He usually ______(not like) fish,but to-day he ____(like) it very much

doesn't like, likes
根据句意，不喜欢吃鱼是一般性的行为，且今天很喜欢。故第一个空，第二个空都用一般现在时。

doesn't like,likes

He usually does not like fish, but today he likes it very much.

He usually does not like fish, but today he liked it very much.

他通常不喜欢（吃）鱼，但是，今天他却很喜欢（吃）鱼。

通常情况，用现在时。但今天他吃了鱼，而且还很喜欢。所以是过去时。