were revisited in June 1973. Observations were 

 made of water temperature, salinity, turbidity, 

 and substrate character; associated faunas at each 

 site were sampled. A few juveniles were trans- 

 ported alive back to Tucson, Ariz., and maintained 

 there for about 80 days. Information on distribu- 

 tion and habitat of the juveniles is presented here; 

 notes on behavior of the juveniles in captivity will 

 be reported elsewhere (C. A. Flanagan in prep.). 



In our discussion of the hypotheses for the 

 decline of the totoaba fishery, we present statistics 

 of Colorado River flow and annual totoaba yield. 

 The annual yield data are those already presented 

 (Figure 1). For flow, we have attempted to es- 

 timate the amount of water delivered to Mexico in 

 the main river channel at the southerly interna- 

 tional boundary on the assumption that it will bear 

 some regular relationship to the volume of fresh 

 water entering the Gulf of California. This as- 

 sumption becomes tenuous with the development 

 of lowland agriculture in Me.xico and with sig- 

 nificant groundwater pumping in the United 

 States, both in evidence since about 1960. Suitable 

 effort data for the totoaba fishery are unavailable 

 but we have assumed that, following the peak 

 catch in 1942, effort was constant or increasing. 

 This assumption is probably warranted given the 

 demand and high price paid for totoaba flesh. The 

 limitations imposed by our assumptions are that 

 no catch datum before 1942 and no flow datum 

 after 1960 may be considered in these analyses. 



FISHERY BULLETIN; VOL. 74, NO. 3 



RESULTS AND DISCUSSION 



Breeding Migration 



The fishers believe that the annual migration of 

 totoaba is prompted by the urge to reproduce and 

 is guided by the search for a suitable estuarine 

 spawning environment. According to their beliefs 

 the breeding population, seeking areas of reduced 

 salinity, leaves deep water in the mid-gulf and 

 follows the Sonora coastline northward; eventually 

 the schools reach the mouth of the Colorado River, 

 where they spawn. Following spawning, the to- 

 toaba supposedly seek out the clearer, deeper 

 waters to which they are more accustomed and 

 follow the Baja California coastline on their return 

 migration southward. These beliefs are based 

 upon commercial catch experience dating back to 

 the late 1920's. 



Localities and dates of capture observed by the 

 senior author in 1972 (Figure 2 and Table 1) appear 

 to document a pattern consonant with the above 

 hypothesis, as do observations by the junior author 

 in earlier years. The regular port statistics also 

 implicitly support the hypothesis, with catches 

 each year reported chronologically first by Puerto 

 Penasco, then by Golfo de Santa Clara, and last by 

 San Felipe fleets. The data in Figure 2 represent 

 but a small fraction of the total 1972 fishing effort, 

 however, and in the most conservative interpreta- 

 tion demonstrate only that experienced fishers 



114- 



. BREiDING PtESERVE 



: OBSERVED CA1CH AREAS 



w Golfo de Santa Clara 



TT,- 



Figure 2.— Locations and dates of 

 observed commercial catches of to- 

 toaba during the 1972 prime fishing 

 season. Catch information in terms of 

 tonnage by day, boat, and area were 

 also obtained from Fisheries Inspec- 

 tors. These latter data are reflected in 

 the early capture date of 12 February 

 and the extended capture period of 

 11-29 March in areas I and III, re- 

 spectively. Chart shows Gulf of 

 California north of lat. 31° N (see 

 locater in upper right-hand corner). 



534 



