SELECTION OF OPTIMAL MEASURES OF GROWTH AND REPRODUCTION FOR THE SUBLETHAL LEPTOCHEIRUS-PLUMULOSUS SEDIMENT BIOASSAY

This article describes the selection process used to identify optimal measures of growth and reproduction for the proposed 28-d sublethal se diment bioassay with the estuarine amphipod Leptocheirus plumulosus. W e used four criteria (relevance of each measure to its respective endp oint, signal-to-noise ratio, redundancy relative to other measures of the same endpoint, and cost [i.e., of labor, training, and equipment]) to evaluate nine growth and seven reproductive measures. Optimal endp oint measures were identified as those receiving relatively high score s for all or most criteria. Measures of growth scored similarly on all criteria, except for cost. The cost of the pooled (female plus male) growth measures was substantially lower than the cost of the female an d male growth measures because the latter required more labor (by appr ox. 25 min per replicate). Pooled dry weight was identified as the opt imal growth measure over pooled length because the latter required add itional labor and nonstandard software and equipment. Embryo and neona te measures of reproduction exhibited wide differences in labor costs but yielded similar scores for other criteria. In contrast, brooding m easures of reproduction (females carrying embryos in the brood pouch) scored relatively low on endpoint relevance, signal-to-noise ratio, an d redundancy criteria. We recommend neonates/survivor as the optimal m easure of L. plumulosus reproduction because it exhibited high endpoin t relevance and signal-to-noise ratios,was redundant to other reproduc tive measures, and required minimal time.