• Title, Summary, Keyword: Neap tide

Search Result 107, Processing Time 0.049 seconds

Environmental Factors and Catch Fluctuation of Set Net Grounds in the Coastal Waters of Yeosu - 2 . Sea Water Circulation in the Vicinity of Set Net Ground - (여수연안 정치망어장의 환경요인과 어황 변동에 관한 연구 - 2 . 어장주변 해역의 해수유동 -)

  • Kim, Dong-Soo;Rho, Hong-Kil
    • Journal of the Korean Society of Fisheries and Ocean Technology
    • /
    • v.30 no.3
    • /
    • pp.142-149
    • /
    • 1994
  • In order to investigate the environmental properties of set net grounds located in the coastal waters of Yeosu. The current in the vicinity of set net grounds was observed by drogue and current meter in 1990 and 1992. The results obtained are summarized as follows: The direction of tidal current at the north enterance of Yeosu bay was southerly in ebb and northwesterly in flood without the distiction of the neap tide and the spring tide. In spring tide the maximum Velocity of the tidal current was 68 cm/sec in ebb and 66 cm/sec in flood. In neap tide the maximum velocity of the tidal current was 37 cm/sec in ebb and 35 cm/sec in flood. And so the direction of residual current was the south ward mainly and 21 cm/sec. The direction of tidal current at set net fishing grounds was southwesterly in ebb and westerly or northwesterly in flood. Regardless of the distinction of neap and spring. The maximum velocity of the current in spring tide was 50 cm/sec in ebb and 40 cm/sec in flood and that in neap was 28 cm/sec in ebb and 25 cm/sec in flood. In spring tide the speed vector along the major axis of semidiurnal tide component was three times as large as diurnal tide. In neap tide, however, the speed vector was about 50% less then that in spring tide, and the semidiurnal tide and diurnal tide were equal in the size of current ellipse and the direction of major axis. The sea area had a southwesterly residual current. 11 cm/sec in spring tide and 7 cm/sec in neap tide. According to the result of drogue tracking, the vicinity of set net fishing ground had a southerly residual current which formed in Yeosu Bay and a weak westerly residual current toward Dolsando from Namhedo. Therefore, set net fishing ground in coastal water of Yeosu was distributed in boundary of inner water which formed from Seamjin river and offshore water supplied from the vicinity of Sorido and Yochido.

  • PDF

Tidal Currents In The Channel Near Incheon Harbour (인천항부근 수로의 조류)

  • Bong, Jong Hon
    • 한국해양학회지
    • /
    • v.13 no.1
    • /
    • pp.29-34
    • /
    • 1978
  • Simultaneous tidal current observation at five or seven stations on the channel near Incheon Habour was conducted at neap, mean and spring tides during the period of August 16 to August 27, 1976 and the characteristic of tidal currents with each tide was studied by the analysis of these data. Times of slack refer to the times of high and low waters at neap, mean and spring tides seem to be small. Times of maximum current refer to the times of high and low waters at the mean tide tends to appear earlier than that of the neap tide and later than that of the spring tide. The velocity ratio of maximum ebb current to maximum flood current at the mean tide has larger value than that of neap tide and has smaller value than that of spring tide. The current velocity ratio of spring tide to neap tide and to mean tide are approximately 1.8 and 1.3, respectively.

  • PDF

Prediction of Pollutant Transport by Dispersion Model on Estuary (확산모형에 의한 하구에서의 오염물질이동 예측(수공))

  • 박영욱;박상현;천만복;이봉훈;권순국
    • Proceedings of the Korean Society of Agricultural Engineers Conference
    • /
    • /
    • pp.371-377
    • /
    • 2000
  • Environmental impact on a land reclamation project, Hwaong tidal barrier was studied using the dispersion and advection model to predict the influence of polluted water discharged from freshwater reservior. The simulation results show that the distribution of concentration by influence of polluted water discharged during a tidal cycle appeared to be extinguished at atmost all points after two tidal cycle. Peak concentration near the sluice gate is found out to be higher during the spring tide than neap tide. Equi-concentration contour line appeared to distributed a longer according to line of sea dike in spring tide than neap tide. The reasons is because influence by currents of northwest direction is a stronger, compared to spring tide and neap tide in the flood tide.

  • PDF

Field Observations and Hydraulic Model Experiments of Tidal Currents in Chinhae Bay (진해만 조류의 현장관측 및 수리모형실험)

  • CHANG Sun-Duck;KIM Cha-Kyum;LEE Jong-Sup
    • Korean Journal of Fisheries and Aquatic Sciences
    • /
    • v.26 no.4
    • /
    • pp.346-352
    • /
    • 1993
  • Tidal currents and tidal residual currents in Chinhae Bay are investigated by the field observations and hydraulic experiments during the spring tide and neap tide. The horizontal and vertical scales of the model are l/2,000 and 1/159, respectively. The hydraulic model results roughly coincide with the field data. Maximum tidal currents during the spring tide and neap tide in the central channel of Chinhae Bay are strong as about 90 and 30cm/s respectively, and strong tidal residual currents take place. Maximum tidal currents during the spring tide and neap tide in the western and northern part of the bay are weak as below 30 and 10cm/s respectively, and also tidal residual currents are weak. Tidal residual currents rotating clockwise occur in the central part of the bay. Northward tidal residual currents in the northern part of Kajo-do are predominant, whereas southward ones in the southern part of Kajo-do are remarkable. The surface currents in the bay depend strongly on the wind and river flow, and it seems to be remarkable during the neap tide.

  • PDF

Catch fluctuation of the Pound Set Net According to Tide Age in the Coastal Waters of Jeju (제주 연안의 소대망에서 조석에 의한 어획량 변동)

  • Kim, Byung-Yeob;Seo, Du-Ok;Lee, Chang-Heon
    • Korean Journal of Fisheries and Aquatic Sciences
    • /
    • v.42 no.1
    • /
    • pp.83-88
    • /
    • 2009
  • The purpose of this paper is to obtain the fundamental data on the catch fluctuation in the pound set net according to the tide age from the catch recorded from the year 1997 to 2004 in the coastal waters of Guideok, Jeju. Total catch by the pound set net had a little connection with the tide age. During increasing tide, total catch were reduced slightly from the neap tide to the high tide while there seemed to be a little sign of rise in the total catch until decreasing tide. But in the relation between the catches and the tide age, the level of the correlation coefficient chosen at $p{\le}0.05$ was not significant. Therefore, the catch of the pound set net seemed not to be influenced by the tide age. In addition, CPUE at the high tide was higher than that at the neap tide. When the catch per operating frequency was graded in the order under 50 kg, 50-100 kg and 100-200 kg, the frequency rate by the pound set net was 38%, 19% and 19%, respectively.

Catch fluctuation of the rectangular set net according to the tide age in the coastal waters of Jeju (제주연안 각망의 조석에 의한 어획량 변동)

  • Lee, Chang-Heon;Choi, Chan-Moon
    • Journal of the Korean Society of Fisheries and Ocean Technology
    • /
    • v.44 no.2
    • /
    • pp.112-119
    • /
    • 2008
  • The fundamental data on the catch fluctuation in the rectangular set net according to the tide age were developed based on the catches recorded from the year 1986 to 2004 in the coastal waters of Hamdeok, Jeju. Total catch by the rectangular set net had a deep connection with the tide age. In particular, during increasing tide, total catch were reduced gradually from the neap tide to the high tide. As it turned out, the slope of total catch declined by degree and showed a correlation coefficient of determination of 0.76. On the contrary, in the case of decreasing tide, there was little sign of rise in total catch. In particular, large catch seemed to occur at the next tide to the neap tide. In the relation between the catch and the tide age, the level of the correlation coefficient chosen at $p{\leq}0.05$ decreased in the order rabbitfish(-0.84) and horse mackerel(-0.71), while the significance of other dominant species were not selected.

Effective sampling of estuarine fauna by a passive net in theWest Sea of Korea occurring strong tide (조류가 강한 서해 하구에서 수동어구를 이용한 하구역 유영생물의 효율적 채집)

  • Hwang, Sun-Do;Im, Yang-Jae
    • Journal of the Korean Society of Fisheries and Ocean Technology
    • /
    • v.47 no.4
    • /
    • pp.338-343
    • /
    • 2011
  • To obtain the effective sampling estuarine fauna by a passive net in the West Sea of Korea occurring strong tide, catch were collected by bag nets with various sampling trials off Ganghwa Island in November 2009. We compared the difference of community structures (on spring tide vs. neap tide, total sample vs. subsample and 4 nets vs. 1 net) with each species composition as a sampling unit by the Pearson chi-square test. Number of individual at the spring tide was more abundant than that at the neap tide (p<0.0001) although number of species at the spring tide was not significantly different with that at the neap tide (p=0.174). Both number of species (p=0.138) and number of individual (p=0.096) were not significantly different between total sample and random subsample. Number of species was not significantly different between the subsample by 1 net and the subsample by 4 nets (p=0.515), but number of individual was a little different on both samples (p=0.024). In conclusion, we suggest the subsample by 1 net at spring tide as the effective sampling estuarine fauna by a passive net in the West Sea occurring strong tide.

Tide-induced changes in marine fish cage-shape cause changes in swimming behavior of cultured chub mackerel (Scomber japonicus)

  • Hwang, Bo-Kyu;Lee, Jihoon;Shin, Hyeon-Ok
    • Fisheries and aquatic sciences
    • /
    • v.23 no.4
    • /
    • pp.14.1-14.14
    • /
    • 2020
  • We performed field measurements of the behavioral changes in cultured chub mackerel (Scomber japonicus) caused by tide-induced changes in the shapes of their small-sized tetragonal fish cages. The field measurements were conducted in two separate periods: neap tide, a period in which the shape of the fish cages was stable; and spring tide, a period in which the fish cages are significantly deformed, which was expected to have significant influences on fish behavior. In the spring tide, the cages were deformed greatly by the moving water, with different water velocities affecting the cages to different degrees; the volume loss was estimated at 4.9% and 7.3% for v = 0.114 m/s and v = 0.221 m/s, respectively. The fish exhibited significantly different behaviors between the neap tide and spring tide. During the neap tide, the fish remained in the lower part of the cage, but during the spring tide they made frequent upward and downward movements, and their horizontal distribution changed significantly due to the changes in the shape of the cage. The cage deformation during the spring tide greatly influenced the swimming behavior of fish.

The Variations of SMC During Tidal Cycle in Deukryang Bay, Korea (대.소조기변동에 따른 득량만내의 부유퇴적물의 변동 및 분포특성)

  • Lee, Byoung-Gul;Kong, Young-Sae;Cho, Kyu-Dae
    • Journal of Environmental Science International
    • /
    • v.5 no.4
    • /
    • pp.473-479
    • /
    • 1996
  • The temnoral variations of the suspended material concentration (SMC) during spring-neap tidal cycle was investigated at more than 30 stations in Deukryang Bay, Korea, in 1 and 23 July, 1992. The averaged total SMC in spring tide was two times more than those in neap tide. It can be explained that the strong tidal current in spring tide disturbed bottom waters and induced higher SMC in the bay. The areal distributions of SMC for the surface and the bottom layers in the bay shows much different patterns during spring and neap tidal cycle. We concluded that the vertical stratification intensity of water mass is important factor of the horizonatal distribution of SMC in the bay.

  • PDF

Saline Water Movement In The Estuary Of The Nakdong River (낙동강 하구의 염수운동)

  • Chang, Sun-duck;Ryu, Cheong-ro;Lee, Mun-ok;Lee, Jae Chul
    • 한국해양학회지
    • /
    • v.16 no.1
    • /
    • pp.31-37
    • /
    • 1981
  • Saline water movements in relation to tidal condition and river discharge in the estuary of the Nakdong River are discussed on the basis of the observation data. The difference of salinity between the surface and the bottom layer was 1∼3 at spring tide forming a vertically homogeneous estuary, while at neap tide, it ranges up to 7∼15 indicating a sharp salt wedge. The maximum salinity appeared approximately at an hour after the high water, that is, three hours after the landward velocity maximum, while the salinity maximum at around an hour after the low water, that is, three hours after the seaward velocity maximum. The density current speed at a section located 10km landward from the river mouth was observed approximately to be 45cm sec$\^$-1/ at 8m layer.The relations between the salinity at Gupo and the river discharge at Jindong are estimated by means of the least square method. The maximum length of the salt wedge is calculated approximately to be 22km at neap tide and 16km at spring tide, which is in accordance with the observed data. The salinity influence area is deduced to be 45km at spring tide and 35km at neap tide. The diffusion coefficient of salinity was estimated approximately to be 1.5 10$\^$8/$\textrm{cm}^2$ sec$\^$-1/ at Samrak and 8 10$\^$5/$\textrm{cm}^2$ sec$\^$-1/ at Gupo at neap tide, while it was 1.4 10$\^$7/$\textrm{cm}^2$ sec$\^$-1/ at Dongwon at spring tide.

  • PDF