Stoner and Waite Habitat associations of Strombus gigas within seagrass meadows 581 



O 



§ 



Q_ 

 O 

 Cl 



U- 

 O 



o 



UJ 

 Q_ 



100 

 80 

 60 

 40 

 20 



100 

 BO 

 60 

 40 

 20 

 



L S L S L S 



MODERATE/SAND 



MS MS MS 



MODERATE/LOW 



ML ML ML 



HIGH/MODERATE 



H M H M H M 



75-100 125-150 Adults 



SIZE CLASS (mm) 



Figure 5 



Percentage of conch in three size-classes found within a haliitat 

 type from a choice of two tyjjes. Choices included combina- 

 tions of bare sand, low and high seagrass biomass. 



between 129 and 136 mm. Distributions at stations 6 

 and 7 were not different {j) = 0.749) (Fig. 4). This pat- 

 tern of size-frequency distribution showed that, in July, 

 conch were significantly larger at the stations with 

 higher macrophyte biomass (stations 6 and 7), while 

 smaller conch were found at sites with moderate-to- 

 low seagrass biomass (stations 3, 4, and 5). In Febru- 

 ary, the two SR stations with more than 10 conch- 

 stations 5 and 6— had significantly different length- 

 frequencies (;?< 0.0001) (Fig. 4). Again, the large conch 

 were associated with high seagrass biomass. 



Habitat preference experiments 



Results of the habitat preference experiments showed 

 that conch were proficient in detecting and choosing 

 habitats with different macrophyte characteristics (Fig. 

 5). Of the conch in all size classes, 90% were associated 

 with the moderate density plots as opposed to sand 

 habitat (10%). Habitat selectivity was less strong in the 

 other habitat pairs, but it is clear that plots with sea- 

 grass present were selected over bare-sand habitats, 

 and moderate-density seagrass was selected over either 

 high- or low-density seagrass. 



Heterogeneity G tests showed that the results of runs 

 within all of the individual habitat preference tests 

 were homogeneous (p<0.05) except one (Low vs. Sand; 

 125-150 mm; Gh= 14.37, p>0.05). Standard G tests 

 were used with the pooled data to test the null 

 hypothesis that animals were distributed equally over 



