For the sessile fauna it was found that the visible first settlers were present 

 after one week and were the incrustant forms of one species of foraminifera and 

 one species of a red calcareous algae. Secondary settlers, and not so abundant, 

 were the branched forms of small green and red algae, some hydrozoans and occa- 

 sional polychaetes worm tubes. The fish that came to the artificial sea-grass 

 to find refuge were mainly of the following species - for the daytime: Small 

 sharpnose puffers ( Canthigaster rostrata ) , yellowtail snappers ( Ocyurus 

 chrysurus ), small tiger grouper that was always at the same place ( Mycteroperca 

 tigris ) , and at night little Caribbean pipefish were seen ( Syngnathus rosseau ) . 

 For the small invertebrate motile fauna, it was found that the small mobile 

 cnidaria ( Boloceroides sp ) did not migrate but just moved around on the leaves, 

 day and night. 



Among the crustaceans, the amphipods and small (ovigerous at the time) caridean 

 shrimp were the predominant forms at daytime. The numbers of crustaceans was 

 reduced up to 15% at night, mainly because the majority of amphipods and shrimp 

 would migrate vertically into the water mass. Around dawn and sunset, molluscs 

 and crustaceans were found in about equal abundance, but at the day hours 

 crustaceans made for about 80% of the totality of the motile fauna. At the 

 middle of the night, molluscs (gasteropods Prosobranchs were the majority) only 

 came up to 607=. 



CONCLUSIONS 



1. The behavior of the small motile fauna follows a set pattern of daily 

 vertical migrations related to the plants metabolism and to the food supply. 

 Only when the artificial sea-grass leaves are covered secondarily by other 

 organisms, the small invertebrate motile fauna move in. The majority of crus- 

 taceans present at daytime among the seagrass leaves move away at night to the 

 open waters, while the molluscs partly move away during daytime down to the 

 sediment. 



2. The different species of small juvenile fish, grunts, yellowtail 

 snappers, groupers, are definitely among the leaves (natural and artificial) 

 mainly for protection from bigger predators. 



3. Artificial sea-grasses as well as any other type of surfaces, when 

 introduced in a marine environment, offer additional bare substratum for organ- 

 isms to settle down and grow, thus increasing the available food supply. In 

 shallow waters, small algae are the predominant organisms that attach and grow 

 on artificial surfaces, thus, other than being available food for grazers, they 

 enrich the environment with a supply of oxygen. (This same principle is used 

 in farming mullets commercially.) 



VI-212 



