASHI2003 Volume 69 Issue 4 Pages 646-648
Published: July 15, 2003
Released on J-STAGE: February 01, 2008
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[in Japanese]2003 Volume 69 Issue 4 Pages 662-666
Published: July 15, 2003
Released on J-STAGE: February 01, 2008
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