cuttlefish
鯣 centers on the cuttlefish, a marine animal related to squid and octopus. The meaning is specific to this creature, with no broader conceptual cluster.
鯣 combines 魚 (fish) with 易, which likely contributes the sound. The character was created specifically for the cuttlefish.
The left side is a fish 魚, and the right side 易 looks like a creature with a head and tentacles. Picture a fish-like animal with waving tentacles: a cuttlefish.
For エキ, imagine extracting ink from a cuttlefish: the ink extraction cues エキ, and the cuttlefish provides the ink.