Use of Threadfin Shad, Dorosoma petenense , 



as Live Bait During Experimental 



Pole-and-Line Fishing for Skipjack Tuna, 



Katsuwonus pelamis , in Hawaii. 



By 



ROBERT T. B. IVERSEN, Fishery Biologist 



National Marine Fisheries Service 

 Hawaii Area Fishery Research Center 

 Honolulu, Hawaii 96812 



ABSTRACT 



The effectiveness of threadfin shad as a live bait for skipjack tuna fishing in Ha- 

 waii was compared with the normal anchovy bait (nehu) during experimental fishing 

 on 37 schools of skipjack tuna during 1967 and 1968 aboard the research vessel 

 Charles H. Gilbert. Threadfin shad proved about as effective as nehu in (1) luring 

 skipjack tuna to the stern of the vessel, (2) concentrating the skipjack tuna at the 

 fishing station, and (3) catch rate of skipjack tuna. Underwater observations of 

 threadfin shad and nehu indicate a general similarity in behavior during fishing. 

 Bait-sized threadfin shad occur in freshwater impoundments in Hawaii during the 

 peak months of skipjack tuna fishing. They are hardy, easily acclimated to salt water, 

 and readily handled in large numbers. 



INTRODUCTION 



Reducing the time now required to catch live 

 bait has been suggested as a major step to in- 

 crease the fishing effort of the pole-and-line 

 fishery for skipjack tuna, Katsuwonus pelamis , 

 inHawaii (Brock and Uchida, 1968; Shang, 1969). 

 For several years, developing a new live bait 

 which could be obtained from a bait station by 

 Hawaiian fishermen has been a goal of the 

 National Marine Fisheries Service, Hawaii Area 

 Fishery Research Center. 



Threadfin shad, Dorosoma petenense , is one 

 baitfish (Figure 1) that has been extensively in- 

 vestigated. Any new baitfish must meet three 

 basic requirements: It should be effective 

 under fishing conditions, capable of mass pro- 

 duction, and hardy. I here report on the ability 

 of shad to fulfill one of these requirements — 

 effectiveness during experimental pole-and-line 

 fishing aboard a research vessel. Observations 



on the behavior and hardiness of bait are also 

 included. 



The fishing methods and catch statistics of 

 the Hawaiian fishery for skipjack tuna have 

 been described by Uchida (1967) and by Brock 

 and Uchida (1968). The fishery produces an 

 average catch of about 5,000 tons of skipjack 

 tuna each year. Each vessel catches its own 

 live bait that is taken to sea in baitwells and 

 chummed into the water to lure skipjack to the 

 stern of the vessel and within range of the 

 fishermen's hooks. A small, silvery anchovy 

 called nehu, Stolephorus purpureus (Figure 2), 

 occurs in several bays in Hawaii and makes up 

 92% of the bait catch. It is a delicate fish and 

 sometimes in short supply. Bait catching takes 

 place during the day and night. Day baiting is a 

 time-consuming activity, making up about 32% 

 of the total time devoted by the boats to scout- 

 ing, fishing, and day baiting. Reduction in the 

 time spent day baiting should result in more 



