HERRNKIND ET AL.: RECRUITMENT OF SPINY LOBSTERS 



and rate of consumption of algal epifauna. Prey 

 were obtained by rinsing large clumps oiLauren- 

 cia through a 100 |jl sieve. Prey included small 

 gastropods, amphipods, isopods, and ostracods 

 ranging in size from 1 to 9 mm (Marx and Herrn- 

 kind 1985a). Prey were individually counted and 

 placed in 1 L plastic beakers containing 750 mL of 

 seawater. One starved (24-h) juvenile lobster (6- 

 8 mm CL) was introduced to each container, al- 

 lowed to feed for 12 hours, and was then removed; 

 the remaining prey were counted. Fifteen spiny 

 lobsters were tested in each experiment; each lob- 

 ster was used once. Three experiments were con- 

 ducted using different prey combinations (Table 

 1), but the total number of prey available re- 

 mained similar and exceeded the amount a single 

 lobster could consume in 12 hours. Electivity in- 

 dices calculated for each experiment were used in 

 multiple comparison tests to determine whether 

 juvenile spiny lobsters fed preferentially or ran- 

 domly (Johnson 1980). 



Table 1 . — Relative prey availabilities (A) and predator usage (U) 

 values (percentages) in the three juvenile spiny lobster prey selec- 

 tion experiments. N = ^5 lobsters per experiment. F-values calcu- 

 lated from Johnson (1980) indicate whether prey choice differed 

 significantly from random in each trial: none of the tests were signif- 

 icant at P = 0.05. 



Gastropoda 



Tncolia sp. 



Batlillaria spp. 



Tegula spp. 



Atys spp. 

 Amphipoda 

 Isopoda 

 Copepoda 

 Ostracoda 

 Decapoda 



F-values 

 df 



43.5 615 714 83.0 58.0 54.5 



8.7 10 4 3 



6.5 00 — 



— — 14.3 



32.6 33.9 10.0 



0.2 



7.2 

 9.6 



8.3 



0.46 

 4,11 



36 



0.40 

 3,14 



7.0 

 17.4 

 11.6 



6.0 



0.09 



4,11 



7.1 

 20.0 

 13.1 



5.3 



RESULTS 



Postlarvae were more abundant on collectors at 

 the silted site than at the unsilted site. Diver 

 surveys revealed that higher numbers of algal- 

 dwelling juveniles (<20 mm CL) resided at the 

 unsilted site despite greater influx of pueruli into 

 the silted area (Table 2). Only one juvenile spiny 

 lobster collected at the silted site was <20 mm 

 CL, most were considerably larger (25—35 mm 

 CL) than those at the unsilted site, and some were 

 possibly large enough to have immigrated there 

 from adjacent unsilted areas. 



Silt recovered from the algal clumps was 

 largely calcareous and formed a cohesive cast 

 around the algal filaments. Classifying algal- 

 bound silts by particle size would yield irrelevant 

 values because sieving caused fragmentation of 

 aggregated particles. Therefore we report only 

 the total dry weight of the silts. Algae at No 

 Name Key carried a higher silt load than algae at 

 Burnt Point ix = 125 vs. 65 g/L algae, respec- 

 tively; t = 2.90, df = 18, P <0.01). Silt at No 

 Name Key was characterized as 12.5 ± 7.4% or- 

 ganic and 28.1 ± 27.6% carbonate by weight, 

 whereas Burnt Point silt was 16.9 ± 1.06% or- 

 ganic and 66.3 ± 14.5% carbonate (means ± 1 SD). 

 There was no significant difference in silt compo- 

 sition between sites (organics: t =0.83, df=4, 

 P > 0.05; carbonates: t = 1.97, df = 4, P > 0.05), 

 although sample sizes at each site were small and 

 sample variance substantial. Algae at both sites 

 contained primarily gastropods, amphipods, and 

 isopods, although significantly more gastropods 

 and echinoderms occupied unsilted clumps 

 (Fig. 2, Table 3; P < 0.05 in Bonferroni pairwise 

 multiple comparisons). 



Significantly more pueruli settled in unsilted 

 algal clumps than in silted clumps during labora- 

 tory settlement choice experiments (38 vs. 11, re- 

 spectively; G = 15.72, P < 0.001). Juvenile spiny 

 lobsters responded similarly in the habitat selec- 

 tion experiment (54 vs. 24; G = 11.78, P < 0.001). 

 We excluded the open sand habitat in aquaria 

 from our analysis because 1) juvenile spiny lob- 

 sters are never found residing on open sand in the 

 field, presumably due to a lack of food and refuge 



Table 2. — (A) Postlarval lobster abundances at silted and unsilted 

 Florida Bay study areas. Postlarval catch per unit effort (CPUE) 

 was estimated from Witham collector catches. (B) Juvenile lob- 

 ster (8-20 mm CL) abundances at the two study sites in 1985 and 

 adjacent areas sampled dunng 1983 and 1984. Juvenile CPUE 

 was estimated via diver surveys. 



ippiip - no ot postlarvae no. o( collectors 

 no. of days between collections 



2CPUE 



no. of lobsters collected 

 no. of diver hours 



335 



