A COMPARISON OF MORPHOMETRIC, 

 BIOCHEMICAL, AND PHYSIOLOGICAL 

 INDEXES OF CONDITION 

 IN MARINE BIVALVE MOLLUSCS 



ROGER MANN 



Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 



ABSTRACT 



A number of morphometric, biochemical and physiological parameters are 

 compared and evaluated for their potential use as indexes of condition in marine 

 bivalve molluscs. Condition is defined as "the ability of an animal to withstand 

 an adverse environmental stress, be this physical, chemical or biological." 

 Laboratory and field data are compared to determine the effect of one 

 environmental stressor, temperature, on gravimetric and volumetric meat/shell 

 condition indexes; percentages of organic content, carbohydrate, carbon, and 

 nitrogen; C/N and cai-bohydrate/N ratios; weight-specific ammonia excretion 

 rates; and oxygen-consumption/ammonia-excretion ratios in a number of 

 commercially valuable species of oyster, clam, and mussel. 



With the increasing use of the sessile, adult bivalve mollusc as an 

 indicator of environmental quality (Goldberg, 1975) and the 

 considerable interest in culturing commercially valuable bivalve 

 species in thermal effluents, there is a pressing need to determine 

 which of many available morphometric, biochemical, and physio- 

 logical parameters can be used as indexes of condition in bivalves. 

 Condition is defined as "the ability of an animal to withstand an 

 adverse environmental stress, be this physical, chemical or biolog- 

 ical." Stress is defined as "a measurable alteration of a physiological, 

 or behavioral, or biochemical, or cytological steady-state which is 

 induced by environmental change, and which renders the individual 

 (or the population, or the community) more vulnerable to further 

 environmental change" (Bayne, 1975). 



Although many stressors, such as disease, starvation, salinity, and 

 exposure, affect the condition of bivalve molluscs, this paper 



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