CALORIC MEASUREMENTS OF SOME ESTUARINE ORGANISMS' 



Gordon W. Thayer,- William E. Schaaf,- Joseph W. Angelovic' 

 AND Michael W. LaCroix- 



ABSTRACT 



The caloric content per gram dry weight, per gram ash-free dry weight, and per gram 

 live weight was determined for 51 species of organisms, representing the Ctenophora, 

 Mollusca, Annelida, Arthropoda, Echinodermata, and Chordata, collected from the shal- 

 low estuarine system near Beaufort, N.C. Least squares regression analysis showed 

 a highly significant correlation between caloric content per gram dry weight and the 

 percentage organic matter. Decalcification of moUuscan tissues did not significantly 

 lower caloric values. We observed significant differences for caloric values of species 

 grouped by phylum, and an evolutionary trend toward increasing energy content per 

 gram live weight. We also observed a frequency distribution of energy which was 

 skewed toward lower values. 



Existing publications on the caloric content of 

 organisms (Golley, 1961; Slobodkin and Rich- 

 man, 1961; Paine, 1964; Cummins, 1967; 

 Brawn, Peer, and Bentley, 1968; Cummins and 

 Wuycheck, 1970) list few species which spend 

 all of or part of their life histories in estuaries. 

 In 1968 we began a survey of the caloric content 

 of estuarine organisms. With knowledge of the 

 caloric content of these species-populations our 

 data on biomass in the shallow system of estua- 

 ries near Beaufort, N.C, could be converted to 

 standing crop energy to facilitate the analysis 

 of energy flow in this system. The means for 

 these populations are presented as calories per 

 gram dry weight, per gram ash-free dry weight, 

 and per gram live weight to permit investigators 

 who do not have access to a calorimeter to esti- 

 mate energy units for their estuarine biomass 

 data. 



' This research was supported through a cooperative 

 agreement between National Marine Fisheries Service 

 and U.S. Atomic Energy Commission. 



^ Atlantic Estuarine Fisheries Center, National Ma- 

 rine Fisheries Service, NOAA, Beaufort, NC 28516. 



* Atlantic Estuarine Fisheries Center, National Ma- 

 rine Fisheries Service, NOAA, Beaufort, NC 28516; 

 present address: National Marine Fisheries Service, 

 NOAA, Washington, DC 20235. 



METHODS 



Organisms were collected in the Newport 

 River estuary and surrounding estuaries near 

 Beaufort. Detailed descriptions of the hydro- 

 graphy of this shallow estuarine system are pre- 

 sented by Williams (1966), Williams and Mur- 

 doch (1966) , and Thayer (1969) . The Newport 

 River has a mean depth of 1.2 m, and the water 

 column generally lacks vertical stratification. 

 Salinity and temperature range from 13 to 35^c 

 and 7° to 32°C. The sediments of this estuary 

 are primarily of shell and sand near the ocean 

 with finer sands, clays, and silts predominating 

 toward the mouth of the river. 



Organisms were processed promptly after col- 

 lection. All organisms, except ctenophores, were 

 rinsed with distilled water, blotted, and weighed. 

 Ctenophores were rinsed with distilled water and 

 weighed intact without blotting. Gut contents 

 of all organisms were included in the analyses, 

 and this may have accounted, especially in the 

 case of ctenophores, for some of the variability 

 in caloric measurements. Meats were removed 

 from the larger molluscs by shucking and from 

 the smaller molluscs by decalcification with 20 ^f 

 HCl. Decalcification normally required 2-4 min, 



Manuscript accepted January 1972. 



FISHERY BULLETIN: VOL. 71, NO. 1, 1973. 



289 



