Influence of sex and body mass on harbor seal (Phoca vitulina) diving behavior

A master's thesis prepared at Western Washington University discusses the impact of harbor seals on fish stocks in the San Juan Islands, where the seals are a year-round predator.

Harbor seal (Phoca vitulina). Photo courtesy of WDFW.
Harbor seal (Phoca vitulina). Photo courtesy of WDFW.

Influence of sex and body mass on harbor seal (Phoca vitulina) diving behavior. MS Thesis. Western Washington University. 2013.

Summary:

Because larger animals have higher energetic needs, they may feed more frequently and at greater volume than smaller members of the same species. The impact of commercial and recreational fisheries on fish stocks is complicated by the presence of these predators. Studies suggest that although they may not be responsible for dramatic declines, they can prevent recovery of depleted stocks.

The author observed dive depth, duration, and number of dives, as well as several other variables, for adult seals in the region.  Seals with greater body mass were observed diving to greater depths and for a longer time than lighter seals, suggesting that they might have a greater impact on prey stocks. Sex of the seal did not influence diving variables.

Download the thesis. 

Author:

A. Sasha McFarland, Western Washington University