Isolation and characterization of Streptococcus sp. from diseased flounder (Paralichthys olivaceus) in Jeju Island

Streptococcus sp. is gram-positive coccus that causes streptococcal infections in fish due to intensification of aquaculture and caused significant economic losses in fish farm industry. A streptococcal infection occurred from cultured diseased olive flounder (Paralichthys olivaceus) in May, 2005 at a fish farm in Jeju Island, Korea. The diseased flounder exhibited bilateral exophthalmic eyes and rotten gills; water temperature was 16~18℃ when samples were collected. Of the 22 fish samples collected, 3 samples were identified as Lactococcus garvieae and 18 samples were identified as Streptococcus parauberis by culture-based, biochemical test. Serological methods such as slide agglutination, hemolysis and antimicrobial susceptibility test were also used as well as multiplex PCR-based method to simultaneously detect and confirm the pathogens involved in the infection. S. parauberis and L. garvieae have a target region of 700 and 1100 bp., respectively. One fish sample was not identified because of the difference in the different biochemical and serological tests and was negative in PCR assay. In the present study, it showed that S. parauberis was the dominant species that caused streptococcosis in the cultured diseased flounder

Molecular detection of betanodavirus in wild marine fish populations in Korea

Viral nervous necrosis (VNN) is a worldwide disease affecting several species of cultured marine fish. In Korea, VNN has been identified in several species of cultured marine fish. In this study, the authors present data of the amplified nested polymerase chain reaction product (420 bp) of 21 nodavirus strains from different species of apparently healthy wild marine fish on the southern coast of Korea. Phylogenetic analysis based on the partial nucleotide sequence (177 bases) of the RNA2 coat protein gene of 21 strains was highly homologous (93–100%) and closely related to that of the known betanodavirus, redspotted grouper nervous necrosis virus. These results indicate that betanodaviruses occur in large populations of wild marine fish in the southern part of the Korean peninsula, suggesting the importance of these subclinically infected fish as an inoculum source of betanodavirus that is horizontally transmitted to susceptible cultured fish species.A Korea Research Foundation grant (KRF-2006-005- J02903) supported this study. The authors are grateful for a graduate fellowship provided by the Ministry of Education through the Brain Korea 21 program for Veterinary Science, Seoul National University. The authors are also thankful to Dr. T. Nakai, Hiroshima University, Japan, for kindly providing the E-11 cell line for virus isolation

Detection of betanodaviruses in apparently healthy aquarium fishes and invertebrates

Betanodaviruses are the causative agents of viral nervous necrosis (VNN) in cultured marine fish. A total of 237 apparently healthy aquarium fish, marine (65 species) and freshwater (12 species) fishes and marine invertebrates (4 species), which were stocked in a commercial aquarium in Seoul, South Korea, were collected from November 2005 to February 2006. The brains of the fish and other tissues of the invertebrates were examined by reverse transcriptase-polymerase chain reaction (RT-PCR) and nested PCR to detect betanodavirus. Positive nested PCR results were obtained from the brains of 8 marine fish species (shrimp fish Aeoliscus strigatus, milkfish Chanos chanos, three spot damsel Dascyllus trimaculatus, Japanese anchovy Engraulis japonicus, pinecone fish Monocentris japonica, blue ribbon eel Rhinomuraena quaesita, look down fish Selene vomer, yellow tang Zebrasoma flavesenes), 1 marine invertebrate species (spiny lobster Pamulirus versicolor), and 2 freshwater fish species (South American leaf fish Monocirrhus polyacanthus and red piranha Pygocentrus nattereri). The detection rate in nested PCR was 11/237 (4.64%). These subclinically infected aquarium fish and invertebrates may constitute an inoculum source of betanodaviruses for cultured fishes in the Korean Peninsula

Feeding ecology of three tonguefishes, genus Cynoglossus (Cynoglossidae) in the Seto Inland Sea, Japan

Feeding ecology was compared among the three tonguefishes Cynoglossus abbreviatus, C. joyneri and C. robustus, collected from Seto Inland Sea, Japan, from June 2000 to May 2001. They are benthivores, consuming mainly gammarid amphipods, shrimps, crabs, gastropods, bivalves and ophiuroids. C. abbreviatus consumed greater proportions of ophiuroids whereas C. joyneri and C. robustus ate more amphipods and shrimps. While C. abbreviatus consumed mostly ophiuroids in all size classes, the diets of C. joyneri and C. robustus showed ontogenetic changes in feeding habits; smaller individuals of C. joyneri and C. robustus consumed gammarid amphipods, whereas larger C. joyneri ate shrimps and gastropods, and larger C. robustus fed mainly on gastropods, crabs, bivalves and polychaetes. Cluster analysis based on diet similarities emphasized that the three Cynoglossus species could be categorized on a size-related basis into three feeding groups: smaller C. joyneri and C. rubustus (25 cm TL) as group B, whereas C. abbreviatus was categorized as group C. This means that some degree of resource partitioning can occur among the three Cynoglossus species. The seasonal changes in the diets were also significant for the three Cynoglossus species.12 page(s

Ontogenetic and diel changes in diets of two sympatric mudskippers Periophthalmus modestus and Periophthalmus magnuspinnatus on the tidal flats of Suncheon Bay, Korea

Variability in the diet breadth of two sympatric mudskippers Periophthalmus modestus and P. magnuspinnatus in the tidal flats of Suncheon Bay, Korea, was compared. The analysis of 494 P. modestus and 455 P. magnuspinnatus specimens revealed that both were carnivores, consuming mainly gammarid amphipods, polychaetes, insects, and crabs. However, adult P. modestus consumed greater proportions of polychaetes whereas P. magnuspinnatus ate more crabs. The diets of both species showed ontogenetic changes in diet; smaller individuals of both species consumed harpacticoid copepods and gammarid amphipods, whereas larger fishes of both species fed mainly on different preys. The stomach content index (SCI) of both species underwent significant size-related and diel changes; the values of both species were higher in the larger size classes and during the late afternoon. Levin's index of diet breadths of both species were lower during the day than at night, indicating high prey selection during the daytime. Non-metric multi-dimensional scaling ordination emphasized that the dietary compositions of the smaller individuals of both species showed some obvious similarities, with dietary similarity gradually reducing with increasing fish size. This indicates that the two species consume gradually different types of prey as they grow, that is, resource partitioning may be occurring between larger P. modestus and P. magnuspinnatus.9 page(s

Temporal variations of fish assemblage in the surf zone of the Nakdong River Estuary, southeastern Korea

To assess temporal variations in fish assemblages, fish samples were collected on a monthly basis in the surf zone of the Nakdong River Estuary in 2004. Surveys were conducted at two sites during day and night neap tides using a 10-m beach seine. In total, 2397 specimens (8146.0 g) comprising 27 species and 16 families were collected during the study period. The dominant fish species were Mugil cephalus, Plecoglossus altivelis, Favonigobius gymnauchen, Opsariichthys uncirostris amurensis, and Hyporhamphus sajori, which accounted for 84.6% of the total number of individuals. The fish sampled were primarily small species or the early juveniles of larger species. The species composition and abundance varied greatly, with a peak in the number of individuals in July (summer) and January (winter), and the peak in biomass during July (summer). The catch rate was low in the spring and autumn months due to the low abundance of the dominant species recorded. A cluster analysis revealed that the fish assemblages were characterized by distinct seasonal groups reflecting the reproductive habits of adult fishes. Fish abundance did not significantly differ between the two sites, although a significant difference in their abundance was detected between day and night, with more fish specimens collected at night than during the day at both sites. The Nakdong River Estuary is an important ecosystem for small and/or juvenile fishes, providing a habitat within the estuary suitable for their development and migration.9 page(s

The annual life cycle of Zebrias zebra in the near shore waters around Imabari, Ehime prefecture.

瀬戸内海における沿岸性底棲魚シマウシノシタの成熟と産卵を中心とした生活サイクルについて, 愛媛県今治市沿岸周辺海域で1999年7月から2001年11月までの間に漁獲された296尾を用いて調べた。採集個体の体長(BL)は, それぞれ雄が101-236mm(128尾), 雌が102-301㎜(168尾)で, 雌に大型個体が多く出現しており, 雌が大型化する性的差異が示唆された。本種の生物学的最小形についても雄が125㎜, 雌が175㎜と雌が大きかった。成魚の生殖腺重量指数(GSI)・肝臓重量指数(HSI)・肥満度(CF)から, 産卵期が6-8月, 産卵期に伴う産卵準備期, 回復期がそれぞれ5-6月, 8-9月, 越冬準備期は10-12月, 越冬期が1-3月という生活サイクルを推定した。本種の産卵期における卵巣からは, 単峰の卵径組成が確認された。本種の産卵は, その単峰の卵団が卵径0.7㎜以上の大型卵団となり, 卵巣における大型卵団の占有率が90%ほどに達した後, 複数回に分けて放卵されるものと判断された。抱卵数は1個体あたり3-15万個であり, 体長と抱卵数(F)に正の相関関係が認められた:F=3.23×10-5BL3.94, r;0.884。The annual life cycle of adult Z. zebra, a heterosomata fish in Seto Inland Sea, mainly focused on maturity and spawning was examined by 296 samples caught in the nearshore waters around Imabari from July 1999 to November 2001. Body lengths of samples were 101-236mm in males (128 fish) and 102-301mm in females (168 fish), which data suggested female has a tendency to grow bigger than male. The biological minimum size, 125mm of male and 175mm of female, also indicated the inclination. Judging from the gonadsomatic index (GSI), hepatosomatic index (HSI), and condition factor (CF) of adult fish, the annual life cycle of this species was calculated as follows: spawning season is from June to August, pre-spawning season and recovering season from spawning are from May to June and from August to September, respectively, pre-wintering season is from October to December and wintering season is from January to March. One modes in frequency distributions of egg diameter was found from the ovaries of samples during spawning season. It was estimated that the spawning of this species is performed by spawning their eggs some times after the mass of eggs indicated by one mode in frequency distribution of egg diameter becomes a mass of large-sized egg more than 0.7mm in egg diameter and the rate of the mass in the ovary reaches around 90%. The fecundity of this species was from thirty thousand to fifteen hundred thousand per individual, and there was a plus correlation of body length (BL) with fecundity (F) : F = 3.23 × 10-5 BL3.94, r; 0.884

Diet composition in summer of rosefish Helicolenus hilgendorfii on the southeastern coast of Korea

The feeding habits of Helicolenus hilgendorfii were studied using 93 specimens (35-135 mm in standard length) collected from the southeastern coast of Korea during the summer season (June-August) from 2005 to 2007. Helicolenus hilgendorfii is a carnivore that mainly consumes shrimps and fishes. Its diet also includes small quantities of mysids, amphipods, euphausiids, copepods, and isopods. Our graphical method for feeding habits revealed that H. hilgendorfii is an opportunistic and specialized predator on shrimps, especially Crangon hakodatei, although H. hilgendorfii showed an ontogenetic dietary shift, the proportion of shrimp decreasing and the consumption of fishes gradually increasing with the increase of fish size.5 page(s

Scoping the effective marine environmental assessment of dredging and ocean disposal of coastal sediments in Korea

The application of scoping is reviewed to improve the efficiency and rationality of the marine environmental impact assessment system applied to the dredging of coastal sediments and the oceanic disposal of dredged material in Korea. Both the impact levels and those items requiring assessment vary in response to differing goals of the coastal activities involved and also to changes in the characteristics of different marine environments. As a consequence, different assessment fields need to be emphasized for evaluation of the impact that both dredging and dumping might have on the sites involved. The status of current assessment procedures is examined and its problems are diagnosed. Following a survey of interested parties and a review of case studies of the oceanic disposal of dredged sediment in other countries, checklists of core assessment items are proposed as part of a revamped review process, along with improvements to the assessment system.Marine environmental impact assessment Dredging of coastal sediment Oceanic disposal of dredged material Core assessment item