LOS ANGELES (REUTERS)- Guadalupe fur seals, a threatened species that breed off Mexico and normally spend much of their time at sea, have washed up dead and dying in record numbers along the California coast this year, another apparent casualty of warming ocean temperatures.
At least 80 emaciated fur seals, mostly pups, have been found beached along the central California shoreline since spring, compared with the 10 to 12 such strandings documented in a typical year, according to US government scientists.
The strandings were declared an "unusual mortality event" by the National Oceanic and Atmospheric Administration (NOAA), a designation that brings greater scrutiny of marine mammal biologists, and sometimes greater research funding.
Of the total strandings, 42 of the seals were found dead. But of the 38 recovered alive, only 16 survived to be released back to the wild, Justin Viezbicke, the West Coast marine mammal strandings coordinator for NOAA Fisheries said on Wednesday (Sept 30).
The die-off coincided with a much larger mass beachings of starving California sea lions, which unlike fur seals tend to remain fairly close to shore.
Roughly 3,500 stranded young sea lions have been recovered alive along the California coast since January - by far the most in any single year.
That figure does not include an uncounted number left dead and dying by overwhelmed rescue teams at the height of the strandings in March and April, Viezbicke said. The fur seal crisis peaked in May.
Scientists believe sea lions fell victim to a scarcity of natural prey that forced nursing mothers to venture farther out to sea for food, leaving their young behind to fend for themselves for longer periods of time.
The disrupted food chain around sea lion rookeries off Southern California was linked to unusually weak winds that have kept ocean temperatures abnormally high in the Eastern Pacific. Stronger winds normally pull nutrient-rich cooler water from the depths of the Pacific to the surface, and with it larger supplies of sardines, smelt, squid and other prey.
This winter's El Nino effect, which alters ocean currents and temperatures, may compound the situation when it arrives, experts say.
NOAA scientists theorize that strandings of Guadelupe fur seals, which depend mainly on squid, may be driven by a similar dynamic. But less is known about the fur seal, which is thought to number about 15,000, as compared with a California sea lion population estimated at 300,000 animals.