HASTINGS ET AL.: FISH FAUNA ASSOCIATED WITH OFFSHORE PLATFORMS 



tary reef species such as Chaetodon ocellatus. 

 These estimates (recorded for all dives in Tables 1 

 and 2) are admittedly subjective but may be use- 

 ful in describing the seasonal changes in the fish 

 populations around the platforms. 



Our dives at Stage II during the SITS II pro- 

 gram were scheduled to occur at approximately 

 5-h intervals from 1 to 4 August 1972. Although 

 this schedule was not always followed because of 

 other diving commitments of the program, we 

 made 10 dives which included at least 2 dives 

 during each quarter of the 24-h day. Times of the 

 dives are presented as Central Standard Time 

 (CST) in this report. During early August 1972, 

 the times of sunrise and sunset at Stage II were 

 approximately 0500 and 1840 CST, respectively. 



During the SITS II program, two censusing sta- 

 tions were set up under Stage II: Station 1 on the 

 bottom at 18.3 m; and Station 2 directly above, 

 about 4.6 m below the water surface. Both sta- 

 tions were the same size and were conveniently 

 delimited by the cross-members at one corner of 

 the platform. The stations measured 4.9 x 4.9 x 

 7.0 m. Counts were restricted to that portion of 

 the water column estimated to extend 1 m up- 

 ward from the base of the cross-members (corres- 

 ponding to the bottom at Station 1). Thus, the 

 water volume included within each station was 

 about 12 m^. 



During each dive at the censusing stations the 

 authors attempted to identify and count all 

 species of fishes present within each station. 

 Counts were recorded on plastic slates during the 

 censusing, then transferred to data sheets after 

 surfacing. Times required to make each census 

 varied because of the great variation in the num- 

 bers of fishes present, but were usually about 

 10-15 min for each station. In most cases both 

 stations were censused on each dive, and counts 

 for Station 2 were made about 15-20 min after the 

 counts for Station 1. On dives 1, 9, and 10, only 

 one of the two stations was censused. Some 

 species were so numerous at times that only es- 

 timates of their abundance could be made. Such 

 estimates offish abundance by two divers making 

 counts at the same time were generally in the 

 same order of magnitude. 



During nocturnal diving operations, an under- 

 water light was suspended near the surface below 

 a ladder (to facilitate diver return) at the corner 

 of the platform farthest from the censusing sta- 

 tions. It was not visible underwater at the census- 

 ing stations and did not appear to affect our 



counts. Although some fishes were attracted to 

 this light, they were mostly juveniles and larvae 

 of pelagic species. 



Nomenclature and arrangement of the families 

 in Tables 1, 2, and 3 follow Bailey et al. (1970). 



RESULTS AND DISCUSSION 



All species recorded at the two stages during 

 this study are listed in Tables 1 and 2. Table 3 is a 

 list of the species recorded in the two stations at 

 Stage n during the SITS II dives. These tables 

 should be examined in connection with the fol- 

 lowing synopsis of the results of this study. At 

 least 101 taxa (identified to family or species) 

 were recorded during this study at the two plat- 

 forms; 61 species were recorded at Stage I during 

 10 dives, and 86 taxa were recorded at Stage II 

 during 21 dives. The greater number recorded at 

 Stage II is probably primarily a result of the 

 greater number of observations there. In gen- 

 eral, the fish faunas of the two stages are quite 

 similar, and most of the species recorded at only 

 one could be expected to occur at both occasion- 

 ally. Of the 101 taxa recorded, about 75 were 

 frequently observed during the study and could 

 be regarded as characteristic members of the 

 fauna, 41 were recorded as common or abun- 

 dant. Of the latter group, 27 species were re- 

 corded at Stage I and 36 at Stage II. 



Faunal Composition 



The two stages represent an artificial reef 

 habitat in an area previously characterized by 

 flat sand bottoms. Thus, the fishes inhabiting the 

 stage environment are a mixture of faunal types, 

 including some species usually expected in such 

 flat, sandy areas, but also including many species 

 more characteristic of other habitats of the north- 

 ern Gulf of Mexico, especially fishes which are 

 attracted to reef environments. 



A number of demersal species characteristic of 

 open sand habitats of the northern Gulf of Mexico 

 were frequently recorded at the stages, but these 

 were usually seen over the open sandy areas sur- 

 rounding the stages. Examples are Dasyatis 

 sp.. Raja eglanteria, Arius felis, Ogcocephalus 

 radiatus, Stenotomus caprinus, Hemipteronotus 

 novacula, Prionotus sp., Paralichthys albigutta, 

 Lactophrys quadricornis, and Chilomycterus 

 schoepfi. In addition, many species recorded at 

 the stages are pelagic fishes characteristic of open 



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