The present situation of utilization and the effects of artificial reefs on the resource density of Japanese butterfish <i>Hyperoglyphe japonica</i> and red seabream <i>Pagrus major</i> in the waters of the Iki Islands, Nagasaki, Japan

Abstract

The present situation of utilization and the eŠects of artiˆcial reefs on the resource density of Japanese butterˆsh Hyperoglyphe japonica and red seabream Pagrus major in the waters of the Iki Islands

Quantitative assessment of multiple fish species around artificial reefs using environmental DNA metabarcoding

“…In particular, those of P. trilineatum , P. major , and T. japonicus clearly decreased even 150 m from AR1 (e.g., W150 and E150). These results are consistent with previous studies showing a higher density of fishes in ARs than reference sites 2,30,31 . In fact, four dominant OTUs, P. trilineatum , Scomber spp., P. major , and T. japonicus , were known to appear and aggregate in ARs 2,31–33 .…”

“…These results are consistent with previous studies showing a higher density of fishes in ARs than reference sites 2,30,31 . In fact, four dominant OTUs, P. trilineatum , Scomber spp., P. major , and T. japonicus , were known to appear and aggregate in ARs 2,31–33 . Only B. splendens was not reported to be dependent on ARs, although it is highly targeted by fisheries and usually caught by vertical longline at midnight in a deeper zone of this region (depth > 200 m, personal communication, M. Sato).…”

“…Yamane 1 indicated that the total number of Japanese AR projects and proportion of shallow fishing grounds with ARs in 1986 reached 6,443 and 9.3%, respectively. After establishing a large number of ARs in Japanese waters, underwater visual census, surveys using fishery gear, and echo sounder surveys have been used to examine fish aggregation and stock enhancement effects of ARs in Japanese waters 2–5 . These survey methods have advantages and disadvantages.…”

The relationship between eDNA density distribution and current fields around an artificial reef in the waters of Tateyama Bay, Japan

“…Although numerous studies on the effects of ARs on fish aggregation and stock enhancement have been conducted, most of them are not quantitative but qualitative in their assessment (Bohnsack and Sutherland 1985). Few studies have estimated the effect of ARs on gradually increasing fish aggregation and fisheries stocks through quantitative methods (Inoue et al 2018). Artificial reefs have an average lifetime of 30-50 years until they disintegrate.…”

“…After ARs were installed in Japanese waters, underwater visual censuses, surveys using fishing gear, and echo sounder surveys were conducted to examine fish aggregation and stock enhancement effects of the ARs (Polovina and Sakai 1989;Kakimoto 1993;Kang et al 2011;Inoue et al 2018). Underwater visual censuses are effective for species identification, fish counts and size estimations; however identification skills in situ and/or extended investigation times are required for large areas, and it may not be possible at ARs in deeper waters (Sato et al 2021).…”