FISHERY BULLETIN: VOL. 79. NO. 1 



ters and sometimes to the nearest centimeter. 

 Other authors whom we quote measured in the 

 same way. Weight offish was measured ungutted, 

 usually at sea, in pounds and ounces. These 

 weights were converted to grams and rounded to 

 the nearest 50 g. Gonads were weighed fresh to the 

 nearest gram, usually at sea. 



Statements about mean positions of isotherms 

 are based on charts by Vaux (1970) and Gorshkov 

 (1974). 



SPATIAL DISTRIBUTION 



Skipjack tuna have an extensive distribution in 

 the Australian region (Figure 1), but prior to 1938 

 they had been recorded only off New South Wales. 

 It is now known that they have a continuous range 

 in east Australian coastal waters from Lady El- 

 liott Island to Storm Bay, although the limits may 

 vary seasonally as discussed later. The RV War- 

 reen and RV Stanley Fowler of the Commonwealth 

 Scientific and Industrial Research Organization 

 (CSIRO) established this distribution from trol- 

 ling surveys between 1938 and 1951. Most speci- 

 mens were taken on the continental shelf, many of 

 them close inshore. 



East coast inshore waters north of Lady Elliott 

 Island lie within the Great Barrier Reef. Skipjack 

 tuna are unknown there, although most of the 

 area is well fished by sports and commercial 

 fishermen (Marshall 1964; Hynd 1968). The War- 

 reen and Stanley Fowler prospected by trolling in 

 northern Australian waters from July to October 

 1949, traversing much of the coast from Torres 

 Strait to Broome. Skipjack tuna were found on 

 banks near the edge of the Australian continental 

 shelf to the south of Timor, but nowhere else, and 

 no other records exist from northern coastal 

 waters. Thus the distribution appears to be quite 

 limited in coastal waters around northeast and 

 northern Australia (Figure 1). This is not true of 

 the adjacent oceanic waters, however. Japanese 

 longline vessels began to fish for tuna in the area of 

 Figure 1 about 1950. They did not seek skipjack 

 tuna but took them incidentally. Figure 1 shows 

 the general areas in which those vessels took any 

 skipjack tuna in the years 1964-67, as established 

 by Matsumoto (1975). Evidently skipjack tuna 

 occur to some extent almost everywhere in ocean 

 waters east, north, and west of the Australian 

 mainland and New Guinea. Skipjack tuna were 

 first recorded in Papua New Guinea waters be- 

 tween 1948 and 1950 by the Australian RV Fair- 



wind, in localities shown in Figure 1 (Munro 1958). 

 Japanese longlining began there at about the 

 same time. About 1969 vessels of the Japanese 

 live-bait fishery began taking skipjack tuna north 

 and northeast of New Guinea, and a similar 

 fishery was later established by nationals of 

 Papua New Guinea within the same area (Kasa- 

 hara 1977; Lewis and Smith 1977). Figure 1 shows 

 the general area of the Japanese live-bait fishery 

 in 1973, as reported by Kasahara (1977). 



Skipjack tuna were first recorded off the west 

 coast of Australia in 1945. By 1951 an apparently 

 continuous range from Onslow to Albany had been 

 established, mostly by trolling surveys of the War- 

 reen. Later surveys, made by the Department of 

 Fisheries and Wildlife of Western Australia, ex- 

 tended this range to Broome (Robins 1975). Skip- 

 jack tuna in Western Australia appear to be less 

 abundant than in southeastern Australia, at least 

 on the continental shelf. Most were taken on the 

 outer part of the shelf or just beyond the shelf edge. 



On the southern coast of Australia east of Al- 

 bany, skipjack tuna were first found by the CSIRO 

 RV Derwent Hunter in 1953, near the edge of the 

 shelf in the eastern part of the Great Australian 

 Bight. Soviet workers extended the known range 

 to the western part of the Bight, again in waters 

 near the shelf edge (Shuntov 1969). In 1978 the 

 CSIRO RV Courageous found skipjack tuna be- 

 tween the western end of the Bight and Albany 

 (Maxwell^). East of the Bight, skipjack tuna have 

 been taken by South Australian tuna fishermen 

 almost to Kangaroo Island, from the shelf edge to 

 near the coast (Olsen ; Williams ). Thus there is 

 probably a continuous distribution along the 

 southern coast of Australia to Kangaroo Island 

 (Figure 1). 



We know of no certain skipjack tuna occurrences 

 between Kangaroo Island and Australian east 

 coast waters. The most westerly of the east coast 

 records are Lakes Entrance in eastern Victoria, 

 the mouth of the Tamar River in northeast Tas- 

 mania (Scott 1975) and Storm Bay in southeast 

 Tasmania (Figure 1). The apparent gap in skipjack 

 tuna distribution to the west of those places is not 

 readily explained. The skipjack tuna food or- 



^J. G. Maxwell, Research Scientist, Division of Fisheries and 

 Oceanography, CSIRO, Cronulla, 2230, Aust., pers. commun. 

 May 1978. 



•'A. M. Olsen, Director of Fisheries Research, Department of 

 Agriculture and Fisheries, Adelaide, 5000, Aust., pers. commun. 

 May 1978. 



^K. F. Williams, Experimental Officer, Division of Fisheries 

 and Oceanography, CSIRO, Cronulla, 2230, Aust., pers. com- 

 mun. May 1978. 



86 



