520 



Fishery Bulletin 97(3), 1999 



resents essential fish habitat for many species fol- 

 lowing NOAA (1996). Bidirectional use of nursery 

 habitats positioned between inshore grassbeds and 

 offshore reefs requires further study. 



From abundance patterns of early life stages and 

 the absence of any nearby natural habitats with high 

 vertical relief, nearshore hardbottom of southeast 

 mainland Florida was estimated to have nursery 

 value for 34 species (Appendix). Empirical correla- 

 tion of variation in early survival with adult popula- 

 tion size is an important but rarely achieved compo- 

 nent of nursery area evaluation. Combining experi- 

 mental studies of habitat requirements with broad 

 field surveys can aid in connecting organism-scale 

 attributes with population-scale patterns (Serafy et 

 al., 1997). Early demersal stages of several of the 

 most representative taxa of nearshore hardbottom 

 (e.g. grunt and damselfish species) can be collected and 

 manipulated in the field and laboratory with relative 

 ease (Lindeman, 1986; 1997a). These taxa may serve 

 as useftil models for nursery habitat studies that ex- 

 perimentally assess habitat requirements. 



Effects of dredge-and-fill activities on ichthyofauna 



Burial of the nearshore hardbottom habitat at Carlin 

 Park with dredged sand significantly lowered the 

 abundances of both species and individuals (Fig. 9). 

 Before burial, 54 species were recorded, with mean 

 abundances of 38 individuals and 7.2 species per 

 transect (?! = 112 transects). After burial, eight spe- 

 cies were recorded with mean abundances of less than 

 one individual and species per transect in=92 

 transects). No quantitative studies on the effects of 

 nearshore hardbottom burial on fishes are available 

 in the peer- reviewed literature for comparison. 



The final supplemental environmental impact 

 statement (EIS) for the Carlin project (Palm Beach 

 Co. Dep. Environ. Resources Management, 1994) 

 summarized several agency and contractor surveys 

 between 1985 and 1990 at Carlin Park. Ten to forty- 

 eight fish species were recorded from qualitative 

 surveys of the hardbottom. Statements regarding the 

 habitat value of nearshore reefs and dredging effects 

 in the Carlin Park EIS emphasized the variable na- 

 ture of reef exposure and forecast that fish impacts 

 would be minimal and temporary. Primary impacts 

 predicted for fishes were 1) short-term displacement 

 during construction; and 2) temporary loss of food 

 sources. The EIS also emphasized that impacts would 

 be reduced by several features of the project design 

 and nearshore environment. These features included 

 the following: 1) the fishery value of impacted spe- 

 cies was low; 2) some amount of hardbottom would 

 remain or would be constructed for mitigation if 



needed; and 3) construction of the project would take 

 place when fish populations were at their lowest. No 

 mention of direct or indirect mortality upon fishes 

 was made. 



The biological assumptions within this EIS are 

 similar to those found in related documents (e.g. 

 ACOE, 1996). For the following reasons, it is sug- 

 gested that some of these assumptions may be tenu- 

 ous. The majority of individuals displaced by 

 hardbottom burial in southeast Florida are early 

 stages of economically and ecologically valuable spe- 

 cies (Appendix; Figure 9). Early demersal life stages 

 are particularly vulnerable to predators (e.g. 

 Shulman and Ogden, 1987). Displacement was per- 

 manent for most individuals because almost all prior 

 habitat was eliminated for at least 15 months (the 

 postburial duration of the present study). Because 

 of behavioral and morphological constraints on flight 

 responses, high mortalities are probably unavoidable 

 for many cryptic species, newly settled life stages, or 

 other site-associated taxa subjected to direct habi- 

 tat burial (Table 4.10 in Lindeman, 1997a). Whether 

 a fish population is seasonally low at the time a 

 project begins is insignificant if dredging will bury 

 the habitat immediately before the peak period of 

 larval settlement,^ as in the Carlin Park project. In 

 addition, loss of reef-associated food sources was 

 probably substantial over this period. 



No substantial habitat structure was present 

 within at least 0.8 km of the Carlin Park reef during 

 its burial. The closest natural structure was east- 

 ward at depths of at least 10 m. These deeper 

 midshelf habitats may be utilized by relatively few 

 grunt and snapper species during the newly settled 

 and early juvenile stages. To the south, no substan- 

 tial hardbottom was present for at least 4 km. To the 

 north, the jetties of the Jupiter Inlet were approxi- 

 mately 2 km away. However, fishes in a northerly 

 flight response had to negotiate a water column with 

 zero visibility because dredge fill was dumped north- 

 to-south. Any early stages of fish reaching the jet- 

 ties would probably encounter high predation from 

 older piscivores utilizing the large cavities among the 

 armor-stone boulders of the artificially deepened jetty 

 area (Lindeman, 1997a). 



A postburial mitigation project using shallow arti- 

 ficial reefs of limestone boulders was proposed in the 



^ Hackney, C. T., M.H.Posey, and S.W. Ross. 1996. Summary 

 and recommendations. In C. T. Hackney, M. H. Posey, S. W. 

 Ross and A. R. Norris (eds.l, A review and synthesis of data on 

 surf zone fishes and invertebrates in the south Atlantic Bight 

 and the potential impacts from beach renourishment, p. 108- 

 111. Rep. to U. S. Army Corps of Engineers. Wilmington Dis- 

 trict, Wilmington. NC. 



