An Experiment on the Tuna Fishery by Long-Line in the Sea off Mangole and Timor Islands

1. Fishing rate per lOOhooks of Tunas and Spear fishes amounted to 3.8% in the Sea off Mangole Island, 5.8% off Timor lsland, and that of sharks amounted to 0.8 % and 1.6% 2. Percentage of fish caught was as fallows: The SeaoffMangole Island : Yellow fin tuna 61.6%, Big eyed tuna 7.4%, Spear fishes 12.6%, Sharks 18.4%. The Sea offTimor Island : Yellow fin tuna 52.2%, Big eyed tuna 16.7%, Spearlishes 8.9%, Sharks 22.2%. 3. Percentage of dead fish caught was as fallows : The Sea off Mangole Island. Yellow fin tuna 75.3%, Big eyed tuna 57.2%, Spearfishes 87.5%, Sharks 17.2%. The Sea off Timor Island. Yellow fin tuna 72.4%, Big eyed tuna 80.0%, Spear fishes 87.5%, Sharks 10.O%. 4. Tuna-Damage amounted to 10.8%. 5. The fishing depth was 80-120 metres. 6. The water temperature for catch was 20-25℃ in the Mamgole Fishing Ground and 20-23℃ in the Timor Fishing Ground. 7. The salinity of fishing-depth-water was about 34.50士0.30‰. 8. 1t was presumed that Cololabis saira was fitter as bait than Trichiurus Japonicus. 9. Body length composition of Yellow fin tuna in the Sea off Mangole Island was in the range of 105-150cm, and the most general size offish was in 125-140cm. Its average length was in 132.2土7.85cm and that in the Timor Island was in 100-155cm, the general size was in 135-150cm and 110-115cm, average length was in 131.4士12.03cm. 10. Body length composition of Big eyed tuna in the Sea off Mangole Island was in the range of 70-160cm and number of individuals measured 135 -160cm in length amounted to 50% of the whole. And that in the Sea off Timor lsland was in the range of 80-145cm and number of 135-145cm was only 65.6%. 11. The male of Yellow fin tuna amounted to 76.6% of the whole, and that of Big eyed tuna amounted to 65.6%. 12. We had difficulty in working on the fishing-boat and in bringing along-side agaiIISt the mother-ship on the sea where thewind force shown 4 or more. 13. Generally speaking, the amount of ammonia in Yellow fin tuna meat is much more than the other usual fish meat. 14. Being examined the relation between freshness of meat and the tmie let alone before ice storage and the author confirmed next result that the Yellow fin tuna must be stored in ice within about 5 hours after being caught in the equatorial sea. 15. In order to protect the calour and tissue of meat, the temperature in hatch must be regulated from O-2℃. 16. Larva and immature of fishes belonging to 22 species of 14 families were collected over the fishing area. Many of them seemed to be similar, to those which are commonly obtainable in Kurosio near Japan in summer. 17. As the stomach contents, sqllids were the most common, and obtained through on the fishing area, Cololabis and Auxis were also found. 18. It is rather significant that some bottom species as Nephrops were obtained in a few stations. 19. At the Mangole fishing ground, zooplankton is more than phytoplankton in species and amount. Especially, Copepoda in zooplankton and Rhizosol. enia sp. in phytoplankton are most abundant. 20. In the Timor fishing ground, the phytoplankton is more than zooplank･ ton in amount. Rhizosolenia in phytoplankton and Copepoda in zooplankton are abundant. 21. The distribution of the plankton of Banda sea is the same as in Mangole Sea