.AROCHE and RICHARDSON: REPRODUCTION OF NORTHERN ANCHOVY 



March through July. October GFs were the lowest 

 values observed in mature fish. Only in May were 

 the GI values of males higher than those of 

 females. The highest mean GFs were observed in 

 July, approximately midway through the spawn- 

 ing season, mid-June to mid- August, (Richardson 

 1973, footnote 5; Richardson and Pearcy 1977). The 

 highest, 22.90 (female) and 15.39 (male), and low- 

 est, 1.55 ( female ), individual values of the GI found 

 in July indicated the presence of both running ripe 

 and spent fish, respectively. 



Sex Ratio 



The male to female ratio of mature and imma- 

 ture northern anchovies before spawning in May; 

 immature, nonspawning, fish in July; and mostly 

 immature fish in October did not deviate signifi- 

 cantly from 1:1 (P>0.05; chi-square test for good- 

 ness of fit) (Table 4). The sex ratio of 506 northern 

 anchovies taken in March was 1.2:1 which, al- 

 though close to 1:1, was significantly different 

 iP<0.05). The overall male to female ratio of ma- 

 ture fish caught during active spawning in July at 

 four different locations was 2.6:1. Values for each 

 catch were 2:1 (167 fish), 8.3:1 (278 fish), 1:1 (186 

 fish), and 5.7:1 (40 fish). The sex ratios in those 

 catches where males outnumbered females all de- 

 viated significantly from 1:1 (P<0.005) and may be 

 related to anchovy spawning behavior. In the 

 three catches where males greatly outnumbered 

 females, the percent of ripe females with hydrated 

 oocytes which were either actively spawning or 

 about to spawn ranged from 33 to 46*;^ . In the catch 

 with a 1:1 sex ratio, only 2% of the females were 

 ripe with ovaries full of hydrated oocytes. 



Ovarian Maturation 



Oocyte Morphology 



The smallest oocytes visible at 50 x magnifica- 

 tion were roughly spherical but by 0.20 mm were 

 becoming elliptical in shape (Figure 2a). Most oo- 

 cytes <0.38 mm lacked yolk and were transparent. 

 Vitellogenesis became evident only in oocytes 

 >0.38 mm. As yolk production continued, oocytes 

 became more opaque and by 0.50 mm the nucleus 



Table 4. — Male to female ratios of northern anchovies collected 

 in March, May, July, and October off Oregon and Washington. 



^Richardson, S. L. 1977. Abundance, distribution and sea- 

 sonality of larval fishes collected 2 to 11 km of Yaquina Bay, 

 Oregon from January 1971-August 1972 — a data sum- 

 mary Oreg, State Univ Sea Grant Coll. Prog. Publ, ORESU- 

 T-77-003, 73 p. 



was obscured. Most oocytes >0.50 mm were com- 

 pletely opaque, and oocytes between 0.50 and 0.68 

 appeared dark in transmitted light (Figure 2b). 

 Oocytes between 0.70 and 0.90 mm often appeared 

 less dense and dark than smaller yolked oocytes. A 

 general lightening occurred first at the poles and 

 then throughout the oocyte. These oocytes were 

 grainy in appearance because globules of yolk had 

 replaced the single amorphous yolk mass of small- 

 er oocytes. The yolk of hydrated oocytes, ranging 

 in size from 0.90 to 1.42 mm, was segmented (Fig- 

 ure 2c). Hydration, the accumulation of fluids of 

 lower specific gravity than seawater in ooc3^es, 

 results in greatly increased volumes and is the 

 final stage of oocyte maturation in many marine 

 fishes ([Fulton 1898] in Leary et al. 1975; Smith 

 1957 ). The largest oocytes ( 1.10-1.42 mm) in Figure 

 2c had been ovulated, i.e., released from their folli- 

 cles, and were lying loose in the ovary. The 

 shadowy areas among the opaque oocytes to the 

 left of the transparent ones in this figure are 

 empty follicles. These structures were dispersed 

 throughout the ovary and were visible without the 

 aid of histological techniques. They appeared as 

 thin, flattened mats of tissue about the size and 

 shape of ripe oocytes with a thinner, oval region in 

 the center. 



In addition to normally developing oocytes, de- 

 generating or atretic oocytes were found in some 

 anchovy ovaries collected before, during, and after 

 the spawning season. Atresia has been observed in 

 both immature oocytes undergoing vitellogenesis 

 and mature oocytes remaining in the ovary after 

 spawning in many teleosts (Wallace 1903; Matth- 

 ews 1938; Hoar 1955; Vladykov 1956; Beach 1959; 

 Barr 1968). Degenerating oocytes of all sizes inE. 

 mordax most frequently appeared as opaque, ir- 

 regularly shaped, masses dispersed among the 

 normal yolked and yolkless oocytes (Figure 3a). 

 Another type of abnormal and presumably de- 

 generating oocyte was found primarily in fish with 

 ripe oocytes. These medium-sized, 0.36-0.54 mm, 

 oocytes were in early stages of vitellogenesis and 

 had irregularly shaped nuclei which frequently 

 appeared partially collapsed (Figure 3b). Within 



607 



