Date Awarded


Document Type


Degree Name

Doctor of Philosophy (Ph.D.)


Virginia Institute of Marine Science


The objective of this study was a comparison of developmental changes and energy utilization in eggs, unfed larvae, and fed larvae of two marine fish species that both have pelagic early stages, but differ in phylogeny and early life ecology. The bay anchovy (Anchoa mitchilli), a clupeiform, spawns in estuaries and shallow coastal waters. The black sea bass (Centropristis striata striata), a perciform, spawns offshore at 15-50 m depths. Densities of zooplankton eaten by first-feeding fish larvae are normally higher in coastal waters than offshore. An important determinant of survival of larval fishes is their ability to fulfill nutritional requirements after yolk energy is exhausted. Faster-growing larvae are less likely to be preyed upon. The manner in which energy is partitioned may indicate relative plasticity with respect to departures from optimal food composition or abundance. Differences among species might result from different feeding strategies or from adaptation to different feeding conditions. Energy utilization was assessed by constructing energy budgets (I = G + M + F&U): ingested calories, I, from feeding rates; growth calories, G, from composition and weight; metabolic calories, M, from oxygen uptake; egested and excreted calories, F&U, by difference. Three lines of evidence were found that suggest black sea bass are able to resist fluctuations in food availability better (survive and grow at lower densities): (1) Sea bass have more time to find food and develop feeding skills--50 hours between first feeding and yolk exhaustion vs 10 hours for anchovies. (2) Sea bass feed more efficiently and probably pay a lower metabolic price for their food. Over the first five days of feeding, capture success averaged 85% for sea bass and 60% for anchovies. (3) During the first five days, sea bass gross growth efficiency (12%) was twice that of anchovies (6%). Sea bass may also be more resistant to starvation from complete food deprivation. their yolk lasts longer. During starvation, their weight-specific metabolism is lower and they lose body calories at a lower rate. The bay anchovy seems to be adapted to the high food densities, and the black sea bass to the low food densities, that characterize their respective habitats. For sea bass the food supply is more difficult to exploit, and this requires greater efficiency.



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