This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
鱊 is a rare character combining 魚 (fish) with 矞, which likely contributes sound. The exact historical development is uncertain.
With 魚 (fish) on the left and the complex 矞 on the right, this kanji likely relates to a type of fish or a fish-like creature, but its exact meaning is obscure.
For イツ, imagine a rare fish that makes a sharp 'itsu!' sound when caught: itsu -> イツ, and the fish component 魚 reminds you it's a fish.