Ocean
Watch
Friday, April 26, 2002
Some fish migrate between
fresh water and the sea
My mother-in-law is one of my most loyal readers. This
may not sound remarkable, but Claire doesn't live here -- she lives near
Seattle. There, each Friday, this 78-year-old marine biology buff boots up
her pretty blue computer, reads this column online and e-mails me some
insightful comment about the subject.
Occasionally, Claire tells me a story. These tales are
always entertaining, but they sometimes seem to stray far from the subject
of marine biology. After all these years, however, I know better. Her
stories not only end with marine punch lines, they also end with
challenging questions.
Here's an example. Claire recently escorted her
granddaughter to a spelling bee. To show the children how it worked, the
emcee asked for adult volunteers. Claire jumped to her feet.
She got the word DOG. "Is there an alternative
pronunciation?" she asked. No. "What is its origin?" Middle English. "Is
it related to the Washington Huskies?" No.
Claire gave it a stab: "D-O-Q"
It brought the house down.
Then the emcee gave her another word to spell:
CATADROMOUS.
Claire had never heard the word and had no clue how to
spell it. This time her questions were for real.
"Alternative pronunciation?" None. "Origin?" Greek
through Latin. "Use it in a sentence, please?" Aquatic life that lives in
fresh water and spawns in salt water is catadromous.
Well, this woman lives in salmon country and knew the
word anadromous, which means animals living in salt water and spawning in
fresh. With that clue, she spelled catadromous correctly.
That was the end of the story, but I saw Claire's
question coming a mile away. "Does Hawaii have any catadromous or
anadromous fish?"
It's a good question and the answer is a definite yes
and no. We have in-between fish.
Hawaii hosts five native freshwater-saltwater gobies,
called oopu. These fish hatch in streams, and then the tiny hatchlings get
washed into the ocean. There the youngsters drift around as oceanic
plankton and either get eaten or mature. After four to six months,
depending on the species, the survivors head back upstream and start the
cycle all over again.
When young oopu hear the freshwater call, their urge to
swim upstream is strong. These little fish, only a few inches long,
maneuver up the sides of waterfalls, using the suction-cup disk on their
bellies to anchor themselves to wet rocks, and their pectoral fins to pull
themselves up. Since oopu are true fish, they occasionally dip their heads
into cascading water to catch their aquatic breath.
As if fish climbing up waterfalls isn't fantastic
enough, Hawaii also hosts several native shrimp and snails that are also
in-betweeners. The shrimp, called opae, hatch in streams, and after
maturing in the ocean, move up directly through flowing water. Three kinds
of snails also follow this pattern, some spending up to a year in the
ocean. In the summertime, careful observers can see these dark, 1 1/2-inch
snails following each other single file up streams.
Now here's a word for your spelling bee, Claire:
amphidromous (am-FID-dre-mus). It's Greek to Latin, and here it is in two
sentences. Animals that migrate between fresh and salt water after
hatching and before spawning are called amphidromous. Since we humans have
altered all of Hawaii's streams in some way, Hawaii's amphidromous animals
are rare today.
Thanks, Claire, for sharing your great stories.
|