Results and Discussion 



Length at Maturity 



The matrix of 2-values is shown in Table 3. 

 Highly significant (2>2.33, P^O.Ol) differences 

 were found between sexes within years for 1975 

 and 1976 and between years for each sex except 

 1973 and 1976 males and 1974 and 1975 females. 

 This indicates that L^q for males and females was 

 greater in 1974 and 1975 than in 1973 and 1976. 

 The greatest difference was found between 1975 

 and 1976 when L^„ decreased approximately 4.8 

 cm for females and 3.6 cm for males. 



Significant long-term changes in L^^ have oc- 

 curred since Wallace's (1940) studies of 

 Chesapeake Bay croakers. The smallest mature 

 female he observed during 1938-40 was 27.5 cm, 

 indicating a L^^ of at least 30 cm. His collections 

 were made during July and August; therefore, due 

 to additional growth during early fall, 30 cm is an 

 underestimation of Lg^ for comparison with my 

 results obtained from September-November. 



Spawning 



The percentage frequencies of maturity stages 

 indicate spawning commenced at least as early as 

 the beginning of September, peaked during Oc- 

 tober, and ended by late December. The maturity 



stages and sample years were combined for 

 analysis (Table 4). The percentage of ripe ovaries 

 remained high during September and October, 

 then dropped to a low level in November. No ripe 

 females were found in December. As would be 

 expected the percentage of spawned fish (partially 

 spent, spent, and resting) increased during the 

 sampling period and indicated spawning was 

 nearly completed by mid-December. Because of 

 difficulty in assigning a specific maturity stage to 

 testes and since ovarian development was the best 

 indicator of spawning, males were not analyzed. 



The beginning of the spawning season was not 

 sampled; however, an examination of Wallace's 

 (1940) maturity stage data for July and August 

 showed that over 50% of the ovaries were develop- 

 ing (stages II and III) and <10% were ripe (stage 

 IV). The remainder was classified as resting (stage 

 I). Wallace made additional collections in 

 November which showed that ovaries were either 

 partially spent (stage VI) or spent (stage VII). His 

 findings support this study, indicating that 

 spawning commenced about mid-August and was 

 completed by the end of December. 



The presence of small juveniles (20-40 mm TL) 

 during April and May have led to speculations of 

 different spawning populations and a spring 

 spawning peak. Chao and Musick (1977) appar- 

 ently detected a modal group "entering" the York 

 River in May and suggested they may represent 



Table 3. — Matrix of 2-values (Natrella 1966) and significance for differences in L,„ (length at which 

 50% of specimens were mature) of male (M) and female (F) Atlantic croaker collected in 1973-76. 



Table 4. — Percentage frequency of maturity stages of female Atlantic croaker collected between 

 Cape May, N.J., and Cape Hatteras, N.C., during 1973-76. 



Maturity stage 



Developing 

 Ripe 



Partially spent 

 Spent 

 Resting 



Total 



192 



