OBSERVATIONS ON THE COMMERCIAL FISHERY AND 

 REPRODUCTIVE BIOLOGY OF THE TOTOABA, CYNOSCION 

 MACDONALDI, IN THE NORTHERN GULF OF CALIFORNIA 



Christine A. Flanagan and John R. Hendrickson' 



ABSTRACT 



Information gathered from fishers and records of the failing totoaba, Cynoscio7i macdonaUli, 

 commercial fishery demonstrate the ability of the three principal ports to fully exploit the dwindling 

 population during its annual breeding migration to the mouth of the Colorado River. Gonadal 

 maturation, daily catch, and capture incidence data document the timing and route of the migration, 

 provide evidence for a tendency toward unisexual schooling in its early phase, and point to the 

 possibility that totoaba may form large aggregations before spawning is initiated. A trend toward 

 reduction in the length of the migratory and spawning period, from 5 or 6 mo in 1965 to 1 mo in 1972 is 

 documented with data from the port of Golfo de Santa Clara. In surveys of the hypothesized nursery 

 area, 28 juvenile totoaba (6-12 cm standard length) were collected at 4 of 14 sampling sites. The four 

 collection sites were commonly characterized only by depth (<1 m) and substrate type (soft clay-silt 

 sediments). Three hypothesized causes of the decline of this commercial fishery are examined by 

 statistical analyses of Colorado River flow and annual totoaba catch data: overfishing, loss of spawning 

 grounds, and loss of nursery grounds. Overfishing was found to be the most likely cause of the decline. 

 Recent trends of catch data among the principal commercial fleets, and evidence that regulatory 

 measures may have resulted in temporary recovery of totoaba production, provide further support for 

 the overfishing hypothesis. The journey of the migrant population along a known route and its 

 concentration into a predictable small area, its hypothesized requirement for dense aggregations prior 

 to spawning, and the added mortality of juveniles taken by shrimp trawls in the near-delta waters are 

 important points of vulnerability that render this endemic species particularly susceptible to fishing 

 pressure. The possibility of the extinction of Cynoscion macdonaldi, without continuation of the newly 

 decreed prohibition of fishing, is reiterated. 



The totoaba,- Cynoscion macdonaldi Gilbert 1891, 

 is the largest species of the family Sciaenidae, 

 with maximum reported lengths of almost 2 m 

 (Berdegue 1956) and weights exceeding 135 kg 

 (Cannon 1966); the larger females in present-day 

 commercial catches approximate 1.5 m and 35 kg 

 (Arvizu and Chavez 1972). The species is endemic 

 to the Gulf of California, where it used to support a 

 fishing industry and popular sport fishery based on 

 its annual spring breeding migration to the shal- 

 low, formerly brackish waters of the Colorado 

 River Delta region at the extreme northern end of 

 the gulf. The major portion of the catch was 

 exported from Mexico to the United States (prin- 

 cipally San Diego) and brought a high price per 

 pound under the influence of apparently unlimited 

 demand. Presently an indefinite closed season on 



'Department of Ecology and Evolutionary Biology, University 

 of Arizona, Tucson, AZ 85721. 



-The common name is often spelled "totuava" by writers from 

 the United States for no known reason. The spelling used here is 

 that preferred and used by Mexicans; it should become the 

 established spelling. 



the totoaba, declared by the Government of Mex- 

 ico on 2 August 1975, prohibits all capture of this 

 species by both commercial and sport fisheries (H. 

 Chavez, pers. commun.). 



Although the species has been heavily exploited, 

 its life history, population dynamics, and general 

 ecology are poorly known. Species accounts are 

 given in Jordan and Evermann (1898, 1902), Jor- 

 dan et al. (1930), Gabrielson and Lamonte (1954), 

 and Lanham (1962). The totoaba was included in 

 accounts of commercial sciaenid species by Croker 

 (1932) and Fitch (1949). Aside from these refer- 

 ences and others cited here, little has been pub- 

 lished on the totoaba; remaining incidental refer- 

 ences may be found in Arvizu and Chavez (1972), 

 the most recent summary of all available infor- 

 mation on this species. Although notes on the 

 ecology of the totoaba were first published in 1916 

 by Jordan, most of the presently accepted life 

 history information is based on fisher's lore. These 

 beliefs were first documented by Berdegue in his 

 1955 study of the fishery in which he also examined 

 scale annuli series and published the only derived 



Manuscript accepted Januar>' 1976. 

 FISHERY BULLETIN: VOL. 74, NO. 3 



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