• Korean Journal of Ichthyology
• /
• v.9 no.1
• /
• pp.22-29
• /
• 1997

Feeding habits of Pholis nebulosa collected from a eelgrass bed in Kwangyang Bay from January 1994 to December 1994 were studied. Pholis nebulosa was a carnivore which mainly consumed epiphytal amphipods. Its diets included minor quantities of caridean shrimps, isopods, copepods, tanaids and polychaetes. It showed ontogenetic changes in feeding habits. In an initial feeding stage, copepods were major food organisms. However, gammarid and caprellid amphipods were heavily selected with increasing fish size. Although gammarid and caprellid amphipods were major prey organisms for all seasons, the relative proportion of these two food items changed with season.

• Ocean and Polar Research
• /
• v.43 no.2
• /
• pp.89-98
• /
• 2021

The seagrass habitats are a highly productive marine ecosystem which provides nursery ground and shelter for many fish and invertebrate species. Pholis nebulosa (Temminck & Schlegel, 1845) is one of the most abundant seagrass fishes in the coastal waters of Korea. The estimation of fish production is key for devising conservation measures and ensuring fish resources sustainability. A total 894 P. nebulosa ranging from 3.83 to 26.5 cm total length (TL) were collected monthly in 2006 with a small beam trawl in a seagrass bed of southern Korea. Growth parameters of P. nebulosa were estimated using the von Bertalanffy growth model, and production was estimated using a general equation which relates daily fish production to ash-free dry weight (AFDW), biomass, and water temperature. The von Bertalanffy's growth equation was estimated as: L_t = 28.3823(1-e^{-0.7835(t+0.9864)}). The densities, biomass, daily, annual production, and P/B ratio were 0.069±0.061/m^-2, 1.022±0.621 g/m², 0.005±0.004 g AFDW/m²/day, 1.676 g AFDW/m²/yr, and 1.641, respectively. Monthly variation in production of P. nebulosa peaked during March and April 2006 (0.0139 and 0.0111 g AFDW/m²/day), whereas the lowest value of 0.0005 g AFDW/m²/day was in December. Monthly change in production of P. nebulosa was positively correlated with biomass and condition factor. Our results will contribute to the conservation of seagrass ecosystems, which are still undisturbed in the study area.

• Journal of Marine Life Science
• /
• v.9 no.1
• /
• pp.47-52
• /
• 2024

Light is a major external environmental factor that influences the circadian rhythm of photosynthetic organisms and various physiological phenomena, such as growth, maturation, and behavior. The number of light-reaching organisms changes depending on the season and atmospheric conditions, and the intensity and wavelength of light differ depending on the organisms inhabiting the environment. Altered light changes the circadian rhythm of fish, which is controlled by clock genes, such as period 2 (Per2), cryptochrome 1 (Cry1), and melatonin. In this study, we set the zeitgeber time (ZT; 14 light-10 dark, LD) based on the actual sunrise and sunset times and examined Per2 and Cry1 activities, levels of aralkylamine N-acetyltransferase (AANAT), and melatonin in Pholis nebulosa, a drifting seaweed species exposed to irregular light. Per2 and Cry1 levels increased during the daytime and decreased after sunset. The AANAT levels decreased during the daytime and increased during the night. Melatonin concentration was highest around midnight (ZT21, 23:30), but exhibited similar concentrations during the daytime. While the activity of Per2, Cry1, and AANAT levels exhibited a typical circadian rhythm observed in most vertebrates, melatonin concentrations did not show a significant difference between the daytime and nighttime. These findings provide insights into the circadian rhythm patterns of organisms exposed to irregular light environments, such as P. nebulosa, which differ from those of typical fish species.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.33 no.2
• /
• pp.148-152
• /
• 2000

To provide basic information on the integumentary system of the blenny, Pholis nebulosa, ultrastructures of epidermal and dermal layer were examined by means of the light and transmission electron microscope. The skin of the blenny consisted of epidermal and dermal layer. Epidermal layer consisted of supporting cell and unicellular gland. The supporting cells were classified into superficial cell, intermediated cell and basal cell, and the gland cells were classified into mucous secretory cell and club cell. The cytoplasm of supporting cells was divided into cortex and medullar part. In the cortex and medullar part, microfilaments and cell organelles were well developed, respectively. Superficial cell of epidermal layer was cuboidal and contained nucleus of horseshoe shape. Intermediated cell had a nucleus of irregular form and the electron density was higher than the other supporting cells, Basal cell was columnar, but nucleus was situated in the upper cytoplasm. Cell organelles of the basal cell were poor than the other supporting cells, but membrane interdigitations were well developed. The cytoplasm of mucous secretory cell had a well-developed ovoid secretory granules, which reacted to red with AB-PAS reaction. The club cell had a we31-developed round secretory granules and endoplasmic reticulum. figment cells were classified into two type. The one contained pigment granules of electron dense, and the other contained reflecting platelets. The cytoplasm of fibrocyte had n well developed rough endoplasmic reticulum.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.33 no.4
• /
• pp.288-301
• /
• 2000

The species composition and seasonal variation of fish assemblage in the coastal water off Gadeok-do, Korea were studied using the monthly trawled samlpes through a year of 1998. During the study period, 110 species of fishes from 57 families were collected. Repomucenus valenciennei, Thryssa kammalensis, Leiognathus nuchalis and Zoarces gilli dominated the fish assemblage throughout the year, and were responsible for $ 57.6{\%}$ and $37.2{\%}$ in the number of individuals and biomass, respectively. Fish species of secondary importance in abundance were Sillago japonica, Apogon lineatus, Pholis fangi, Engraulis japonicus, Thryssa adelae, Pho;is nebulosa, Conger myriaster, Liparis tanakai, Acentrogobius pflaumii, Limanda yokohamae, Chaeturichthys hexanema, Erisphex pottii and Cunoglossus abbreviatus. Higher numbers of species were collected in spring and autumn than in summer and winter. Abundance was high in spring and autumn, and low in summer and winter, Species diversity indices showed that the fish assemblage was more diverse in autumn than any other seasons.

• Fisheries and Aquatic Sciences
• /
• v.13 no.3
• /
• pp.254-256
• /
• 2010

Length-weight relationships were estimated for 19 fish species in sargassum beds of Gamak Bay: Aulichthys japonicus, Pseudoblennius cottoides, Pseudoblennius percoides, Ditrema temmincki, Acanthogobius lactipes, Chaenogobius heptacanthus, Cryptocentrus filifer, Pterogobius elapoides, Pterogobius zonoleucus, Hyporhamphus sajori, Hexagrammos agrammus, Rudarius ercodes, Lateolabrax japonicus, Pholis crassispina, Pholis nebulosa, Scomber japonicus, Sebastes inermis, Ernogrammus hexagrammus, and Takifugu niphobles. Samples were caught by surrounding net at depths of <7 m between November 2007 and June 2008. The most abundant families were Gobiidae (26.3%), Cottidae (10.5%), and Pholididae (10.5%). Estimates for parameter b of the length-weight relationship (W=$aL^b$) ranged between 2.491 and 3.354.

• Korean Journal of Ichthyology
• /
• v.24 no.3
• /
• pp.191-200
• /
• 2012

Fish species composition in eelgrass bed of Punghwa-ri in Tongyeong, Korea was determined using monthly samples collected by a surf net from November 2010 to October 2011. During the study period, a total of 30 species, 5,511 individuals and 6,933.4 g of fishes were collected. The dominant fish species were Pholis nebulosa, Syngnathus schlegeli, Rudarius ercodes, Pseudoblennius cottoides, Sebastes inermis, and Aulichthys japonicus which accounted for 93.4% of total number of individuals collected. Most fishes collected in the eelgrass bed belong mainly to small fish species or juveniles of large fish species. Eelgrass shoot density reached a peak in April 2011, and then decreased to a minimum in January 2011. The seasonal variation of fish assemblage in an eelgrass bed of Punghwa-ri was correlated to the variations in the water temperature, eelgrass density and biomass, and abundances of major prey organisms.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.18 no.4
• /
• pp.227-233
• /
• 2013

A total of 25 species, 3,880 individuals and 3,145.1 g of fishes were collected by a surf net from the eelgrass bed in Minyang. Most fishes collected in the eelgrass bed belong mainly to small fish species or juveniles. The dominant fish species were Gymnogobius heptacanthus, Rudarius ercodes, Pholis nebulosa, Chaenogobius gulosus, and Gymnogobius castaneus which accounted for 89.1% of total number of individuals collected. The number of individuals and biomass were higher from June to September when the water temperature was high. However, both the number of individuals and species showed the lowest from January and February. Highest species diversity index (H') was observed in April, 2012.

• Korean Journal of Ichthyology
• /
• v.9 no.2
• /
• pp.202-220
• /
• 1997

A total of 57 species of fish species was collected by a trawl from the eelgrass bed in Kwangyang Bay. The dominant species were Pholis nebulosa, Syngnathus schlegeli, Leiognathus nuchalis, Pseudoblennius cottoides, Sebastes inermis, Favonigobius gymnauchen, which accounted for 69.9% of the total numbers of fish collected. Fish collected in the study area were primarily small fish species or early juveniles of large fish species. Only about 10% of fishes which were collected in the eelgrass bed exceeded 15cm in standard length. Seasonal variations in both species composition and abundance were major characteristics in the study area. The peak abundance occurred in spring, while the number of species was the highest in fall. However, both the number of species and abundance of fishes showed the lowest values in winter. High species diversity indices were observed in fall. Temperature, eelgrass standing crop and abundance of food organisms influenced seasonal changes of the fish community in the study area. More abundant and more diverse fishes were collected during nighttime than daytime.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.17 no.1
• /
• pp.15-21
• /
• 2011

Species composition and seasonal variation of fish assemblages in Sargassum beds in Gamak Bay was determined using fish samples collected monthly by a surrounding net from October 2008 to September 2009. A total of 21 species, 582 individuals and 5,345.1 g of fishes were collected during the study period and Perciformes accounted for 47.6 % of the total number of species. Takifugu niphobles, Engraulis japonicus and Lateolabrax japonicus predominated in number, accounting for 55 % of the total number of individuals. Higher number of species and individuals occurred in June and in September-October. Species were grouped into three by cluster analysis: A) dominant species such as Leiognathus nuchalis and Takifugu niphobles, B) fish collected mainly in spring such as Sebastes inermis, Chaenogobius heptacanthus, Pterogobius zonoleucus, Pholis nebulosa, and Trachyrhamphus serratus, and C) fish collected mainly in autumn such as Engraulis japonicus, Lateolabrax japonicus, and Hyporhamphus sajori.