NIPPON SUISAN GAKKAISHI
Online ISSN : 1349-998X
Print ISSN : 0021-5392
ISSN-L : 0021-5392
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Volume 78, Issue 6
Displaying 1-39 of 39 articles from this issue
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  • Performance evaluation of fishing lamp using oval-shaped blue LEDs for squid jigging fishery in offshore fishing grounds in the Sea of Japan
    TAKAFUMI SHIKATA, KUNIHARU YAMASHITA, MITSUSHI SHIRATA, YOUICHI MACHID ...
    2012 Volume 78 Issue 6 Pages 1104-1111
    Published: 2012
    Released on J-STAGE: November 28, 2012
    DOIhttps://doi.org/10.2331/suisan.78.1104
    JOURNAL FREE ACCESS
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      The effectiveness of a light emitting diode (LED) fishing lamp consisting of 950 oval-shaped blue LEDs was investigated in offshore fishing grounds for the Japanese common squid Todarodes pacificus in the Sea of Japan. Squid jigging operations were conducted by R/V Hakusan-Maru (167 gross tonnes) equipped with 216 LED lamps and 78 metal halide (MH) lamps. Mean catch per unit effort was markedly lower in operations using only the 216 LED lamps (15 kW in total) but slightly lower in operations using both the 216 LED lamps and 24 MH lamps (87 kW in total) than using the 78 MH lamps (234 kW in total). The light from MH lamps widely spread in the sea surface layer but that from the LED lamps irradiated only a limited area near the vessel, suggesting that light distribution affected catch performance. Fuel consumption of the generator engine for lighting these lamps was proportional to the total electric power consumption of the lamps. Fuel consumption for lighting both the 216 LED lamps and 24 MH lamps was 37% of that for lighting the 78 MH lamps. These results indicate that fuel can be saved by the combined use of LED and MH lamps without a remarkable reduction of squid catch.
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  • Catching efficiency of toothed dredges for ark shell Scapharca broughtonii in Sendai Bay, Northeastern Japan
    TORU TANABE, KAZUHITO WATANABE, NORIAKI SUZUKI, TOSHINORI ONO
    2012 Volume 78 Issue 6 Pages 1112-1117
    Published: 2012
    Released on J-STAGE: November 28, 2012
    DOIhttps://doi.org/10.2331/suisan.78.1112
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      The catching efficiency of toothed dredges estimated in the 1960-70s is still used for stock assessments of ark shell Scapharca broughtonii, although the fishing power of ark shell dredge fishery has improved during the last four decades with the modification of fishing gear and vessels. This study presents the catching efficiency of the toothed dredges currently used for ark shell fishery in Sendai Bay, based on the results of mark-recapture experiments. An experimental area was located at a depth of 23 m in the central part of the fishing ground. The experimental area where the marked ark shells were released extended 20 m in length from north to south in the area. After marked shells had been released along the area, they were recaptured the next day by towing ark shell dredges across the area from west to east. The catching efficiency was estimated to be 0.54 from the catchability coefficient estimated by the DeLury method and the ratio of the experimental area to the dredge-swept area, and was higher than those obtained in previous studies. This result suggests that it is necessary to reconsider the underestimated efficiency for the stock assessment and fisheries management of ark shell. To investigate ark shell resources, the obtained result should be substituted for the previous catching efficiency of ark shell dredges.
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  • Growth pattern and age composition of roughscale sole Clidoderma asperrimum off the Pacific coast of northern Honshu, Japan
    RYO INAGAWA, TSUTOMU HATTORI, KAZUHITO WATANABE, YOJI NARIMATSU, MASAK ...
    2012 Volume 78 Issue 6 Pages 1118-1126
    Published: 2012
    Released on J-STAGE: November 28, 2012
    DOIhttps://doi.org/10.2331/suisan.78.1118
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      We examined the age and growth of roughscale sole Clidoderma asperrimum caught off the Pacific coast of northern Honshu, Japan, using the otolith sectioning method. A theoretical growth equation for this sole was fitted by the von Bertalanffy growth equation for both sexes, indicating that males approach the maximum length (l∞) faster than females; total length (TL, cm)=39.5(1−e-0.474(t+0.172)) for males and TL=52.6(1−e-0.366(t-0.003)) for females. The maximum ages observed for 303 samples were 15 and 22 years for males and females, respectively, and it was considered that this sole is one of the most long-lived fish among pleuronectids. A bimodal length-frequency distribution with peaks at 39 and 49 cm TL was estimated from the catch data at Ishinomaki (main fishing port for roughscale sole) in 2008-2009. The age composition divided by the age-length key showed that the smaller and larger peaks were mainly composed of males of 6-10 years and females of 6-16 years, respectively. These results suggest that older fish were mainly caught by offshore bottom trawl fisheries in this area. Furthermore, differences between the otolith sectioning and surface methods for this sole were discussed, and underestimation of ages using the surface method was confirmed in 7+year-old fish.
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  • Ruggedness of the seafloor and distribution of demersal fishes in the fishing grounds on the continental slope off the Pacific coast of Hokkaido, Japan
    TOMONORI HAMATSU
    2012 Volume 78 Issue 6 Pages 1127-1134
    Published: 2012
    Released on J-STAGE: November 28, 2012
    DOIhttps://doi.org/10.2331/suisan.78.1127
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      To clarify the impacts of fisheries on the marine ecosystem, the relationship between the ruggedness of the seafloor and the distribution of demersal fishes was estimated on the basis of observation by a deepwater video-camera system in the fishing grounds on the continental slope off the Pacific coast of Hokkaido, Japan. Some demersal fish species (cutthroat eel, rattails, kichiji rockfish, walleye pollock, eelpouts, sculpin, and flounders) were observed. Kichiji rockfish preferred a rugged seafloor to a flat area, and the density of kichiji rockfish was higher in a topographically rugged area with high bottom water temperature. Conservation of a rugged seafloor may be necessary to maintain a favorable habitat for kichiji rockfish.
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  • Vertical distribution of Manila clam Ruditapes philippinarum larvae characterized through year-round observations in Tokyo Bay, Japan
    MITSUHARU TOBA, HIROSHI YAMAKAWA, NORIHIKO SHOJI, YUTAKA KOBAYASHI
    2012 Volume 78 Issue 6 Pages 1135-1148
    Published: 2012
    Released on J-STAGE: November 28, 2012
    DOIhttps://doi.org/10.2331/suisan.78.1135
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      The spatial density of the Manila clam Ruditapes philippinarum larvae was monitored during 2001-2003 at intervals of 2-4 weeks in Tokyo Bay. Clam larvae were sampled at 3-6 depth layers at four coastal sites (water depth 6-8 m) and four central sites (10-24 m) of the bay. In the coastal sites, small clam larvae (shell length <144 μm) were abundant in the surface and middle layers, whereas large larvae (>176 μm) were mainly sampled at the bottom layers. Similar patterns of vertical distribution of larvae were observed commonly in three divisions of water temperature (15.1-20.0, 20.1-25.0, 25.1-30.0℃) and in two divisions of salinity (25.1-30.0, 30.1-35.0). Clam larvae appeared to shift swimming position to deeper depths in accordance with their growth in the coastal sites. The vertical shift of larval abundance was assumed to be influenced by the change of swimming behavior of larvae. Relationships between larval size and sampled depth were less clear at the central sites than the coastal sites. Before clam larvae reach a sufficient growth stage to settle, their swimming depth may change to near the bottom in the coastal areas in Tokyo Bay.
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  • Assessment of the characteristic traits of hatchery-reared ayu as a recreational fishing target: comparison of two breeds subcultured under identical conditions
    MASAYUKI MIURA, JUN-ICHI TSUBOI, TAKUMI OKAZAKI, HIDEKI OOHAMA, AKIHIK ...
    2012 Volume 78 Issue 6 Pages 1149-1158
    Published: 2012
    Released on J-STAGE: November 28, 2012
    DOIhttps://doi.org/10.2331/suisan.78.1149
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      Multiple characteristics of two breeds of hatchery-reared ayu Plecoglossus altivelis (YD, Yamanashi Dam breed; YS, Yamanashi Sea breed) as a fishing resource were assessed in a natural river. The breeds were reared under identical conditions from egg fertilization to stocking. From June to October 2009, recapture experiments were conducted for fin-clipped and stocked ayu using casting nets and “tomo-zuri” fishing, i.e., using a live decoy, in the studied river. The results indicated that YD was more vulnerable to fishing than YS, especially early in the fishing season. However, as YD matured earlier, it had a shorter fishing season than YS. Conversely, YS exhibited symptoms of bacterial cold water disease (BCWD) less frequently than did YD, showing that YS better tolerated BCWD. This finding was consistent with the results of experimental infection. We concluded that the characteristic traits of the two breeds of hatchery-reared ayu differed after stocking in a natural river, although both breeds were raised under identical hatchery conditions.
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  • Delay of budding and growth inhibition of the reed Phragmites australis caused by reaping of withered stems and submergence of the cut ends
    KOH-ICHI FUJIWARA
    2012 Volume 78 Issue 6 Pages 1159-1169
    Published: 2012
    Released on J-STAGE: November 28, 2012
    DOIhttps://doi.org/10.2331/suisan.78.1159
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      The influence of winter reaping of withered stems of the reed Phragmites australis on their budding and growth was examined in Lake Biwa. When the cut ends of withered stems were flooded in spring, growth of new shoots was inhibited probably because of limited oxygen supply to the rhizomes. As an adaptation, the reeds rapidly extended shoots to the water surface to obtain oxygen. However, it was thought that this adaptation would not function easily in natural lake areas because these shoots were easily damaged by wind and waves. On the other hand, it was confirmed that withered stems have a function to protect new shoots from wind and waves. Furthermore, the importance of the humus originating from the litter of reeds was confirmed for the budding and growth of the reeds. Thus, it was concluded that the withered stems should not be reaped in areas where submergence is expected at the time of budding.
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  • Age and growth of barfin flounder Verasper moseri in the eastern coastal waters of Cape Erimo, Hokkaido, Japan
    YOSHIYA SHIKISHIMA, TETSUYA TAKATSU, TOYOMI TAKAHASHI, MASAMITSU NINOM ...
    2012 Volume 78 Issue 6 Pages 1170-1175
    Published: 2012
    Released on J-STAGE: November 28, 2012
    DOIhttps://doi.org/10.2331/suisan.78.1170
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      The age and growth pattern of barfin flounder Verasper moseri collected with gill nets, bottom set nets, and beam trawl nets in the eastern coastal waters of Cape Erimo, Hokkaido, Japan from April to December in 2007-2009 were examined. Numbers of individuals with an opaque edge on the blind side otolith increased in April-July but decreased in August-December. Age was determined by counting the outer margins of the transparent rings. Both males and females showed high growth rates in summer, but stagnated from November to May. Total lengths (in mm) and the ages of the fish (in years) in the catch were fitted to von Bertalanffy growth equations assuming a hatch date of April 1. Estimated equations were as follows: TLt=854.3{1−exp[−0.249(t−0.021)]} for females and TLt=518.5{1−exp[−0.512(t−0.089)]} for males. Compared to data in the literature for V. moseri from western waters, barfin flounder from the eastern waters of Cape Erimo exhibited faster growth. The summer water temperatures in the eastern waters (≤20℃) may be more suitable for rapid growth of this species.
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  • Nutrient elimination in an artificial dam reservoir, Lake Okutsu
    SHUZO TAKAGI, MASAYOSHI KONDO, SEIJI TSUCHIE, TATEKI FUJIWARA
    2012 Volume 78 Issue 6 Pages 1176-1186
    Published: 2012
    Released on J-STAGE: November 28, 2012
    DOIhttps://doi.org/10.2331/suisan.78.1176
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      To clarify the change in water quality caused by dam impoundment, we researched variance of total nitrogen (TN), total dissolved nitrogen (TDN), dissolved inorganic nitrogen (DIN), total phosphorus (TP), total dissolved phosphorus (TDP), dissolved inorganic phosphorus (DIP), dissolved silicate (DSi), water temperature and amount of phytoplankton in Lake Okutsu (Tomata dam). A thermocline developed in summer. Planktonic algae dominated by dinoflagellate bloomed in the surface throughout the seasons. The concentration of each kind of nutrient in the outflow water was lower than that in the inflow water. The lower nutrient surface water consumed by planktonic algae was drained to downstream. Concentrations of TN, TP, DSi in the outflow water became lower than those in the inflow water by 27.8%, 21.2%, and 18.9%, respectively.
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