Steep Decline in the Rare Flat Abalone, Haliotis walallensis, Following Fishing Exploitation and a Marine Heat Wave: The Next Neoextinction?

Abstract

Ocean warming is impacting marine systems directly and indirectly via intensifying multiple stressors such as hypoxia, acidification and kelp forest collapse potentially exacerbating neoextinctions. Abalones are extremely vulnerable to both ocean warming and fishing stressors making them marine "canaries in the coal mine". The rare flat abalone, Haliotis walallensis, has been subject to a targeted commercial fishery and then exposed to an extreme marine heat wave. We examine the current status of flat abalone before and after a marine heat wave of 2014-2016 and the concomitant collapse of the bull kelp (Nereocystis leutkeana) forest in 2015. We find that flat abalone density (as assessed in surveys) and abundances (inside deployed "abalone modules") in the core of the range dropped to near zero after the marine heat wave and have not recovered. Further, we examine the status of flat abalone in southern Oregon after both overfishing and the kelp forest collapse and find dramatic declines, especially in former fishery hot spots. Our results show that flat abalone have experienced a major decline and may be an example of a neoextinction in the making. A standardized and well funded status review and proactive restoration plan, if not too late, are both critically needed for flat abalone throughout its range.