Numerous fishes ingest sono plant 

 material, while relatively few of these 

 species &re strict herbivores; exceptions 

 are the Scarids and Acanthurids already 

 mentioned. Host plant and detrital mats- 

 rial is probably taken incidentally while 

 feeding on other organisms, Orthopri stis 

 chrys optera and Lagodon rhonboides are two 

 Mory abundant grass bed fishes in south 

 Florida and apparently during so^ne feeding 

 stages are O'lnivores, ingesting substan- 

 tial ainounts of epiphytes, detritus and 

 seagrass (Carr and Adains 1973; Adams 



1976a, 1976b; Kinch 1979). 

 include some filefishes, 

 nies, and qobies. 



Other oiiimvores 

 porgies, blen- 



Castropods are fed upon by a variety 

 of fishes including wrasses, porcupine 

 fishes, eagle rays, and the permit Trac h- 

 notus folcatus. Randall (1967) listed 71 

 species of fishes that feed on gastropods, 

 25 ingesting 10/c or more by volume. Most 

 species crush the shell while ingesting, 

 but a few swallow the gastropod whole. 

 The white grunt ( Hacnulon plumeri ) appears 

 to snap off the extended head of Cerith- 

 iuni , ignoring the shell. The southern 

 stingray ( Dasyatu s americana ) has been 

 observed turning over the queen conch 

 ( Strombus gigas )' and wrenching off the 

 conch's extended foot with its jaws as 

 the conch tries to right itself (Randal 

 1964). The spiny lobster (Panul irus 

 argus ) is an active predator on seagrass 

 molluscs. 



epi fauna, the impact of blue crab pre- 

 dation may be greatest on epibenthic 

 fauna. 



The majority of fishes within the 

 grass bed feeds on small, mobile epi fauna 

 including copepods, cumaceans, amphipods, 

 isopods, and shrimp. f^ishes feeding in 

 this manner include all the seasonally 

 resident fishes of the south Florida grass 

 beds, such as the Sciaenids, Pomadasyids, 

 Lutjanids, and Cerrids, as well as many of 

 the permanent residents, like Syngnatbids, 

 and Clinids. As such, they are deriving 

 inuch of their nutrition indirectly from 

 seagrass epiphytes and the detrital com- 

 munity present in the grass bed rather 

 than the grasses theriselves. Many of these 

 fishes, as adults, will feed on other 

 fishes; however, as juvenile residents in 

 the grass beds, their snail size limits 

 them to eating epi fauna. 



Important piscivores are present in 

 south Florida grass flats. These include 

 the lemon shark ( Negaprion brevirostires ) 

 and the bonnethead shark ( Sphyr na tibu ro), 

 the tarpon ( Megalops atlanticaT T the liz- 

 ardfish ( Synodon foetensT J the coronet 

 fish (Fistul aria tob acaria), the barracuda 

 ( Sphyraena barracuda" ), carangids, the grey 

 snapper ( Lutj anus orie sus), and the spot- 

 ted seatrout TC>'noscion nehulosus). 



U.2 DIRECT HERBIVORY 



The southern stingray and the spotted 

 eagle ray ( Aetobatis narinari ) are tv/u of 

 a relatively few number of fishes that 

 feed on infauna within the grass bed. 

 These fishes excavate the sediments. 

 Other similar feeders are wrasses, goat- 

 fishes, and mojarras. Adult yellowtail 

 snapper ( Oryhurus chrysurus ) have been ob- 

 served foraging in back reef seagrass sed- 

 iments (Zieman, personal observation). 

 That the infauna is not heavily preyed 

 upon is typical of seagrass beds (Kikuchi 

 1974, 1980). Apparently the protection 

 from predation afforded the Infauna of 

 grass beds is great enough that few fishes 

 specialize on infauna when feeding (Orth 

 1977b). The blue crab ( Call inectes 

 sapldus ) has been observed to shift its 

 feeding from Zostera infauna to epibiota 

 and thus, because of the protective rhl- 

 zor.e layer and the accessibility of the 



Caribbean grass beds may be unique 

 for the numbers and variety of direct con- 

 sumers of blade tissue (Ogden 1980) as 

 relatively few species Ingest green sea- 

 grass in significant quantities (Table 

 10). Prominent herbivores Include urchins, 

 conch, fishes, as well as the green tur- 

 tle, Chelonia mydas , and Caribbean manatee 

 ( Trichechus manatus ). The elucidation of 

 the role of direct herbivory as a pathv/ay 

 of energy flow in seagrasses has been 

 slow In developing. Until recently. It 

 was assumed that few organisms consumed 

 seagrasses directly, and that herbivory 

 had substantially decreased with the 

 decline of the populations of the green 

 sea turtle. Direct grazing of seagrasses 

 In south Florida is probably of greatest 

 importance in the grass beds of the Flor- 

 ida Keys and outer margin of Florida Bay 

 which are relatively close to coral reefs. 



59 



