FISHERY BULLETIN: VOL. 78, NO. 2 



Table 6. — Variation explained by multiple regression of surface abundance (logml^ + 1]) of Callinectes larvae on temperature, 

 distance from shore, salinity, and depth as estimated by the coefficient of determination (r^). Data were entered in the order indicated 

 in the Statistical Package for the Social Sciences (Nie et al. 1975) stepwise multiple regression procedure. 



Table 7. — ANOVA table for regression of surface abundance 

 (logiQ[X + l]) o{ Callinectes larvae on temperature and distance 

 from shore. 



Source of 

 variation 



Degrees of 

 freedom 



Sum of 

 squares 



IVIean 

 square 



Total 



Regression 



Residual 



41 3723161 0908088 

 2 23.24224 11.62112 

 39 13.98937 



32.39773" 



— P'sOOOI. 



peak abundances of inshore and estuarine genera 

 such as Uca (zoeae and megalopae), Emerita 

 (zoeae), Palaemonetes (zoeae), Upogebia (zoeae), 

 Libinia (zoeae and megalopae), and Ovalipes 

 (zoeae and megalopae). Few of the above were 

 found beyond the inner shelf (Figure 1: CI, Dl, 

 LI). At offshore stations Callinectes larvae fre- 

 quently occurred with larvae of shelf forms such as 

 Cancer, which dominated neuston collections 

 made in the spring. Megalopae and a few zoeae of 

 Portunus usually occurred with Callinectes. 

 Megalopae of Ocypode quadrata were ubiquitous 

 across the shelf during summer 1977. Megalopae 

 of Dromidia antillensis and other forms of south- 

 ern origin often occurred at central and outer shelf 

 stations. 



DISCUSSION 



Temperature-salinity tolerances of Callinectes 

 larvae are available from several laboratory and 

 field studies. Optimum temperature-salinity 

 ranges, experimentally determined, for survival 

 during zoeal development of laboratory-reared C 

 sapidus were 21-28%o, 19°-29° C (Sandoz and Rog- 

 ers 1944) and 20-32%o at 25° C (Costlow and 

 Bookhout 1959). Sandifer (1972) collected C. 

 sapidus zoeae in Chesapeake Bay in the range 

 15.7-32.3%o (most at 20-30%o) and 14°-27.9° C (75% 

 at 25°-26° C). Nichols and Keney (1963) found lar- 

 vae (zoeae and megalopae) to be most abundant 

 offshore (Florida-North Carolina) at 27.3°-29.1° C 

 and least abundant at 14.3°- 16.4° C. 



Costlow (1967) reported survival of megalopae 

 to first crab in temperature-salinity combinations 



of 15°-30° C, 5-40%o. Survival was similar at 20°, 

 25°, and 30° C, 10-40%o (75% survival) and oc- 

 curred at salinities as low as 5%o at 25°-30° C. 

 Survival in the lower salinity ranges (5-10%o) in- 

 creased with increasing temperature to 95% at 30° 

 C, 10%o. Survival in the upper salinity ranges 

 (30-35%o) decreased from 95-100% at 25° C to 

 42-50% at 15° C. At 15° C larvae did not survive 

 below 20%o, and at 15° C survival was highest at 

 35%o(50%). 



Costlow and Bookhout (1959) found zoeal de- 

 velopment to require 31-49 days, with no sig- 

 nificant difference in larval duration at salinities 

 from 20.1 to 31.1%o (at 25° C). Duration of the 

 megalopal stage ranged from 5-11 days at 30° C 

 (5-40%o) to 30-67 days at 15° C (20-40%o) (Costlow 

 1967). Costlow ( 1967) reported significant interac- 

 tion between temperature and salinity only at 15° 

 C. Larval duration at 35%o, 15° C was 37-56 days. 

 Costlow ( 1967) did not rear larvae at temperatures 

 <15° C and did not include a regression equation 

 for extrapolation to lower temperatures. 



Based on experimentally determined tolerances 

 noted above, summer temperatures in the es- 

 tuaries and inshore waters along most of the mid- 

 dle Atlantic and southeastern U.S. coast are 

 sufficiently warm for completion of larval de- 

 velopment. Metamorphosis of megalopae may 

 occur during the warmer months at salinities 

 found from offshore to upper estuaries. Greatest 

 survival, however, is at higher salinities (30- 

 40%o), and at 15° C occurs only in the range of 

 oceanic salinities. Furthermore, at these oceanic 

 salinities the duration of the megalopal stage in- 

 creases as temperature decreases. Thus, 

 megalopal life may be extended in the cooler, 

 offshore water of the Middle Atlantic Bight, a con- 

 clusion supported by the presence of Callinectes 

 megalopae at outer shelf stations (11°-12° C, 35- 

 36%o). 



Results of multivariate analysis of data were 

 predictable (Figure 5; Tables 5-7). The importance 

 of temperature (positive correlation) reflected the 

 seasonal nature of spawning and development (in 



260 



