Composition And Distribution Of Zooplankton In Surf Zone Of Sandy Beach In Si Jiao Island And The Correlation With Fish Larvae And Juveniles

Composition and distribution of zooplankton in the surf zone of sandy beach in Si Jiao Island were studied. Based on the data of fish larvae and juveniles at 8 stations in the surf zone of sandy beach in Si Jiao Island and the data of diurnal variation of fish larvae and juveniles in the surf zone of sandy beach at Tian’ao, Si Jiao Island, the correlation between zooplankton and fish larvae and juveniles were discussed.In order to find out the composition and seasonal changes of zooplankton in the surf zone of sandy beach in Si Jiao Island, zooplankton were collected at the 8 stations by a zooplankton net(0.3 cm mouth-diameter, 0.2 mm mesh-aperture) during the spring tide each month from August 2010 to August 2011. During the study period, 67 species and 10 kinds of planktonic larvae were collected. It included 56 crustacean species(43 copepod species,3 cladoceran species and other 10 species), 4 chaetognath species, 7 medusa species. There were 13 dominant species in total, such as Paracalanus parvus, Paracalanus crassirostris and Centropages dorsispinatus. The zooplankton in the surf of sandy beach in Si Jiao Island could be divided into four ecotypes: estuarine low salinity group(2 species), offshore warm temperate group(2 species), offshore warm water group(52 species), and eurytopic group(5 species). The results indicated that, zooplankton community in surf zone of sandy beach were most offshore warm water group. Affected by salinity, water temperature, ocean current and other environmental factors,seasonal changes were obvious. In spring, the mean density of zooplankton was highest, lowest in winter.To clarify diurnal variation of zooplankton in the surf zone of sandy beach at Tian’ao, this work was set up during the spring tide period from December 2010 to August 2011, using a zooplankton net( 0.3 cm mouth-diameter, 0.2 mm mesh-aperture). The sampling was taken every 4 hours from 16:00 to 12:00 the next day. The speciments were fixed in the formalin of 5% concentration. The water temperature and salinity were measured at the sampling spot. During the study period, 36 species and 6 kinds of planktonic larvae were collected. It included 31 crustacean species(23 copepod species, 1 cladoceran species and other 7 species), 1 chaetognath species, 4 medusa species. The number of Paracalanus aculeatus was largest, next was Paracalanus crassirostris. The results showed that the diurnal density of zooplankton was higher in day than at night, except winter. And the species number was also higher in day.According to the analysis of the data of zooplankton and fish larvae and juveniles, the results showed that zooplankton and fish larvae and juveniles in surf zone of sandy beach in Si Jiao Island, especially in Tian’ao diurnal survey, to some extent, changed with the same rhythm, such as terms of illumination, tides.