FISHERY BULLETIN: VOL. 76, NO. 2 



Table 5.— Estimates of grazing, production (corrected for natural physiological mortality!, and ammonia nitrogen excretion of 

 zooplankton collected from to 150-m depth with NORPAC net (0.35-mm mesh) in the Kuroshio and adjacent seas, together with 

 primary production values from the literature (Anonymous 1967, 1968, 1969; Saijo et al. 1972). For designation of subareas, see 

 Figures IB and 2B. 



Item 



Subarea 



Zooplankton: 



a. Herbivorous zooplankton grazing (mg C/m^ per day) 



b. Herbivorous zooplankton production (mg C m^ per day) 



c. Herbivorous zooplankton natural physiological mortality (mg C/m^ per day) 



d. Zooplankton excretion (mg Nm^ per day) 

 Phytoplankton: 



e. Primary production (mg C m^ per day) 



f. Phytoplankton nitrogen requirement (mg N/m^ per day) 

 Phytoplankton:zooplankton relation 



g. Ratio of herbivorous zooplankton grazing to primary production (aJe) (%) 



h. Ecological efficiency from primary production to secondary production (b/e) (%) 



I. Ratio of zooplankton nitrogen excretion to phytoplankton nitrogen requirement (d/f) (%) 



Engelmann ( 1969) summarized annual produc- 

 tion (Pq) and respiration (R^) of animal popula- 

 tions (mostly terrestrial invertebrates and verte- 

 brates) and found that logioPo was proportional to 

 logio/?^. His findings were further confirmed with 

 a large amount of data by McNeill and Lawton 

 (1970). For comparatively short-lived poikilo- 

 therms (generation time <2 yr) the relation is 

 expressed in the following equation (McNeill and 

 Lawton 1970), 



logioP,, =0.8262 logioi?„ -0.0948 



0.8262 



or 



P, = 0.804 R^ 



This empirical equation resembles P = 0.75 R 

 (Equation (11)) that we derived from Winberg's 

 equations for marine zooplankton in this study. 



Mullin ( 1969) reviewed production estimates for 

 marine zooplankton and gave 5-224 mg C/m^ per 

 day as a summary value for zooplankton produc- 

 tion at various sea areas, exclusive of values on a 

 single species. Our estimate of secondary produc- 

 tion ( 10-60 mg C/m^ per day) falls in these ranges. 

 It is noted, however, that some data cited by Mul- 

 lin (1969) are on mixed zooplankton (herbivores 

 plus carnivores) so that these are not comparable 

 to our results which referred only to herbivorous 

 zooplankton. For the same reason, the ecological 

 efficiency between primary production and secon- 

 dary production obtained in our study (5-22%) is 

 not necessarily comparable to the ratio of zoo- 

 plankton production to primary production (9- 

 58%) in Mulhn (1969). 



Ammonia Excretion 



The Kuroshio and its adjacent region in the 

 364 



Pacific Ocean (south of the subarctic boundary at 

 ca. lat. 40°N) are oligotrophic (Reid 1962). 

 Taniguchi (1972) studied geographical variation 

 of primary production in the western Pacific 

 Ocean and suggested that nutrients are the most 

 important factor limiting the primary production 

 level in the Kuroshio region. In situ primary pro- 

 duction reported in this area is in the range of 

 50-500 mg C/m2 per day (Anonymous 1967, 1968, 

 1969; Saijo et al. 1972) which is equivalent to 9-88 

 mg N/m^ per day from a C:N ratio of 5.7:1 on 

 phytoplankton (Redfield et al. 1963). Our estimate 

 of ammonia-nitrogen regeneration through zoo- 

 plankton excretion which can support 11-44% of 

 the nitrogen requirement for primary production 

 was 4-24 mg N/m^ per day. Eppley et al. (1973) 

 estimated that 40-50% of nitrogen demand for 

 primary production was supplied by zooplankton 

 excretion in the nutrient depleted subtropical gyre 

 of the northern Pacific Ocean. A significant con- 

 tribution of zooplankton excretion (up to 77-90% of 

 the nitrogen requirement for primary production) 

 was reported in Long Island Sound (Harris 1959) 

 and offshore waters off the Washington and 

 Oregon coasts in summer (Jawed 1973). The im- 

 portance of ammonia as a nitrogen source for phy- 

 toplankton is further substantiated by its prefer- 

 ential utilization by phytoplankton (cf. Dugdale 

 1976). 



Future Aspects 



The production and ammonia regeneration mod- 

 els presented here are advantageous for under- 

 standing the marine zooplankton community 

 which includes diversified species and widely di- 

 vergent body sizes, like those inhabiting subtropi- 

 cal and tropical seas. Models require basically 



