446 



Fishery Bulletin 88(3), 1990 



APR 78 

 n=4 



o-¥i 1 1 M . 



MAY 78 

 11=6 



0CI78 

 n=45 



DEC 78 

 11=38 





APR 79 

 n=5 



MAY 79 

 n=94 



IUN79 

 n=100 



IUL79 



SEP 79 

 n=71 



MAR 80 

 n=2 



MAY 80 

 11=100 



OCT 8 



11=22 



APR 81 

 n=2 



MAY 81 

 n=79 



11=175 



SEP80 

 n=30 



10181 

 n=l59 



MATURITY STAGE 



A0G81 



n=t37 



Figure 7 



Monthly gonad maturity stages (defined in Table 

 1) of immature and female Pi)lydaclylux uctoui'- 

 mus. 



3-4 months of age recruited in abundance in mid- 

 April-early May 1978, fish 50-70 mm and 2 months 

 old in early April 1979, fish 65-115 mm and 2-4 months 

 old in mid-May 1979, fish 75 mm and 3 months old in 

 mid-March 1980, fish 55-115 mm and 2-4 months old 

 in May 1980, and fish 60-115 mm and 2-4 months old 

 in early April-early May 1981. Few fish 50-115 mm 

 were collected from late August through February, in- 

 dicating little spawning during late April-late October 

 or November. 



Calculated hatching dates were 11 January 1978, 16 

 February 1979, 26 January 1980, and 7 February 1981 

 for the 1978-1981 cohorts, respectively (Fig. 2). Other 

 dates could have been calculated depending on data 

 points included; however, the basic spawning period 

 and coefficients of determination would be similar 

 (Dentzau 1985). We deleted the earliest two collections 



in 1980 and earliest three in 1981 from calculations 

 because mean sizes in these collections were as large 

 or larger than those in subsequent ones and may have 

 reflected incomplete recruitment or gear selection for 

 larger fish, causing an upward size bias. 



Gonad maturity data support the major mid-Decem- 

 ber-mid-March spawning period indicated by length 

 frequencies. Except for one gravid age-I fish collected 

 in April 1979, all fish collected in March-June were im- 

 mature or maturing virgin (Fig. 7); none were in the 

 Early Developing or later stages. Early and/or Late 

 Developing stage fish were most common in October- 

 December. Except for the one individual caught in 

 April 1979, gravid fish were collected only in December 

 as they approached age I. No ripe fish were collected, 

 and few were gravid or late developing. Mean and/or 

 maximum GSI values, although usually low, were high- 



