Two forces act on the fish, and these are:
1) Its weight mg, downwards and
2) pressure in the string, T, upwards which is 22 N when the string breaks.
In the result of these two forces, the fish had an acceleration of 2.5 m/s^2 in
the upward way.
So, T - mg = m*2.5
=> m = T / (2.5 + g)
=> m > 22 / (2.5 + 9.8) ( when the string snaps )
=> m > 1.79 kg.
As a result, the mass of the fish is more than 1.79 kg as the line has been broken.
