No.76 (Octobor,2009)
No.76 (Octobor,2009)
A－435 Noboru HOSHINO, Takahiro TAKASHIMA, Masamichi WATANOBE and Takashi FUJIOKA
Age-structures and catch fluctuations of Arabesque greenling (Pleurogrammus azonus ) in the coastal area of southern Hokkaido, Japan.
We investigated the age-structures and catch fluctuations of Arabesque greenling (Pleurogrammus azonus ) caught in principal fisheries of the coastal area of southern Hokkaido in order to understand the resource dynamics. The age-structures of the fish products from the south of Shiribeshi and coastal area around the Matsumae Peninsula included the newly recruited (1-year old) and adult cohorts (2-years and above). In the coastal area around the Kameda Peninsula, fish products consisted of immature fish that were 1-2- years old. The age-structure of the fish products from the Tsugaru Strait had a higher proportion of older fish than those from other areas. The trend of catch fluctuation has been declining since the 1990s in the Matsumae Peninsula area, in contrast to the Shiribeshi area, although the rate of annual catch in both these areas has changed in the similar pattern. The difference in a catch fluctuation trend between the Matsumae Peninsula and Shiribeshi areas may have been due to the unusual recruitment of the 1991 -cohort because of a remarkable change in water temperature during the spawning season after 1990.
We investigated the age-structures and catch fluctuations of Arabesque greenling (Pleurogrammus azonus ) caught in principal fisheries of the coastal area of southern Hokkaido in order to understand the resource dynamics. The age-structures of the fish products from the south of Shiribeshi and coastal area around the Matsumae Peninsula included the newly recruited (1-year old) and adult cohorts (2-years and above). In the coastal area around the Kameda Peninsula, fish products consisted of immature fish that were 1-2- years old. The age-structure of the fish products from the Tsugaru Strait had a higher proportion of older fish than those from other areas. The trend of catch fluctuation has been declining since the 1990s in the Matsumae Peninsula area, in contrast to the Shiribeshi area, although the rate of annual catch in both these areas has changed in the similar pattern. The difference in a catch fluctuation trend between the Matsumae Peninsula and Shiribeshi areas may have been due to the unusual recruitment of the 1991 -cohort because of a remarkable change in water temperature during the spawning season after 1990.
A－436 Noboru HOSHINO, Yukio MIHARA and Akihiro INAMURA
Early growth of sand eel (Ammodytes personatus ) in the south coastal area of Shiribeshi, Hokkaido based on daily growth increments in otoliths.
We investigated hatch date, individual early growth, and the effect of water temperature on the juvenile sand eel (Ammodytes personatus ) that was caught in the south of Shiribeshi, Hokkaido using otolith microstructure. The hatching period of A. personatus caught by commercial fishing in the 2008 fishing season, extended for over two months i.e., from March to April. The frequency distribution of hatch dates showed a polymodal form, suggesting that the spawning was intense at several points during the 2008 spawning season. A positive correlation was found between the hatch date and individual growth rate. The daily growth curves for each hatch group (i.e., middle March, last March, and early April) were estimated to be BL=46.7/[1+exp(-0.05(t-38.3))],40.4/[1+exp(-0.06(t-29.9))],and41.8/[1+exp(-0.07(t-28.7))] , respectively. The daily growth rate was estimated to be 0.5-0.7mm day-1 based on the growth curves of the 2008 fishing season. Daily growth characteristics depended on the hatch time; this was attributed to the water temperature after hatching. This result suggests that the water temperature in April may have a strong effect on the timing of fishing season.
We investigated hatch date, individual early growth, and the effect of water temperature on the juvenile sand eel (Ammodytes personatus ) that was caught in the south of Shiribeshi, Hokkaido using otolith microstructure. The hatching period of A. personatus caught by commercial fishing in the 2008 fishing season, extended for over two months i.e., from March to April. The frequency distribution of hatch dates showed a polymodal form, suggesting that the spawning was intense at several points during the 2008 spawning season. A positive correlation was found between the hatch date and individual growth rate. The daily growth curves for each hatch group (i.e., middle March, last March, and early April) were estimated to be BL=46.7/[1+exp(-0.05(t-38.3))],40.4/[1+exp(-0.06(t-29.9))],and41.8/[1+exp(-0.07(t-28.7))] , respectively. The daily growth rate was estimated to be 0.5-0.7mm day-1 based on the growth curves of the 2008 fishing season. Daily growth characteristics depended on the hatch time; this was attributed to the water temperature after hatching. This result suggests that the water temperature in April may have a strong effect on the timing of fishing season.
A－437 Keizo YOSHIMURA, Daisuke TSUTSUI, Keiji MAEDA, Mitsuru SAN-NOHE, Kohsuke HAGA
Validation of daily increments in the otolith microstructure of sailfin sandfish, Arctoscopus japonicus, larvae in Erimo, the Pacific coast of Hokkaido
The otolith microstructure of larval sailfin sandfish, Arctoscopus japonicus, was studied at Erimo, on the Pacific coast of Hokkaido. Compared to the populations in the Sea of Japan, this local population experiences noticiably colder water temperature during eggs and larval stage by the influence of the Oyashio current. We attempted to find an appropriate ageing technique for this population using artificially fertilized eggs in December 2004. We reared larvae from March to May 2005, aged 0 to 60 days and examined at 10-day intervals.
The lapilli provided apparently lower incremental counts to age under optical microscopy (mean±SD: -21.1±4.5), in spite of a previous study had recommended as precisely representing daily increments. We hypothesize that the relatively smaller size of lapilli to the body and very cold rearing water temperature resulted in narrower increments. In addition, there were many invisible increments around the hatch check, resulting in considerable counting error.
In the sagittae, regular concentric rings were found and increment counts were closely correlated with age (-2.8±1.9). Again, some increments around the hatch check were difficult to resolve, but the estimated increment deposition rate between 30-60 days was one per day. The sagittae of larger juveniles (N=5: 30.5-35.7mm in TL) exhibited some accessory layers around the edge. However, these increments had regular deposition and it was possible to track growth. We conclude that in this population, the analyses of daily increments should be performed with sagittae, not lapilli.
The otolith microstructure of larval sailfin sandfish, Arctoscopus japonicus, was studied at Erimo, on the Pacific coast of Hokkaido. Compared to the populations in the Sea of Japan, this local population experiences noticiably colder water temperature during eggs and larval stage by the influence of the Oyashio current. We attempted to find an appropriate ageing technique for this population using artificially fertilized eggs in December 2004. We reared larvae from March to May 2005, aged 0 to 60 days and examined at 10-day intervals.
The lapilli provided apparently lower incremental counts to age under optical microscopy (mean±SD: -21.1±4.5), in spite of a previous study had recommended as precisely representing daily increments. We hypothesize that the relatively smaller size of lapilli to the body and very cold rearing water temperature resulted in narrower increments. In addition, there were many invisible increments around the hatch check, resulting in considerable counting error.
In the sagittae, regular concentric rings were found and increment counts were closely correlated with age (-2.8±1.9). Again, some increments around the hatch check were difficult to resolve, but the estimated increment deposition rate between 30-60 days was one per day. The sagittae of larger juveniles (N=5: 30.5-35.7mm in TL) exhibited some accessory layers around the edge. However, these increments had regular deposition and it was possible to track growth. We conclude that in this population, the analyses of daily increments should be performed with sagittae, not lapilli.
A－438 Setsuo SAITOH, Tatsunari MORI, Shingo ITO and Kunio SUZUKI
Evaluation of traits of clonal lines induced by chromosome manipulation in Japanese flounder (Paralichthys olivaceus)
I . Differences in growth performance and disease resistance
Growth performance by rearing experiment and disease resistance to viral infection test were conducted to characterize the clonal lines in Japanese flounder, Paralichthys olivaceus. Six different clonal lines were produced by chromosome manipulation techniques gynogenetically and used as materials. Juvenile clone fish were reared in the same tank under natural water temperature or 14 ℃ constant water temperature conditions for almost one year. Clear differences of growth performance were observed among the several clonal lines from six months later to the end of the experiment. Fish in no. 82 clonal line represented significantly faster growth compared with the fish of other lines and control group both under natural water temperature condition and 14 ℃ constant one. Fish in no. 82 clonal line clearly resisted HIRRV virus infection and no fish died during the experimental period, but fish in no. 71 and 77 clonal lines showed as same mortality as control group. The cumulative mortality of no. 72 and 75 clonal lines represented about three times higher than that of control group. These results revealed that these clonal lines may be useful as breeding stock and immunological experimental fish.
I . Differences in growth performance and disease resistance
Growth performance by rearing experiment and disease resistance to viral infection test were conducted to characterize the clonal lines in Japanese flounder, Paralichthys olivaceus. Six different clonal lines were produced by chromosome manipulation techniques gynogenetically and used as materials. Juvenile clone fish were reared in the same tank under natural water temperature or 14 ℃ constant water temperature conditions for almost one year. Clear differences of growth performance were observed among the several clonal lines from six months later to the end of the experiment. Fish in no. 82 clonal line represented significantly faster growth compared with the fish of other lines and control group both under natural water temperature condition and 14 ℃ constant one. Fish in no. 82 clonal line clearly resisted HIRRV virus infection and no fish died during the experimental period, but fish in no. 71 and 77 clonal lines showed as same mortality as control group. The cumulative mortality of no. 72 and 75 clonal lines represented about three times higher than that of control group. These results revealed that these clonal lines may be useful as breeding stock and immunological experimental fish.
A－439 Setsuo SAITOH and Tatsunari MORI
Evaluation of traits of clonal lines induced by chromosome manipulation in Japanese flounder (Paralicthys olivaceus)
Ⅱ . Differences in gonadal sex differentiation and morphological development
Gonadal sex differentiation and morphological development by rearing experiment were conducted to characterize the clonal lines in Japanese flounder, Paralichthys olivaceus. Clone fish produced by chromosome manipulation techniques gynogenetically were artificially reared to juvenile stage and examined their sexuality and morphology. Female rates of no. 72, 75 and 82 clonal lines were high values (70.8%, 77.8% and 88.5%) and those of no. 71, 77 clonal lines and control group were almost 50%, but no. 83 clonal line showed the lowest rate (27.1%). Pseudoalbinism on the ocular sides of clonal lines were slightly (0.0～6.0%) observed compared with control group (35.0%), but the ambicoloration on the blind sides of them were recognized severely (57.5～100.0%) except the no. 82 clonal line (2.5%). Severe vertebral fusions (abdominal region 36.3%, caudal region 53.6%) were observed in no. 83 clone fish which body proportions (body height/standard length) were significantly different from other clonal lines. The appearance of no. 83 clone fish showed so-called shortened trunk.
Ⅱ . Differences in gonadal sex differentiation and morphological development
Gonadal sex differentiation and morphological development by rearing experiment were conducted to characterize the clonal lines in Japanese flounder, Paralichthys olivaceus. Clone fish produced by chromosome manipulation techniques gynogenetically were artificially reared to juvenile stage and examined their sexuality and morphology. Female rates of no. 72, 75 and 82 clonal lines were high values (70.8%, 77.8% and 88.5%) and those of no. 71, 77 clonal lines and control group were almost 50%, but no. 83 clonal line showed the lowest rate (27.1%). Pseudoalbinism on the ocular sides of clonal lines were slightly (0.0～6.0%) observed compared with control group (35.0%), but the ambicoloration on the blind sides of them were recognized severely (57.5～100.0%) except the no. 82 clonal line (2.5%). Severe vertebral fusions (abdominal region 36.3%, caudal region 53.6%) were observed in no. 83 clone fish which body proportions (body height/standard length) were significantly different from other clonal lines. The appearance of no. 83 clone fish showed so-called shortened trunk.
A－440 Katsuhisa BABA, Akira MIYAZONO, Shoui KOHNO and Shin KUBOTA
The symbiosis of the bivalve-inhabiting hydroid Eutima japonica in juvenile of Japanese scallop Mizuhopecten yessoensis in Funka Bay: preventive measure against the symbiosis
To make preventive measures against symbiosis of the bivalve-inhabiting hydroid Eutima japonica with cultured juvenile (age zero) scallop Mizuhopecten yessoensis, we investigated the ecological relationships between the hydroid, the main host Mytilus galloprovincialis, and the juvenile scallop in Funka Bay, Hokkaido, Japan. Interannual variation of the association rate with juvenile scallop was very large; the mean rates were between 9.3 % (2004) and 69.5 % (2006). The period of the inhabitation in the juvenile scallop was from September to February, and the spread and cessation of the inhabitation occurred rapidly within about one and two months, respectively. The peak of medusa bud was July in M. galloprovincialis, whereas the inhabitation occurred from beginning of September in the juvenile scallop. The symbiosis probably initiates when the juvenile scallop encounter with the planula larva. Since the hydroid does not inhabit in adult scallop nor age zero M. galloprovincialis, high age M. galloprovincialis, especially inhabiting at the culture facilities of the scallop, is probably the source of the planula larvae of the hydroid for the inhabitation in the juvenile scallop. Therefore, the cleaning up the facilities after harvest of the scallop is considered to be effective to prevent the inhabitation of the hydroid in the juvenile scallop.
To make preventive measures against symbiosis of the bivalve-inhabiting hydroid Eutima japonica with cultured juvenile (age zero) scallop Mizuhopecten yessoensis, we investigated the ecological relationships between the hydroid, the main host Mytilus galloprovincialis, and the juvenile scallop in Funka Bay, Hokkaido, Japan. Interannual variation of the association rate with juvenile scallop was very large; the mean rates were between 9.3 % (2004) and 69.5 % (2006). The period of the inhabitation in the juvenile scallop was from September to February, and the spread and cessation of the inhabitation occurred rapidly within about one and two months, respectively. The peak of medusa bud was July in M. galloprovincialis, whereas the inhabitation occurred from beginning of September in the juvenile scallop. The symbiosis probably initiates when the juvenile scallop encounter with the planula larva. Since the hydroid does not inhabit in adult scallop nor age zero M. galloprovincialis, high age M. galloprovincialis, especially inhabiting at the culture facilities of the scallop, is probably the source of the planula larvae of the hydroid for the inhabitation in the juvenile scallop. Therefore, the cleaning up the facilities after harvest of the scallop is considered to be effective to prevent the inhabitation of the hydroid in the juvenile scallop.
A－441 Yoshiyuki UEDA, and Yukio MIHARA
Migration between inshore and offshore of shishamo smelt (Spirinchus lanceolatus) in the Pacific coastal waters off southwestern Hokkaido （Short Paper）
A－442 Keizo YOSHIMURA, Daisuke TSUTSUI, Nobukazu SATOH, Shin-ich TAKABATAKE
Variations in egg size, hatching larvae size and otolith size of sailfin sandfish, Arctoscopus japonicus, correlated with female parent age（Short Paper）
A－443 Yoshiyuki TAKAYA, Keizo YOSHIMURA, Hidetsugu YOSHIDA, Takaaki KAYABA, Taihei MATSUDA and Minoru KIMURA
Feeding , nutritional conditions and survival of juvenile barfin flounder, Verasper moseri, reared in small net cages （Short Paper）
A－444 Hidetsugu YOSHIDA, Yoshiyuki TAKAYA and Taihei MATSUDA
Recapture of ALC-marked barfin flounder Verasper moseri in the Pacific waters off southern Hokkaido （Short Paper）
A－445 Hidetsugu YOSHIDA, Yoshiyuki TAKAYA and Taihei MATSUDA
Influence of size at release on migration and recapture of barfin flounder Verasper moseri （Short Paper）