Answer:
川+田 SEN, kawa - river / DEN, ta - paddy field
春 SHUN, haru - spring
占 SEN, shi(meru), urana(u) - occupy, hold, tell fortunes
旨 SHI, mune - purport, content, instruction
伏 FUKU, fu(su), fu(seru) - bend down, lie down, turn over, conceal
They all take the "fish" radical (魚 GYO, sakana, uo - fish) to become other characters.
鯔 bora - flat head grey mullet
鰆 sawara - spanish mackerel
鮎 ayu - sweetfsh
鮨 sushi
鮲 made, kochi - mullet