BARHAM, GOWDY, and WOLFSON: ACANTHASTER IN GULF OF CALIFORNIA 



Table 2. — Locations in the Gulf of California and adjacent areas where Acanihaster ellisii 



was not observed. 



centrated. The nine specimens reported by 

 Faulkner (pers. comm.) at Ensenada de los 

 Muertos constitute the only sizeable population 

 known to the south of the La Paz island com- 

 plex, but density figures are not available. 



"PINK CUFF" STUDY 



Observations at Pink Cliff station provide an 

 insight into the behavior of A. ellisii. We made 

 preliminary observations there on four speci- 

 mens in November 1970; a further study was 

 conducted over a 48-h period in March 1971. 



Study Area 



The Pink Cliff study area covers about 2,000 

 m^ in the northeast corner of El Cardonal Bay 

 on the west side of Isla Partida (lat. 24°32'10" 

 N; long 110°23'30"W). The pink-pumice cliff ex- 



tends about 3 m underwater and then curves 

 into a wave-cut platform which interfaces at 

 about 10 m with the sand bottom. Several large 

 monument-like rocks with truncated tops stand 

 isolated from the cliff. A few reeflike ledges lie 

 farther seaward, and an extensive pile of large 

 boulders is located near the northern edge of 

 the platform. (Figure 2, based on underwater 

 sketches and substrate measurements, gives 

 a schematic picture of the area.) 



Coralline algae predominate on rock and 

 cliff faces. A rich growth of sessile organisms, 

 dominated by sponges, tunicates, hydroids, and 

 gorgonians, is concentrated on and near the 

 vertical cliff and monument rocks. The upper 

 rock surfaces and much of the platform are 

 covered with a thin veneer of filamentous algal 

 material. At the deepest levels, on the inshore 

 sides of the rock pile, there is a luxuriant stand 

 of the brown alga, Padina. 



931 



