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One commenter insisted they were decorative marbles someone had thrown into the lake.
Another claimed aliens were finally invading—but had started with underwater egg deposits.
The discussion became both informative and hilarious.
Eventually, several experienced anglers and fisheries experts joined the conversation.
They immediately recognized what was actually visible in the photograph.
The mysterious craters weren’t mysterious at all.
They were spawning nests.
More specifically, they were known as redds.
These shallow depressions are carefully created by certain fish species, particularly salmon and trout, during spawning season.
Unlike many fish that simply scatter eggs randomly into the water, these species invest considerable effort preparing safe nesting sites.
The process is fascinating.
When spawning season begins, a female fish searches for an area with clean gravel, gentle current, and well-oxygenated water.
Once she finds the perfect location, she begins using powerful movements of her tail.
Back and forth.
Again and again.
Each sweep pushes away sand, mud, and debris.
Gradually, a shallow bowl-shaped depression forms.
This depression becomes the nest.
After preparing it, the female releases hundreds—sometimes even thousands—of eggs into the gravel.
A nearby male immediately fertilizes them.
The female then often moves slightly upstream and sweeps gravel over portions of the eggs.
This provides protection while still allowing fresh water to circulate through the nest.
That constant water movement is essential.
The developing embryos depend on oxygen-rich water flowing around them.
Without it, many eggs would fail to develop.
Looking at the lake from above, people often mistake these nests for strange underwater craters because the fish have cleared away darker sediment, exposing lighter gravel beneath.
Combined with the pale eggs, the nests become highly visible in clear water.
One detail in the photograph attracted particular attention.
Among the pale eggs appeared to be one bright pink object.
Many viewers assumed it was an unusually colored egg.
However, experts explained that it was probably something entirely different.
Sometimes small stones, artificial fishing bait, berries, or other colorful debris become mixed into spawning nests.
Without examining the object directly, it’s impossible to identify exactly what it is.
It simply happened to stand out among the natural eggs.
The discovery sparked another important discussion.
Many people had never realized how vulnerable fish eggs can be.
Because spawning nests often appear in shallow water, hikers, swimmers, and even pets may accidentally walk directly over them.
Doing so can crush delicate eggs hidden beneath the gravel.
That’s why many parks and wildlife agencies encourage visitors to avoid stepping into visible spawning areas during breeding season.
Protecting these nests helps maintain healthy fish populations for future generations.
Artificial lakes can sometimes support spawning fish if conditions are suitable.
Clean water, gravel bottoms, appropriate temperatures, and adequate oxygen create an environment where certain species successfully reproduce.
For many people, discovering fish nests in such locations is a positive sign that the ecosystem is functioning well.
Nature has an incredible way of surprising us.
Something that initially appears mysterious often turns out to reveal an extraordinary natural process taking place quietly beneath the surface.
Most visitors walk past lakes without ever noticing the hidden activity below.
Fish are building nests.