Biology Reference
In-Depth Information
cies of sturgeon—White (
Acipenser transmontanus
) and Green (
Acipenser
medirostris
)—can be found in estuary waters.
White Sturgeon are both the largest and longest-lived freshwater fish in
North America. They attain lengths of over 20 feet, grow up to 1,400
pounds—close to the mass of a small whale—and live up to 100 years. In
California, however, the record is about 10 feet long and 495 pounds. They
have a much stubbier snout than Green Sturgeon have. Green Sturgeon
have slightly shorter life spans, and they are a third the size of White Stur-
geon. Able to reach nine feet long and 385 pounds, they still outlive and
outsize salmon.
Both species of sturgeon enter the bay and travel up the Sacramento
River to spawn. Whites are found as far north as Colusa and Greens up to
Red Bluff. Unlike salmon, they don't build nests and lay eggs in clear moun-
tain streams where everyone can see them, so their spawning habits remain
a mystery. Scientists do know that sturgeon frequent two kinds of habitat in
bay watersheds: they favor 15-foot-deep holding pools, and they release
their eggs and milt in turbulent waters near beds of cobbles and boulders.
Their fertilized eggs settle on hard rock or in the crevices beneath rocks,
where fast-moving water keeps them aerated and prevents smothering by
silt. A single White Sturgeon female can carry up to five million eggs, and
their mass can occupy up to a quarter of her body when she's fully ripe.
As befits their stately lives, adult Green Sturgeon don't start spawning
until they're 11-18 years old—later than any other freshwater fish in North
America. Once they enter the bay, these massive fish spend six to nine
months breeding upriver before returning to the ocean. Juveniles live the
first one to three years of their lives in the river and bay and then head out
to the ocean, not to return for a decade or more. They may grow from an
egg about the size of pearl barley to a fish a foot long in a single year.
Genetic and tagging studies show that the southern population of
Green Sturgeon, which spawns in the Sacramento River, matures far from
natal waters. After attaining a seaworthy size in estuary rivers and marshes,
juveniles swim out the Golden Gate to wander as far north as the estuaries
of Washington and Oregon. “One of the cool things about Green Sturgeon
is that they go on these really long marine migrations,” says sturgeon ex-
pert Josh Israel, now with the Bureau of Land Management. Israel's work
on the species was instrumental in establishing that the Sacramento popu-
lation is genetically distinct from all others along the Pacific Coast. “While
young salmon will go out to the ocean for two to three years, Green Stur-
geon will hang out in the ocean for 10, 15, 20 years. Then, over the course
of their lives, they'll make multiple migrations in and out of estuaries, par-
ticularly in summer.”
Israel chose to study Green Sturgeon because so little is known about
these ancient survivors. “They've been around a long time, but they've
