FISHERY BULLETIN: VOL, 78, NO. 4 



Table 2.— Number of blacksmith per survey, average (median), in midwater surveys at the east and west ends of Naples Reef, 

 southern California. Freq. = frequency of occurrence (percent of surveys). Short transects total 480 m; long total 960 m. 



Current 

 direction 



East to 

 west 



West to 

 east 



Length of 

 transects 



No. 

 surveys 



short 

 long 

 short 

 long 



Adults 



Halfgrowns 



Juveniles 



Freq. 



(°o) 



East 



West 



Freq. 

 (%) 



East 



West 



Freq. 



(%) 



East 



West 



16 100.0 44.2 (32.5) 0.6 (0.1) 



7 10C.0 162.3 (171.0) 0.6 (0.4) 



3 100.0 6.0 (8.0) 28.3 (25.0) 



1 100.0 3 (3) 84 (84) 



31.3 0.9 (0.2) 0.3 (0.2) 12.5 



85.7 39.1 (18.0) 5.4 (1.6) 71.4 



66.7 0.0 (0.0) 2.3 (1.0) 



100.0 3 (3) 3 (3) 100.0 



1.9 (1.0) 10.9 (3.4) 



6.7 (3.0) 123.9 (198.0) 



(0) (0) 



30 (30) 30 (30) 



Table 3. — Abundance of zooplankton at the east and west ends of Naples Reef, southern California. For each collec- 

 tion, differences in abundance between ends of the reef were tested with a Mann-WTiitney U-test. 



-Ps0.05; --PssO.Ol: ns, not significant. 



quickly migrated to the opposite end of the reef. I 

 began the survey by counting fish at the west end. 

 The current w^as flowing from the east and I did 

 not count any adult blacksmith, although visibil- 

 ity averaged 12.2 m. I then started the survey at 

 the east end and counted 81 adults, when the 

 currents shifted and flowed from the west. While 

 swimming the transects, I saw small schools of 

 adults (5-15 individuals) moving toward the west 

 (now incurrent) end. I returned to the boat and 

 followed adults as they swam toward the west end, 

 where I repeated the transects. Even though 

 water visibility dropped to 5.0 m, I counted 43 

 adults over the area where, 2 h earlier, I had 

 counted none. 



The movements of halfgrown blacksmith were 

 less clear. Counts were generally higher at the 

 east end when the current came from the east 

 (Table 2; Wilcoxon's signed-ranks test: short sur- 

 veys, P = 0.14; long surveys, P = 0.06; short and 

 long combined, P = 0.05). However, the pattern 

 was inconsistent, and counts were actually great- 

 er at the west end in 3 of the 11 surveys in which 

 halfgrown fish were sighted. The proportion of 

 halfgrown fish at the east end averaged 0.90 (95% 

 CI = 0.38-1.0). A similar inconsistency occurred 

 when the current flowed from the west. All half- 

 grown fish counted were at the west end on the two 

 short surveys in which they were seen, but the 

 three individuals counted in the long survey were 

 at the east end. 



Juvenile blacksmith did not gather at the incur- 

 rent end. When the current flowed from the east, 

 all juveniles were at the west end of the reef in the 

 two short surveys in which they were seen and in 

 the five long surveys (Table 2; Wilcoxon's signed- 

 ranks test; long stirveys, P< 0.05). The proportion 

 of juveniles at the east end averaged only 0.03 

 (95% CI = 0-0.18). When the current flowed from 

 the west, juveniles were not seen in the short 

 surveys, and were equally abundant at both ends 

 of the reef on the one long survey. However, these 

 data do not accurately describe the response of 

 juveniles to water currents. Observations along 

 the bottom indicate that, regardless of the current 

 direction, many juveniles occurred throughout the 

 reef in stationary aggregations that form around 

 shallow rocky prominences. The large number of 

 juveniles counted at the west end reflected the 

 location of the transects on the reef: almost 87% of 

 the juveniles counted in the midwater surveys 

 were seen in the two transects at the west end, 

 which were the only transects over the shallowest 

 part of the reef (Figure 1). 



Zooplankton Densities 



I took eight collections of zooplankton from mid- 

 August to mid-October 1977 (Table 3). In six of the 

 collections, the current flowed from the east; in the 

 other two the current was reversed and flowed 

 from the west. 



834 



