Start with the loop, not the leaderboard
Claw Fishing is built around a repeating cycle. You travel by boat, use the claw to catch fish, return those fish to your aquarium, and let the aquarium generate income. That income supports future upgrades and access to more demanding areas.
Take your boat to a fishing area
Treat the boat as your route between the aquarium and the water. Before chasing a distant area, make sure you can complete the full trip comfortably and return with a catch.
Use the claw and watch what you catch
Lower the claw, recover a fish, and pay attention to the information the game shows you. Those visible labels and income values are more useful than an unsourced list elsewhere.
Move fish into your aquarium
The aquarium turns your catch into ongoing income. Once a fish is placed, note its displayed income and quantity. You can then calculate what your aquarium earns per hour without relying on guessed values.
Use income to evaluate the next upgrade
Upgrades are easier to compare when you separate price from benefit. Record the cost and the added income you observe, then use the upgrade payback calculator to rank your options by recovery time.
Repeat with better observations
Your best notes are the ones gathered from your own current session. As your aquarium changes, recalculate the total from your latest fish list and make the next choice from fresh information.