Abstract Mass-mortality events are seldom reported in sea cucumbers (Echinodermata: Holothuria), but here we document a localized mass die-off of giant California sea cucumbers (Apostichopus californicus) in Western Canada from August to October 2021. We recruited volunteer divers to count wasting and healthy sea cucumbers, resulting in observations spanning 500?km of coastline. Reports of dead and wasting sea cucumbers were restricted to Nanoose Bay, BC (Snaw-naw-as First Nation territory, 49°17'N, 124°08'W), with the exception of a single report from Hornby Island, some 55?km away. In Nanoose Bay in 2021, up to 94% of observed sea cucumbers were affected, with healthy sea cucumbers generally observed below 16?m. Following reports of wasting sea cucumbers, population abundance declined sharply. We returned in September 2022 to survey a subset of sites and observed similarly spatially isolated but less severe wasting symptoms. Although the mass-die off in 2021 occurred after an unprecedented summer heatwave, the cause of this event remains uncertain. This case study shows that mass illness events in echinoderms can be geographically isolated and negatively impact local populations.
展开▼
