Nauplii of the brine shrimp Artemia , predominantly Artemia franciscana Kellogg 1906, are the most common live food used in marine larviculture. Through aquaculture activities, this species may get dispersed into nearby saltworks, resulting in competition with, and sometimes extinction of the local Artemia populations. This work assesses, how the Artemia species composition in the Bohai Bay, China, an area with intensive aquaculture activities, has changed over recent years. Seventeen Artemia cyst samples, harvested in Bohai Bay saltworks from 1989 onwards, were used for HpaII analysis of a 1500 bp mitochondrial rDNA fragment in the individual cysts. The results were compared with a database consisting of 133 different populations belonging to all known Artemia species. The sex ratio of the populations was determined through laboratory culture tests. Four different genotypes represented by RFLP patterns typical for parthenogenetic populations, Artemia sinica Cai 1989 and A. franciscana, and one new pattern, very similar to the A. franciscana pattern, were observed. Nearly all samples consisted of varying mixtures of parthenogenetic and A. franciscana and/or A. sinica individuals. The results of the laboratory culture tests were less conclusive due to limited hatching and/or survival in several samples. The fact that the HpaII franciscana genotype shows up in 11 out of 17 samples, demonstrates that A. franciscana has become a competitor - and in view of its competitive advantage, probably a threat - for the autochthonous parthenogenetic Bohai Bay populations. The presence of A. sinica in a coastal environment is a new observation. This expansion of the exotic A. franciscana is discussed in the light of similar observations elsewhere in the world. |
