Table 1.— Number of zooplankton samples for each cruise from 

 which both carbon and nitrogen were measured. The general loca- 

 tion of the stations for these samples are given in Wiebe et al. 

 (1975). 



volume, wet weight, dry weight, and carbon. Fish. Bull., 

 U.S. 73:777-786. 



Peter H. Wiebe 



Nitrogen (mg/m^) = -0.0247 



+ 0.2324 carbon (mg/m^) 



Essentially the carbon/nitrogen ratio of the bulk zoo- 

 plankton we collected is a constant (4.30) over a 

 broad range of values and oceanographic habitats. 

 As an atomic ratio, 5.02, this value is lower than that 

 predicted by the Redfield ratio, 6.63 (Redfield et al. 

 1963), an indication that zooplankton are nitrogen 

 rich relative to their phytoplankton counterparts. 



Acknowledgments 



We would like to express our appreciation to F. A. 

 Ascioti for his correspondence and attention to 

 detail which enabled us to correct the mistakes in 

 our previous publication. This research was sup- 

 ported by NSF Grant OCE-8709962 and is Contri- 

 bution No. 6839 from the Woods Hole Oceanograph- 

 ic Institution. 



Literature Cited 



Davis, C. S., and P. H. Wiebe. 



1985. Macrozooplankton biomass in a Warm-Core Gulf 

 Stream Ring: Time series changes in size structure, tax- 

 onomic composition and vertical distribution. J. Geophys. 

 Res. 90:8871-8884. 

 Redfield, A. C, B. H. Ketchum, and F. A. Richards. 



1963. The influence of organisms on the composition of sea- 

 water. In M. N. Hill (editor). The Sea, Vol. 2, The composi- 

 tion of sea-water, p. 26-77. Intersci. Publ., John Wiley and 

 Sons, N.Y. 

 Richer, W. E. 



1973. Linear regressions in fishery research. J. Fish. Res. 

 Board Can. .30:409-434. 

 Wiebe, P. H., S. H. Boyd, and J. L. Cox. 



1975. Relationships between zooplankton displacement 



Woods Hole Oceanographic Institute 

 Woods Hole, MA 0251,3 



ELECTROPHORETIC IDENTIFICATION OF 



EARLY JUVENILE YELLOWFIN TUNA, 



THUNNUS ALBACARES 



Early juveniles, 13 mm standard length (SL) or 

 larger, of yellowfin tuna, Thunnus albacares, and 

 bigeye tuna, T. obesus, cannot be distinguished on 

 the basis of meristic, morphological, or pigmenta- 

 tion characters (Matsumoto et al. 1972). Collette et 

 al. (1984) reported that most species of the genus 

 Thunnus can be distinguished at the larval stage by 

 melanophore patterns. Matsumoto et al. (1972) and 

 Nishikawa and Rimmer (1987) suggested that T. 

 albacares and T. obesus larvae can be separated by 

 the respective absence or presence of postanal ven- 

 tral melanophores. Confirmation of the identifi- 

 cation of T. albacares larvae has been obtained 

 through laboratory rearing studies (Harada et al. 

 1971; Mori et al. 1971). However, the use of post- 

 anal ventral pigmentation patterns as reliable char- 

 acters to distinguish yellowfin and bigeye tuna 

 larvae has been questioned by Richards and Pothoff 

 (1974). Nishikawa and Rimmer (1987) stated that 

 it is virtually impossible to identify to species the 

 early juvenile stages, 15 to 60 mm SL, of Thunnus 

 because larval pigmentation patterns become 

 obscured and are no longer diagnostic. Further- 

 more, Pothoff (1974) was unable to separate T. 

 albacares and T. obesus as early juveniles, 8 to 100 

 mm SL, on the basis of osteological characters. 



Electrophoresis of water soluble proteins has been 

 used to distinguish morphologically similar larval 

 and early juvenile marine fishes (Morgan 1975; 

 Smith and Crossland 1977; Sidell et al. 1978; Smith 

 and Benson 1980). Sharp and Pirages (1978) 

 presented starch gel electrophoretic patterns for 

 several loci of adults of many scombrid species, in- 

 cluding most members of the genus Thunnus. Al- 

 though electrophoretically very similar, adults of 

 yellowfin and bigeye tuna can be unambiguously 

 distinguished by the electrophoretic pattern of the 

 muscle isozyme of glycerol-3-phosphate dehydrog- 



FISHERY BULLETIN: VOL. 86. NO. 4, 1988. 



835 



