To calculate how many fish can be found in 1/3 of the pond you must first calculate the size of this.
To make calculations we use different types of units of measurement, in this case the meter measures the distance between two points in one direction.
The square meter measures the area of a surface, that is, the meters in one direction for each meter in the other.
The cubic meter measures the volume of an object, that is, the meters in one direction for each meter in each of the other two.
For this case we have a pond with an area of 34 square meters and a depth of 34 meters, that is 34
* 34
= 1156
*
* must remember that the units of measure should always be operated
Now, the density tells us the amount of objects or matter in a given space, in this case 12 in 1
, then in this pond would fit

= 13872 fish so that in 1/3 of tank would fit 13782 / 3 = 4624 fish
Answer
In 1/3 of the lake you can find 4624 fish