salmon
鮭 centers on the fish salmon, a specific type of fish commonly eaten in Japan.
鮭 combines 魚 (fish) with 圭, which likely contributes the sound. The character specifically denotes salmon.
The left side is a fish 魚, and the right side 圭 looks like stacked earth 土. Imagine salmon swimming upstream, leaping over earthen dams to spawn.
For カイ, picture a salmon leaping out of the water and shouting 'Kai!' as it flies through the air: Kai -> カイ.
salmon (Salmonidae spp.)
keiji; juvenile chum salmon
sockeye salmon (Oncorhynchus nerka); red salmon
salted salmon
dried salted salmon
Atlantic salmon (Salmo salmar)
summer-catch salmon
biwa trout (Oncorhynchus masou rhodurus); biwa salmon
grilled salmon
smoked salmon; lox
fresh salmon; unsalted salmon
chum salmon (Oncorhynchus keta)
coho salmon (Oncorhynchus kisutsh); silver salmon
salmon jerky; dried salmon; cured salmon
salmon fishing
canned salmon; tinned salmon
chazuke with salmon