HASTINGS ET AL.: FISH FAUNA ASSOCIATED WITH OFFSHORE PLATFORMS 



pardus, Antennarius ocellatus, Centropristis 

 ocyurus, Diplectrum formosum, Mycteroperca 

 microlepis , Serranus subligarius, Rypticus mac- 

 ulatus, Apogon pseudomaculatus , Lutjanus cam- 

 pechanus, L. griseus, Rhomboplites aurorubens, 

 Haemulon aurolineatum, H. plumieri, Diplodus 

 holbrooki, Equetus lanceolatus, E. umbrosus, 

 Chaetodipterus faber, Chaetodon ocellatus, C. 

 sedentarius, Holacanthus bermudensis, Chromis 

 enchrysurus, C. scotti, Pomacentrus variabilis, 

 Halichoeres bivittatus, H. caudalis, Blennius 

 marmoreus, Hypleurochilus geminatus, loglos- 

 sus calliurus, Acanthurus chirurgus, and Balistes 

 capriscus. A few natural rock outcrops which 

 support reef faunas occur in the area, especially 

 offshore from Stage I, but these are characteris- 

 tically low in relief and are quite distinct in some 

 ways from the habitats at the stages. They do 

 support populations of the reef species listed 

 above (and usually larger numbers than at the 

 stages), but usually do not attract large masses 

 of pelagic schooling and predatory species. 



A few reef species observed at the stage 

 habitats (such as Abudefduf saxatilis, Pomacen- 

 trus partitas, Thalassoma bifasciatum, and Acan- 

 thurus coeruleus) do not normally occur on the 

 natural rocky reefs off the northwest Florida 

 coast, but are tropical coral reef species which 

 may be carried into the northern Gulf of Mexico 

 by currents (see Hastings 1972). Such species are 

 not permanent residents of the northern gulf, but 

 are apparently usually killed by low winter 

 temperatures, except for possibly during mild 

 winters. 



Comparison of the Two Stages 



Although the fish faunas of the two stages were 

 quite similar (Tables 1, 2), there were a few nota- 

 ble differences between the species lists for the 

 two stages which may be significant. The most 

 numerous species at Stage II during the summer 

 and fall were the clupeids, Harengula pensacolae 

 and Sardinella anchouia, and rather irregularly, 

 Etrumeus teres and Opisthonema oglinum. These 

 fishes formed dense schools (Figures 2, 3) below 

 the platform during daylight hours, usually also 

 with large numbers of carangids such as Decap- 

 terus punctatus, Selar crumenophthalmus, and 

 Trachurus lathami, and the mackerel. Scomber 

 japonicus. Such schools of baitfishes were consid- 

 erably less abundant at Stage I except for during 

 the fall and early winter (especially November 



and December) when large numbers o^Sardinella 

 anchovia and D. punctatus were present. Most of 

 these had disappeared by January, however. 



As might be expected, typical estuarine species, 

 such as Orthopristis chrysoptera, Lagodon rhom- 

 boides, and Leiostomus xanthurus, were rare or 

 absent at Stage I, even though they were quite 

 numerous at Stage II. In contrast, E/ag^a^is bipin- 

 nulata, a species typical of open, pelagic waters 

 (Hiatt and Strasburg 1960), was recorded at 

 Stage I, but not at Stage II, although Klima and 

 Wickham (1971) found this species to be the most 

 common jack congregating about artificial struc- 

 tures near Stage II in 1969. Other pelagic species 

 such as Seriola dumerili and Sphyraena bar- 

 racuda were also more numerous at Stage I. Simi- 

 larly, some benthic species, which are charac- 

 teristic of the deeper water, natural reefs in the 

 northern Gulf of Mexico and may be rare in in- 

 shore waters as shallow as 18 m, were occasion- 

 ally recorded at Stage I, but not at Stage II. 

 Examples are Chaetodon sedentarius, Chromis 

 enchrysurus, C. scotti, Coryphopterus punctipec- 

 tophorus, and loglossus calliurus. 



The tropical coral reef species, such as Abudef- 

 duf saxatilis, Pomacentrus partitus, Thalassoma 

 bifasciatum, Acanthurus coeruleus, and Canth- 

 igaster rostrata, were recorded only at Stage I. 

 These tend to be shallow- water species which ap- 

 parently were able to survive by settling on the 

 pilings and cross-members near the surface at 

 Stage I. Such species are occasionally recorded in 

 inshore artificial reef habitats in the northeast- 

 ern gulf (Caldwell and Briggs 1957; Caldwell 

 1959, 1963; Haburay et al. 1969, 1974; Hastings 

 1972) and should be expected to occur occasion- 

 ally at both stages. 



Winter-Summer Contrast 



Seasonal changes in the faunal composition at 

 the stages were striking in some cases. Water 

 temperatures recorded during this study ranged 

 from 17° to 29°C at Stage I and from 13° to 30°C at 

 Stage II. Lowest temperatures were recorded in 

 January at Stage I and in February at Stage II. 

 Highest temperatures were recorded during Au- 

 gust and September. Changes in the fish fauna 

 were apparently correlated with temperature, 

 since the largest percentages of species recorded 

 (93% at Stage I; 95% at Stage II) were present 

 during the summer and fall, while the lowest 

 numbers were recorded during either the winter 



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