Progressive Deepening in the Depth of Fishing for a Pelagic Fish in the Arabian/Persian Gulf

ABSTRACT Several observations indicate that fish are progressively shifting to deeper waters, with some of the recently proposed key drivers including ocean warming and fishing intensity. While the effect of ocean warming on fish migration has been extensively documented, case studies that examine the relationship between both drivers and the deepening of fish remain relatively limited. Here, we investigate a progressive change in the depth of fishing for the kingfish ( Scomberomorus commerson ), a widely exploited pelagic fish in the Arabian/Persian region, using fishers' perceptions and time‐series datasets of fishing depth, sea surface temperature, and fishing mortality. Our findings show that most surveyed fishers indicated that the overall current mean of fishing depth is 19.44 m, whereas it was 12.43 m when fishers started fishing. Fishers' perceptions were consistent with the fishing depth time‐series, which showed two key observations. First, the depth of fishing increased from 22.81 m (±13.53 m standard deviation) to 29.86 m between 2007 and 2018 (last year of data). Second, fishing deeper, from the shallowest fishing depth (22.81 m) in 2007 to the 2018 fishing depth (29.86 m; ±17.94 m standard deviation), was associated with a sharp increase in fish catch. Regression analysis showed a positive but weak association between sea surface temperature and the depth of fishing for kingfish ( R 2 = 0.2; p = 0.179); while consistent, the association between fishing mortality and fishing depth trends was much stronger ( R 2 = 0.5; p = 0.01) than with sea surface temperature. We discuss the implications for fisheries and management, highlighting the alleviation of the controllable driver, fishing mortality, through effective fishery regulations.