Basic HTML Version
18
On certain nights during the
spring and summer mooths, saody
California beaches are the scene of
a spectacular display put on by
sma ll si lvery fish called grunion.
By the thousands these fish come
out of the ocean to lay their eggs in
the wet beach sand, in accordance
with a most amazing and uncanny
built-in clock. lndeed, a keen sense
of timing is absolutely essential for
their survival.
Of all the varieties of fish in the
world, only the grunion show such
spawning habits.
To understand sorne of the rea–
sons why the sex life of the grun–
ion is such a remarkable example
of a "living clock," we need to con–
sider sorne facts about ocean tides.
First, there are two low tides and
two bigh tides roughly every 25
hours. Second, the highest tides oc–
cur at the time of the full moon
and at the time of the new moon
(at intervals of about two weeks).
The grunion, with little varia–
tion, spawn at high tide on the
second, third, and fourth nights af–
ter the fuU moon and after the new
moon. This means that they are
spawning after the time of the
highest tides of the month (at a
time when the high tides are de–
clining).
Sex
by
the Clock
Sand is carried away from
beaches when tides are increasing,
so the grunion spawn on nights
and at that time of night when
tides are declining and their eggs
will be covered by sand. If they
spawned at that time of the month
or at that time of night wben tides
were getting higher, their eggs
would be washed away by suc–
ceeding tides and grunion would
become extinct.
Moreover, since it takes about
nine days for their eggs to develop,
they must spawn at a time when
their eggs will have nine days in
the sand before they are washed
free. Eggs which are laid on the
second, third. and fourth nights
following the highest tides will
usually batch from one to three
nights before the next highest tide.
But if the grunion were to spawn
later than these three nights, their
eggs would be washed out before
they were ready to batch.
Finally, it is essential that the
eggs batch within a few minutes
after they are agitated, but not un–
ti!
they are agitated. If the eggs
hatcbed as soon as they got wet ,
they would probably hatch pre–
maturely and the baby grunion
would die. In nature, the vital agi–
tation comes when the eggs are
washed free from the sand by
waves of rising tides.
Thus the grunion must take a
multitude of factors into account
in order to reproduce. No one
knows the exact mechanism con–
trolling the precise timing of
the grunion, but precise it is .
Without this timing, they would
have little chance of survival as a
species.
Yet how did the grunion acquire
their incredible built-in dock? If
they "evolved" their sense of tim–
ing over thousands or millions of
years, the grunion would have
long ago become extinct! Remem–
ber, the timing must be almost
perfect; the eggs must be laid at
just the right time- just after the
highest tide for that month- other–
wise the eggs would be washed
away before they could develop.
And the eggs must develop in nine
days so they will be ready to ha tch
when the next highest month ly
tide comes in . If they aren' t ready
to hatch, the tide will take them
away and they will die.
Truly the clockwork-like sex life
of the grunion is an awesome spec–
tacle. The grunion's incredible and
intricate sense of timing is a pow–
erful testimony to the handiwork
of the Creator.
The
PLAIN TRUTH April 1978