FLANAGAN and HENDRICKSON: FISHERY AND REPRODUCTIVE BIOLOGY OF TOTOABA 



Table L-Totoaba captures observed in 1972 (see Figure 2 for 

 areas and timing). The figures shown here are personal observa- 

 tions of the senior author. 



'These data are displayed in Figure 5. Although catch data are 

 available for area III only in terms of tonnage, not head count of 

 fish taken, use of the 35-kg average per fish would give a con- 

 servative estimate of at least 2,500 individual fish taken In area 

 III during 1972. 



know where and when to find fish. Ideally, Figure 2 

 should reflect the results of an even pattern of 

 standard net sets through the February-June 

 period. 



To our knowledge, no one has investigated the 

 salinity preferences or tolerances of spawning 

 adults, but this raises the question of totoaba 

 spawning sites in estuarine areas of other major 

 gulf rivers. Spawning totoaba have never been 

 reported from locations other than the Colorado 

 River mouth. While further investigation is clear- 

 ly warranted, at present we accept the fisher's 

 hypothesis as an adequate predictor of population 

 migratory patterns. 



Spawning Concentration 



Because the annual breeding migration results 

 in a high density of fish within a limited area, it 

 has become the single most important aspect of 

 the fishery: total prime season catch is a function 

 of the number of fish arriving in the spawning 

 area before 31 March in an average year. The 

 appearance of migrant schools of totoaba in shal- 

 low coastal waters, as signaled by catches from 

 exploratory boats which have ventured out in 

 anticipation of their arrival, usually occurs in 



mid-February, but may take place as early as 

 December or as late as the end of March. 



Three references exist in the literature regard- 

 ing the spawning period. Nakashima (in Jordan 

 1916) said that the main spawning period was in 

 early May, while Berdegue (1955) reported the 

 reproductive season as extending from the end of 

 February or early March until early June. Obser- 

 vations by D. A. Thomson (1969) and the junior 

 author over the last four seasons indicate peak 

 spawning as late as April and early May but, more 

 commonly, in mid- to late March. Historical data 

 and existing statistics confirm the fisher's claims 

 that the period of concentrated catch (which 

 apparently coincides with peak spawning) has 

 become progressively abbreviated during the past 

 20 yr. The monthly catch data for Golfo de Santa 

 Clara for the 1964-72 period show a clear reduction 

 in length of season from 5 or 6 mo to an ab- 

 breviated period in March-April at present 

 (Figure 3). We believe (see below) that the catch of 

 the Golfo de Santa Clara fleet is a good reflection 

 of spawning activity and suggest that a pattern of 

 repeated spawnings formerly extending from 

 January-February to May and June has collapsed 

 to a single event which coincides with the old 

 temporal mode. A small remnant population might 

 be expected to react more uniformly to environ- 

 mental cues than would a large one, a factor 

 leading to progressively shorter migratory and 

 spawning periods. This is consistent with our 

 observation of breeding population residence time 

 of only 18 days on the spawning grounds in 1972 

 (from 11 March to 29 March, see discussion below). 



A limited amount of qualitative data on gonadal 

 maturation, collected during the 1972 prime 

 fishing season (Figure 4), indicates that males 

 ripen before females and retain spawning readi- 

 ness for longer periods of time-a common occur- 

 rence among fishes. It also provides evidence for a 



400-1 

 350- 



300 



g 250 - 



o 



a 



- 200 - 



UJ 



S 



J. 150 - 



o lOO - 



50 



D 



Q. 



_n 



sAl 



rn^ 



J F M i M 

 1964 



1965 



1966 



W A M J 

 1967 



w a w . 



1968 



F M A M . 

 1969 



M A M J 

 1970 



F M A W J 

 1971 



W A M J 

 1972 



Figure 3.- Monthly yield in metric 

 tons of totoaba, port of Golfo de Santa 

 Clara. Data for 1966-70 from Arvizu 

 and Chavez (1972); H. Chavez (pers. 

 commun.) supplied data for 1964-65 

 and 1971. The 1972 catch data were 

 obtained from F. Aguilera, Fisheries 

 Inspector (15 additional metric tons 

 recorded in 1972 are not shown 

 because month of capture was 

 uncertain). 



535 



