FISHERY BULLETIN: VOL. 78, NO. 1 



N.C. 



Figure l.— Continental shelf off North 

 Carolina and South Carolina and important 

 ba thy metric features that relate to the ver- 

 milion snapper study. 



l)^"^ 



CAPE LOOKOUT 



/ 



REA 1 



Isobath 



1 



100 km 



the RV Onslow Bay and the RV Eastward; most 

 juveniles were trawled from RV Dolphin. 



Temperature was taken by expendable 

 bathythermograph, and photoperiod was obtained 

 from the National Ocean Survey tide tables (U.S. 

 Department of Commerce 1971, 1972, 1973). 

 Specimens were weighed (nearest gram) and mea- 

 sured (nearest millimeter). Gonads were removed, 

 preserved in 10% Formalin"* for at least 1 wk, 

 washed in tap water for several days, and then 

 placed in 70% isopropyl alcohol. Frequency dis- 

 tributions of ovum diameters were plotted by 

 month to determine seasonality, frequency, and 

 duration of spawning (Hickling and Rutenberg 

 1936; Fahay 1954). The diameters of approxi- 

 mately 100 randomly selected ova from each of two 

 females per month were measured to the nearest 

 0.05 mm by dissecting binocular microscope at 

 25 X . To validate measuring ova from any portion 

 of an ovary, we determined by analysis of variance 

 that ova sizes were distributed uniformly (indicat- 

 ing uniform development) throughout the ovaries 

 (Table 1). 



^Reference to trade names does not imply endorsement by the 

 National Marine Fisheries Service, NOAA. 



138 



Later, the gonads were removed from preserva- 

 tive and weighed (nearest 0.1 g) after surface 

 moisture was absorbed by blotting. 



A gonosomatic index was used as a measure of 

 reproductive development (Finkelstein 1969) for 

 determining spavvTiing seasonality and maturity. 

 The index was calculated according to the formula 

 KG =W/TL^ where KG = gonad index, W = pre- 

 served (blotted dry) gonad weight in grams, TL = 

 total length in millimeters. We realize that as- 

 suming the cubic relationship is arbitrary. Quast 

 (1968) has showm for kelp bass, Paralabrax clath- 

 ratus, that the percentage of body weight con- 

 tained in gonads increases with fish length. There- 

 fore, the true exponent is undoubtedly >3, but 

 data limitations preclude more accurate 

 formulation. 



Ovaries used for fecundity studies were pre- 

 served in modified Gilson's fixative (Bagenal and 

 Braum 1968). The ovarian tunic was removed and 

 washed free of adhering ova. Additional washings 

 separated developing ova from undifferentiated 

 oocytes and follicular material. A small subsam- 

 ple of ova (about 1,000 or less) was stored wet for 

 later counting in a gridded Petri dish under a 

 binocular dissecting scope. Subsamples and origi- 



