We investigated the own- and cross-price elasticity of supply (PES) of 20 fish and shellfish species, caught in mixed fisheries off southwestern Taiwan and serving the local fresh seafood market. Because the licensed fishermen face little regulation constraining their behavior, we hypothesize that they adjust their catch profiles so as to maximize the expected value of their catch, instead of fishing indiscriminately at the mercy of the elements. However, because catches are auctioned after the landing, fishermen face uncertain price. Using daily data from 2001--2015, we found that price-taking fishermen are capable to respond to price changes of 17 of the 20 species by shifting the catch profile. The species with the highest PES are those corresponding to the highest revenues, and the fishermen are the most price elastic during the season when the catches are highest. Input substitution effect and by-catch effect offset each other, leading to weak and mostly insignificant cross-PES for most of the species. Weather conditions such as wave height, wind speed and wind direction do not appear to affect fishermen's targeting decisions for most of the 20 species, but they do affect fishermen's exit decision, i.e., going fishing or not.