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Fishery Bulletin 95(3), 1 997 
ported for other sciaenids (Beckman et al. 1990, 
Murphy and Taylor 1991), including species of 
Cynoscion, a closely related genus (Gonzalez, 1977; 
Blake and Blake, 1981; Shlossman and Chittenden, 
1982; Barbieri et al., 1994; Lowerre-Barbieri et al., 
1994). The well-defined seasonality in temperature 
in the Gulf of California (Alvarez Borrego et al. , 1973; 
Paden et al., 1991) also suggests that the marks seen 
in totoaba otoliths are annual because such tempera- 
ture changes are an important factor in ring deposi- 
tion (Brothers, 1978; Beckman et al., 1990). Berdegue 
(1955) considered scale rings to be annual on the 
basis of the migratory pattern and reproductive pe- 
riod of totoaba. 
The recent creation of the Upper Gulf of Califor- 
nia and Colorado River Delta Biosphere Reserve will 
enhance conservation efforts for totoaba by protect- 
ing important spawning and nursery habitat. Fur- 
thermore, fishing pressure from commercial shrimp 
trawls and gill nets will be greatly decreased. 
Barrera-Guevara (1990) reported that 92% 
of young-of-the-year totoabas were killed 
in the commercial shrimp fishery. In our 
study we were not able to sample organ- 
isms between ages 5 and 11 because they 
were not available to trawls and gill nets 
and because we did not sample in areas 
where prerecruit totoaba concentrate. 
These areas are difficult to sample because 
of their depth; the Guaymas basin reaches 
more than 200 m depth. It has been sug- 
gested that the summer migration of 
totoaba is toward deep waters in the cen- 
tral Gulf of California (Berdegue, 1955; 
Arvizu and Chavez, 1972; Flanagan and 
Hendrickson, 1976). These fish, however, 
are accessible to hook and line fishing, and 
“catch and release” sport fishing practices 
should be encouraged. 
It is clear that the current available 
habitat for totoaba will not allow signifi- 
cant population increase. Nevertheless, we 
found a population age-structure similar 
to that existing during the early 1890’s (as- 
suming that fish of ages 3-11 years exist 
but were unavailable to our sampling as 
previously described), and we suggest that 
continued conservation efforts should al- 
low for the survival of a stable but small 
population of totoaba in the Gulf of Cali- 
fornia. Estimates of adult survival pro- 
posed by Cisneros-Mata et al. (1995) be- 
fore and after the 1975 moratorium also 
support evidence of stability in the current 
population age-structure. 
Acknowledgments 
We thank the fishermen of the Gulf of 
Santa Clara and Puerto Penasco for their 
collaboration in sampling adult totoaba, 
especially Heriberto Amaya, Rosario 
Angulo, and their families. We thank per- 
sonnel of the Centro Regional de Investi- 
Years 
Figure 7 
Von Bertalanffy growth model curve fitted to observed ( ) and back- 
calculated ( — ) data of age (number of rings) and standard length (the 
year-class midpoint was used for age). Open triangles are observed data. 
