FISHERY BULLETIN: VOL. 85, NO. 4 



MATERIALS AND METHODS 



All samples considered here were taken in an 

 area between Lizard Island, approximately mid- 

 way across the Great Barrier Reef Lagoon, to 10 

 nmi seaward of the outer ribbon reefs of the Great 

 Barrier Reef in the Coral Sea (Fig. 1). 



The Great Barrier Reef Lagoon is modally 30 m 

 deep in this region (range 25-40 m). The outer 

 ribbon reefs are located along the shelf break, and 

 the bottom falls off sharply with distance into the 

 Coral Sea reaching depths >2,000 m within 6 nmi 

 (Fig. 1). 



The samples immediately to windward of 

 Lizard Island were taken from a 7 m boat with a 

 net of 0.4 m^ mouth area (see Leis 1986 for further 

 details of sampling). Other samples were taken 



from RV Sunbird, a 14 m catamaran. The neu- 

 ston net, with mouth dimensions of 1 x 0.3 m and 

 0.5 mm mesh, was towed between the bows of the 

 catamaran, and normally fished to a depth of 0.1 

 m. Bongo nets of 0.85 m diameter and fitted with 

 a depressor were towed in a double-oblique pat- 

 tern to study horizontal distribution or in 

 opening-closing mode to study vertical distribu- 

 tion. Nets were towed at approximately 1 m/sec- 

 ond, were of 0.5 mm mesh, and were equipped 

 with a flowmeter. During the vertical distribu- 

 tion study, a depth sensor with a deck display was 

 fitted to the net. At other times, a mechanical 

 depth-distance recorder was used. 



The neuston net, when used, fished during the 

 bongo net tow. The oblique bongo net tows were 

 done to the greatest calculated depth that was 



Figure 1. — Map of the study area. One sampling block is the Great Barrier Reef Lagoon beween Lizard Island and the ribbon reefs, 

 this is delineated by the broken lines. In the Coral Sea, there are five sampling blocks A-E as defined in the t«xt. Depths in the Lagoon 

 range from 20 to 40 m. Depths to 400 m are encountered in Coral Sea block A, to 1,000 m in block B and > 1,500 m in C-E. Outer 

 ribbon reefs are 1) Day, 2) Carter, 3) Yonge, 4) No Name, and 5) Number 10 Ribbon. None of the outer reefs are emergent. 



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