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Fishery Bulletin 100(3) 



ate and the southmost boundary being 

 semitropical (Zieman and Zieman, 1989). 

 This dimate change results in latitudinal 

 variation in the shallow water communities 

 along the WFS: from a mainly West Indian 

 fauna in the south to a Carolinian fauna in 

 the north (Smith, 1976; Lyons, 1979). 



The goal of our study was to improve our 

 understanding of the recruitment dynam- 

 ics of gray snapper by determining the spa- 

 tial and temporal patterns in spawning and 

 settlement along the WFS. The objectives 

 of this study were 1) to establish spawning 

 time through otolith back-calculation and 

 the examination of adult gonads, 2) to de- 

 termine settlement time (i.e. planktonic lar- 

 val duration) from otolith microstructure, 

 3) to estimate growth rates for juvenile gray 

 snapper, 4) to compare estimated spawning 

 times, settlement times, and growth rates 

 between sampling regions and years, and 5) 

 to examine the potential influence of lunar 

 phase on spawning and settlement events. 



Materials and methods 

 Sampling and collection 



We collected juvenile reef fish from the sea- 

 grass beds of the WFS from St. Andrew Bay in northwest 

 Florida to Ft. Myers in southwest Florida. For spatial com- 

 parison of the results, we divided the study area into three 

 sampling regions chosen on the basis of the differences in 

 faunal composition (Lyons and Collard, 1974; Smith, 1976; 

 Hoese and Moore, 1977) and type of coastal environment 

 (Price, 1954) (Fig. 1). Region 1, the Florida Panhandle, 

 embraces St. Andi'ew Bay to the St. Marks River, an area 

 of sand beaches and barrier islands. Region 2, the Big Bend, 

 spans the area from the St. Marks River south to Tarpon 

 Springs. The Big Bend is unlike the other regions in that it 

 has no barrier islands and is considered a zero-energy coast- 

 line (Murali, 1982). Region 3, Southwest Florida, includes 

 the area from Tarpon Springs south to Ft. Myers. This region 

 is similar to region 1 in that it is composed largely of sand 

 beaches and banner islands (Zieman and Zieman, 1989). 



Station locations within these regions were chosen ac- 

 cording to abundance of economically important fin fish 

 species (Koenig and Coleman'^). The 20 stations were lo- 

 cated where there were large dense areas of seagi-ass in 

 close proximity to the open gulf The dominant species of 

 seagrass in the study area is turtle-grass, Thalassta testu- 

 dinum, followed by manatee-grass, Syringodium filiforme. 



St. Andrew Bay 



St. Joseph Bay 



Turkey Point 



Tampa Bay 

 Sarasota Bay 

 Ft. Myers 



..;>*' 



Figure 1 



Sampling regions and station locations along the West Florida shelf (WFS). 

 Thick black lines demarcate the three sampling regions: region 1, the Flor- 

 ida Panhandle; region 2, Big Bend; and region 3, Southwest Florida. 



Koenig, C. C, and F. C. Coleman. 1998. Recruitment indices 

 and seagrass habitat relationships of the early juvenile stages of 

 gag, gray snapper, and other economically important reef fishes 

 in the eastern Gulf of Mexico. Final report (MARFIN award 

 no. NA.57FF0055) to Florida State University, 66 p. Depart- 

 ment of Biological Sciences, The Florida State Univ., Tallahas- 

 see, FL 32306-2043. 



and shoal-grass, Halodule wrightii (Zieman and Zieman, 

 1989). Station depth generally ranged from 1 to 3 meters. 

 We collected juvenile fish for this study every other 

 month in 1996 and 1997, beginning in late February of 

 1996 and early March of 1997. At each station we made 

 five replicate tows of 150 meters (m) in approximately 5 

 minutes (1.8 km/hour) using two different types of trawls. 

 To collect the smallest postsettlement juveniles, a 1-m by 

 0.40-m benthic scrape constructed of a stainless steel frame 

 with a 2-mm nylon mesh tail bag was used. This trawl was 

 used from the beginning of the year until the fall. We used 

 a 5-m by 3-m otter trawl with a 3-mm nylon mesh tail bag 

 to collect larger individuals year round. The contents of 

 each trawl were sorted and all juvenile fish of commercial 

 value were removed, bagged, and stored on ice. At the end 

 of a sampling trip, all juvenile fish collected were frozen. 

 In the laboratory juvenile gray snapper were removed from 

 samples, thawed, measured (standard length [SL] to the 

 nearest 0.1 mm), and weighed to the nearest 0.1 g. 



Otolith preparation and interpretation 



Both the sagittae and lapilli were extracted from each 

 snapper under a dissecting microscope by the "open-the- 

 hatch method" (Secor et al., 1992). One lapillus was chosen 

 at random from each fish for measurement. Whole lapilli 

 were viewed with a compound microscope at 50x magni- 

 fication with a video camera and monitor and the image 

 was digitized on a microcomputer with image analysis 

 software (BioScan, 1990). A measurement (nearest pm) 



