RALSTON ET AL.: BOTTOM FISH RESOURCE AT JOHNSTON ATOLL 



atures vary little throughout the year, as do sea sur- 

 face temperatures, which are in near equilibrium 

 with the air. Strong easterly trade winds prevail all 

 year but increase during the summer period. Annual 

 mean wind speed at Johnston Island is 13 kn (7.5 

 m/s) and monthly means range from 11 to 14 kn 

 (5.5-7.0 m/s). 



METHODS 



Makalii 



The Makalii is operated by the National Undersea 

 .esearch Laboratory at the University of Hawaii. It 

 is a two-man, battery powered, 1-atmosphere sub- 

 mersible which is 4.8 m long, with a pressurized cap- 

 sule 1.5 m in diameter. When carrying a pilot and 

 one observer, its normal operating speeds range 

 from 1 to 3 kn (0.5-1.5 m/s). Maximum dive duration 

 is 4-5 h and depth capability is 365 m. Equipment 

 carried in this study included hydraulic manipulator, 

 internal and external color video cameras, 2 video 

 monitors, video recorder, video flood lights, Photo- 

 sea 3 35 mm still camera with strobe, current and 

 temperature meters, and a dictaphone tape recorder. 

 In addition, the Makalii is equipped with an environ- 

 mental monitoring system for continuous recording 

 of temperature, salinity, conductivity, oxygen, solar 

 radiation, and depth. 



All three authors participated as observers dur- 

 ing a series of dives at Johnston Atoll over the 2-wk 

 period between 22 September and 5 October 1983. 

 Once on station, a launch-recovery-transport plat- 

 form was submerged to 20 m and divers released the 

 Makalii, usually in 120 m of water. The submersible 

 descended until encountering the bottom and 

 locating the atoll's shelf break. Observations made 

 on fishes during the dives were voice and video re- 

 corded for later analysis. Slope angle was periodi- 

 cally measured with a hand-held inclinometer. 



Visual estimates of the density of commercially im- 

 portant bottom fishes (sensu Ralston and Polovina 

 1982) were made by a series of "quadrat" samples. 

 These fishes included Cookeolus boops, Epinephelus 

 quernus, Aphareus furcatus, A. rutilans, Etelis car- 

 bunculus, E. coruscans, Pristipomoides auricilla, P. 

 filamentosus, P. zonatus, Carangoides orthogram- 

 mus, Caranx lugubris, Seriola dumerili, and Pon- 

 tinns macrocephalus. 



During quadrat sampling the observer would look 

 out his port and count the total number of bottom 



3 Reference to trade names does not imply endorsement by the 

 National Marine Fisheries Service, NOAA. 



fish, without regard to species, over an area of the 

 bottom judged to be 30 m 2 . Quadrat areas always 

 lay on the oblique planar surface of the slope face 

 and were away from the immediate vicinity of the 

 submersible A sampling period consisted of four 

 counts systematically performed, one every 15 s. To 

 the extent possible, each count was made at an in- 

 stant in time. All bottom fish seen in the water 

 column above the sample area were included in 

 counts. 



The submersible progressed stepwise down the 

 slope (100-365 m) in a clockwise direction around the 

 atoll, with the observer's starboard port always 

 oriented to the slope face. Upon reaching the 

 Makalii' s depth limit, a slow stepwise ascent would 

 begin to 100 m, where the dive would end. Descents 

 generally lasted 2.5 h and ascents 1.5 h. Thus the 

 entire vertical distribution of the deep slope was 

 sampled more or less equally (i.e, observations were 

 not concentrated in any particular depth zone). 



Townsend Cromwell 



The National Oceanic and Atmospheric Adminis- 

 tration's (NOAA) RV Townsend Cromwell is 50 m 

 long and when rigged for bottom handline fishing 

 carries four hydraulic fishing gurdies (Charlin motors 

 and Pacific King fishing reels), each with 365 m of 

 braided prestretched 90 kg Dacron line The terminal 

 rig is composed of four No. 28 Tonkichi round fishing 

 hooks and a 2 kg weight. Stripped squid was used 

 for bait and fishing was conducted only during the 

 day. 



The vessel spent 3 d (3-5 November 1983) at John- 

 ston Atoll sampling deep slope bottom fish by drift 

 fishing. After wind and current directions had been 

 determined, the vessel was positioned over the 

 desired depth and fishing lines were dropped. Fish- 

 ing continued until the vessel drifted over an un- 

 suitable water depth, when lines were retrieved and 

 the Townsend Cromwell repositioned. Single drifts 

 were the fundamental sampling unit by which catch 

 and effort statistics were summarized. Six fishing 

 stations were occupied (Fig. 1), one during the morn- 

 ing and afternoon of each day. Fork length to the 

 nearest millimeter and depth of capture were re- 

 corded for all fish landed. 



RESULTS 



Makalii 



Ten dives were completed at Johnston Atoll (Fig. 

 1). Due to precipitous dropoffs which occur through- 



143 



