FISHERY BULLETIN: VOL. 78, NO. 2 



persion. Based on Costlow and Bookhout ( 1959), n 

 was set at 10 for eight zoeal stages, a megalopa, 

 and an adult. 



Comparisons between Callinectes abundance in 

 neuston and bongo (surface vs. subsurface) collec- 

 tions at each station were made for: 1) maximum 

 abundance for each gear type; 2) mean abundance 

 of the consecutive pair of tows with the largest 

 collective abundance; and 3) mean abundance for 

 each gear type. Significance of differences for 

 these means was determined by the Wilcoxon 

 signed rank test (Wilcoxon 1945), a distribution- 

 free method (Hollander and Wolfe 1973). 



Comparisons between neuston and bongo collec- 

 tions are comparisons between abundances in a 

 single "layer" and abundances integrated over the 

 water column. Therefore, abundances in bongo 

 collections represent mean abundances in the 

 water column (excepting the surface) and do not 

 indicate vertical distribution of the animals. 



Diel patterns in neuston abundance during each 

 cruise were represented by total numbers per 100 

 m^ for each sampling time interval (3 h) summed 

 over the stations in a cruise. To weight frequency 

 as well as abundance during a single cruise, ranks 

 were assigned to abundance during each time in- 

 terval (lowest to highest) at each station. The rank 

 sum of each time interval was calculated as the 

 sum of the ranks during that time interval over all 

 stations during a single cruise. 



For neuston collections the relationship be- 

 tween mean abundance per station and environ- 

 mental factors (temperature, salinity, station 

 depth, and distance from shore) was examined. 

 Data were analyzed using subprograms ( multiple) 

 Regression and Partial Corr (partial correlation) 

 of the Statistical Package for the Social Sciences 

 (SPSS, Nie et al. 1975). Relationships between 

 abundance and factors were examined in terms of 

 bivariate as well as multivariate distributions. 



RESULTS 



Identification 



Callinectes zoeae were identified and staged on 

 the basis of Sandifer's ( 1972) key and descriptions 

 of laboratory -reared zoeae of C. sapidus (Costlow 

 and Bookhout 1959) and C. similis (Bookhout and 

 Costlow 1977). Key characters include: 1) relative 

 length of the antennal exopodite (<'/3 protopodite 

 length) and the presence of two unequal terminal 

 setae on the antennal exopodite; 2) the presence of 



lateral projections on abdominal somites 2 and 3; 

 3) the presence of relatively long, sharply pointed 

 posterolateral spines on abdominal somites 3-5; 

 and 4) the presence of one dorsal and one lateral 

 spine in each telson furca. Structure and setation 

 of mouthparts and appendages were compared 

 with published descriptions for further confirma- 

 tion. The above characters effectively separated 

 Callinectes zoeae from all other zoeal types in my 

 collections. The planktonic material appeared to 

 include seven or eight distinct zoeal stages after 

 allowance for individual variation in certain 

 structures, setal counts, relative lengths, etc. (e.g., 

 the antennal endopodite "bud" denoting stage 5, 

 which varied from little more than a swelling to a 

 definite projection). 



Identification of Portunidae megalopae was 

 based on Kurata's (1975) list of familial and sub- 

 familial (Portuninae) characters, which include 

 the presence of sternal cornua (paired spines pro- 

 jecting posteriorly from the fourth sternal seg- 

 ment beyond the base of the fifth leg) (Figure 2), 

 and the presence of paddlelike dactyls with long, 

 hooked setae on the fifth pereopods. 



Callinectes and Portunus megalopae were sepa- 

 rated on the basis of the characters listed by 

 Bookhout and Costlow (1974), which include the 

 absence in Callinectes and the presence in Por- 

 tunus of a ventral spine on the coxa of the second 

 pereopod ( Figure 2), and carpal spine(s) on the first 

 pereopod. 



My collections included numerous megalopae 

 attributable to Portunus; all had a coxal spine on 

 the second pereopod and a carpal spine on the first 

 pereopod. The basischiopodite hook reported for 



Abdominal somife 



Portunus 



Coxal / 

 Spine 



Sternal cornua 



Callinectes 



Figure 2. — Lateral profile including the abdomen ofCalUnectes 

 and Portunus megalopae. Distinguishing characters are indi- 

 cated. Sizes are not relative. 



254 



