Studies by Ueyanagi (1960) indicate that a black marlin may 

 spawn in the northwestern Coral Sea in early summer 

 (November). Recaptures are reported in the spring and early sum- 

 mer near the point of tagging about 1, 2, 3, and 4 yr after tagging. 

 This would indicate that at least some of these black marlin 

 tagged show a returning migration trend toward a suspected 

 spawning area. 



Geographical areas fished by commercial longline gear vary in 

 amount of fishing effort expended and changes in longline effort 

 may affect the number of recoveries and recovery location. From 

 1965 to 1975, black marlin catch rates from the Japanese longline 

 fishery in many areas of the southwest Pacific averaged 2.1-5.1 + 

 and >5.1 fish/1,000 hooks effective hooking effort (Suzuki and 

 Honma 1977); peak hooking rates were recorded near the tagging 

 area off north Queensland from October through December. The 

 distribution of longline effort and CPUE should be reflected in 

 the distribution of recovery locations for black marlin tagged in 

 the western Coral Sea. The effective effort for black marlin fished 

 in the Coral Sea is high. The effectiveness index (£) of the effort 

 on black marlin (effective hook/nominal hooks) exceeds 1 .0 in 19 

 of 24 yr (1952-75) as reported by Suzuki and Honma (1977). 



Figure 13 outlines the 10-yr average level of Japanese longline 

 fishing effort by 5° longitude and 5° latitude for the Coral Sea and 

 adjacent areas from 1968 to 1977 (Anonymous 1970-79). Exten- 

 sive longline fishing effort is evident north of the Solomon 

 Islands, east of Queensland, and off the southeast coast of Vic- 

 toria, Australia, and off the eastern coast of New Zealand. A 

 substantial amount of longline effort was expended off the Great 

 Barrier Reef area (north Queensland) from lat. 20°S northward. 



Figure 13. — Average distribution of Japanese longline fishing effort for 1968-77 by 

 5" longitude x latilude areas from Japanese Fishery Agency data. Effort levels for 

 the 10-yr period were determined by averaging effort level 0-99, 100-199, 200 or 

 greater x 10 4 hooks in terms of 1 = 0-99, 2 = 100-199, and 3 = 200 or greater x 

 10 4 hooks. 



No longline effort is reported in the eastern Arafura Sea and Tor- 

 res Strait between Cape York and Papua. Fishing effort isolines 

 also indicate an area of reduced effort extending from near New 

 Caledonia eastward, centering on about lat. 20°S. The effort 

 levels for the 5° areas given in Figure 13 for the period 1968-77 are 

 indicated by numbers of hooks fished x 10". The strata of hook 

 effort, levels 1-3, representing 9-99, 100-199, and 200 or greater x 

 W, respectively, were averaged for the 1968-77 period. 



The distributions of longline fishing CPUE for black marlin as 

 a measure of apparent abundance in the area from near northern 

 New Zealand, and near the New Guinea-Solomon Islands are 

 shown in Figure 14a, b, c (from Suzuki and Honma 1977). 



A review of CPUE for June-August (Fig. 14a) shows CPUE 

 levels of 0.6-2.0 black marlin/ 1,000 hooks are common in the 

 New Guinea-Bismark Archipelago-Solomon Islands area 

 throughout the winter months. Average effort levels are high in 

 this area, 100-199 hooks x 10" per 5° longitude x 5° latitude 

 area. In September-November (Fig. 14a, b) the tagging area has a 

 high CPUE. The first indications of a poleward shift of high 

 CPUE areas for black marlin, in the range of 0.6-2.0 fish/1,000 

 hooks along the western coast of the Coral Sea, occurs during 

 September. By examining the changes in CPUE for the area off 

 north Queensland during and after the months of September, Oc- 

 tober, and November, some insight into the shift of high black 

 marlin CPUE away from the tagging areas can be observed. High 

 catch rates (>5.1 black marlin/1,000 hooks) are common in the 

 western Coral Sea from lat. 10° to 20°S in October and 

 November. The high CPUE areas for September-November are 

 near long. 150°E x lat. 15°S and have a hook effort of < 99 

 hooks x 10" per 5 6 longitude x 5° latitude area. In December 

 (Fig. 14b), increasing catch rates are observed south to about lat. 

 25°S. These higher catch rates are observed to the west within a 

 latitudinal band of lat. 15° to 20°S. Longline hook effort level is 



< 99 hooks x 10" per 5° longitude x 5° latitude area. In January 

 (Fig. 14b), catch rates increase along the Australian coast to about 

 lat. 35°S. Catch rates per 5° square are lower than those observed 

 previously off the north Queensland area (lat. 10° to 20°S), but re- 

 main in the range of 2.1-5.G black marlin/1,000 hooks. The 

 center of high black marlin CPUE is in an area having an effort 

 level of < 99 hooks x 10" per 5° longitude x 5° latitude. By Feb- 

 ruary (Fig. 14c), black marlin CPUE in the lat. 15° to 20°S area has 

 decreased to 0.5 black marlin/1,000 hooks. The high CPUE areas 

 continue to be off the Queensland and New South Wales coast, 

 from lat. 20° to 35°S. Average effort levels in the high CPUE 

 areas for February are at a higher level than during the previous 

 months, >_100 hooks per 5° longitude x 5° latitude area but 



< 199 hooks x 10" per 5° area. CPUE patterns for March (Fig. 

 14c) change considerably, with higher CPUE areas noted north of 

 lat. 15°S, and reduction in high CPUE areas to the south. Catch 

 rates averaged 0.6-2.0 black marlin/1,000 hooks per 5° longitude 

 x 5° latitude area. Effort levels in the higher CPUE areas are less 

 than averages observed for high CPUE areas in February, and 

 average < 99 hooks x 10" per 5° longitude x 5° latitude area. 

 Most catches in April (Fig. 14c) are being made north of lat. 20°S. 

 Catches average 0.6-2.0 fish/hooks per 5° longitude x 5° latitude 

 area. A further retraction of high CPUE areas from latitudes 

 south of 15°S is evident in May (Fig. 14c). Some catches at levels 

 of 0.6-2.0 black marlin/1,000 hooks are observed for areas east 

 of the Queensland coast, but the center area of high CPUE is in 

 the New Guinea-Bismark Archipelago-Solomon Islands area. 

 Average effort levels are higher in this area and are between 100 

 and 199 hooks x 10 4 per 5° longitude x 5° latitude square. 



13 



