If you go to Hokkaido and don't eat the seafood, there's no point in going.
Literal
Hokkaido [to-に] go-[if-たら], as-expected sea's-bounty [object-を] don't-eat-if go [of-の] meaning [subject-が] not-exist probably.
やっぱり ('as expected, after all') is a colloquial filler of conviction — 'of course.' 海の幸 literally 'sea's happiness/blessing' is a poetic, traditional word for seafood — richer than 魚 or シーフード. 食べないと行った意味がない combines negative conditional と ('if not') with 行った意味 ('the meaning of having gone') + がない. A recommendation phrased as a near-warning.