Comparison of abalone (Haliotis discus hannai) catches in natural habitats affected by different current systems: Implication of climate effects on abalone fishery

Climate variability influences fishery production in a variety of ecological processes. There are increasing concerns with ecosystem level impacts of climate variability on fisheries. To understand climate effects on abalone fishery, two climate indices, Arctic Oscillation Index (AOI) and Aleutian Low Pressure Index (ALPI), were compared to abalone catch fluctuations in Hokkaido and Miyagi regions in Japan, affected by the Tsushima Warm Current (TWC) and the Kuroshio and Oyashio Currents (KOC), respectively. The species compositions and trophic structures of benthic communities in natural habitats of abalone Haliotis discus hannai were investigated at Iwanai (Hokkaido) and Tomarihama (Miyagi) coasts. The long-term catch fluctuations were closely related with AOI and ALPI for Hokkaido and Miyagi, respectively. Species replacement from a competitor gastropod Homalopoma amussitatum to a congener H. sangarense was detected in Tomarihama, showing that the latter is non-competitive with juvenile abalone. Species interactions appeared different, possibly affecting recruitment success: favourable [weak competition and weak predation] at Tomarihama and unfavourable [strong competition and strong predation] at Iwanai, setting up a hypothesis for the recent notable catch increase in the KOC region. This study highlights that climate variability could influence benthic fisheries by changing species interactions in a benthic ecosystem.

► Abalone fisheries were compared between coastal waters affected by different current systems.
► Long-term catch fluctuations were different between two abalone fishing grounds.
► Species replacement and changed trophic interactions were suggested during last decade.
► Climate effects on abalone fishery could work in different ways via ecosystem level effects.