818 



Fishery Bulletin 101(4) 



Strong offshore transport of surface waters 

 occurs during upwelling events, so that a rapid 

 metamorphosis to the demersal stage may be 

 critical for the coastal recruitment of white mullet. 

 This rapid metamorphosis is suggested for several 

 offshore spawning fishes with pelagic larvae that 

 subsequently recruit to estuaries (Creutzberg et 

 al., 1978; Heath, 1992) or that remain near the 

 bottom during ebb flow, once close to the coast, 

 thereby reducing offshore transport (Bartsch and 

 Knust, 1994). White mullet undergo metamorpho- 

 sis to the demersal stage 14 days after hatching 

 (Houde et al., 1976) at which time they would be 

 entrained in the inshore transported water that 

 occurs at depths greater than 50 m in the coastal 

 zone of northeastern Venezuela (Quintero, unpubl. 

 data). Several studies suggest that increased mor- 

 tality is caused by increased predation associated 

 with the change to bottom habitat (Johannes, 

 1978; Bakun, 1986). Heath (1992) suggested that 

 mortality from predation is particularly high dur- 

 ing migration to nursery areas. Given the time 

 to metamorphosis (14 days) and the age of white 

 mullet when they enter the lagoon (50 to 70 days 

 for the first cohort), metamorphosis to the demer- 

 sal stage most probably occurs at least one month 

 before entry into the lagoon (Anderson, 1957; 

 Caldwell and Anderson, 1959; Yanez-Arancibia, 

 1976;Vieira, 1991). 



During the demersal period at sea, white mullet 

 may be exposed to considerable mortality due to 

 benthic predators. Variation in the abundance of 

 recruitment pulses into La Restinga Lagoon may 

 reflect the interplay between spawning time and 

 the mortality during transport to the coastal area. 

 At some point between metamorphosis and lagoon 

 entry, juvenile mullet also develop active swim- 

 ming behavior to facilitate passive transport. We 

 observed intensive recruitment of small mullet 

 into the lagoon between March and June by indi- 

 viduals that had hatched the previous December 

 to February. The timing of their hatching means 

 that their return to the lagoon was likely facilitat- 

 ed by prevailing currents. In contrast, recruitment 

 of mullet to the lagoon over the remainder of the 

 year was weak and sporadic, and fish were much 

 larger and older At its first appearance in the 

 lagoon, the third cohort was twice the age of the 

 first cohort. These fish were not produced during a 

 period when currents would likely have facilitated 

 lar\'al transport to the lagoon (little upwelling) 

 and their lower densities may partially reflect 

 increased mortality during the more prolonged 

 return to the lagoon. We propose that spawning 

 during periods of weak upwelling causes a delay 

 in transport to coastal nursery areas and conse- 

 quently decreased survival. 



Periods of hatching leading to successful recruitment, 

 from late December to March, coincided with moderate 

 peaks in the upwelling index. This successful recruitment 



JL 



I  ii I 



n n nlllLnn 



. I. . 



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Mn 



.ndnnn Jl I 



—O a II nn n nHI n 



I ru-n .,~,n^ 



ntlnnnn U nO n W 



nnrlln, 



jJlu 



. on n rinnii n„ 



I . 1.1 



Jllll_ 



_llllll„ 



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n = 32 Mar-05 



n = 27 Apr-02 



n = 22 Apr-30 



n = 20 May-28 



n = 23 Jun-25 



n = 22 Jul-23 



n= 16 Aug-20 



n = 20 Sep-17 



n = 20 Oct-15 



n=19 Nov-10 



n = 25 Dec-10 



n = 27 Jan-08 



n=14 Feb-04 



n = 6 Mar-18 



n= 19 Apr-15 



n = 27 May-13 



n= 17 Jun-10 



n= 16 Jul-08 



40 80 120 160 200 240 280 320 360 400 



Age (days) 



Figure 9 



Monthly age distributions of juvenik' white mullet from March 1992 

 to July 199.3. Age wa.s calculated by counting daily growth ring.s start- 

 ing with the hatch mark. From top to bottom, open bars represent 

 cohort 1, black bars represent cohort 2, gray bars represent cohort 3 

 and black bars represent cohort 4. n = number of otoliths examined. 



may be the result of moderate levels of wind speed (<6 m/s-), 

 that promote moderate upwelling and yield optimal trophic 

 conditions for fish larvae (Cury and Roy, 1989). Coastal 

 upwellings in northeast Venezuelan waters are caused by 



