FISHERY BULLETIN: VOL. 78, NO. 3 



R +E =A; 110 + 105 + 2 =217cald"';/ = A/0.34 

 = 638 cal d~'J. This is equivalent to 1.10 g wet 

 Spartina alterniflora detritus [assuming 3,760 

 cal/dry g (Gosselink and Kirby 1974) and SAA% 

 water'*], or about 20. 07^^ of the shrimp's body mass 

 per day. Daily growth rates of brown shrimp have 

 been reported as rapid as 3.3 mm (Ringo 1965). 

 This is more than three times the rate used for our 

 calculations and would substantially increase the 

 amount of ingested food and consequently the per- 

 cent of food mass intake relative to body mass. 



Table 12. — Daily calorie values for energy ingested (/) and that 

 utilized for growth (G), respiration (R), and excretion iE) based 

 on assimilation rates of 25 £ind 1A% for a 5.2 g (live mass) Penaeus 

 aztecus. 



Assimilation efficiency (°o) 



/ 



25 



74 



110 

 110 



105 

 105 



868 

 293 



'Calculated from Nelson et al. (1977) and Brafield and Solomon (1972). 



Qasim and Easterson (1974) obtained caloric as- 

 similation efficiencies as high as 96.84% for M. 

 monoceros , but they fed shrimp small particle de- 

 tritus, which they settled from estuarine waters. 

 This detritus was composed of a substrate of "fine 

 silt and sand" (Qasim and Sankaranarayanan 

 1972), and its caloric value was nearly an order of 

 magnitude less than that of S. alterniflora detritus 

 (Gosselink and Kirby 1974). The low caloric de- 

 tritus used in Qasim and Easterson's experiments 

 may be responsible for the high assimilation 

 efficiencies (assimilation calculated on ingested 

 mass would probably be less efficient). We believe 

 that the wide range of assimilation efficiencies 

 used in our calculations are representative of most 

 wild shrimp even if efficiencies for ingested mass 

 and calories differ considerably. Also, diets of 

 shrimp are not readily ascertained and more re- 

 fined estimates may not be practical. Shrimp 

 grown in intensive culture situations and fed a 

 prepared diet, however, exist in relatively stable 

 conditions; energy budgets for these shrimp could 

 be more accurately determined and used to reduce 

 feeding costs and possibly to increase production. 



The wide tolerance of P. aztecus to temperature 

 and salinity allows it to make maximum use of 

 estuaries. Although we obtained evidence indi- 

 ciating that larger shrimp can regulate hypoos- 

 motically to a better degree than smaller shrimp, 

 smaller shrimp can readily grow and survive Gulf 



^Unpublished data of senior author 



754 



salinities (Hoese 1960; Zein-Eldin 1963). Thus dur- 

 ing years when shrimp populations are unusually 

 dense in estuaries, shrimp can emigrate from the 

 estuaries to Gulf waters at a size less than that of 

 shrimp during average population years. This 

 may reduce competition for space and food in the 

 nursery areas (Parker 1970) and result in greater 

 estuarine shrimp production. The suitability of 

 estuaries as nursery grounds for shrimp results 

 from several important circumstances including 

 food abundance (Zein-Eldin 1963; Copeland and 

 Bechtel 1974), protection (Hoese 1960), cover (Wil- 

 liams 1955; Giles and Zamora 1973), substrate 

 (Williams 1958), absence of competition between 

 juveniles and adults, and to a lesser degree, the 

 shrimp's osmoregulatory abilities. 



ACKNOWLEDGMENTS 



We thank P. E. Schilling for his consultation on 

 experimental design and analyses of data; J. D. 

 Woodring for use of his osmometer; N.J. Gazaway 

 and L. H. Hodges for typing; C. J. Poche for draft- 

 ing; D. E. Wohlschlag and anonymous reviewers 

 for editorial comments; and W B. Stickle, R. D. 

 Adams, and E. M. Bishop for assisting in various 

 ways. N. L. Mickelberry supported and encour- 

 aged the senior author throughout this study; her 

 efforts are particularly appreciated. This research 

 was submitted by the senior author in partial 

 fulfillment of the requirements for the degree of 

 Doctor of Philosophy at Louisiana State Univer- 

 sity. This report is the result of research supported 

 by the Louisiana Sea Grant Program, a part of the 

 National Sea Grant Program maintained by the 

 National Oceanic and Atmospheric Administra- 

 tion, U.S. Department of Commerce. 



LITERATURE CITED 



Aaron, R. L., and W. J. Wisby. 



1964. Effects of light and moon phase on the behavior of 

 pink shrimp. Gulf Caribb. Fish. Inst., Proc. 16th Annu. 

 Sess.,p.l21-130. 



Bishop, J. M. 



1974. The influence of selected conditions on the oxygen 

 consumption and hemolymph osmolality of the brown 

 shrimp, Penaeus aztecus Ives. Ph.D. Thesis, Louisiana 

 State Univ., Baton Rouge, 150 p. 



1976. A continuous recording, differential respirometer for 

 a closed, flowing seawater system. Oikos 27:127-130. 

 BISHOP, J. M., AND W. F. HERRNKIND. 



1976. Burying and molting of pink shrimp, Penaeus 

 duorarum (Crustacea: Penaeidae), under selected photo- 

 periods of white light and UV-light. Biol. Bull. (Woods 

 Hole) 150:163-182. 



