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Dissertation - NSU Access Only
Ph.D. Oceanography/Marine Biology
Richard E. Spieler
Mahmood S. Shivji
Grunts (Haemulidae: Percoidei) represent one of the most abundant and speciose families on western North Atlantic coral reefs including 15 diverse species from the genus Haemulon. For this dissertation focusing on Haemulon, three studies were conducted to examine 1) spatio-temporal distributions of early-life stage (newly settled and early juvenile) individuals throughout the southeast mainland Florida reefscape, 2) species-specific, depth-variable distributional patterns of newly settled individuals and the potential influence of predation on the observed patterns, and 3) the effects of burying nearshore hardbottom settlement habitat and the efficacy of mitigating for the lost habitat using limestone boulder reefs. The combined results of the studies suggest that newly settled Haemulon spp. utilize shallow reef habitats (highest densities on nearshore hardbottom) with peak abundances in summer months. While newly settled individuals were never observed on natural reef habitats below 12 m depth, studies using artificial reefs (ARs) showed that new settlers were commonly recorded at depths of 21 m. Species-specific patterns of new settler depth utilization were found when replicate ARs at three sites (8 m, 12 m, and 21 m depth) were examined. Of the three most abundant species collected during fortnightly sampling of ARs, newly settled H. flavolineatum and H. aurolineatum were found at all three sites while H. striatum was found almost exclusively at the 21-m site. Comparison of caged and noncaged ARs allowed for inferences to be made regarding depth-variable predation pressure on newly settled Haemulon spp. Results (based on delta density differences between caged and noncaged ARs at each site) suggest lower predation pressure at the 8-m site, relative to the 12-m and 21-m sites. Depth-variable predation pressure may, in part, explain the distributional patterns exhibited by newly settled Haemulon spp. on the natural reef. I examined annual change in early-stage Haemulon spp. populations on nearshore hardbottom (NHB) to assess the impact of habitat burial caused by a large-scale beach nourishment. Newly settled Haemulon spp. represented the most abundant fish taxa on NHB. Populations of this life-history stage exhibited high variability among annual surveys and no direct effect of NHB burial was detected. In contrast, early juvenile individuals showed a significant decline during the annual survey corresponding with the timing of the beach construction (burial of NHB habitat). Furthermore, the beach-nourishment activities altered the entire fish assemblage structure of the NHB adjacent to the beach fill area. This change in the NHB fish assemblage structure had not returned to pre-impact conditions three years after the conclusion of the nourishment. Limestone boulder reefs deployed to mitigate for buried habitat exhibited lower newly settled Haemulon spp. abundance than NHB. Contrastingly, early juvenile abundance was higher on the boulder reefs than on the NHB. Fish assemblage structure on the boulder reefs differed substantially from the NHB for which it was intended to resemble; with more mid- and large-bodied predators present on the boulder reefs. The results suggest mitigation boulder reefs did not provide equitable settlement habitat for Haemulon spp. Based on the combined results of this dissertation, it appears that shallow reef habitats (especially NHB) represent important settlement habitat for Haemulon spp. by providing spatial refuge from predators, which were more prevalent at deeper sites. Although burial did not appear to directly cause changes to newly settled Haemulon spp. populations on the NHB, fish assemblage structure was altered. Changes in species composition and abundance can have unforeseen ecological consequences for future Haemulon spp. populations. Relative to other reef habitats, the high densities of new settlers supported by the NHB suggests this unique habitat deserves protection from future nthropogenic impacts.
Lance K. B. Jordan. 2010. Multi-Experimental Examination of Haemulon Species (Haemulidae) Early-Life Ecology on Southeast Mainland Florida Coral Reefs. Doctoral dissertation. Nova Southeastern University. Retrieved from NSUWorks, Oceanographic Center. (83)