changes in salinity. Juveniles are positively rheotactic within a current of 

 water. However, when the salinity of that water is decreased, downstream 

 swimming ensues. There is evidence that the responsiveness of juveniles to 

 decreases in salinity is under rhythmic control. The postlarvae respond to a 

 decrease in salinity by dropping to the substrate, where they remain inactive 

 and evade displacement by the ebbtide. When the salinity increases (floodtide) 

 they become active in the water column and are displaced inshore. 



The apparent dependence of tide-associated m.ovements on changes in salinity 

 is indicated by the extent of rainfall in the vicinity of "nursery" areas and 

 the commercial catch of the following year. 



75. HURME, A.K., "Rubble-Mound Structures as Artificial Reefs," Pvoaeedings 

 of the Speaiatty Conferenae on Coastal Structures 79, American Society 

 of Civil Engineers, Vol. 2, Mar. 1979, pp. 1042-1051 (also Reprint 79-4, 

 U.S. Army, Corps of Engineers, Coastal Engineering Research Center, Fort 

 Belvoir, Va., Aug. 1979, NTIS A073277). 



Structures armored with rubble can have a positive effect on coastal ecol- 

 ogy by functioning as artificial reefs, particularly when they are placed in 

 areas with a barren bottom. The desirable qualities of these reef structures 

 are frequently overlooked. Many people think of rubble groins, jetties, and 

 breakwaters as desirable places to fish, but do not realize that the structures 

 themselves have a major influence on the success of their fishing. 



Creating fishing reefs through the placement of solid materials in coastal 

 waters has a long history of success and has helped support a fishery that 

 contributes millions of dollars to coastal recreation. Rubble-mound structures 

 (constructed by the U.S. Army, Corps of Engineers) are ideal artificial reefs. 

 They are built of natural stone and have many varying sized cracks and crevices 

 exposed to the entire water column so they can be colonized by the greatest 

 diversity of reef dwellers. Most potential environmental problems can be over- 

 come by careful planning and site selection. Although benefits appear great, 

 quantifying them is a difficult task. From both the standpoint of biomass and 

 sport-fishing success, rubble-mound reefs are biologically highly productive. 



76. HUTTON, R.F. , "The Ecology of Boca Ciega Bay With Special Reference to 

 Dredging and Filling Operations," Technical Series, Vol. 17, No. 1, 

 Florida State Board of Conservation, Tallahassee, Fla., 1955. 



The study shows that the proposed "furen fill" and the proposed "green 

 fill" would seriously damage the sports and commercial fishing in the Boca 

 Ciega Bay area. The bay provides protected animal habitats, breeding, and 

 feeding grounds for marine animals. The greatest variety and number of animals 

 occur in areas where attached turtle grass is abundant. Dredging and filling 

 operations on submerged banks of turtle grass are harmful to the associated 

 plant life and destroy feeding and breeding grounds. There is some evidence 

 that dredging operations, under certain conditions, may be beneficial to filter 

 feeders such as some echinoderms, ascidians, and sponges. 



77. INGLE, R.M., "Studies on the Effects of Dredging Operations Upon Fish and 

 Shellfish," Technical Series No. 5, Florida State Board of Conservation, 

 Division of Oyster Culture, Tallahassee, Fla., Oct. 1952. 



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