624 
Fishery Bulletin 95(3), 1997 
Sulcal groove 
Figure 5 
Photograph of transverse thin section of an adult totoaba otolith showing 24 annual rings, sulcal groove, and core. 
Core 
2 mm 
age. No “Lee’s phenomenon” (Ricker, 1969) was ob- 
served, and the von Bertalanffy growth model result- 
ing from back-calculated data was very similar to that 
derived from observed data (Fig. 7 ; Table 2). 
Gauldie and Nelson (1990) commented that otolith 
growth is typically repressed on the ventral plane 
because this part of the otolith is in direct contact 
with the skull, which restricts otolith growth; al- 
though otolith growth ceases in the ventral 
plane, it continues to grow in the sulcular re- 
gion. For totoaba, otolith growth seems to con- 
tinue on the proximal side along the sulcal 
groove. The ventral arm of the sulcal groove 
has been reported as the best area for otolith 
reading in other sciaenids (Beckman et al. , 1990; 
Lowerre-Barbieri et al., 1994). 
Major increases in length occur during the 
first and second years, diminishing once 
totoaba reach their sixth or seventh year, the 
age at first maturity. After this stage, the 
growth curve reaches an asymptote from about 
the twelfth to fourteenth year. The observed 
adult mean standard lengths at age in our study 
are very close to those calculated by VBGM from 
observed data and also from back-calculated 
data. 
In a comparison of age determinations with 
scales (Nakashima, 1916; Berdegue, 1955; 
