sea wrack community, feeding on 

 insects, mollusks, crustaceans, and 

 fish, returning during the day to 

 the pinelands hammocks and mangrove 

 forests (Rabkin and Rabkin 1978). 

 In the shallow flats through which 

 the sea wrack passes and in which it 

 partially originates, the flotsam is 

 somewhat like a floating island 

 accumulating even more marine peri- 

 phyton, while yielding a diverse 

 food source to shallow water fishes 

 and other predators. These floating 

 islands are a likely transport mech- 

 anism for terrestrial insect fauna 

 between isolated keys (Simberloff 

 1976). 



Examples of category (3) in- 

 clude nocturnally active coral reef 

 fishes of several families (includ- 

 ing Holocentridae , Lutjanidae , and 

 Pomadasyidas ) which feed over the 

 adjacent seagrass beds at night 

 (Zieman 1982). On a somewhat more 

 regional scale the spiny lobster 

 ( Panulirus arqus ), pink shrimp 

 ( Penaeus duorarum ) , andgrey snapper 

 ( Lutjanus qriseus ) are examples of 

 organisms that range over a wide 

 area and numerous habitats as a 

 function of their life history 

 (Zieman 1982). 



9.32 INVERTEBRATES 



To adequately summarize, or 

 even highlight the distribution and 

 ecology of marine and terrestrial 

 invertebrates in the Florida Keys is 

 beyond the scope of this report. 

 The Florida Keys are a living labo- 

 ratory for the study of marine 

 invertebrates. As the site of one 

 of North America's very few coral 

 reef ecosystems and certainly its 

 most accessible, much attention has 

 been focused on studying its diver- 

 sity and function (Jaap 1982). 



Two of the more commercially 

 important (and often studied) compo- 

 nents of the invertebrate fauna are 

 the pink shrimp ( Penaeus duorarum ) 

 and the spiny lobster ( Panulirus 

 arqus ) ♦ Commercial shrimp landings 

 from the Florida Keys constitute a 

 major portion of the total statewide 

 fishery. For the years 1970-1972, 

 Monroe County landings of pink 

 shrimp ( Penaeus duorarum ) averaged 

 5,389,587 kg (11,871,337 lbs) per 

 year or roughly 35% of the total 

 statewide shrimp haul (Prochaska and 

 Cato 1974). For the most part, com- 

 mercial shrimping focuses around the 

 Tort ugas shrimping grounds northwest 

 of Key West. Due to the great value 

 of this resource, a significant body 

 of research has been conducted over 

 the years on shrimp ecology and 

 population dynamics. Particularly 

 after 1954, when additional markets 

 developed for smaller size shrimp, 

 the question arose as to how to best 

 manage the Tortugas grounds for sus- 

 tained optimum yield (Iversen and 

 Idyll 1959). 



Intensive sampling and analysis 

 of the Tortugas grounds in the mid 

 fifties revealed that the smaller 

 shrimp tend to inhabit the shallower 

 waters of the grounds, a conclusion 

 that is generally reinforced by many 

 investigators as well as fishermen. 

 In an effort to prevent excessive 

 exploitation of the shrimp popula- 

 tion, a "controlled area" was de- 

 fined off of Key West within which 

 shrimp could not be harvested. This 

 "controlled area" corresponds to a 

 sort of refuge on the shallower 

 portions of the Tortugas grounds and 

 the area surrounding the Marquesas 

 Keys (Ingle et al. 1959). Table 41 

 presents data on the size range 

 distribution of shrimp within the 

 controlled area. 



201 



