Ichthyofaunistic biogeography of the Japan (East) Sea

Aim The aim of the present study is the distribution analysis of species richness of ichthyofauna at the east and west coasts of the Japan Sea for the purpose of identification of natural biogeographic boundaries, subsequent faunistic zoning and comparison between faunistic and bioclimatic (bio-oceanographic) zoning patterns. Location Japan Sea (Korean-East Sea). Methods All statistical procedures are based on well-tried and widely accepted numerical methodology and the STATISTICA program package. For identifying the statistically meaningful (non-random) maxima and minima in species richness, arithmetical differences in the number of species at ith and i + 1st latitudes are calculated, also trend residuals obtained by smoothing, the moving average by three points and residuals in polynomial trends are analysed. Subsequent clustering of species lists for separate biogeographical units marked by local maxima and minima in species richness permits to identify the extent of mutual correspondence between the units and to make an outline for faunistic zoning. Similarity degree of faunistic lists was estimated in terms of Czekanowski-Sorensen coefficient. Results Quantitative analysis of latitudinal distribution of species richness (1130 species) of the Japan Sea ichthyofauna is indicative of the position of the following 10 local maxima and minima: at 35, 40, 43, 47, 49 and 51 degrees N on the west coast and at 36, 39, 43 and 46 degrees N on the east coast. In most cases local minima of the polynomial trend residuals are coincident with southern boundaries of faunistic units while local maxima with northern boundaries. Separated analysis of qualitative composition of ichthyofauna of the west and east coasts of the japan Sea discloses 11 areas of the greatest faunistic similarity. Main conclusions The latitudinal variations in the species richness near both sea coasts represent an alternation between relatively flattened smooth portions (each 1 unit long) and sufficiently steep jumps between them. Regular interchange between local minima and maxima of species richness is accountable to spatial non-uniformity of hydrological structure resulting from alternation of variously directed and differently heated (warm and cold) circulations of waters and frontal zones. It is notable that faunistic zoning does not initially require any exact knowledge of biotic taxonomic composition and may be produced only from the variation pattern of the species richness under study The suggested faunistic zoning scheme distinguishes the following provinces: South Korea, East Korea, South Primorie, North Primorie, Northern Japan Sea, Middle Honshu, Uetsu, Tsugaru, Soya and West Sakhalin. The comparison between faunistic units and distribution of temperature parameters and currents permits identification of subarctic, cold-temperate, mild-temperate and warm-temperate bioclimatic zones existing in the Japan Sea.