The Marine Mammal Center’s Harbor Seal Health Study

Harbor seal health project – June 25, 2008 Update

Click on a link below to download google earth files of the last ten days of transmissions for the 3 separate releases:

Cypress PRC released 6/7/08
Fitzgerald moonlight releases 6/18/08
Fitzgeral PRC released 6/28/08

Click on a link below to view images of the last ten days of transmissions for the 3 separate releases:

Cypress PRC released 6/7/08
Fitzgerald moonlight releases 6/18/08
Fitzgeral PRC released 6/28/08

Examples of Harbor seals outfitted with satellite tag and red hat tag

As part of the next phase of The Marine Mammal Center’s Harbor Seal Health Study, a group of harbor seals have now been released with satellite tags to track their survival and location, and the first data are coming back. The goal of this project is to evaluate human impacts on the health of wild harbor seals by examining differences in health profiles, disease exposure, and contaminant levels among stranded harbor seals admitted to the Center, and wild caught harbor seals at two locations (SF Bay- heavily influenced by human activities, and Tomales Bay – more pristine). There are four specific objectives for the project:

Objective 1. Estimate survival for stranded and wild caught harbor seal pups and investigate whether survival probability is correlated with health status and contaminant level.

Objective 2: Determine whether the prevalence of pathogen exposure in stranded harbor seals reflects prevalence in the wild population.

Objective 3: Determine whether there is a difference in prevalence of pathogenic, zoonotic bacteria in animals from San Francisco Bay compared to those from Tomales Bay.

Objective 4. Measure levels of persistent organic pollutants among the three groups and identify factors resulting in any differences

Harbor seals outfitted with satellite tags are released at Pebble Beach in Monterey on June 7, 2008.

Last year we used colored and numbered hat tags to estimate survival, and while we were able to get some data on individual animals, they traveled further than we expected, making them extremely difficult to keep track of. This year we were able to upgrade our technology and purchase satellite tags. The tags use the government’s NOAA satellites to triangulate a seal’s position (latitude and longitude) and then transmit the location to a service which decodes it and forwards it to us. Because we’re hoping to get transmissions until the seals molt their pup coats in Apr/May 2009, the tags are programmed to transmit every other day to extend the life of their batteries. This means we will receive general information about dispersal patterns, but not at a scale that allows us to track their movements by the hour or by the day.

We started putting tags out in May and currently have 30 tagged seal pups. Already they have traveled further than expected, ranging from Humboldt County down to Mexico. Here is a map of their recent locations. We plan to create a map separating out pups rehabilitated at The Center from the wild seals, however the raw dataset is only sent to us once a month, so this particular analysis will not be real time. Stay tuned for more information.

Click here for photo album.

Click here for flyers to print and distribute.

The Marine Mammal Center’s marine biologist, Denise Greig, is conducting a study of the effects of pollutants and environmental factors on San Francisco Bay Area harbor seals, and is requesting the help of the public to report sightings of the seals along the California coast.  The Harbor Seal Health Project will attempt to shed some light on the prevalence and health effects of marine contaminants in the San Francisco Bay Area. The rehabilitated seals included in the study are released with “hat tags”, brightly colored hat-shaped tags with numbers that identify each animal. Members of the public who view one of the seals outfitted with the tags should take care not to disturb the animal. They are asked to note the number and color of the tag, the location of the sighting, and the general condition of the animal, and report the data to The Marine Mammal Center’s 24-hour response hotline at (415)289-7350 or sealhat@tmmc.org.

“The harbor seal’s coastal habitat is influenced by human-produced pollutants including sewage, agricultural and surface runoff, and industrial pollution,” says Greig. “Our study may tell us if exposure is affecting seal health, and the seals in turn may tell us about possible impacts on human health. If the seals are affected by pathogens and contaminants in the marine environment, then it is possible that people, who feed at the same level in the food chain, could be affected as well.”

In May, June, and July, harbor seals were released wearing the hats, as well as short-range radio tags to track them locally. How they and future seals released with the hat tags fare is all part of the data that Greig will collect. The data collection relies heavily on community outreach and awareness of the program. The effectiveness of the public in reporting sightings of the seals will be an essential factor in the success of the program. If you would like to help spread the word to the public about the study, you can print out flyers, available by clicking the link above, and distribute or post them in California coastal communities.