NIPPON SUISAN GAKKAISHI
Online ISSN : 1349-998X
Print ISSN : 0021-5392
ISSN-L : 0021-5392
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Volume 72, Issue 4
Displaying 1-18 of 18 articles from this issue
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  • Target strength measurements of black rockfish, goldeye rockfish and black scraper using a 70-kHz split-beam echo sounder
    DAE-JAE LEE
    2006 Volume 72 Issue 4 Pages 644-650
    Published: 2006
    Released on J-STAGE: July 27, 2006
    DOIhttps://doi.org/10.2331/suisan.72.644
    JOURNAL FREE ACCESS
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      Black rockfish, goldeye rockfish and black scraper are commercially important fish species due to the increasing demand in Korea. When estimating the abundance of stocks for these species acoustically, it is of crucial importance to know the target strength (TS) to length dependence. In relation to these needs, target strength experiments were conducted on three species in an acrylic salt water tank using a 70-kHz split-beam echo sounder. The target strength for these three species under controlled conditions was simultaneously measured with the swimming movement by a DVR system and analyzed as a function of fish length (L). Equations of the form TS=a log (L)+b were derived for their TS-length dependence. The best fit regression of TS on fish length for two species of black rockfish and goldeye rockfish was TS=22.2 log (L)−74.6 (r2=0.73), and in the standard form TS=20 log (L)−71.5 (r2=0.74). The best fit regression of TS on fish length for black scraper was TS=24.1 log (L)−72.5 (r2=0.90), and in the standard form TS=20 log (L)−66.9 (r2=0.76).
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  • Age and growth of flathead flounder Hippoglossoides dubius collected off Kyoto Prefecture, Japan
    NAOKI YAGISHITA, ATSUSHI YAMASAKI, EIJI TANAKA
    2006 Volume 72 Issue 4 Pages 651-658
    Published: 2006
    Released on J-STAGE: July 27, 2006
    DOIhttps://doi.org/10.2331/suisan.72.651
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      Age and growth of flathead flounder Hippoglossoides dubius collected off Kyoto Prefecture were estimated, using body length increment data of 14 males and 120 females from tagging experiments, and the age-length data obtained by counting annual rings of sagittal otoliths from small individuals of 175 males and 186 females. The von Bertalanffy's growth curves for body length (Lx, mm) at full age in years (x) were estimated as follows: Lx=267.4[1-exp {-0.185(+0.284)}] for males; Lx=381.9[1-exp {-0.130(x+0.136)}] for females. The body length at each age of females was greater than that of males. Based on the growth curves, ages at 50% maturity were estimated to be 5 years for males and 9 years for females.
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  • Accumulation performance of large-scale set nets in Iwate Prefecture for chum salmon Oncorhynchus keta
    SEIJI AKIYAMA, SATOSHI KAIHARA
    2006 Volume 72 Issue 4 Pages 659-664
    Published: 2006
    Released on J-STAGE: July 27, 2006
    DOIhttps://doi.org/10.2331/suisan.72.659
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      The accumulation performance of the large-scale set net for chum salmon Oncorhynchus keta was evaluated using catch data in Iwate Prefecture from 1994 to 1998. The accumulation index (ratio of catch per intermittent haul to catch per successive haul) was higher than unity with an average of 1.85, showing that intermittent haul led to significantly higher catch. The accumulation performance was not influenced by the set net design or the bag net volume. However, there was a significant correlation between the bag net volume and the catch per haul. We consider that a high level of capacity in the bag net and final trap can successfully accumulate chum salmon.
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  • Forecasting ascending population sizes of amphidromous juvenile ayu Plecoglossus altivelis in the Nagara River
    KEIICHI SHIMADA, KOICHI GOTO, KAZUO YAMAMOTO, YOSHIHIRO WADA
    2006 Volume 72 Issue 4 Pages 665-672
    Published: 2006
    Released on J-STAGE: July 27, 2006
    DOIhttps://doi.org/10.2331/suisan.72.665
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      Many surveys regarding the ascending juvenile ayu Plecoglossus altivelis and the descending larval ayu have been conducted, in the wake of the construction of the Nagaragawa Estuary Barrage. By statistically analyzing the relationship between those survey results and the ecological characteristics of ayu and physical environment factors, we found that the river discharge from the spawning season to the descending season of ayu and the water temperature in the sea-dwelling season of juvenile ayu affect the variation of ascending juvenile ayu in the Nagara River. Thus our regression model would be able to forecast the ascending ayu population in terms of merely environmental factors.
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  • Fecundity of snow crab Chionoecetes opilio off Wakasa Bay in the Sea of Japan
    TOHSHI KON, TATSUNORI ADACHI
    2006 Volume 72 Issue 4 Pages 673-680
    Published: 2006
    Released on J-STAGE: July 27, 2006
    DOIhttps://doi.org/10.2331/suisan.72.673
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      To determine fecundity, female snow crabs Chionoecetes opilio were caught off Wakasa Bay. The number of oocytes for pubescent females (prior to the terminal molt; mean carapace width 66.2 mm previously reported off Wakasa Bay) and for young adults (spawners less than 4 years after the terminal molt; 77.4 mm) correlated with the carapace width. However, the number of oocytes for pubescent females was 62.8% that of young adults. The difference in the number of oocytes might be caused by the body size when they developed their ovaries. Because the number of eggs attached to pleopods for primiparae (primary spawners) and young multiparae (repeat spawners within 1.5 to <4 years after the terminal molt) originated during the ovarian development of pubescent females and young adults, respectively, the number of eggs for primiparae was 66.3% that of young multiparae. The number of oocytes and eggs for aged multiparae (more than 4 years after the terminal molt) was less than those for young multiparae and there was no correlation with their carapace width, probably because of the decline of ovarian activity in addition to insufficient number of sperm to accomplish full fertilization.
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  • Spatio-temporal differentiation of bivalve larval settlement sites in estuarine waters
    RYOGEN NANBU, TOMOMI MIZUNO, TAKASHI KAWAKAMI, KAORU KUBOTA, HIDEO SEK ...
    2006 Volume 72 Issue 4 Pages 681-694
    Published: 2006
    Released on J-STAGE: July 27, 2006
    DOIhttps://doi.org/10.2331/suisan.72.681
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      Variations in the abundance of planktonic larvae and new settlers of bivalves were examined in the Kiso estuaries, central Japan, for 4 years from 2001 to 2004. Planktonic larvae and new settlers were mainly dominated by 4 bivalve species (i.e. Corbicula japonica, Ruditapes philippinarum, Mactra veneriformis, Musculista senhousia) showing marked seasonal and interannual variations in densities of each bivalve species: M. senhousia was most abundant in the planktonic larvae, whereas C. japonica was most abundant in the new settlers. This indicates that larval mortality until settlement may be highest in M. senhousia and lowest in C. japonica. It was concluded that there was no significant relationship between the abundance of planktonic larvae and new settlers. Spatio-temporally, larval settlement sites within the Kiso estuaries were different among these 4 bivalve species: C. japonica, common in the brackish water, settled mainly in the upper part of the estuaries, while the other 3 species settled mainly in the lower part (larval settlement site of each species was temporally not overlapped). A difference in salinity preference of the new settlers may drive the differentiation of larval settlement sites within the estuaries between C. japonica and the other 3 species: new settlers of C. japonica prefer less saline water, whereas those of the other 3 species prefer more saline waters.
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  • Behavioral responses of the snow crab Chionoecetes spp. to the groundrope of a bottom trawl
    KAORU FUJITA, TOSHIHIRO WATANABE, DAIJI KITAGAWA
    2006 Volume 72 Issue 4 Pages 695-701
    Published: 2006
    Released on J-STAGE: July 27, 2006
    DOIhttps://doi.org/10.2331/suisan.72.695
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      To understand the capture process of the snow crabs Chionoecetes opilio and C. japonicus to the groundrope of a survey trawl net, observations with an underwater video camera were conducted in Pacific coastal waters of northern Japan at depths ranging between 440 m and 700 m in June of both 2000 and 2001 with R/V Wakataka-maru (692 T, 1471 kW). The underwater video camera was attached at the center of the headrope of the survey trawl net to observe crab behavior toward the groundrope. A total of 466 crabs were observed. Ninety-four percent of crabs observed did not respond when the groundrope approached the crabs. Therefore, the handropes and the legs of the trawl net do not herd the snow crabs. The crabs that were not captured escaped under the groundrope. The groundrope has an important effect on the catch of snow crabs.
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  • Effects of delayed initial feeding on larval feeding, early survival, and growth of red spotted grouper Epinephelus akaara larvae
    KENZO YOSEDA, KAZUHISA TERUYA, TAKUMA SUGAYA, SACHIO SEKIYA
    2006 Volume 72 Issue 4 Pages 702-709
    Published: 2006
    Released on J-STAGE: July 27, 2006
    DOIhttps://doi.org/10.2331/suisan.72.702
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      This study investigated the effects of delayed initial feeding on the growth, feeding, and survival of early stage red spotted grouper Epinephelus akaara larvae in relation to the absorption of endogenous reserves at 26°C. Five different feeding regimes were prepared as follows: No. 1: rotifers fed initially at 0 hours after the onset of feeding (HAOF), No. 2: rotifers fed initially from 6 HAOF, No. 3: rotifers fed initially from 12 HAOF, No. 4: rotifers fed initially from 18 HAOF, and No. 5: starved control. The larvae were fed rotifers (a small Thai strain) at a density of 20 ind./mL except for No. 5. Feeding amounts and survival showed a tendency to be lower when the onset of feeding was delayed. Larval growth showed significant differences between No. 1 and No. 2-4 at 66 HAOF (p<0.05 or 0.01). In contrast, starved larvae (No. 5) showed negative growth from 12 to 66 HAOF. The beginning of the negative growth point coincided with the time of complete oil globule absorption. These results indicate that larval growth was closely related with endogenous reserves, and larvae possess a very short period during which they are resistant to food deprivation. We conclude that their growth and survival are affected if they fail to initially feed within 6 HAOF at 26°C.
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  • Mitochondrial DNA and microsatellite DNA as genetic tags for stocked population of black rockfish Sebastes inermis of hatchery origin
    TOMOYA MURAKAMI, SATOSHI AIDA, KOUJI YOSHIOKA, HARUMI YOSHIDA, ENRIQUE ...
    2006 Volume 72 Issue 4 Pages 710-716
    Published: 2006
    Released on J-STAGE: July 27, 2006
    DOIhttps://doi.org/10.2331/suisan.72.710
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      Black rockfish juveniles (Sebastes inernis) obtained from five broodstock females in the hatchery were marked with alizarin complexon (ALC), and a total of 81,000 juveniles marked were released in the coastal waters of Ikuno Island, central Seto Inland Sea, western Japan. Variation of the mitochondrial DNA (mtDNA) control region sequence and a microsatellite DNA marker were investigated on 81 individuals caught at the same site a year later. Sixty-one mtDNA haplotypes were observed in 81 individuals and four individuals shared identical mtDNA sequence with broodstock females. The genotypic analysis on a single microsatellite DNA marker also showed that the four individuals shared the same allele with the female broodstocks, and that all individuals were found to carry ALC marking. These results indicate that genetic tags are useful as well as ALC marking as stock separation tools of black rockfish.
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  • Effects of oscillating water flow on feeding of rabbitfish Siganus fuscescens on kelp
    SHIGERU KAWAMATA, MASATOSHI HASEGAWA
    2006 Volume 72 Issue 4 Pages 717-724
    Published: 2006
    Released on J-STAGE: July 27, 2006
    DOIhttps://doi.org/10.2331/suisan.72.717
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      Laboratory experiments were conducted in a recirculating flow tank to evaluate the effects of waves on herbivory by the rabbitfish Siganus fuscescens. Rabbitfish (27 cm FL) increased feeding on the kelp Ecklonia cava or Eisenia bicyclis in a faster oscillating flow with a seasonally increased appetite. When feeding activity was highest, oscillating flow reduced feeding to 50% at the velocity amplitude of 1.1 m/s and to nil at ca 1.5 m/s. Swimming speeds observed in different fish sizes suggested that the upper velocity limit for feeding increased little for larger fish. The results and the wave-induced water velocity predictions indicate that destructive feeding by rabbitfish on kelp is very unlikely to be inhibited by waves on the Pacific coast of central Honshu.
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  • Larval development and occurrence of morphological abnormalities in hatchery-reared Japanese flounder Paralichthys olivaceus larvae fed marine rotifer Brachionus plicatilis at different population growth stages
    TSUTOMU TOMODA, MASAHIKO KOISO, JAU-NENG CHEN, TOSHIO TAKEUCHI
    2006 Volume 72 Issue 4 Pages 725-733
    Published: 2006
    Released on J-STAGE: July 27, 2006
    DOIhttps://doi.org/10.2331/suisan.72.725
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      We assessed the dietary value of rotifers at different population growth stages for hatchery-reared Japanese flounder, Paralichthys olivaceus, in terms of larval development and the occurrence of morphological abnormalities. Rotifer cultures were prepared daily and continued for up to eight days. Rotifers were harvested on day 2 from the start of batch culture (early-exponential growth phase), as well as on day 4 (late-exponential phase) and day 8 (stationary phase), and equally enriched with freshwater Chlorella containing n-3 HUFA. The flounder larvae were supplied until 24 days after hatching (DAH) with rotifers at each of these growth phases. During 18-30 DAH, larvae fed rotifers at the late-exponential growth phase showed higher performance in growth and morphological development than those fed stationary-phase rotifers. All groups of larvae were raised until approximately 40 mm total length (55 DAH), at which time the juveniles that had been fed late-exponential-phase rotifers had the lowest incidence of malpigmentation and/or skeletal malformation (p<0.0001). The population growth stage of the rotifers used for enrichment had a large influence on the occurrence of morphological abnormalities in larviculture of Japanese flounder.
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  • Development of semi-pelagic/bottom trawl net for a coastal trawl fishery
    YOSHIKI MATSUSHITA, TAISEI KUMAZAWA, MINORU TOMIYAMA, HIROSHI INADA, Y ...
    2006 Volume 72 Issue 4 Pages 734-742
    Published: 2006
    Released on J-STAGE: July 27, 2006
    DOIhttps://doi.org/10.2331/suisan.72.734
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      We engaged in development of a semi-pelagic/bottom trawl net mainly for off-bottom species instead of demersal species, for coastal trawl boats in Ise Bay, Aichi, Japan. Bottom contact of otterboards could be controlled by changing warp length. The semi-pelagic/bottom trawl net reduces the area where the gear contacts the seabed more than a conventional trawl net when otterboards are kept away from the seabed. The measurement of gear dimensions during towing suggested that the filtered water volume of the semi-pelagic/bottom trawl net was approximately twice that of a conventional trawl net, while the swept area was less.
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