I would say that this is just my hypothetical imagination and see the thing differently. My childish brain accepted this way. But the thing I learnt that helping other creation is also our duty as bird was helping the fishes.
in other way, we are killing sea with waste and may be mother fish don't find foods for kids? and she wished to come out from the water as we very cleverly designed our lands with enough foods. So we also should ensure safe lives below water.
Yes, thanx for thoughtful reply !