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USGS Report Shows Stagnant Population for Sea Otters

August 22, 2012

The U.S. Geological Survey’s spring census report on sea otter populations was released today. Signs show that the population index of sea otters has increased compared to 2010, however not to the levels we would like to see.  The USGS lists this year’s population index for the southern sea otter at 2,792, an almost 2% increase in the marine mammals’ population index since 2010.

Although a halt in the decrease of the population seems encouraging, these numbers are not strong enough to celebrate. This survey strongly helps reinforce the need to increase the southern sea otters’ range geographically. Small population growth in the center of their geographic range, where maximum sea otter populations exist, suggests that populations could be leveling off.

The survey also reports that 335 otters died last year, close to 12% of the current population. Harmful algal toxins, parasites and infectious diseases, mating trauma, emaciation, bacterial infections, heart disease and boat strikes were some of the main causes of death for the southern sea otter. As well, on top of these causes, the report shows an increase in the number of sea otters attacked and killed by Great White sharks last year, the highest on record. More studies will be needed to determine the recent spike in shark attack rates, but it should be noted that this is an alarming trend.

Friends of the Sea Otter is cautiously optimistic of these results as the increase in population numbers is not yet a sustained trend and recovery is slow. The highest mortality number on record occurred last year, which is still a major concern for us. As well, we are not any closer to discovering the array of reasons for this increase in mortality and we would like to emphasize that disease and pollution are just a piece of this complex puzzle.  Moreover, we need to understand what is causing these populations to stagnate. As studies reveal more information, Friends of the Sea Otter will ensure that our members and followers will be updated accordingly.

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