FISHERY BULLETIN: VOL. 85, NO. 2 



is somewhat surprising that so little information con- 

 cerning its reproduction, other than the seasonal 

 spawning time, is available. For instance, little 

 attention has been paid to the dynamics of oocyte 

 development and ovarian recrudescence in natural 

 striped mullet populations. A staging system for the 

 ovary itself that would simply and meaningfully 

 represent the extent of ovarian recrudescence in this 

 species is lacking. And, although there have been 

 numerous references to size of age at sexual matur- 

 ity (Jacot 1920; Stenger 1959; Timoshek 1973; Ape- 

 kin and Vilenskaya 1979), these are generally not 

 based on comprehensive sampling. Similarly, al- 

 though there have been equally numerous reports 

 of striped mullet fecundity (Nash et al. 1973; Pien 

 and Liao 1975; review by Alvarez-Lajonchere 1982), 

 most derive from counts of eggs (or oocytes) in only 

 a very limited number of fish, while body size-related 

 data are virtually nonexistent. 



We recently initiated several studies dealing with 

 the reproduction of M. cephalus in coastal waters 

 of northeast Florida and related topics. The specific 

 purposes of this investigation include describing the 

 patterns of oocyte growth during seasonal ovarian 

 recrudescence, developing an ovarian staging sys- 

 tem based on these patterns, and providing defin- 

 itive determinations of both the size at maturity and 

 the size-specific fecundity of female striped mullet 

 in the area. 



MATERIALS AND METHODS 



Fish 



Female striped mullet approximately 18 cm stan- 

 dard length (SL) or larger were captured by cast net 

 from the Matanzas River Inlet south of St. Augus- 

 tine, FL. Collections were made periodically from 

 October 1984 through January 1985, and again from 

 August 1985 through January 1986, for a total sam- 

 ple of 340 fish. Standard length and fork length (FL) 

 were determined to the nearest 0.1 cm, and body 

 weight (BW) to the nearest 0.1 g for all fish. Ovaries 

 of most (248) fish >20 cm SL were removed and 

 transferred to a buffered salt solution (FO: Wallace 

 and Selman 1978), and any adhering non-ovarian 

 tissue was removed. Whole ovaries were then patted 

 dry and weighed to the nearest 0.01 g. The GSI for 

 each fish was calculated as GSI = (ovary weight/ 

 body weight) x 100. 



Oocyte Size-Frequency Profiles 



Oocyte size-frequency profiles were constructed 

 188 



for each fish in the following manner. A represen- 

 tative (see below) piece was gently teased free from 

 the middle of each newly collected ovary, patted dry, 

 weighed to the nearest 0.1 mg, and placed in a petri 

 dish containing FO solution. Pieces weighed from 

 1 to 9 mg and contained from 100 to 500 oocytes 

 >0.10 mm in diameter. Individual follicle-enclosed 

 oocytes were manually measured to the nearest 0.02 

 mm with an optical micrometer mounted on a dis- 

 secting microscope. Oocyte size-frequency profiles 

 were not determined for fish with largest oocyte 

 diameters (LODs) <0.10 mm, although their LODs 

 were noted. 



Profiles and LODs derived from a sample of ovary 

 can be considered representative because oocyte 

 development is known to occur uniformly through- 

 out the mullet ovary (Ochiai and Umeda 1969; She- 

 hadeh et al. 1973; Timoshek and Shilenkova 1975). 



Oocyte Stages 



The oocyte size at which vitellogenesis (the period 

 of protein yolk accumulation) begins in the striped 

 mullet was determined by the appearance of specific 

 yolk protein bands in oocyte homogenates subjected 

 to polyacrylamide gel electrophoresis (see Greeley 

 et al. 1986b). Groups of small oocytes with mean 

 diameters of 0.14, 0.16, 0.18, and 0.20 mm were 

 isolated from surrounding ovarian tissue, homog- 

 enized in a sodium dodecyl sulfate (SDS) contain- 

 ing buffer solution, and heated at 100°C for 5 

 minutes. Samples were loaded onto a 0.75 mm thick 

 polyacrylamide gradient gel (gradient: 3.5-20.4%) 

 and were electrophoresed in SDS buffer with a con- 

 stant applied current of 30 mAmps until the 

 bromophenol blue marker migrated from the gel. 

 Protein fixation, visualization with Coomassie blue, 

 and molecular weight determinations were con- 

 ducted as in Wallace and Selman (1985). Biochem- 

 icals and reagents were highest available grades 

 from Sigma Chemical Company^ and Bio-Rad 

 Laboratories. 



The minimum oocyte size competent to resume 

 meiotic maturation (leading to the development of 

 a mature fertilizable egg) in response to steroid hor- 

 mone stimulation was determined in vitro by the 

 methods of Greeley et al. (1986a). Larger follicle- 

 enclosed oocytes were isolated in FO and assigned 

 to one of four pools with mean diameters of 0.52, 

 0.56, 0.60, and 0.64 mm. Oocytes from each pool 

 were randomly subdivided into treatment (steroid 



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 National Marine Fisheries Service, NOAA. 



