FISHERY BULLETIN: VOL. 78, NO. 1 





z 



UJ 



Table 2. — Maturity stages of Atlantic mackerel ovaries. 



30 



Figure l. 



32 34 36 38 40 42 44 



FORK LENGTH 10.5 cm midpoints I 



-Length frequencies of male and female Atlantic 

 mackerel used in this study. 



larger opaque, yolked eggs; and 3) large translu- 

 cent eggs. There appeared to be no clear size sep- 

 aration between egg types, which is indicative of 

 serial spawners (Hickling and Rutenberg 1936). 

 Therefore, the method described by Hislop and 

 Hall (1974) for whiting, Merlangus merlangus, 

 was used to determine which eggs would be shed 

 during the current spawning season. Since yolk 

 deposition indicates eggs are ripening for spawn- 

 ing, random samples of 300 eggs were measured 

 from ovaries at successive maturity stages to de- 

 termine the average minimum size of yolked eggs. 

 Eggs 0.20 mm and larger contained yolk and were 

 included for fecundity estimation. Ovaries were 

 classified into four maturity stages based upon 

 macroscopic examination and the occurrence of 

 mature eggs (Table 2). Egg diameter frequencies 

 of yolked eggs from ovaries in the developing, ripe, 

 running ripe, and partially spent condition are 

 shown in Figure 2. 



Ovaries in the ripe condition (Figure 2b) were 

 used for fecundity estimations. If large translu- 

 cent eggs (1.00-1.35 mm) were present in the 

 lumen of the ovary, which is indicative of the run- 

 ning ripe condition (Figure 2c), the ovary was not 

 utilized for fecundity because some eggs may have 

 been shed and fecundity would be underestimated. 



Stage 



Description 



1 . Developing 



2. Ripe 



3. Running 

 ripe 



4. Partially 

 spent 



Ovary enlarged, usually orange colored with a 

 granular appearance No translucent eggs, 

 maximum egg diameters 0,8-0.9 mm. 



Ovary fills most of gut cavity, yellow colored, 

 in advanced stage some translucent eggs are 

 visible ttirough wall. Maximum egg diameter 

 1 0-1.2 mm. 



Similar in appearance to stage 2, eggs are ex- 

 truded with pressure on abdomen of fish, 

 t^aximum egg diameters 1.2-1.4 mm. 



Ovary is flaccid, often hemorrhaging is evi- 

 dent at anterior portion of ovary, some 

 residual mature eggs (1.1-1.4 mm) present. 



^^^ 



25 

 20 

 15 

 10- 



1 



InJ 



IL 



N . nrJI 



0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 12 1.3 1.4 



EGG DIAMETER I mm I 



Figure 2. — Egg diameter frequencies of Atlantic mackerel ova- 

 ries in stages: developing (a), ripe (b), running ripe (c), and par- 

 tially spent (d). Each graph based on 300 egg measurements. 



Suitable ovaries were removed from the Formalin 

 solution, placed in glacial acetic acid for 5 min, and 

 washed, and the eggs were separated with a gentle 



104 



