In a new study published in the journal PNAS on June 22, 2020 researchers from Hungary and Spain have found that fish can migrate to highly isolated lakes through the digestive system of birds.
These birds eat eggs of fish, and then hatch eggs that survive and out through their litter in the new places that they migrated to.
Fish in isolated lakes
Over the years, scientists have found fish swimming in highly isolated lakes, which have raised many questions about how they got there.
Previous research showed that most of these fish are associated with fish in other, less isolated areas, suggesting that fish in isolated locations must have migrated in one way or another.
Scientists have suggested that the most obvious explanation for such migration is that fish eggs are consumed by birds that carry them in their digestive systems, and then put them in a new place when excreta comes out, but no one has thought about testing this theory before.
In the new study, researchers sought to test this theory through scientific experiment, and the research team from the Danube Research Institute, the National Center for Agricultural Research and Innovation in Hungary, the Diana Biological Station in Spain and the National Council for Spanish Research "CSIC" reported that it is possible Fish eggs can survive the flight through the birds' digestive system, after which they hatch.
Bird droppings theory test
The researchers experimented with feeding birds with fish eggs, then trying to retrieve the eggs from the feces of the birds at a later time, and then tested these eggs after placing them in an incubator to see whether they will hatch or not, after passing through the flight into the bird's digestive system.
Specifically, the researchers fed 8 "ducks" with 500 fish eggs for each fish species (Prussian carp and common carp), and they waited for the ducks to take out their droppings, it took only an hour on average, then they calculated the number of eggs they found and were able to retrieve them .
The wild ducks that were tested are migratory birds, also known as "vegetable ducks", and they usually live in lakes and swamps, and it is well-known as "wild" because there is another species raised in rural homes and farms.
After the survey conducted by the researchers, the data showed that 6 of the ducks had leftovers containing viable eggs, and 18 of them were found, of which only 12 were subject to work and more tests.
Of the 12 eggs, only two were hatched, one for a Prussian carp and the other for a common carp, and the figures showed a survival rate of 0.2%.
The researchers confirm that the final number of eggs that have survived and hatched was not very high, but it was sufficient to demonstrate that it is possible for fish to migrate in the digestive system of birds.
And for some types of carp it is observed that it requires only one individual to reproduce, because it reproduces sexually.