CHAPTER 7. COMMUNITY COMPONENTS - FISHES 



Of the six mangrove community types 

 discussed in section 1.5, fishes are an 

 important component of four: (1) basin 

 forests, (2) riverine forests, (3) fringe 

 forests, and (4) overwash island forests. 

 For convenience we have divided fringe 

 forests into two sub-components: (a) 

 forests which fringe estuarine bays and 

 lagoons and (b) forests which fringe 

 oceanic bays and lagoons. This division 

 is necessary because the fish communities 

 differ markedly. 



Mangroves serve two distinct roles 

 for fishes and it is conceptually impor- 

 tant to distinguish between them. First, 

 the mangrove-water interface, generally 

 red mangrove prop roots, afford a rela- 

 tively protected habitat which is particu- 

 larly suitable for juvenile fishes. 

 Secondly, mangrove leaves, as discussed in 

 section 3.6, are the basic energy source 

 of a detritus-based food web on which many 

 fishes are dependent. The habitat value 

 of mangroves can be considered strictly a 

 function of the area of interface between 

 the water and the mangrove prop roots; it 

 is an attribute shared by all four types 

 of mangrove communities. The importance 

 of the mangrove detritus-based food web is 

 dependent on the relative contribution of 

 other forms of energy in a given environ- 

 ment, including phytopl ankton, benthic 

 algae, sea grass detritus, and terrestrial 

 carbon sources. Figure 11 provides a 

 diagrammatic representation of the rela- 

 tive positions along a food web continuum 

 of the four mangrove communities. 



Fishes recorded from mangrove habi- 

 tats in south Florida are listed in Appen- 

 dix B. Although the fish communities are 

 discussed separately below, they have been 

 combined into certain categories in Appen- 

 dix B; fishes from mangrove basins and 

 riverine forests have been combined under 

 the heading of tidal streams; fishes from 

 fringing forests along estuarine bays and 

 lagoons are listed under the heading of 

 estuarine bays; fishes from oceanic bays 

 and lagoons have been listed under oceanic 

 bays. Since no surveys have been 

 published specifically relating to over- 

 wash island forests, there is no listing 

 for this community type in Appendix B. 



Site characteristics and sampling methods 

 for these community types are summarized 

 in Appendix A. Nomenclature and taxonomic 

 order follow Bailey et al. (1970). 



7.1 BASIN MANGROVE FORESTS 



The infrequently flooded pools in the 

 black mangrove-dominated zone provide an 

 extreme habitat which few species of 

 fishes can tolerate. The waters are 

 darkly stained with organic acids and 

 tannins leached from the thick layer of 

 leaf litter. Dissolved oxygen is 

 frequently low (1-2 ppm) and hydrogen 

 sulfide is released from the sediments 

 following physical disturbance. Salini- 

 ties are highly variable ranging from 

 totally fresh to hypersaline. The fish 

 families best adapted to this habitat are 

 the euryhaline cyprinodonts (killifishes) 

 and the poeciliids (1 i vebearers). The 

 killifishes include Fundulus confluentus 

 (Heald et al. 1974), Rivulus marmoratus 

 (M. P. Weinstein, Va. Commonwealth Univ., 

 Richmond, Va.; personal communication 

 1981), Floridichthys ca rp i o, and 

 Cyprinodon variegatus (Odum 1970"). The 

 poeciliids include Poecilia latipinna 

 (Odum 1970) and, the most common, Gambusia 

 affinis (Heald et al. 1974). While the 

 species richness of fishes in this habitat 

 is low, the densities of fish are often 

 very high. Weinstein Qjers. comm.) has 

 recorded up to 38 fish/m . 



All of these fishes are permanent 

 residents, completing their life cycles in 

 this habitat. They feed primarily on 

 mosquito larvae and small crustaceans such 

 as amphipods which, in turn, feed on man- 

 grove detritus and algae. These small 

 fishes enter coastal food webs when they 

 are flushed into the main watercourses 

 during high spring tides or following 

 seasonally heavy rains. Here they are 

 eaten by numerous piscivorous fishes in- 

 cluding snook, ladyfish, tarpon, gars, and 

 mangrove snappers. The alternate energy 

 pathway for fishes of the black mangrove 

 basin wetlands occurs when the pools 

 shrink during dry weather, the fishes are 

 concentrated into smaller areas, and are 

 fed-upon by various wading birds including 



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