Marginal metabolic scope and growth of hatchery-produced, juvenile red drum by progeny group

Due to the character of the original source materials and the nature of batch digitization, quality control issues may be present in this document. Please report any quality issues you encounter to digital@library.tamu.edu, referencing the URI of the item.Includes bibliographical references (leaves 50-53).Issued also on microfiche from Lange Micrographics.Nine broodstock groups of red drum Sciaenops ocellatus (each consisting of two males and three females) at a State of Texas fish hatchery spawned 13 concurrent progeny groups for which two performance factors, marginal metabolic scope (MMS) and growth, were evaluated and compared by progeny group. After grow-out of the fish under common conditions, MMS was measured via automated respirometry for two temporal blocks of individuals, each representing all 13 progeny groups. Although it had been intended that the two blocks be treated as replicates, the fish became sick with the viral disease lymphocystis during the 10-day interval between blocks. Compared with their apparently healthy counterparts (n = 52), the sick fish (n = 43) exhibited a 24 % reduction in MMS, which measures capacity for metabolic performance. However, there was no significant effect of progeny group on MMS. Growth, measured as percentage weight gain per day, was significantly different between the one progeny group with largest fish and each of three progeny groups with smallest fish. Differences in growth may have been due to minor differences in early environment, inequity in resource partitioning, and/or genetics. An ecophysiological model, Ecophys.Fish, was employed to integrate the MMS and growth results. For the healthy fish, the model indicated a high degree of consistency between metabolic performance during respirometry and prior growth: For all 13 progeny groups, median MMS could be used to accurately simulate median growth for the group (R² = 0.98, for observed median growth vs. simulated growth; n = 13). Similarly, for all except 9 (15 %) of the 52 individuals, the same degree of concordance obtained (R² = 0.94; n = 43). For the 9 statistical outliers, growth was under-simulated. The same pattern-simulated growth less than observed growth-was presented by the median data from the fish making up the sick block. In both cases, performance of the fish during terminal respirometry was inferior to that exhibited as growth over the entire lifespan. Perhaps, the seemingly healthy outliers of the first block were getting sick when respirometry was performed