FISHERY BULLETIN: VOL. 86, NO. 2 



Table 4. — Parameters and coefficients for linear regressions of chlorophyll 

 concentration on nauplius concentration for each cruise. Y = a + b(X) where 

 y = naupliar concentration as number per liter, and X = chlorophyll concentra- 

 tion as fjig per liter. Significance level tested is 0.01. 



ent from all others, cruise II was different from 

 all the others, and cruises I and III were not dif- 

 ferent from each other but different from cruises 

 II, IV, and V. The slopes of all relationships ex- 

 cept cruise V were significantly different from 

 zero. 



The size-frequency distribution of nauplii did 

 not vary in any systematic manner (Fig. 6). For 

 example, at station IV-1, the bulk of the nauplii 

 were between 20 and 100 \x.m at all depths sam- 

 pled during both the daytime and nighttime peri- 

 ods. The size-frequency distribution was essen- 

 tially identical at station IV-2, off Louisiana (data 

 not shown). 



At some stations, copepodid stages <600 ixm in 

 length (50-200 \xm in width) were counted in ad- 

 dition to nauplii because they are potential prey 

 items for menhaden larvae. Copepodites were 

 usually not as abundant as nauplii, especially at 



stations with high naupliar abundances. On occa- 

 sion, they were as abundant or, at specific depths, 

 more abundant than the nauplii (Table 5). The 

 ratio of nauplii to copepodites varied widely, be- 

 tween 16.3 and 0.3, so it is not possible to assign 

 a constant factor to naupliar abundances to esti- 

 mate the increase in available prey attributable 

 to copepodid stages. 



Other microzooplankton were usually not as 

 abundant as nauplii or copepods. In our samples, 

 various forms of eggs reached a maximum density 

 of 6 eggs/L (cruise III station 6 at 3 m, data not 

 shown). Pelecypod larvae at one station (III-ll) 

 were abundant, reaching a maximum of 29 lar- 

 vae/L at 4 m, compared with 22 nauplii, 7 cope- 

 podites, and 2 eggs/L in the same sample. Only on 

 this one occasion were organisms other than cope- 

 podites or nauplii the dominant form of micro- 

 zooplankton. 



Table 5. — Abundance (number/liter) of other microzooplankton in addition to nauplii at 



selected stations during cruise III. 



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