Blenny Fish Are Invading

It is not easy to be blenny fish especially when they find themselves in water. And as fish, what else is there for them to do? Well, blenny fish have one exciting trait, and that is that they can survive on land as successfully as they can in water. And due to an alarming number of predators plaguing them underwater they are deciding more and more to move to land.

All of this is happening on a remote island located in the Pacific, called Rarotonga.

Previous studies have shown that blenny fish do jump out of the water to escape predators, but scientists could not be sure whether this was the exact and only reason why this behavior occurs. Recent data indicates that this might be the main reason behind their behavior. Their chances to be eaten increase by as much as three times if they spend time underwater, as compared to spending time on land.

Research has shown that almost all of their predators live in the sea with them. When they venture on to land, they only need to worry about birds. To determine this, a team of researchers from Sydney went to Rarotonga Island to examine the various species of blenny fish that can be found there. To determine this, the scientists fabricated 250 plastic blennies. They placed one half into the water and one half on land. The team then observed the mimics for eight days straight. After the eighth day, the scientists realized that the blennies were much safer when they were out of the water. Even the mimics were attacked three times more when they were in the water.

Being picked apart to death by birds is not a fun way to go, but it happens rarely enough for blennies to move to land instead of staying in predatory waters.

While observing the mimics, the scientists also looked at the live blennies. What they noticed is that during low tide the fish moved to the rocks above water. As the tide rose, the fish moved upwards, trying to stay above sea level. So even instinctively the fish try to evade water to be safe from the aquatic predators.

But the team also thinks that avoiding water is not just a survival thing. Lions and bears do a similar thing when they sense danger and climb up trees. But the blenny fish are doing something different. It seems as though they are in the process of moving out of the water and moving onto land permanently.

Even though blenny fish do not have legs, they are reasonably mobile on land. When they exit the water, they do not just stick to one spot, but they move around and interact with one another. There is even one species of blenny fish which spends its entire adult life on dry land and socializes with other amphibious fish.

And the Rarotonga island is not the only place where this sort of behavior is present. Blenny fish are doing the same in Guam, Japan, Tahiti, as well as Mauritius and Seychelles.

As things stand the blenny fish is not yet a land-dweller, but they are getting there. They mostly breathe through their gills, but some of the oxygen absorption is done through the skin. To move around, they use their sausage-shaped bodies as best they can. Their tails even help them to hop across intertidal rocks.

Scientists will have to observe blennies more in the coming years and track their evolution from sea-dwelling fish into full-fledged land-dwellers. This is a fascinating time in the lives of these fish and let us hope that birds do not catch on quickly to their shift.


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