DEPARTMENT OF THE INTERIOR Applications for COMMERCIAL FISHERIES REVIEW, which is mailed tree to members of the fishery industries and allied interests, should be addressed to the Director, Fish and Wildlife Service, United States Department of the Interior, Washington, 25, D.C. PRELIMINARY FISHERIES SURVEY OF THE HAWAIIAN-LINE ISLANDS AREA -- PART 11 NOTES ON THE TUNA AND BAIT RESOURCES OF THE HAWAIIAN, LEEWARD, AND LINE ISLANDS, BY FRED C. JUNE The present report is a digest of the miscellaneous information gathered on the tunas2 and tuna bait-fish resources of the Hawaiian, Leeward, and Line islands; together with related information on the physical characteristics of the various land masses and surrounding seas. The data have been assembled from available lit- erature, discussions with fishermen, and field observations made at various islands in the region. In many instances, desired data could not be obtained without addi- tional field work, which conditions did not permit. However, it is hoped that this summary will be of some aid to those interested in commercial tuna fishing in these INTRODUCTION: The Hawaiian Islands proper consist of eight major islands: 1/PARTI THE HAWAIIAN LONG-LINE FISHERY BY THE SAME AUTHOR APPEARED IN COMMERCIAL FISHERIES REVIEW, JANUARY 1950, PP. 1-23; ALSO AVAILABLE AS SEPARATE NO. 244. 2/DR. SIDNEY SHAPIRO, FISHERY RESEARCH BIOLOGIST, U. S. FISH AND WILDLIFE SERVICE, COLLABORATED IN THE PRELIMINARY PHASES OF THIS INVESTIGATION. 3/THE VARIOUS TUNA SPECIES CONSIDERED HERE INCLUDE: YELLOWFIN TUNA (NEOTHUNNUS MACROPTERUS), BIG-EYED TUNA PARATHUNNUS SIBI), ALBACORE (THUNNUS GERMO), OCEANIC SKIPJACK (KATSUWONUS lava rocks. In general, the fringing reef extends only a few hundred yards from shore. Climate is fairly uniform through the year. Mean monthly air temperature at Honolulu varies from 71° F. in January to 78.4° F. in August. Northeast trade winds prevail throughout the year, but from October to April they are occasionally interrupted by "Kona" (southerly or southwesterly) winds. "Kona" weather is often accompanied by rainstorms which may last from a few hours to three or four days. SEA TEMPERATURES: The average annual sea-surface temperature in the Hawaiian area is about 770 F. Maximum and minimum monthly averages are shown in table 1. It is at once apparent that, Since the tunas are primarily warm-water forms, it is to be expected that the vertical and horizontal distribution of the various species is to some extent governed by sea temperature conditions. The results of the Japanese exploratory investigations in the region of the Inner South Seas, for example, indicate that sea temperature had a close bearing on the occurrence of skipjack and yellowfin tuna, especially in the region of the equatorial countercurrent, where the main fishing grounds for these species were located. Their findings indicate that when temperatures in this zone were below normal, a marked decrease in the catches of skipjack and yellowfin tuna occurred, followed by an increase in the long-line catches of big-eyed tuna and albacore. Although no basic studies on the relation of sea temperatures to the occurrence and abundance of tunas in Hawaiian waters have been completed, the Territorial Division of Fish and Game has been gathering data on the relation of subsurface temperatures to tuna long-line fishing. The commercial catch records indicate a marked increase in the landings of yellowfin tuna and skipjack, as the waters in this region become progressively warmer during the summer months. As the season advances and the waters again become cooler, the numbers of these two species entering the commercial catches show a decided decline. Big-eyed tuna and albacore, which may be less tolerant of the higher summer temperatures, occur in the catches in fewer numbers during the summer season. These two species enter the catches in the greatest abundance during the winter months, and their increased appearance follows closely the decline of the yellowfin and skipjack. OCEAN CURRENTS: The waters surrounding the Hawaiian Islands are subject to strong and variable currents through the year (figure 3). In general, currents run southwesterly and westerly offshore, due to the influence of the northeast trade winds. Close inshore, however, the flow is northward along the coastlines, except off the Puna (southeast) coast of Hawaii, where the inshore current flows in a southwesterly direction. In the channels between the islands, the currents are tidal, but to some extent, are influenced by the prevailing winds and the position of the islands with respect to each other. In Kauai Channel, the main current approaches from the northeast, but abruptly changes its direction of flow to the northwest as it strikes the shallow water bank that extends northwestward off Kaena Point, Oahu. It continues northwestward until it reaches the east coast of Kauai; here it divides in the vicinity of Nawiliwili Bay. North of the bay it follows the coastline and joins the main current north of the island. South of Nawiliwili Bay it joins a large eddy movement that exists south and west of Kauai. This eddy rotates in a clockwise pattern, extending a maximum of about 30 miles offshore. The north |