Many
species of fish take extreme measures to make sure their eggs survive.
Some migrate thousands of miles, others swim up freshwater rapids to
safer habitat, and others time their spawning just right to avoid
predators and unwanted currents.
One genus of fish, on the
other hand, leaves the water completely to spawn. The grunion is the
only fish known to lay its eggs on land, and is composed of
two species; the California grunion (Leuresthes tenuis), native to
southern California, and the Gulf grunion (Leuresthes sardinas), native
to Baja California. Grunions are very specially adapted to tidal cycles,
and come onto shore to spawn during the highest tides in spring and
summer months. They lay their eggs as the tide begins to recede, so the
eggs will not be washed out to sea until they are fully developed in 8
to 10 days, when the next set of high tides comes to wash the new
hatchlings out to open water. This only happens a handful of times
between March and August, and the timing is easy to predict.
When they do come onto the beach, they come by the thousands, sometimes
tens or hundreds of thousands. Females ride large incoming waves with a
group of males trailing behind. She'll continue to drag herself up
slightly beyond the wave's reach, and there she will begin to drill her
body into the sand until only her head sticks out. As she begins to lay
her eggs (up to 3000) into the sand, the males swarm her and release
their milt around her, which it will slide down her body and to the eggs
underneath. When all is said and done, the males begin to flop back to
the waves first, and the female releases herself and follows them back
to the water. This entire process takes less than a few minutes.
The outgoing tide piles more wet sand on top of the eggs, until they
are buried under ~12 inches (~30cm) of sand. They will remain here until
they are freed by the next high tide cycle, when they will be washed
out to sea and hatch a few minutes after entering the water.
This is an ingenious method of avoiding predators in open water, but it
comes at a cost to the parent fish. There is a threat of predators above
the water, such as birds and crabs and even humans, who visit these
beaches at night during so-called "Grunion Runs" where they can be
caught by hand only (no nets). Still, the species as a whole thrives,
and the eggs are mostly protected underground as they develop.
Sources:
http://www.npr.org/2012/08/17/
http://www.dfg.ca.gov/marine/
Image Source: flickr.com/globe_trotter
Many
species of fish take extreme measures to make sure their eggs survive.
Some migrate thousands of miles, others swim up freshwater rapids to
safer habitat, and others time their spawning just right to avoid
predators and unwanted currents.
One genus of fish, on the other hand, leaves the water completely to spawn. The grunion is the only fish known to lay its eggs on land, and is composed of two species; the California grunion (Leuresthes tenuis), native to southern California, and the Gulf grunion (Leuresthes sardinas), native to Baja California. Grunions are very specially adapted to tidal cycles, and come onto shore to spawn during the highest tides in spring and summer months. They lay their eggs as the tide begins to recede, so the eggs will not be washed out to sea until they are fully developed in 8 to 10 days, when the next set of high tides comes to wash the new hatchlings out to open water. This only happens a handful of times between March and August, and the timing is easy to predict.
When they do come onto the beach, they come by the thousands, sometimes tens or hundreds of thousands. Females ride large incoming waves with a group of males trailing behind. She'll continue to drag herself up slightly beyond the wave's reach, and there she will begin to drill her body into the sand until only her head sticks out. As she begins to lay her eggs (up to 3000) into the sand, the males swarm her and release their milt around her, which it will slide down her body and to the eggs underneath. When all is said and done, the males begin to flop back to the waves first, and the female releases herself and follows them back to the water. This entire process takes less than a few minutes.
The outgoing tide piles more wet sand on top of the eggs, until they are buried under ~12 inches (~30cm) of sand. They will remain here until they are freed by the next high tide cycle, when they will be washed out to sea and hatch a few minutes after entering the water.
This is an ingenious method of avoiding predators in open water, but it comes at a cost to the parent fish. There is a threat of predators above the water, such as birds and crabs and even humans, who visit these beaches at night during so-called "Grunion Runs" where they can be caught by hand only (no nets). Still, the species as a whole thrives, and the eggs are mostly protected underground as they develop.
Sources:
http://www.npr.org/2012/08/17/
http://www.dfg.ca.gov/marine/
Image Source: flickr.com/globe_trotter
One genus of fish, on the other hand, leaves the water completely to spawn. The grunion is the only fish known to lay its eggs on land, and is composed of two species; the California grunion (Leuresthes tenuis), native to southern California, and the Gulf grunion (Leuresthes sardinas), native to Baja California. Grunions are very specially adapted to tidal cycles, and come onto shore to spawn during the highest tides in spring and summer months. They lay their eggs as the tide begins to recede, so the eggs will not be washed out to sea until they are fully developed in 8 to 10 days, when the next set of high tides comes to wash the new hatchlings out to open water. This only happens a handful of times between March and August, and the timing is easy to predict.
When they do come onto the beach, they come by the thousands, sometimes tens or hundreds of thousands. Females ride large incoming waves with a group of males trailing behind. She'll continue to drag herself up slightly beyond the wave's reach, and there she will begin to drill her body into the sand until only her head sticks out. As she begins to lay her eggs (up to 3000) into the sand, the males swarm her and release their milt around her, which it will slide down her body and to the eggs underneath. When all is said and done, the males begin to flop back to the waves first, and the female releases herself and follows them back to the water. This entire process takes less than a few minutes.
The outgoing tide piles more wet sand on top of the eggs, until they are buried under ~12 inches (~30cm) of sand. They will remain here until they are freed by the next high tide cycle, when they will be washed out to sea and hatch a few minutes after entering the water.
This is an ingenious method of avoiding predators in open water, but it comes at a cost to the parent fish. There is a threat of predators above the water, such as birds and crabs and even humans, who visit these beaches at night during so-called "Grunion Runs" where they can be caught by hand only (no nets). Still, the species as a whole thrives, and the eggs are mostly protected underground as they develop.
Sources:
http://www.npr.org/2012/08/17/
http://www.dfg.ca.gov/marine/
Image Source: flickr.com/globe_trotter
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