• Title, Summary, Keyword: Neap tide

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Short-term Variation in Species Composition of Surf-zone Fishes at Daechon Beach, the Yellow Sea of Korea (대천 해빈 쇄파대어류 종조성의 단기 변화)

  • Lee, Tae-Won
    • Korean Journal of Ichthyology
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    • v.13 no.1
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    • pp.32-39
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    • 2001
  • Surf-zone fishes in Daechon Beach, situated at the mouth of Cheonsu Bay, Korea, were collected by a beach seine during the spring and neap tides in August 1999. Short-term variation in species composition was analyzed based on tidal range, tidal level, and time of day. Of 24 species identified, juvenile pelagic fishes predominated in the number of individuals captured. Wilcoxon signed-rank test revealed that the number of individuals was significantly higher during the spring tide than during the neap tide. During the spring tide the fishes were more abundant at the low level than at the high level, while during the neap tide there was no significant difference. The mean density of pelagic fishes did not show significant differences between high and low tides. Demersal fishes were caught mainly in the water below the low level of the neap tide.

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On the Fluctuation of Trawl Fishing Condition in the Atlantic Coast of Africa 1. On the fishing condition of cutle fish, squid and octopus. (대서양 아프리카 연안 트로올 어장의 어황변동에 관하여 1. 오징어, 살오징어, 문어 종의 어황)

  • 김진건
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.13 no.2
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    • pp.27-32
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    • 1977
  • The paper deals the fishing condition of the stern trawlers operated in the Atlantic coast of Africa. The datas are gathered from the Korean stern trawlers operated in the area from June, 1975 to May, 1976. The obtained results are summarized as follows: 1. The mean catch per haul are calculated as, cuttle fish 14.5kg, large size squid(more than :lOOg of body weight) 28.2kg, small size squid(less than 300g) 36.4kg, octopus 47.0kg. 2. Small size cuttle fish(less than5OOg of body weight) are caught much during after spring tide in July to September, yet, large size ClIttle fish(more than 500g) are caught much during neap tide in October to January. 3. Small size squid(less than 300g of body weight) are cBught much during after spring tide in October to December, yet, large size squid(more than 3OOg) are caught much during before spring tide in October to March. 4. Octopus are caught during neap tide in July to August.

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Tidal Exchange Ratio in Masan Bay (마산변의 해수교환율)

  • Kim, Jong-Hwa;Jang, Seon-Deok;Kim, Hae-Yong
    • Journal of the Korean Society of Fisheries and Ocean Technology
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    • v.22 no.3
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    • pp.29-35
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    • 1986
  • The characteristics of tidal exchange in Masan Bay were studied on the basis of salinity observations and current measurements in the summer of 1985. The exchange ratio of the sea water was calculated using three different formulas. The tidal exchange rate was estimated to be smaller than that of another bays in the southern coast of Korea. The tidal exchange ratios in Masan Bay at spring tide were deduced to be 2.4-11.7%. While those at neap tide were 2.0-9.1%. Though tidal range of neap tide is smaller than that of spring tide. the tidal exchange ratio in the bay can be increased in case of highly stratified vertical structure.

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The Characteristics on the Mixing of Freshwater in Suyoung Bay (수영만의 담${\cdot}$염수의 혼합특성에 관한 연구)

  • PARK Cheol-Suck;KIM Jong-Kyu;CHANG Sun-Duck
    • Korean Journal of Fisheries and Aquatic Sciences
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    • v.26 no.4
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    • pp.353-362
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    • 1993
  • Behaviors of effulent are observed and discussed with reference to the tide and freshwater discharge in the estuary of Suyoung Bay. The esturine front is located at $0.5{\sim}1.3km$ seaward from of the Suyoung Bridge at the spring tide, and $0.8{\sim}1.0km$ at the neap tide. After the heavy precipitations, the front moved seaward and was located at $1.3{\sim}2.5km$ southeast of the Suyoung Bridge. Internal Froude numbers in the estuarine salinity front are estimated approximately to be 1 both at the spring and neap tide. Entrainment coefficient decreases down stream to the estuarine front, and then increases seaward from the estuarine front due to the tidal mixing.

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Investigation of Water Quality in the Laver Bed at Yongwon Ri, Changwon Gun During the Spring and Neap Tide in March 1970 (경남 창원군 능동면 용원리 김밭의 수질에 대하여)

  • Won, Chong Hun
    • 한국해양학회지
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    • v.5 no.1
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    • pp.30-36
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    • 1970
  • The water quality of the laver bed at Yongwon Ri, Changwon Gun was investigated during the spring and neap tide in March 1970. The effect of tide on the contents of various chemical constituents was irregular and the variation ranges of the contents were narrow. The pH value during flood and ebb tide was a constant of 8.2. The chlorosity range varied from 19.15 to 19.33g/l, the difference of 0.18g/l being comparatively small for coastal waters. The nutrient salts contents varied irregulary with the change in tide, but nitrite and soluble iron were not detected. In local distribution, chlorosity and silicate- silicon contents were found to be more at Sts. 1, 2 and 3 in the eastern area than at Sts. 4, 5 and 6 in the western area, wheras nitrate and ammonia contents were found to be more at Sts. 4, 5 and 6. The nitrate content was especially high, being twice as much as that at Sts. 1, 2 and 3 in the eastern area. In the spring tide, chlorosity was found, on the average, to be as much as 0.06g/l higher than in the neap tide, but the contents of nutrient salts were higher in the neap tide, especially the nitrate content was twice as much. When compared with other selected local laver beds, i.e., the tidal flats of the Nackdong and Somjin rivers, and of Wan Do Gun, the chlorosity level was highest but the nutrient salts contents level was, in general, slightly lower and the variation ranges narrow in the laver bed at Yongwon ri. The nitrate content, in particular was one tenth smaller than the others.

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The Variation of Current by the Building of Artificial Upwelling Structure ( I ) (인공용승구조물 설치에 의한 유동변화 ( I ))

  • Kim, Dong-Sun;Hwang, Suk-Bum
    • Journal of the Korean Society of Marine Environment & Safety
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    • v.12 no.4
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    • pp.301-306
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    • 2006
  • In order to estimate the characteristics of water movements around artificial upwelling structure, current measurements were carried out along lines E-W and S-N on May 4th(neap tide} and May 30th(spring tide), 2006. In the study area, southeastward flow was dominant during the field observations, and the pattern of water movement in the upper layer above 30m depth was different from that in the lower layer below 30m depth Vertical flow(w-component} around the artificial structure area and western area was shown to be upward flow, but downward flow occurred in the southern, northern and eastern parts at the neap tide. At the spring tide, the ebb current along E-W line showed upwelling flow in the eastern part and western area and showed upwelling flow near the artificial structure area and downwelling flow far away that one. At the spring tide, upward flow was dominant along S-N line during the flood current Volume transport by upward flow was higher than that by downward flow. Volume transport by upward flow during ebb of neap tide was greater than during flood current of neap tide, but was reverse at the spring tide.

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Intraspecific Zonation of the Benthic Amphipod Pontogeneia rostrata in Relation to Diel and Tidal Cycles (저서성 단각류 Pontogeneia rostrata의 종내 대상분포와 주야-조석주기)

  • YU Ok Hwan;SUH Hae-Lip;SOH Ho Youn
    • Korean Journal of Fisheries and Aquatic Sciences
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    • v.31 no.4
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    • pp.500-507
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    • 1998
  • Using a sledge net, the benthic amphipods were taken over one cycle of the neap and spring tides in January 1993 at the sandy shore surf zone of Dolsando, southern Korea. From these samples, we investigated the diel and tidal effects on the intraspecific zonation of Pontogeneia rostrata. The density of p. rostrata was higher during neap tide than spring. Of three categories (adult males and females and juveniles), juveniles and males attained to its highest density during neap and spring tides, respectively. Length- frequency data show that the high mortality of juveniles seemed to occur in winter. In the surface at night, it is significant that juveniles were significantly more abundant during neap tide than spring, whereas both adult males and females were more abundant during spring tide than neap. This suggests that the vortical migration patterns of juveniles and adults vary with the type of tides. During flood of spring tide, more than $90\%$ of population collected at the area above the mean sea level (MSL) were adults. With a decrease of female/male ratio, size of males increased there but that of female did not change, indicating an active migration of large males. This behavior can provide an extension of distribution area far large males, and also give a competitive advantage to large male against small one for mate and feeding. Although adult p. rostrata was collected at 100 cm above MSL at night during spring tide, a major portion of population as usually present on the shore below MSL. The center of zonation was restricted from 50 cm to 250 cm below MSL.

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The Characteristics of Tidal Current and Water Mass in the Narrow Channel 1. Tidal Current and Water mass in the Chungmu Channel (협수로의 수리 특성과 수괴구조 1. 충무수로의 조류와 수괴구조)

  • Park, Byung-Soo
    • Journal of Fisheries and Marine Sciences Education
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    • v.13 no.2
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    • pp.168-177
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    • 2001
  • The flow pattern and water mass structure in the Chungmu channel were investigated using the field observations during June and July, 2001. The currents in the channel may be regarded as a hydraulic current decided by difference of tide levels between two sides in the channel. The strongest current in the channel occurs around in high water and low water. The coefficient C to be determined the characteristics of velocity in the channel was obtained from an equation, $u=C{\sqrt{2gh}}$ and ranges from 0.37 to 0.65 in the Chungmu Channel at the spring tide and from 0.23 to 0.37 at the neap tide. Eastward tidal transport is usually larger than that of westward transport in Chungmu the Channel. Sea water exchange rates are 39.2% in spring tide and 20.5% in neap tide respectively. The water mass structure in the channel is changed by the speed of the tidal current. The water mass is well mixed at the high water when the current is strong and is stratified at slack water when the current is weak.

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On the Tides, Tidal Currents and Tidal Prisms at Inchon Harbor (인천항의 조석, 조류 및 조량에 대하여)

  • Yi, Sok-U
    • 한국해양학회지
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    • v.7 no.2
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    • pp.86-97
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    • 1972
  • The tides, tidal currents and tidal prisms at Inchon Harbor are studied with recent data. The tides at Inchon Harbor is of semi-diurnal type having a spring range of 798cm and a phase age of 2 days. The monthly mean sea level at Inchon has a maximum at August and a minimum at January with a annual range of about 40cm. the tidal currents at Inchon Outer Harbor are of semi-diurnal type same as tides and nearly reversing type. The flood and ebb currents set north and south with a velocity of about 90-175 cm/sec and 120-225 cm/sec at spring tide and begin 0.2 hours after L.W. and 0.7 hours after H. W., respectively. Non-tidal currents flow southward with 10-20 cm/sec at west side of the stream and northward with 15-20 cm/sec at east side of the stream at Inchon Outer Harbor. The flood volume through the Inchon Outer Harbor fluctuates fortnightly from 590 10$\^$6/㎥ spring tide to 260 $10^6/m^3$ at neap tide and ebb volume changes from 470 $10^6/m^3$ at spring tide to 200 $10^6/m^3$ at neap tide, respectively. The flow area along the channel to the Estuary of Yeomha is controlled by the tidal prism as expressed by $A=1.14{\times}10^{-4}P^{0.966}$

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CIRCULATION DYNAMICS OF THE KEUM RIVER ESTYARY (금강 하구의 해수순환역학)

  • Chung, Jong Yul;Lee, Jae Hak;An, Hui Soo
    • 한국해양학회지
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    • v.18 no.2
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    • pp.142-148
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    • 1983
  • In order to understand the circulation dynamics of the Keum River estuary, an extensive study was conducted; (i) variability of salinity boundary layer (ii) fluid dynamic characteristics (iii) tides and tidal currents (iv) circulation, diffusion, and dispersion (v) numerical modelling. As first part of this series of work, the salinity data obtained at six sites by using instantaneous profil]ing technique were analyzed in detail. it is found that the amplitude of salinity variation increases toward the upstream direction and its magnitude is greater at neap tide than spring tide. And also duration of salinity boundary layer is much longer during the neap tide than the spring tide, As a result of this study, the Keum River estuary is classified as a typical standing wave type estuary. Finally, we present a schematic diagram for the duration of the salinity boundary layer, which will be useful for further study on flocculation phenomena and sedimentation dynamics.

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