Long-term fluctuation in the abundance of abalone and top shell in Japan and factors affecting those fluctuations

Abstract

We studied the trend of long-term fluctuation in the abundance of abalone and top shell catch in Japan and examined the relationship of those long-term fluctuations with global climate change. Trend of fluctuation index (TFI) was derived from time-series of yearly catch in five sea areas around Japan by removing the dependence of amplitude of catch fluctuation on its level and calculating the slope of regression line at each year. Approximately two decadal scale fluctuations were found in TFI of each resource. There were significant positive correlations between TFI of three abalone species (Haliotis discus discus, H. gigantea, H. madaka), which inhabit in four sea areas influenced by the warm currents, and moving means of Aleutian Low Pressure Index (ALPI). In two sea areas along the coast of the Pacific, TFI of these three abalone species was positively correlated also with that of agar, red algae belonging to the Gelidiaceae. In contrast, TFI of H. discus hannai, which inhabits in one sea area influenced by the cold current, was negatively correlated with ALPI or TFI of agar. We could not find any coherent relationship of TFI of top shell, Turbo (Batillus) cornutus, with ALPI or TFI of agar. The results of this study suggest the possibility of the influence of global climate change to the long-term fluctuation in the abundance of rocky shore resources, which have been thought to be “local” stocks, and of the difference of such influences among species.