BIOENERGETICS AND GROWTH OF 

 STRIPED BASS, MORONE SAXATILIS, EMBRYOS AND LARVAE 



Maxwell B. Eldridge, Jeannette A. Whipple, and Michael J. Bowers 1 



ABSTRACT 



Fluctuations in year class size of striped bass are known to be related to development and survival in 

 the early life stages. Bioenergetic aspects of growth and development of striped bass embryos and 

 larvae were determined in the laboratory to discover some of the physiological needs and processes 

 of these stages from fertilization to metamorphosis. 



Energy was provided by endogenous (yolk and oil globule) and exogenous (Artemia sp.) sources. 

 Initial amounts of yolk and oil varied significantly among eggs from seven different females, and 

 these differences were reflected in different patterns of consumption and growth. Feeding larvae 

 consumed their endogenous oil at rates related to exogenous food intake. Daily food rations of larvae 

 from the onset of feeding to metamorphosis were estimated for field and laboratory conditions. 

 Rations increased with size and age of the larvae. Wild larvae were estimated to have daily rations 

 substantially greater than those of cultured larvae. 



Energy outputs were measured in growth and oxygen consumption. Egg size (total dry weight) 

 directly influenced early periods of growth, but later compensatory growth, seen in more rapid 

 growth in larvae from smaller eggs, made up for initial differences. Growth and food consumption 

 were linearly related and, again, different growth characteristics were seen in each batch of fish. 

 Embryos and prefeeding larvae had the highest Qo 2 , while metabolism on a weight-specific basis 

 increased with tissue dry weight and was best described by a power function. 



Gross caloric conversion efficiencies were highest from fertilization to initial feeding. Feeding 

 larvae used their resources at levels under 20% and their conversion efficiencies did not appear to 

 correlate with food concentration. 



In an energy budget model, striped bass embryos and larvae given the highest food density con- 

 sumed yolk energy at constant rates until totally absorbed. Oil globule consumption fluctuated in 

 relation to growth and nonassimilation, rising sharply after first feeding then declining as food in- 

 take increased. Metabolism fluctuated according to developmental stage, rising with the onset of 

 active feeding. Nonassimilation steadily increased as larvae relied more on exogenous food. 



Striped bass, Morone saxatilis, populations have 

 fluctuated historically throughout their ranges, 

 but in recent years they have declined consis- 

 tently and unexplainably, especially on the west 

 coast of the United States. Present estimates 

 place the population of the San Francisco Bay/ 

 Delta estuary at 33% to 40% of its 1960 peak abun- 

 dance and it is forecasted to decline further 

 (Stevens 1980). Despite availability of consider- 

 able information on striped bass (Pfuderer et al. 

 1975; Rogers and Westin 1975; Horseman and 

 Kernehan 1976; Setzler et al. 1980), factors that 

 control or influence these fluctuations and de- 

 clines are not known. Field researchers con- 

 cluded from 20 yr of data collection that year 

 class size directly correlates with survival and 

 growth during the first 60 d of life and this, in 

 turn, is controlled by environmental conditions— 



principally the interrelated factors of fresh- 

 water flow, water diversion, and food supply 

 (Stevens 1977a, b; Chadwick 1979 2 ; Stevens 

 1980). 



To determine the direct causal mechanisms 

 operating between these environmental condi- 

 tions and early life stage growth and survival, we 

 conducted a series of laboratory experiments 

 over a 6-yr period. Our working hypothesis was 

 that a combination of inherent and environmen- 

 tal factors determined the ability of striped bass 

 embryos and larvae to meet metabolic require- 

 ments for successful growth and survival to the 

 pivotal age of 60 d. These factors involve a vari- 

 ety of physiological, morphological, and behav- 

 ioral functions, and are controlled and/or limited 

 by environmental conditions. Whole organism 



'Southwest Fisheries Center Tiburon Laboratory, National 

 Marine Fisheries Service, NOAA, Tiburon, CA 94920. 



Manuscript accepted January 1982. 

 FISHERY BULLETIN: VOL. 80, NO. 3. 1982. 



2 Chadwick, H. K. 1979. Striped bass in California. Pre- 

 pared for U.S. Environmental Protection Agency, Region II, 

 27 p. 



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