Review of molluscan bivalve condition index calculations and application in Northern QuahogsMercenaria mercenaria

Condition index (CI) is a widely used parameter in ecological and physiological studies. For molluscan bivalves, no universal consensus exists for CI calculation. A literature review revealed that a total of 19 methods have been used for CI calculation in molluscan bivalves. To evaluate the CI calculation in northern quahogsMercenaria mercenaria(also called hard clams), market-sized clams at 12-14 months old (n = 300 from three populations) were collected for gravimetrical and volumetric measurements. Significant correlations were identified among body sizes (body length, height and width), body weights (total weight, wet meat weight, dry meat weight, wet shell weight, dry shell weight) and body volume (p < .0001,Rvalues >= .800). Referencing previously used CI equations for molluscan bivalves, a total of 18 equations were evaluated the suitability, considering non-lethal measurements, for northern quahogs through correlation analysis of the CIs from different equations. With equations constructed as the percentages of dry or wet meat weight out of total weight, dry shell weight, dry shell plus meat weight, body volume, body length*height*width, shell length or cubic of shell length, CIs were significantly correlated, meaning that these equations were exchangeable. Specifically, three equations with non-lethal measurements (percentages of total body weight out of total body volume, body length*height*width or cubic of body length) were evaluated effective. Overall, this publication provided a review for CI calculations in molluscan bivalves and evaluated the CI equations for northern quahogs.

Automated summary

The text provides a review of condition index (CI) calculations in molluscan bivalves, evaluating the CI equations for northern quahogs and identifying several interchangeable and effective equations.