Doctrine of karma---reaction to an article

An author of an article on Karma in Bhavans journal  was playing the devils's advocate in his supposedly first instalment [the next issue didn't carry the next  instalment with alternate arguments] by questioning the irrationality of this doctrine by posing the question as to how a fish condemned to its lowly state due to its previous karma know that it was suffering due to its past deeds?So this doctrine is laughable as there is no repentance.

To my knowledge the doctrine of karma is propounded for the benefit of a human being with his sense of right and wrong ,who is warned of the pitfalls that await him in due course of time ,if not  then in his next birth ,that of being born as a lowly form of life without any power of reasoning.It is not necessary for the fish to know its former birth but for human beings endowed with reason to know that a birth as a fish may await that person as a result of his karma / deeds.
That person could be born as better person viz,in a good family with scholarship and prosperity.Even then that person enjoying the fruits of past deeds has no knowledge of his prior birth because  Sri Krishna has said in the Gita "Arjuna i have the knowledge of my previous births [as a bhagwan] but you as a mortal do not have",must be taken by all reposing faith in karma doctrine  as its justification  and rightly so.Learnt this
by personal experience.
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