FISHERY BULLETIN: VOL. 75, NO. 1 



Our length frequencies suggest that two year 

 classes occurred, but only one was abundant. This 

 agrees with other reported length frequencies 

 from warm-temperate waters (see references cited 

 in section on Age Determination and Growth by 

 the Length-Frequency Method). Therefore, the 

 typical croaker life span in warm-temperate water 

 appears to be only 1 or 2 yr. Age 11+ fish captured 

 in March were the oldest fish we examined in 

 agreement with other estimated maximum ages 

 from the Carolinian Province (Gunter 1945; 

 Suttkus 1955; Bearden 1964; Hoese 1973). Fish 

 associated with oyster reefs are larger and a year 

 older than trawl-caught bay or Gulf fish during 

 the summer. However, the abundance of these age 

 I croaker must be small compared with the 

 abundance of age croaker, because the geograph- 

 ical area occupied by oyster reefs is comparatively 

 small. 



Croaker have a high total annual mortality rate 

 as their short life span requires. We found only six 

 age 11+ fish in 1,123 aged. Greatest mixing of 

 age-groups probably coincides with fall spawning 

 in the Gulf. We observed 1 1 age I + and 250 age 0+ 

 fish in random samples from trawl catches made 

 25-27 September 1974, so that the observed total 

 annual mortality rate was about 96% assuming 

 negative exponential survivorship. This must 

 approximate the total annual mortality rate 

 throughout the Carolinian Province because 

 maximum sizes and ages, length frequencies, and 

 life spans appear similar throughout this area. 

 The observed total annual mortality rate agrees 

 closely with the theoretical total annual mortality 

 rate. Following the reasoning of Royce (1972:238) 

 the negative exponential survivorship relation S 

 = N t /N = e~ Zt can be solved for an approximate 

 instantaneous total mortality rate over the entire 

 life span which can be used to estimate average 

 annual total mortality rates. A species with a life 

 span of 1 or 2 yr would have a theoretical 

 approximate total annual mortality rate of 90- 

 100%. 



TOTAL WEIGHT-LENGTH AND 

 GIRTH-LENGTH RELATIONSHIPS 



The regression of total weight in grams (Y) on 

 total length in millimeters (X) was expressed by 

 the equation: 



log 10 Y = -5.26 + 3.15 log 10 X. 



This relationship was based on a sample size of 

 2,081 fish in the length range 90-360 mm. About 

 98% of the variation in log 10 total weight was 

 associated with variation in log 10 total length. The 

 arithmetic mean log 10 X was 2.21056, and 

 arithmetic mean log 10 Y was 1.71546. 



The regression of girth in millimeters (Y) on 

 total length (X) in millimeters was expressed by 

 the linear equation: 



Y = -11.84 + 0.71X. 



This relationship was based on a sample size of 

 2,081 fish in the length range 90-360 mm. The 

 arithmetic mean girth was 108.07 mm. About 94% 

 of the variation in girth was associated with 

 variation in total length. 



GENERAL DISCUSSION 



Many aspects of the life history of Atlantic 

 croaker in the Carolinian Province appear dif- 

 ferent than those of fish found in cold-temperate 

 waters north of Cape Hatteras except that the 

 growth rates appear similar. In general, our data 

 and the literature agree that in warm-temperate 

 waters: 1) peak spawning occurs about October 

 but the spawning season is long and lasts from 

 about September to at least March, 2) maturity is 

 reached at about 140-180 mm long as the fish 

 approach age I, 3) maximum size is about 300-350 

 mm and most fish are so small (about 200 mm or 

 less in length) that they do not support commercial 

 food fisheries, 4) the life span is about 1-2 yr and 

 maximum age is typically about 2 yr, 5) most fish 

 live only to about age I, and 6) total annual mor- 

 tality rate is about 95%. In contrast, fish living 

 north of Cape Hatteras generally: 

 1) Have a spawning season (July or August- 

 December?) that starts earlier and may end 

 earlier (Welsh and Breder 1924; Hildebrand 

 and Schroeder 1928; Wallace 1940; Pearson 

 1941; Massmann and Pacheco 1960). 

 However, the time when spawning ends is 

 not certain. Haven (1957) captured many 

 young 20-30 mm TL from February to April, 

 but their significance is not clear; they could 

 represent late-winter spawning or, perhaps, 

 fall spawning with little or no overwinter 

 growth. Peak spawning seemingly occurs no 

 later than midfall, because all the adult fish 

 that Wallace (1940) examined had spent or 



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