I’ve heard theories like red tide. The die offs of mammals, birds, fish, sea stars etc - no one has a good answer or proof.
Japan’s Salmon
http://russgeorge.net/2017/01/31/japanese-salmon-fisheries-in-historic-collapse/
KIng Salmon
http://juneauempire.com/local/2017-03-06/spring-king-fishing-canceled-emergency-order
Chinook Salmon
https://www.facebook.com/TheYurokTribe/photos/a.153436974726777.36742.140327912704350/1542536569150137/?type=3&theater
Chum Salmon
https://www.undercurrentnews.com/2016/11/17/japan-chum-salmon-landings-the-worst-in-24-years/
Starving Alaskan Sea Birds
http://www.ktuu.com/content/news/Following-last-years-massive-die-off-of-Alaskan-seabirds-scientists-still-looking-for-answers-413757753.html
Murres and tufted puffins dying due to lack of fish to eat
http://www.ktuu.com/content/news/Following-last-years-massive-die-off-of-Alaskan-seabirds-scientists-still-looking-for-answers-413757753.html
Unusual Mortality Event: Whales
http://www.nmfs.noaa.gov/pr/health/mmume/faqs_2015_large_whale.html
Sea Star Wasting disease:
http://www.eeb.ucsc.edu/pacificrockyintertidal/data-products/sea-star-wasting/
Lots and lots of articles about whales and pinnipeds. Geographically dispersed etc.
Fukushima, it starts and ends when the radiation quits leaking into the sea, then maybe about 100,000 years later more or less. That disaster is the worst nuclear accident ever, and still has not ended. It puts the Russian meltdown to shame.