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Strolling Down the River with a Sea Turtle

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Thursday, October 25, 2012


Hugh's Field Notes from the San Gabriel River

Strolling down the river with a sea turtle. A falcon hunts egrets and grebes. Sea lions creatively foraging in the river. A look at some of my field notes from a summer of Green Sea Turtle research at the San Gabriel River for the Aquarium of the Pacific and NOAA.

Excerpts from Hugh’s Field Notes from Aquarium Sea Turtle Research at the San Gabriel River Summer 2012:

Following a Turtle Down a River

11:05 a.m.: First spotted a medium size green sea turtle swimming just underwater while at DWP discharge station 2 (DS-2) as it was hugging the bank headed downstream.

On a whim I decided to follow it as it journeyed down the San Gabriel River. It swam in shallow water along the East Bank headed toward DWP discharge station 1 (DS-1) which is a little over a football field away (350 feet). Along the way it surfaced twice.

11:10 a.m.: Sea Turtle encountered discharge flow out of DS-1 and used the current like an updraft to bank completely around. It then started swimming back upriver. For about half the way back it swam along the bank before making a 90 degree turn at 11:13 a.m. toward the deeper water in the middle of the river. Once it reached mid-river it again turned upriver and swam back towards DS-2.

11:18 a.m.: Sea Turtle arrived back at DS-2.

Incidental Sightings

Falcon Attack

A Peregrine Falcon was sitting on a pole near DS-2. The falcon was watching a distressed looking pie-billed grebe swimming down river. As the grebe took off and flew near the water’s surface the falcon took off and dove down toward the grebe. The grebe in either a defensive maneuver or after being struck a glancing blow from the falcon hit the water and dove underneath. The falcon went back onto the pole. The visibly shaken grebe came to the surface and stayed on the water as it continued downstream. The falcon never repeated its attack and the grebe never left the water within the observation area.

Peregrine Falcon earlier incident: Last year I observed a falcon (possibly the same?) attacking a Snowy Egret as it flew down the river. This egret also escaped by diving into the water.

Foraging Sea Lions

  • California sea lion corralling a large ball of fish: I observed a young adult male sea lion drifting down the river with a large ball of schooling fish. Occasionally the sea lion would circle the fish apparently herding them back into a ball when the school started spreading out. Every now and then the sea lion swam through the ball and appeared to catch a fish. I observed this behavior for over three hundred yards as the fish and marine mammal drifted downstream. This sea lion was like an aquatic border collie.
  • California sea lion foraging at Edison Discharge Station: A large California sea lion was observed making apparent foraging runs into the discharge station’s cooling water outflow. The sea lion swam into the current and disappeared for several minutes, possibly entering the discharge pipe line. It would then “surf” out of the discharge station riding the current like a body surfer. I used to hear about sea lions entering power plant pipe lines to catch the fish concentrating in there during my marine mammal rescue days. This was the first time that I actually witnessed one possibly doing it.

Never a dull moment on the river.

Strolling Down the River with a Sea Turtle
I followed this sea turtle for over two hundred yards as it swam just off the bank of the San Gabriel River.  | Hugh Ryono
Strolling Down the River with a Sea Turtle
A Peregrine Falcon attacks a Snowy Egret above the San Gabriel River. The egret escaped.  | Hugh Ryono
Strolling Down the River with a Sea Turtle
A sea lion herds a school of fish into a ball in the San Gabriel River. The round dark spot in the water by the sea lion is the school of fish being herded.  | Hugh Ryono
Strolling Down the River with a Sea Turtle
A sea lion prepares to dive into the outflow of the Edison Powerplant along the San Gabriel River.  | Hugh Ryono

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