Bivalve Condition Index
GSI Protocol #06
Published: January 2024
Prepared by: Sarah W. Hutchins, M.S., Staff Scientist; Stephen G. Hesterberg, Ph.D., Executive Director; Mallory A. Sea, Ph.D., Research Scientist
MATERIALS
Bristle brush
Distilled water
Rubber bands
Plastic freezer bags (3.79 L)
Aluminum weighing boats (~80 mL)
Microbalance
Gloves, nitrile or work
Shucking knife
Drying oven
Tray line with paper towels
INSTRUCTIONS
Remove biofouling, clean shells with a bristle brush, and rinse shells with distilled water. Either process immediately or fasten shells shut with a rubber band and freeze in a labeled, sealed plastic freezer bag until further use.
If processing frozen samples, thaw on a tray lined with a paper towel at room temperature. Samples should be thawed by the time weighing boats are labeled.
Label two aluminum weighing boats for each specimen with unique identifiers for the shell and tissue components, respectively. Record the initial mass of each weighing boat.
Shuck each specimen over the tissue weighing boat and on a tray. Separate tissue from the valves and place the tissue into the tissue weighing boat. Rinse valves and the knife with distilled water to ensure collection of all tissue content.
Place both valves, interior side down, in the shell weighing boat.
Dry tissue and shell in a drying oven at 60°C until weights are constant (~48 h). Record final weights.
Subtract initial mass of weighing boats from final mass to obtain dry weight of tissue and shell, respectively. Calculate dry weight condition index for each specimen using:
dry weight condition index = dry tissue weight x 100 / dry shell weight
REFERENCES
Beninger, P. G. and Lucas, A. (1984) Seasonal variations in condition, reproductive activity, and gross biochemical composition of two species of adult clam reared in a common habitat: Tapes decussatus (L) (Jeffreys) and Tapes philippinarum (Adams and Reeve). Journal of Experimental Marine Biology and Ecology, 79:19-37.
Lucas, A. and Beninger, P. G. (1985) The use of physiological condition indices in marine bivalve aquaculture. Aquaculture, 44:187-200.