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Fishery Bulletin 102(3) 



Figure 1 



Map of sampling locations along the Texas Gulf coast for 

 S. dumerili. Inshore (<15 nautical miles) and offshore (>15 

 nautical miles I zones off Galveston, TX, are shown. 



Materials and methods 



Field collections 



Seriola dumerili associated with pelagic Sar-gassum mats 

 were collected off Galveston, Texas, from May to July 

 over a two-year period (2000 and 2001) (Fig. 1). Inshore 

 (<15 nautical miles |nmi]) and offshore (15-70 nmil 

 zones were sampled to evaluate the potential importance 

 of physiochemical conditions because inshore waters off 

 the coast of Texas are heavily influenced by estuarine 

 processes (Smith, 1980; Sahl et al., 1993). Replicate 

 samples (3-5 per trip) in both the inshore and offshore 

 zones were collected monthly by using a larval purse 

 seine (20 m long x 3.3 m deep, 1000-pm mesh). The purse 

 seine was deployed into the water as the boat encircled a 

 randomly chosen mat. The seine was pursed, the Sargas- 

 sum was discarded, and fishes were tunneled into the 

 codend, collected, and frozen on dry ice. Distribution and 

 abundance were expressed as relative abundance, and 

 catch per unit of effort (CPUE) represented the number 

 of fishes per purse-seine collection. In addition, a small 

 number of YOY S. dumerili were collected with hook- 

 and-line for age and growth information only. Standard 

 lengths (SL) were measured to the nearest 0.1 mm, and 

 weights to the nearest 0.1 g before otolith extraction. 

 GPS locations and mat volume (lengthx widthxdepthi 

 were recorded at each sample location. Environmental 

 parameters measured included sea surface temperature, 

 salinity, and dissolved oxygen. Daily sea surface tem- 



perature data were also taken from NOAA buoy 42035, 

 22 nmi offshore of Galveston, TX. 



Otolith procedures 



Sagittal otoliths were extracted from S. dumerili. Oto- 

 liths were measured to the nearest 0.001 mm and 

 weighed to the nearest 0.0001 g. Left or right sagittae 

 were randomly selected and mounted in epoxy resin 

 (Spurr, 1969). Once mounted, a Buehler isomet low- 

 speed saw equipped with a diamond wafering blade 

 was used to transversely cut embedded otoliths. Otolith 

 sections were then attached to petrographic slides with 

 Crystalbond thermoplastic cement. Type A alumina 

 powder 1 0.3 fim) and 400- and 600-grit sandpaper were 

 used to grind both sides of the otolith, and a polishing 

 cloth was used for final preparations. 



Age was determined by counting growth increments 

 along the sulcus from the core to the outer margin by 

 using a Nikon Labophot-2 light microscope and Opti- 

 mas 6.2 image analysis software (Media Cybernetics, 

 Silver Spring, MD). Because of the difficulty of enu- 

 merating some inner increments near the otolith core, 

 a relationship between age and otolith radius of several 

 clear specimens was used to predict the number of 

 increments within the unclear region. Age was deter- 

 mined by adding the correction factor to the increment 

 count from the first identifiable increment to the otolith 

 margin (Rooker and Holt, 1997). Correction factors 

 consisting of mure than five days were applied to 499r 



