bullhead, (kokuji)
鮖 is a kokuji (Japan-made kanji) for a type of fish called bullhead (かじか). Its meaning is specific to that fish and has no broader conceptual center.
鮖 is a kokuji formed by combining 魚 (fish) and 石 (stone), likely referring to a fish associated with stones or rocky riverbeds, such as the bullhead.
A fish 魚 that lives among stones 石: the bullhead hides in rocky riverbeds.
For かじか, imagine a bullhead fish hiding under a stone, and a child exclaiming 'かじか!' (kajika) when they see it. The sound of the word itself is distinctive and tied to the fish.
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