ASTORIA (AP) — It’s 6:30 a.m. in Astoria’s East Mooring Basin. The sun is just coming up, boats are leaving the harbor for a day of fishing, and six men sneak up and drop a cage door on 11 California sea lions lying on a floating trap in the harbor.
   Now the men, all employees of the Oregon Department of Fish and Wildlife, corral the animals into a series of smaller cages tied together on a connecting barge, where hot branding irons are waiting to number their hides.
Sea lions in the Columbia
   A cacophony of barking fills the harbor from the dozens of sea lions lying on the dock nearby. California sea lions are a type of marine mammal called a pinniped, and hundreds of them travel up the Columbia River every year to find food in between mating seasons.
   The Port of Astoria has conceded an entire dock to these hefty pinnipeds, some weighing as much as 800 pounds.
   The floating cage sits beside the dock, luring sea lions to sleep on it at night.
   The men, led by department biologist Matt Tennis, bang on the sides of the cage to scare the sea lions into a smaller trap on the barge, where the branding takes place. The first sea lion to go onto the barge is often a veteran, one that’s already been branded, according to Tennis.
   Process ‘isn’t harsh’
   ‘‘That shows me the procedure isn’t harsh on them,’’ he said. ‘‘Usually, a pilot sea lion will lead the others through. One has been through 17 times. It’s the naive ones that are scared; they haven’t been through yet.’’
   When an unmarked sea lion passes through the cages on the barge, he lands in the metal claws of a collapsible trap that looks like two warped bike racks fitted together on a hinge.
   He groans and squirms as the bars close down on him.
   The trap holds the animal in place while department workers take measurements and attach tags to both flippers.
   The back quarter of the trap is then opened to reveal a section of the sea lion’s backside.
   Tennis stands on top of the trap and steadies the hide with his foot while Bucky Barnett hands him a glowing red branding iron. The hot metal hisses as it touches the sea lion’s fur, and an acrid, yellow smoke billows out from the trap and hovers over the barge.
   The sea lion is quiet as Tennis burns a permanent ‘‘C’’ into his skin.
   Tennis proceeds to burn the numbers 5, 8 and 3 onto the animal’s back, each with a separate branding iron — none of them eliciting so much as a groan. When the branding is done, officials open the claws of the trap, and C583 hops out and splashes off the barge.
   From now on, this sea lion will be known as the 583rd captured on the Columbia River since the department started the branding program in 1997.
   Why brand a sea lion?
   As the original sea lion project leader in Astoria, Barnett started studying the impact of fishermen on sea lions for department in 1990. But over the years the key issue has become how sea lions affect salmon.
   An exemption
   Sea lions are protected under the Marine Mammal Protection Act, which imposes strict rules on how they can be handled.
   However, certain sea lions, like the ones that have been preying on fragile salmon runs passing through Bonneville Dam, could qualify for an exception under the law.
   And the branding program helps officials identify the culprits.