FISHERY BULLETIN: VOL. 74, NO. 3 



growth estimates for this species. His work con- 

 cluded with a warning that the totoaba is a 

 declining species, in danger of extinction from a 

 combination of overfishing and the disappearance 

 of brackish water spawning grounds due to diver- 

 sion of Colorado River waters for agricultural and 

 other purposes. Cause (1969) and Sotomayor (1970) 

 later echoed this view. 



In this paper we present a short history of the 

 commercial fishery and report new information on 

 totoaba life history. We summarize what is known 

 about the ecology of the species and speculate on 

 consequences of the present small population size 

 and the intense fishing effort to which the fish have 

 been exposed. We discuss the three most probable 

 causes for the decline in the fishery: degradation of 

 spawning grounds, degradation of nursery 

 grounds, and overfishing. We examine Colorado 

 River flow data and annual catch data in the light 

 of these hypotheses, and discuss our results. In 

 conclusion, we draw together all these elements in 

 an attempt to assess the present and future status 

 of this commercial population. 



HISTORY OF THE FISHERY 



Until about 1920, commercial exploitation of the 

 totoaba was confined to export of dried air blad- 

 ders to the Orient as an ingredient of a gourmet 

 soup (Chute 1930). Craig (1926) reported the first 

 export of totoaba flesh to the United States. In 

 these early, developing years, the totoaba fishery 

 was directly responsible for the establishment of 

 three northern gulf fishing villages: Golfo de 

 Santa Clara and Puerto Penasco in the State of 

 Sonora, Mexico, and San Felipe in the State of 

 Baja California Norte (Berdegue 1955). Analysis 

 of registered catches by all Mexican ports for the 

 1966-70 period shows that these three ports 

 produced from 94.9 to 97.7% of the total catch (H. 

 Chavez, pers. commun.). 



From 1929 (when Mexican Government statis- 

 tics were first collected) onward, the fishery re- 

 sponded to a growing U.S. market by developing 

 transportation and refrigeration capabilities and 

 by improving fishing gear and boat facilities. 

 Annual yield began to increase rapidly in 1934 and 

 the catch peaked at 2,261 metric tons^ in 1942 



</l J 000 - 



 I ' ' 



19 10 



'  I  





YEAR 



Figure 1.- Yield of commercial totoaba fishery, northern Gulf of 

 California for the 1929-75 period. Figure modified from Arvizu 

 and Chavez (1972). Data for 1971-75 were obtained from H. 

 Chdvez (pers. commun.). 



(Figure 1). After 1942, despite intensified fishing 

 effort and increased gear efficiency, the annual 

 yield exhibited erratic fluctuation to the all-time 

 minimum of approximately 58 metric tons in 1975 

 (H. Chavez, pers. commun.^). 



Fishing methods evolved from spearing out of 

 dugout canoes and primitive handlining in the 

 early years, through dynamiting and primitive gill 

 netting, to the use of eflficient nylon gill nets. The 

 usual modern net has a stretched mesh size of 

 approximately 25 cm and measures 100-200 x 4-5 

 m. Gill nets were managed from diesel-powered 

 shrimp trawlers (12-18 m, some temporarily 

 diverted from shrimping during prime season 

 totoaba fishing), and from 4.5- to 7.5-m wooden or 

 fiber glass "pangas" (launches) fitted with out- 

 board motors. The activities of commercial fishers 

 have been largely limited to the prime breeding 

 season (January-March) when the spawning 

 adults are in the shallow waters of the extreme 

 northern gulf. Prior to the 1975 total protection of 

 totoaba, the prime fishing season ended with the 

 advent of an oflficial closed season, 1 April-15 May 

 (Arvizu and Chavez 1972), a protective measure 

 enacted by the Mexican Government in about 1955 

 (Berdegue 1955).^ At the same time, a sanctuary 

 was designated at the mouth of the Colorado 



^We follow the example of Arvizu and Chavez (1972) in giving 

 yields as weights of cleaned fish lacking heads and viscera unless 

 specifically designated otherwise. To convert to whole weights, 

 multiply by 1.1 (H. Chavez, pers. commun.). 



^The 1975 yield reported here is based on catch from principal 

 ports for the prime season only (through the month of March). 

 The final figures may be as much as 10% higher. 



^According to Berdegue (1955), before 1955 there was a closed 

 season extending from 20 March to 1 May; the prohibited period 

 was changed to the later dates because active spawning was 

 observed after 1 May. In 1969 and 1970 the beginning of the 

 closed season was delayed 15 days in response to the fishers' 

 petitions when breeding schools had not appeared by the end of 

 March (H. Chavez, pers. commun.). 



532 



