Guam - If you were in the Pago Bay area last week, you may have noticed dead fish washing along the shore. The area was a dead zone for marine life last week.

According to University of Guam associate professor Jason Biggs, a number of environmental factors could be to blame. "In the summertime, we have really low tides and those tides are so low that most of the reef flat is exposed during the summertime low tides. And the thing with that is that if there is no mixing of water from the ocean, that will actually heat up so much that oxygen levels start to drop."

The scenario resembles what happens when you open a can of warm soda: the soda fizzles over and gas starts to escape. Or, it could've been last week's heavy rains and flooding. Heavy rains combined with low tides could've turned Pago Bay waters fresh. "So if it's super-low tide, but there's only a couple of inches of water that the fish are in, you have four inches of water and it quickly turns it into almost fresh water," said Biggs.  "And a lot of fish can't handle being in fresh water."

Although the Department of Agriculture reports its common for fish to wash-up dead in summer months, Biggs is concerned as this is the first time he's heard of the scenario at Pago Bay, the island's largest estuary. "So it makes me wonder whether or not sedimentation is also a problem," he stated.

"Another thing that can happen is that if there's a lot of mud that flows into the water and it mixes with the ocean all of a sudden the fish are swimming around in muddy water. Well, the problem with that is that the dirt particles are small enough to get stuck in the gills to suffocate the fish while they're trying to breathe in the water."

As of today, DOA fishery biologist Brent Tibbatts reports the area is back to normal with no signs of dead fish.  Biggs urges the public to get involved. If they see dead fish along the shore or floating in the water to collect a sample, freeze the fish in a plastic bag, and contact the marine lab or Department of Agriculture's Aquatic and Wildlife Resources in order to properly identify the cause of death.