CalCOFI Reports, Vol. 11, 1967 - California Cooperative Oceanic ...

50CALIFORNIA COOPERATIVE OCEANIC FISHERIES INVESTIGATIONSing grounds of sirasu, especially on the southern Pacificcoast of Japan. These two species of Stolephorinaeare distinguished from one another by meristic countsat a stage of 19 mm in total length (Hayasi and Tadolroro1962).Juvenile stage. Competition of the postlarval anchovywith those of the mackerels and jack mackerelsaffect the stock size of the anchovy in the south Pacificregion (Yokota et al. 1961). The above rare species ofStolephorinae is easily distinguished from the anchovyby shape of head at a stage over 26 mm TL althoughthese two species are caught incidentally (Hayasiand Tadokoro 1962).Juvenile through adult stages. Anchovies competewith or are consumed by the fishes listed in the intrcductorypart.FeedingThe investigation covers the form of digestive organsand the food species of the Japanese anchovy.These works are summarized as follows (Kubo 1961) :“The gill rakers are fine and numerous. The intestinelength increases more rapidly than the bodylength with growth of fish. The copepods comprisesmajor food of the fish throughout the life span. Sizeof food is linearly correlated with size of the fish.”Postlarval stage. Nakai et al. (1962) investigatedfeeding habit of the Japanese anchovy as well as sardinein the Pacific waters of Honsyu. The results aresummarized as follows :“Postlarvae of less than 5 mm TL just after absorbingyolk take mainly nauplii and eggs of copepods.Only a few of them were found with protozoa,small mollusca and diatom in their digestive tracts.Postlarvae of 5-10 mm TL still mainly eat nauplii ofcopepods, but copepodid larvae increase in numberfrom before. Generally, sizes of postlarvae and foodorganisms are correlated with each other. Number ofpostlarvae with food in the digestive tract occupyless than 20 percent on the average. They take thefood most actively in the day time. The copepod eggsand larvae are more abundantly distributed in thecoastal waters than in the offshore. ”Juvenile through adult stages. Copepods comprisesmajor food of the anchovy. Other food organismsare diatoms, and various types of small crustacea,larvae of mollusca, Chaetognatha and othersmall animals. The adults eat eggs and larvae of fishesincluding the anchovy (Nakai et al. 1955, Kubo 1961).MigrationNo systematic knowledges have been obtained on migrationof the anchovy. The following review coversfragmental information.Egg and larval stages. It is shown that someamount of eggs are carried by the Kurosio Currentfrom southern K:yusyu to the Pacific coast along Honsyu(Hayasi 1961, Asami 1962).Postlarval stage. Some postlarval anchovy assemblein the coastal waters (Yokota 1953, Tanaka 1956,Hayasi 1961).Juvenile through adult stages. It is widely acceptedthat some of anchovy stocks enter into andleave from bays and inlets during spring throughsummer and during autumn, respectively (Kubo1961). Most of sexually matured fish move from thecoastal waters to the edge of continental shelves(Hayasi 1961).ShoalingThe anchovy swim near the sea surface as schoolsthroughout their life span.Egg and larval stages. Since eggs and larvae aredispersed by currents after they are discharged, theirgeometrical distribution pattern changes dependingupon age (Yokota 1953).Postlarval stage. The postlarval anchovy activelyforms schools so densely as to support commercialfisheries.Juvenile through adult stages. In the live car, theanchovy tend to swim clockwise rather than counterclockwise(Suehiro 1947). The fish can swim at a speedof 10-12 cm/sec. (Kimura 1934). Three swimmingmanners have been noticed in the fishing grounds(Inoue and Ogura 1958). As mentioned in abioticfactors, the species reacts sensitively against soundand light.Xpawning cycle. The anchovy discharge ova andsperm at a duration of time between sunset and midnight(Nakai et ab. 1955, Yamanaka and Ito 1957,Kubo 1961).Reproduction and RecruitmentTwo problems are left unsolved about fecundity ofthe anchovy: (1) How many times an individualspawns in a year, and (2) how many times a group ofthe fish having occurred at a spawning season in aspawning ground spawn in a year. In addition, it isnot yet confirmed whether or not the anchovy in offshore,extending 1,000 nautical miles from the coast,are recruited to the fishing grounds.Larval and postlarval stages. The minimal sizeof the anchovy caught by commercial fisheries is 13mm in total length. Recruitment to the boat seine iscompleted during the postlarval stage of 23 mm intotal length (Ex. Com., Conf. Invest. Neritic-PelagicFisher. Japan 1961-63, Hayasi 1961).Juvenile and immature stages. Juveniles of 3 emin body length are taken by the fisheries that mainlyexploit the immature anchovy. The fish are completelyrecruited at 7-8 ern to the stocks for these fisheries(Asami 1962, Hayasi and Kondo 1957, Hayasi 1961,1962a). Immature fish over 6 cm in body length aretaken by the large sized two-boat purse seines thatmainly exploit the adult fish (Hayasi and Kondo1957, 1959, Hayasi 1961, 1962a). Immature fish over5 cm in body length are often distinguished by sex(Kubo 1961).Adult stage. Examination of ovum frequency indicatesthat anchovies discharge their ova or spermone or more times in a spawning season (Kubo 1961).Number of ova discharged by a female has been esti-