Standing Crops and Trophic Levels— Blackburn 
59 
Richards, F. A., with T. G. Thompson. 1952. 
The estimation and characterization of plank- 
ton populations by pigment analyses, II. A 
spectrophotometf ic method for the estimation 
of plankton pigments. J. Marine Res. 11(2): 
156-172. 
Riley, G. A. 1963. Theory of food-chain rela- 
tions in the ocean. In: M. N. Hill fed.], The 
Sea; Ideas and Observations on Progress in 
the Study of the Seas. Interscience Publishers, 
New York, v. 2, pp. 438-463. 
Schaefer, M. B. 1962. Report on the investiga- 
tions of the Inter-American Tropical Tuna 
Commission for the year 1961. [In English 
and Spanish.} Ann. Kept. I titer -Am. Trop. 
Tuna Comm. 1961, pp. 44-171. 
— — Y. M. M. Bishop, and G. Y. Howard. 
1958. Some aspects of upwelling in the Gulf 
of Panama. [In English and Spanish.} Bull. 
Inter-Am. Trop. Tuna Comm. 3(2) : 79—132. 
Scripps Institution of Oceanography, 
University of California. I960. Physical, 
chemical and biological data: Costa Rica 
Dome Cruise. Data rept., SIO Ref. 60-20, 
33 pp. 
— ~ 1961. Step-1 Expedition, Preliminary 
Report, II. Biological, photometric and addi- 
tional chemical data. Prog, rept., SIO Ref. 
61-18, 66 pp. 
— _ — — 1962. Oceanic Observations of the Pa- 
cific: 1955. University of California Press, 
Berkeley and Los Angeles. 
Slobodkin, L. B. I960. Ecological energy rela- 
tionships at the population level. Am. Nat. 
94(876) :213-236. 
Strickland, J. D. H. I960. Measuring the pro- 
duction of marine phytoplankton. Bull. Fish. 
Res. Bd. Canada 122, 172 pp. 
Thrailkill, J. R. 1956. Relative areal zoo- 
plankton abundance off the Pacific coast. Spec. 
Sci. Rept. Fish. U. S. Fish Wildlife Service 
188, 85 pp. 
Tranter, D. J. I960. A method for determin- 
ing zooplankton volumes, j. Cons. Intern. 
Explor. Mer 25(3) : 272-278. 
Wooster, W. S. 1959. Oceanographic observa- 
tions in the Panama Bight, "Askoy” Expedi- 
tion, 1941. Bull Am. Mus. Nat. Hist. 118(3): 
113-152. 
— — — and T. CROMWELL. 1958. An oceano- 
graphic description of the eastern tropical 
Pacific. Bull. Scripps Inst. Oceanog. 7(3): 
169 - 282 . 
WYRTKI, K. 1962. The oxygen minima in rela- 
tion to ocean circulation. Deep-Sea Res. 9: 
11-23. 
— 1963 . The horizontal and vertical field 
of motion in the Peru Current. Bull. Scripps 
Inst. Oceanog. 8 (4) : 313-346. 
1964. Upwelling in the Costa Rica 
Dome. Fish. Bull. U. S. Fish Wildlife Service 
63 ( 2 ) : 3 5 5 — 372 . 
The thermal structure of the eastern 
Pacific Ocean. Unpublished manuscript.- 
Yentsch, C S., and J. F. Hebard. 1957. A 
gauge for determining plankton volume by 
the mercury immersion method. J. Cons. 
Intern. Explor. Mer 22 (2 ): 184-190. 
