Preliminary Study Of The Ichthyoplankton Assemblage Structure In Laizhou Bay In Spring And It's Correlation With Environmental Factors

Based on the ichthyoplankton data environmental factors data collected in two surveys conducted from May 28 to June 1, 2008 and from June 14 to June 17, 2008, respectively, in Laizhou Bay, ichthyoplankton species composition, abundance and distribution were studied. Nonparametric, multivariate analyses were used to analyse the influence of environmental factors on ichthyoplankton composition and distribution. The decadal ichthyoplankton biodiversity variations were studied according to historical research in 1982, 1993 and 2003.16 species of fish eggs with total abundance of 14281 ind. and 9 species of fish larvae with total abundance of 1691 ind. were identified in the May survey. 11 species with total abundance of 1596 ind. and 13 species of fish larvae with total abundance of 411 ind. were identified in the June survey.The southern and south-eastern offshores area has the highest ichthyoplankton abundance, especially the south of Laizhou Bay and the area off Penglai. Comparison between two surveys indicated that it was coming to end for most species'spawning in middle of June. Some other species like Setipinna taty had just started spawning.Multivariate analyses showed that the distribution of fish eggs had a significant correlation with environmental factors(r=0.351,p=0.001)while fish larvae had not(r=0.119,p=0.067). BIOENV(Biota-Environment matching)and BVSTEP(Biota- Environment matching using step algorithm ) analyses showed that fish eggs assemblage was infected mainly by surface temperature, surface DO, surface pH value and bottom salinity combined(r=0.410)and fish larvae aaemblage was infected mainly by bottom salinity and bottom DO(r=0.317).The decadal variations of ichthyoplankton sampled in the same location of the Laizhou Bay in 1982, 1993, 2003, 2008 were analysed. The number of species had decreased substantially since 1982. There were highest abundance and lowest biodiversity in 1993 and lowest abundance in 2008. Ichthyoplankton assemblage changed significantly between decades and tended to change more frequently.