FISHERY BULLETIN: VOL. 74, NO. 3 



9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 

 MARCH 1972 



Figure 4.-Degree of gonadal maturation observed on specific 

 days during the 1972 prime fishing season. See text for explana- 

 tion of maturation categories. Each symbol represents one or 

 more individual fish. Open squares represent females; solid 

 squares represent males. 



tendency toward sexually segregated schooling, at 

 least in the case of male fish. It will be noted that 

 all the records for the early portion of the period 

 portrayed in Figure 4 show a single sex per catch, 

 while the records for the later portion of the period 

 show both sexes in all but one instance. It must be 

 clearly understood that some of the catch records 

 portrayed in Figure 4 represent single fish, mak- 

 ing those data points meaningless in this context, 

 but a majority of the data points represent multi- 

 ple individuals. This apparent sexual separation of 

 prespawning schools conforms with general ob- 

 servations by Hendrickson in years before 1972 

 and with the caption for figure 84 in Chute's (1928) 

 paper describing the earlier hook-and-line fishery: 

 "Practically all of the fish in this picture were 

 males . . . ." (the figure, depicting the butchering 

 process, shows about 15 large fish caught by three 

 men in 3 h). 



Success of the Golfo de Santa Clara panga 

 fishery is related to the size of the migrant totoaba 

 population, the length of the period in residence on 

 the fishing grounds, and population behavioral 

 patterns. Because the fishing grounds are identical 

 with, near to, or in the path to the spawning 

 grounds, analysis of the panga fishery catch sta- 

 tistics can yield valuable insight into the breeding 

 biology of this species. We have used "capture 

 incidence" as a measure of fishing success, em- 

 ployed here to give a quantitative indicator of the 

 presence of breeding adults on or near the sus- 

 pected spawning grounds (Figure 5). One capture 

 incident is defined as the catch of at least one 

 totoaba per panga per day; the daily total reflects 

 the number of individually successful net sets. We 

 assume that: 1) fishing effort is constant after a 

 given date within the prime season and 2) fishers 

 individually and collectively fish in the same area 

 each day throughout the period. These assump- 

 tions are in keeping with the nature of the Golfo 

 de Santa Clara fishery. This village waited in 



MARCH 1972 



Figure 5.-Golfo de Santa Clara catch and capture incidence 

 plotted against days of March for 1972 prime fishing season. See 

 text for explanation of capture incidence unit. Between 15 and 22 

 March the number of individually successful nets remained 

 comparatively constant, despite the peak catch on 22 March. 

 Official statistics indicate that 15 metric tons in addition to the 

 total of 71 metric tons shown in Figure 3 were recorded for this 

 port in 1972 (H. Chavez, pers. commun.). These additional data 

 cannot be traced to daily catch for inclusion in this figure. 



readiness each year for the arrival of the migrant 

 population and, within a few days of the first 

 catches by exploratory nets, virtually all available 

 gill nets were deployed for fishing of totoaba. 

 Despite daily success or failure, fishing effort 

 continued at this level until the season closed on 1 

 April. Most of the panga fishers worked a definable 

 area of the delta where "canals" (extensions of 

 Colorado River channels) deep enough to accom- 

 modate the large totoaba gill nets are separated by 

 shallow mud bars (see area III in Figure 2). 



In 1972 the first catch off Golfo de Santa Clara 

 occurred on 11 March and was followed by a period 

 of increasing catch and capture incidence due to 

 increasing effort until 15 March (Figure 5). During 

 the March 15-22 period, capture incidence was 

 relatively constant and high. During this same 

 period, catch varied somewhat erratically and 

 peaked on 22 March, after which both catch and 

 capture incidence fell off drastically despite no 

 reduction in fishing effort. The 22 March catch 

 amounted to 27% of Golfo de Santa Clara's yield 

 for that year and represented 9% of the total 

 recorded yield from all ports for 1972. The average 

 Golfo de Santa Clara net must have contained over 

 twice as many fish on 22 March as on 21 March and 

 3-5 times as many as on other "good" days in the 

 prime season. 



What factors in totoaba reproductive biology 

 might explain these results? Catch per net may be 

 considered an index of migrant arrivals if we 



536 



