FISHERY BULLETIN: VOL 72. NO. 1 



(0.5-mile) intervals. Their arrangement in the 

 experimental site is shown in Figure 2. The 

 eight structure mooring locations were used 

 with different .structures as required for specific 

 exj)eriments. 



The 15-m (49-ft) single boat-rig bait purse 

 seiner, Gidf Ranger, was chartered to make 

 quantitative collections at selected artificial 

 structures using a tom-weight type purse seine, 

 22 m (12 fathoms) deep and 110 m (60 fathoms) 

 in length, with 3.2 cm (lV4-inch) stretched mesh 

 webbing. A 6-m (20-ft) inboard -outdrive power 

 boat was used as a diving platform and for pick- 

 ing up and resetting structures sampled by the 

 purse seine. 



Daily visual estimates of the number and 

 species of fisti present at each structure were 

 made independently by scuba divers. We ob- 

 tained quantitative data from selected structures 

 by collecting all the fish around these structures 

 with the purse seine. Diver estimates and purse 

 seine catch data are given in Table 1. 



Scuba divers made visual estimates of the fish 

 aggregation at a structure prior to beginning the 

 purse seine set. The structure anchor was picked 



Figure 1. — Artificial structure design and mooring 

 arrangement. 



up by the divers as soon as the seiner began 

 setting its net. When pursing was half completed, 

 the structure counterweight was retrieved to 

 l^revent its being tangled in the jiurse line. After 

 the purse rings were up, the dive boat would 

 take the structure aboard, pass over the cork- 

 line, and reset the structure clear of the net. 



The captain of the Gulf Ranger estimated the 

 catch weight after each purse seine set and the 

 biologist aboard sanij^led each catch to provide 



30'I0' 



Figure 2. — Map of experimental site with numbered circles illustrating positions where 

 artificial structures were deployed. Stage II is a Navy research platform west of the study 

 area. 



182 



