Shrimp lure and rod
Use the Crab-Fishing Rod ($3) with its default Ham and fish around the Lighthouse; Shrimp takes 44.4% of bites, Brown Crab the rest.
Fitting a Hot Dog switches the pool away from Shrimp, so leave the slot empty while you hunt for it.
Drip Shrimp
There is a drip Shrimp, and each hooked Shrimp has the standard 10% drip roll (25% with the full Wishbone).
Expect about 23 Ham bites per drip Shrimp, or 9 with the Wishbone; release Brown Crabs with right-click instead of reeling them in.
Shrimp sell price
Shrimp sells for $5, the better of the two Ham catches, so a run of Shrimp is the quickest free money before the Hot Dog upgrade.