290 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



Figure 3. — Albacore ovaries in various developmental stages (only part of each ovary is shown). Left to right: a ribbon- 

 like ovary taken from a sexually immature, 75.8-cm. fish (ovary weight 9 grams) ; an early developing ovary from a 

 99.2-cm. fish (ovary weight 74 gms.) ; a late developing ovary from a 98. 5-cm. fish (ovary weight 275 gms.) ; and an 

 advanced ovary from a 107.6-cm. fish (ovary weight 916 gms.). Photograph by H. Yoshida. 



They become progressively enlarged in length and 

 girth as the fish attain sexual maturity, and with 

 the final ripening of the eggs, they may attain a 

 diameter of more than 40 mm. In the more ad- 

 vanced stages, the ovaries are nearly circular in 

 cross section and the right ovary is usually slightly 

 larger than the left. They have a ribbed internal 

 cavity throughout their length and unite poster- 

 iorly with a thick-walled oviduct which opens ex- 

 teriorly through t he urogenital orifice. 



SUBSAMPLING THE OVARY 



An objective method for determining the degree 

 of maturity of an ovary is to measure the diameters 

 of the constituent eggs. In order to reduce the. 

 amount of work involved in measuring the tre- 

 mendous number of eggs within an ovary, it was 

 necessary in our study to resort to subsampling. 

 To subsample an ovary with confidence, however, 



requires that the distribution of eggs of various 

 sizes throughout an ovary as well as differences 

 between the two ovaries of a pair be determined. 

 The procedure followed in this study was in 

 general similar to that described by Yuen (1955) 

 who investigated the maturity and fecundity of 

 the bigeye tuna in the Pacific. Eggs from a 

 sample were measured in a Sedgewick-Rafter 

 counting chamber ruled with parallel guide lines. 

 The parallel lines prevented duplicate measure- 

 ments of the same egg. Measurements were 

 made to the nearest micrometer unit (0.0167 mm.) 

 using an ocular micrometer. Because the forma- 

 lin-preserved eggs of the albacore are not perfectly 

 spherical, we adopted the method of Clark (1934), 

 June (1953), Yuen (1955), and others of measuring 

 the random diameter parallel to the ruled lines in 

 the counting chamber in whatever axis the egg 

 lies. 



