By Raza H. Tehsin & Arefa Tehsin
Udaipur city in India is known as the city of lakes. The three lakes inside the premise of the city are – Pichola, Swaroop Sagar and Fatehsagar. All the three lakes are connected to each other. Pichola is directly connected to Swaroop Sagar and Swaroop Sagar is connected to Fatehsagar by a canal that has two sluice gates to regulate the excess water.
Prior to 1989, there were scanty rains for five consecutive seasons. For the years 1987-88 there was no exchange of water between Fatehsagar and Swaroop Sagar. In 1989 there were good rains and all the lakes overflowed.
During this season Swaroop Sagar received plenty of water. By opening the gates the excess water of Swaroop Sagar was taken into Fatehsagar. When both the lakes were full the gates were closed. Because the level of water in both the lakes was the same, there was no seepage from the gates. When the gates are closed, a portion of the gates remains about 4 feet above the water level.
On 7th Sep 1989, we were standing near the two sluice gates of the canal. At about quarter to six in the evening, suddenly a Rohu (Labeo rohita) broke the surface of the water about 9 feet from the gates and cleared the first gate. The height of the gates above the surface of the water was 4 feet.
Now it was trapped in the water of the canal between the two gates. After a lapse of 5 minutes, it took yet another jump which was very high and cleared the next sluice gate. It landed squarely into Fatehsagar and went off. This time during the jump it grazed to the channel of the gate before landing into Fatehsagar.
We measured the height of the jump. The distance between the surface of the water and the place on the channel where the Rohu touched it fully was 11 feet and 9 inches. Such a high jump, almost perpendicular to the surface of the water, by a Rohu is remarkable.
How did the fish know that if it cleared one obstacle it would land in water and not on ground? How did it know that after clearing yet another iron gate it would land in the large water body? What did it not jump on either side of the gate? Extensive researches have been done lately on fish intelligence.
According to the fish scientist Dr. Culum Brown of Australia, these observations are fine examples of spatial learning in fishes. It is fairly known these days that fish have the capability to form mental maps in their heads.
Having visited a location (perhaps at high water, or when the gates were open) the fish is quite capable of remembering where that location is. There is a fantastic study done in rockpool fish that have learnt the location of all the surrounding rockpools and are capable of jumping between them at low tide.
Nature is what we know But have no art to say, So impotent our wisdom is To Her simplicity.
- Emily Dickinson