FISHERY BULLETIN: VOL. 76, NO. 2 



zooplankton taxonomic groups among stations 

 was less pronounced, with copepods dominant 

 (56-657r of total individual number), followed by 

 Noctiluca (S-lS'/f ), appendicularians (G-T^'r), and 

 chaetognaths (4-5'7f) (Yamazi et al. 1972). 

 Biomass expressed per cubic meter was converted 

 to per square meter by multiplying by depth of 

 sampling. 



The habitat temperature of zooplankton from 

 0-150 m was represented by that at 100 m 

 (Japanese Oceanographic Data Center 1967, 

 1969). In the east China Sea, which is shallower 

 than 150 m, the temperature at 50 m was taken as 

 the habitat temperature (Figures lA, 2A). 



From data summarized by Yamazi (1971), the 

 biomass of zooplankton per haul was divided by 

 total number of individuals per haul to obtain 

 average body weight. Values thus obtained at all 

 sampling stations were grouped into warm or cold 

 season, and assumed as a general size distribution 

 in each season (Figure 3). The highest frequency 

 was observed in the range 0.1-0.2 mg wet weight/ 

 animal in both seasons. Faunal differences south 



50 



40 



30 



^20 



z 10- 



UJ 



o 

 u 



a 

 li. 



« 



I 



•7. 



30- 



hm 



ft^ 



-15 -0 5 5 



LOG »V BODV WT 



s~^ \- 



•.'.0 



"=30 



20- 



10- 



I I "" t 



N:U7 



•/, 

 20- 



(0-3'/.) 



m 



flv 



•> n n 



-15 -05 05 



LOG AV BODY WT 



- ~Ti~>-^ 



(2 6'/.) 



T 1 1 1 1 1 1 1 1 



0501 3 5 7 9 11 13 15 17 19 



AVERAGE BODY WEIGHT OF A ZOOPLANTER (mg wet wt) 



Figure 3. — Relative frequency of average size of zooplankton 

 (biomass/number of zooplankton at each sampling station) in 

 warm (June-October) (upper figure) and cold (December- April) 

 (lower figure) seasons in the Kuroshio and adjacent seas. A 

 normalized frequency distribution fitted by logarithmic trans- 

 formation of body weights is superimposed on the right side of 

 each figure. N is number of sampling stations. 



and north of the subarctic boundary (ca. lat. 40°N) 

 reported by Motoda and Marumo (1965) were ig- 

 nored here, because no systematic difference was 

 found in average body size of zooplankton between 

 these areas. The skewed size distribution was con- 

 verted to a normal distribution curve by 

 logarithmic transformation (base 10). Fitness to 

 the curve was tested primarily by the normal 

 probability paper (Harding 1949) and finally 

 confirmed by chi-square test (warm season: x^ = 

 17.85,df = 6, P<0.01; cold season: x^ = 7.24, df = 

 6, 0.25<P <0.5). The normal distribution curves of 

 log body size thus obtained were /x = -0.8033 

 (SD = 0.2856) for the warm season and 

 fi = -0.7350 (SD = 0.3705) for the cold season. 



Respiration and Ammonia Excretion 



From measurements of respiration and am- 

 monia excretion rates on various zooplankton 

 species from tropical to boreal seas, Ikeda (1974) 

 found that the body weight and habitat tempera- 

 ture are most important factors which affect rates. 

 As a result of stepwise regression analyses, the 

 relationship among these parameters was expres- 

 sed as: 



RorE= aW' 



(1) 



or logioP or logjo^; = logioO + b log^^W (2) 



where R is respiration rate {/A 02/animal per h); 

 E, ammonia excretion rate ()u.g N/animal per h); 

 and W, body dry weight (mg/animal). Constants, a 

 and b, are given as a function of habitat tempera- 

 ture (°C) (Ikeda 1974 amended the bias introduced 

 by logarithmic transformation), 



for/?.- b = -0.01089T + 0.8918 

 logioo -0.02538T - 0.1259 



forE: b = -0.00941T + 0.8338 

 logioo =0.02865T - 1.2802. 



Combining the normalized body size distribu- 

 tion of zooplankton obtained above and the values 

 in Table 1, total respiration and ammonia excre- 

 tion rates were estimated from the sum of the rates 

 of six classes of the normal distribution curve 

 equally divided by the SD, i.e., -3 to -2, -2 to -1, 

 -1 to 0, to 1, 1 to 2, and 2 to 3, which covers over 

 99% of the total area under the curve. In each 

 class, body size of zooplankton was represented by 

 the median value, i.e., SD = -2.5, -1.5, -0.5,0.5, 



360 



