The main purpose of this study is to fulfill the science research on the fisheries resourcesof baby bottom trawler in the northern waters of Taiwan. It is expected to better utilizethose resources reasonably by the real operating status. The experimental method can besummarized as two aspects. Firstly, basic fishes condition are collected from the chosencommercial fishing boats which had been fished in the northern waters of Taiwan(including the waters of Ilan Bay, and the waters from Latitude 27°N, Longitude124°E southwestward to Fu-Kuei Chiao, Pai-Sha Tun and Houlung). Former datumused to analyze this fishery's catch per unit effort, catches composition, temporal andspatial distribution, and mechanism of variation of baby trawler. Meanwhile, marketablefish and discard fish are also collected to study their biological characteristics.Secondarily, four cruises are carried out to study the selectivity of mesh size on cod net ofbaby trawler by research vessel "Hai-Fu" and “Fishery Researcher 1”, for obtain asuitable mesh size on baby bottom trawler fishing to protect the young fishes. It isexpected to have former biological results to offer the entrepreneur and fisheriesauthorities as science information, keep going a reasonable utilization and managementon demersal fishery resources in northern waters of Taiwan.