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Birds Responsible for Fish Migration to Isolated Lakes

Birds Responsible for Fish Migration to Isolated Lakes

Friday, 26 June, 2020 - 05:15
Cots and a goose looking for food at Lake Eymir in Ankara on January 17, 2019. (Photo by Adem Altan/AFP Photo)
Cairo - Hazem Badr

A team including Hungarian and Spanish researchers found that fish eggs consumed by birds, and then deposited in a new locale when birds defecate, may be the reason behind finding fish in isolated lakes.


Fish have been found swimming in extremely isolated lakes over the years, raising the question of how they got there. Prior research has shown that most such fish are related to fish in other less isolated areas, which suggests that fish in isolated places must have somehow migrated there.


In their study, researchers from the National Agricultural Research and Innovation Center in Hungary, and the Donana Station for Biology in Seville, Spain, reported that the most obvious explanation for such migration is fish eggs being consumed by birds that carry them in their digestive tracts and then deposit them in a new locale when they defecate. Surprisingly, no one has thought to test this theory until now. The study was published Tuesday in the PNAS journal.


The work involved feeding fish eggs to birds and then retrieving them from their feces at a later time, and then testing them in an incubator to see if they would hatch.


According to a detailed report published by the Science X Network "the researchers fed eight mallard ducks 500 fish eggs each from two kinds of fish (Prussian carp and common.) They waited for the ducks to defecate (which took only an hour on average). They then counted the number of eggs they found and were able to retrieve."


The data from their survey showed that six of the ducks had viable eggs in their excrement, for a total of 18 from all of them. Just 12 of the eggs were deemed viable enough for further testing. Of the 12, only two hatched: one Prussian, one common.


Not very high, but high enough, the researchers contend, to show that it is possible for fish to migrate to isolated lakes in the digestive tract of birds.


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