724 



Fishery Bulletin 102(4) 



on the lower Texas coast during February, and Gunter 

 (1945), Simmons (1957), and Hoese (1965) have reported 

 postlarval finescale menhaden from the middle and low- 

 er Texas coasts from January to May. Gulf menhaden 

 have received considerable attention in fishery science 

 because of their large population sizes and resulting 

 ecological and economic importance in the northern 

 Gulf of Mexico (Nelson and Ahrenholz, 1981; Smith, 

 19911, whereas finescale menhaden are less numerous 

 and not directly sought by any recognized fishery (Ahr- 

 enholz, 1991). Our study describes for the first time the 

 development of postflexion (late larval), prejuvenile, and 

 juvenile finescale menhaden. 



Materials and methods 



squares regression techniques (SigmaPlot, version 5.0, 

 SPSS Inc., Chicago, IL) in order to graphically illustrate 

 any development differences between the two species. 

 Increasing ratios (BD/SL, CP/SL, and EYE/SL) were 

 described with an exponential rise-to-maximum equation: 



y = a(l 



-bx 



), 



whereas, the decreasing ratio of PAL/SL measurements 

 were described with a exponential decay equation: 



y = ae 



-bx 



In both equations, y = body proportion ratio; .r = SL: 

 a = intercept; and b = SL specific exponential rate of 

 change. 



A total of 170 wild-caught finescale menhaden larvae 

 and juveniles were used to describe early development. 

 All specimens came from ichthyoplankton collections 

 in Nueces Bay, Texas (27.87°N, 97.5TW), during May 

 and June 2003. Individuals were collected in the tidal 

 channels of Nueces Delta with a side-mounted push net 

 (60-cm ring net, 0.505-mm mesh). For comparison, 357 

 wild-caught gulf menhaden larvae and juveniles col- 

 lected during May and June of 1999, 2000, and 2002 

 from two nearby stations outside the delta (less than 1.5 

 km away), in addition to the tidal channel collections of 

 2003. were also studied. All individuals were initially 

 fixed in either 10% formalin or 95% ethanol and trans- 

 ferred to fresh 95% ethanol after 48 hours. 



Pigment patterns were recorded and specimens of fin- 

 escale menhaden were illustrated. Gulf menhaden were 

 not illustrated because the figures in Hettler (1984) are 

 adequate. 



Morphometries 



Body measurements were made to the nearest 0.1 mm 

 with an ocular micrometer fitted to a dissecting micro- 

 scope. All individuals collected were postflexion, preju- 

 venile, or juvenile stage as defined in Leis and Rennis 

 (1983), and standard length (SL) was measured as the 

 distance from the tip of the snout along the midline to 

 a vertical line through the posterior edge of the hypural 

 plate. All lengths are SL unless otherwise noted. Defini- 

 tions and other terms are as follows: 



BD = body depth; vertical depth at the pectoral sym- 

 physis. 



CP = caudal peduncle; horizontal distance from the 

 posterior edge of the dorsal fin base to the pos- 

 terior edge of the hypural plate. 

 EYE = eye diameter; horizontal distance between the 

 anterior and posterior edges of the fleshy orbit. 

 PAL = preanal length; distance from the tip of the 

 snout to the origin of the anal fin. measured 

 along the midline. 



Ratios of these four body proportion measurements in 

 relation to SL were fitted by means of nonlinear least 



Meristics 



Each specimen was examined to determine whether 

 scale formation had been initiated, and a total count 

 of ventral scutes for specimens in which they were suf- 

 ficiently developed was obtained. A total of 37 finescale 

 and 48 gulf menhaden from the 2003 collections were 

 cleared and stained according to Potthoff ( 1984) and 

 used for fin-ray and vertebrae counts. Because of the dif- 

 ficulty in accurately counting myomeres in transforming 

 clupeids (Hettler, 1984; Ditty et al., 1994), we chose to 

 count total vertebrae and use the number of postdorsal 

 and preanal vertebrae instead of postdorsal and preanal 

 myomeres as a potential diagnostic character. Fin-ray 

 counts included dorsal, anal, and caudal fins (both prin- 

 cipal and procurrent rays). 



Results 



Morphological development 



Finescale menhaden larvae were first collected at 9.7 mm 

 and ranged to 22.5 mm as transforming juveniles (Fig. 

 1). Transformation from the larval to the juvenile form 

 began around 14 mm and was completed by around 20 

 mm (Fig 2). Ratios of body depth, caudal peduncle, and 

 eye diameter all increased in relation to standard length 

 as larvae grew, whereas snout-to-anal length decreased 

 i Table 1). The decrease in snout-to-anal length reflected 

 the transformation from the elongate fusiform shape of 

 the larvae to the laterally compressed deep-bodied shape 

 of the juvenile. Scales began to form at around 15 mm on 

 the caudal peduncle region and progressed forward along 

 the ventral and lateral surfaces towards the dorsal sur- 

 face. None of the individuals examined had the enlarged 

 and fringed median scales preceding the dorsal fin, 

 which are an adult characteristic of the genus Brevoor- 

 tia. Ventral scutes also began forming around 15 mm, 

 and the full complement of 27-31 scutes (McEachran 

 and Fechhelm, 1998) was found by 19 mm. 



Gulf menhaden ranged from 11.7 mm as larvae to 

 40.4 mm juveniles. For gulf menhaden, body depth. 



