FISHERY BULLETIN: VOL. 84, NO. 3 



Youngs 1981). Not all fish collected were aged, so 

 fish of known age were grouped into 1 cm length 

 intervals by gear type for each survey to calculate 

 percentages of each age in each size interval. These 

 percentages were applied to the number of C. striata 

 in each length interval to estimate age composition 

 for the unaged fish (Ricker 1975). 



Population Estimates at 

 Specific Reef Sites 



Petersen mark-recapture experiments were con- 

 ducted at site 1 (lat. 32°30.3'N, long. 79°41.9'W; 

 depth = 20 m; area =160 ha) during the summer 

 of 1981 to estimate the population size of C. striata 

 on this reef. In the summers of 1982 and 1983, we 

 studied a second reef also (site 2: lat. 32°28.3'N, 

 long. 78°14.5'W; depth = 23 m; area = 120 ha). 

 These reef areas were defined by the presence of 

 attached algae and invertebrate growth (porifera, 

 corals, echinoderms, bryozoans, anthozoans, and 

 ascidians) as observed with a HYDRO products 

 TC-125-5DA low-light-level underwater television 

 camera during transects across the sites (for more 

 details, see Wenner 1983). Study areas were mapped 

 with an EPSCO C-Plot II LORAN-C plotter inter- 

 phased with a SITEX 707 LORAN-C receiver. 



Black sea bass were captured and recaptured at 

 each site with commercial traps (Rivers 1966) and 

 Florida snapper traps (0.9 m wide x 1.2 m long x 

 0.6 m high) fished for 45-90 min with cut clupeid bait 

 (Brevoortia tyr annus and Alosa aestivalis). Black 

 sea bass >20 cm TL, the approximate size of full 

 retention in the traps, were measured to the nearest 

 mm TL and tagged with 13 mm diameter plastic disc 

 tags attached under the first dorsal fin with a nickel 

 pin trimmed to the proper length and held in place 

 with a 13 mm diameter plastic backing disc. Expan- 

 sion of the swim bladder, due to reduced hydrostatic 

 pressure, caused captured fish to float, so gas was 

 released from the swim bladder with a 20-gauge 

 hypodermic needle to enable fish to return to the 

 bottom. For each experiment, 50-75 tagged fish, 

 handled in the same fashion as those released, were 

 held on the bottom in wire cages for about 24 h to 

 determine tag-related mortality. Tagged fish were 

 released over the reef, and sampling for recaptures 

 started 24 h after tagging began. Experiments were 

 completed in 48 h except at site 2 during the sum- 

 mer of 1982 when tagging was interrupted for 48 

 h by weather. 



Preliminary estimates of population size are 

 needed to determine sample sizes required for 

 precise Petersen estimates (Everhart and Youngs 



1981). Powles and Barans (1980) estimated the mean 

 density of C. striata on reefs was 51 fish/ha from 

 underwater television transects; expansion to the 

 areas of our study sites gave preliminary estimates 

 of 8,160 C. striata on site 1 and 6,120 on site 2. At 

 site 1 we needed to tag 1,000 fish and examine 550 

 for tags to have an error no greater than 25% for 

 19 times out of 20 (1 - a = 0.95 and P = 0.25). At 

 site 2, we needed to tag 1,000 fish and examine 500. 

 We used the adjusted Petersen estimate (Ricker 

 1975, p. 78): 



N* = 



(M + 1) (C + 1) 

 (R + 1) 



where N* 

 M 

 C 

 R 



estimated population size 

 number of fish tagged 

 sample taken for census 

 number of tags returned in the sam- 

 ple taken for census. 



The biomass of C. striata for each year and site 

 was estimated as 



Biomass = 21— x PE x g\ 



where n 1 = number of tagged fish in each 1 cm 

 TL interval 



n = total number of tagged fish 



PE = population size from the Petersen 

 estimate 



g = weight in grams for the midpoint of 

 each 1 cm TL size interval derived 

 from the total length-weight rela- 

 tionship 



a = number of 1 cm TL intervals of 

 tagged fish. 



In addition, the upper and lower confidence limits 

 were substituted for PE in the above expression for 

 estimates of the biomass at those population sizes. 



RESULTS 



Age and Growth 



We believe that the central opaque zone of the 

 sagitta may represent the first 1-4 mo of life in C. 

 striata. This zone varied in length from 1.16 to 3.60 

 mm in the anteroposterior plane and from 0.56 to 

 1.54 mm in the dorsoventral plane (Fig. 4). We were 

 not always able to make counts along a continuous 



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