Rickey: Maturity, spawning, and seasonal movement of Atheresthes stomias 



131 



Market 

 n = 2,167 



15 20 25 30 35 40 45 50 55 60 65 70 75 80 



Discard 

 n = 185 



014 



012 

 0.10 

 08 

 0.06 

 0.04 

 02 



000 



15 20 25 30 35 40 45 50 55 60 65 70 75 60 



Survey 

 n = 351 



15 20 25 30 35 40 45 SO 55 60 65 70 75 



Length (cm) 

 Figure 2 



Length-frequency distributions of 

 arrowtooth flounder by sample category. 

 Dark bars = males; clear bars = females. 



same size as fish in winter market samples, discard 

 and market samples were pooled by common month 

 and by keeping years separate. Throughout the year, 

 samples almost always included large spent/resting 

 females that did not show signs of ovarian recrudes- 

 cence. Gravid females first appeared consistently in 

 September 1991. The proportion of developing, 

 gravid, and spent females stayed relatively constant 

 through November. In December the first ripe/run- 

 ning fish and a substantial increase in the propor- 

 tion of spent females were seen. The next available 

 sample was March 1992 when all the mature females 



were in the spent/resting stage. Developing females 

 reappeared the following May, and their proportion 

 increased into the fall. In 1992, the first gravid and 

 ripe/running fish were seen in November. 



Length at 50% maturity calculated from survey 

 data was 28.0 cm for males and 36.8 cm for females 

 (Table 5). Estimates of L 50% from pooled market and 

 discard ("commercial") data were lower for males and 

 higher for females than estimates from survey data, 

 although confidence intervals for L 50% overlapped. 

 For females, seasonal estimates of L 5m varied widely. 

 The greatest L 5Q% (>41 cm) was seen before spawn- 

 ing (May-August) and the lowest (<37 cm) during 

 spawning (September-December). Parameters for 

 the logistic function were compared with a likelihood- 

 ratio test (Kimura, 1980). Estimates from commer- 

 cial data were significantly different from survey 

 estimates for both females (x 2 =145.490, P«0.001; 

 Fig. 4) and males (x 2 =79.383, P«0.001). In a com- 

 parison of years, logistic curves fit to September- 

 December 1991 (commercial) and September-Novem- 

 ber 1992 ( survey) data were significantly different (like- 

 lihood-ratio test, x 2 =143.257,P«0.001) although again 

 confidence intervals for L 5QC/c overlapped. 



Ovarian tissue samples were analyzed histologi- 

 cally from 111 female arrowtooth flounder collected 

 late December 1991 during spawning. Each of the 

 five macroscopic maturity stages was represented 

 and no two macroscopic stages showed the same fre- 

 quency distribution of oocyte types (Fig. 5). Chroma- 

 tin nucleolar, perinucleolar, and atretic oocytes were 

 present in all the sampled ovaries. In ovaries of im- 

 mature fish, none of the oocytes had progressed be- 

 yond the perinucleolar stage. Vitellogenic or yolked 

 oocytes were prevalent in developing and gravid stage 

 ovaries, and hydra ted oocytes were seen frequently 

 in gravid and ripe/running stage ovaries. Oocytes 

 with cortical alveoli were most frequently seen in 

 spent/resting ovaries. 



Atresia was more prevalent in all the ovarian 

 stages of spent/resting fish than in immature fish 

 (Table 6). The percent occurrence of a atretic oocytes 

 was lowest in ovaries from developing fish and high- 

 est in ovaries from spent/resting fish. Beta atresia 

 was most common in spent/resting ovaries but also 

 occurred in developing, gravid, and immature ova- 

 ries. All the immature and 43.8% of the spent/rest- 

 ing females had perinucleolar stage ovaries. 

 Postovulatory follicles (POF) were present in ovaries 

 from all macroscopic stages except immature. POF 

 were most frequently seen in ripe/running ovaries 

 and were common in gravid and spent/resting ova- 

 ries; whereas 7 of 29 developing females examined 

 for histology had ovaries with POF. Postovulatory 

 follicles were also present in 7 of 21 spent/resting 



