368 



Fishery Bulletin 102(2) 



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Trawls - 1 1 

 28 Jun-1 Jul 



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Reefs = 5 

 25 May-2 Jun 



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Trawls = 31 

 10-19 Jul 



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Reefs = 13 



1-25 Jul 



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Trawls = 32 

 31 Jul-12 Aug 



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9 Aug 



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Trawls = 26 Reefs = 2 



•23 Aug 23 Aug 



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Trawls = 32 



9 Se P Reefs = 3 



6 Sep 



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Trawls = 25 

 25-28 Sep 



Reefs = 4 

 28 Sep-6 Oct 



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Trawls = 25 

 12-21 Oct 



Reefs = 4 

 19-24 Oct 



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Trawls = 26 

 30 Oct-9 Nov 



Reefs = 3, 9-18 Nov 



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Trawls = 15 

 12-16 Dec 



Reefs = 6 

 5-8 Dec 



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Trawls = 26 

 9-12 Jan 



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Reefs = 3 

 25Mar-15 Apr 



100 200 100 



Standard length (mm) 



200 



Figure 2 



Movement patterns for age-0 red snapper iLutjanus campechanus) from the 

 northern Gulf of Mexico in 1994. Black bars represent trawl samples, grey bars 

 represent reef drop-net samples, and white bars represent SCUBA visual surveys 

 of concrete reefs. 



size and habitat type) in Euclidian space based on the 

 Bray-Curtis index. Thus, comparisons of red snapper diets 

 were based on all prey taxa, yet independent of capture 

 habitat and fish size. 



Results 



In the sampling areas during the summer and fall of 1994, 

 salinity ranged from 30 to 35 ppt. Dissolved oxygen was 

 7 ppm in the early summer, decreased to 3 ppm in July and 

 August, and increased to 7 ppm in the fall. Temperature 

 was 22°C in June, increased to 28°C in late August, then 

 dropped to just below 20°C by December. No significant 

 differences were detected between trawl and reef sites for 

 these environmental measures U-test, Ps0.05). 



Red snapper showed a clear shift in habitat during their 

 first few months of life (Fig. 2). Fish first recruited to open 



habitat at the end of June, at sizes <40 mm SL. Fish con- 

 tinued to recruit to open habitat until early September, at 

 which time they were larger ( 30 to 100 mm SL ) and began 

 shifting to more structured habitat. By mid-October most 

 age-0 fish had moved to reef habitat. During the initial 

 settlement no new recruits were collected or visually ob- 

 served on the artificial habitats (Fig. 2). Overall, only red 

 snapper <160 mm SL were collected from open habitat, 

 whereas only red snapper >70 mm SL were collected from 

 reef habitat. Size overlapped from 70.0 to 160 mm SL be- 

 tween habitats (Fig. 3). 



A total of 1639 red snapper stomachs were analyzed: 

 570 from open substrate and 1069 from reef habitat. Prey 

 were found in 789 (48'< ) of the total stomachs examined, 

 346 (61%) from the open habitat and 443 (41%) from the 

 reef habitat (Fig. 3). Trawl-collected red snapper were 

 mostly collected from site one, but sample sizes were also 

 large (>30 with prey) at two other sites (Table 1). Total red 



