MacFarlane and Norton; Nutritional dynamics of embryonic-stage Sebastes 



279 



other fishes (Sargent, 1995). The relative contribu- 

 tion of TAG and PL to the energy demands of embry- 

 onic development varies by species. Whereas in cod 

 iGadusmorhua) iFraseretal., 1988; Finn etal., 1995) 

 and Atlantic herring iClupea harengus) (Tocher et 

 al., 1985) PL was the major source of energy, in 

 Senegal sole (Mourente and Vasquez, 1996) and 

 gilthead sea bream ( Ronnestad et al., 1994), TAG was 

 primarily catabolized. In Atlantic salmon (Salmo 

 salar), the PL phosphatidylcholine and TAG were 

 used equally to meet energy requirements (Cowey 

 etal., 1985). 



The changes in lipid composition during embryo- 

 genesis in yellowtail and shortbelly rockfishes de- 

 scribed here represent the first data of this kind for 

 rockfishes or any viviparous marine teleost. The use 

 of PL as a primary source of energy may be consis- 

 tent with results from previous research revealing 

 that phosphatidylcholine was supplied to develop- 

 ing embryos of yellowtail rockfish from maternal 

 sources both before and during development 

 (MacFarlane and Bowers, 1995). Perhaps the facil- 

 ity to supply phospholipids matrotrophically en- 

 hances their use as energy-yielding substrates. High 

 concentrations of TAG in prefertilized eggs (EMS 1) 

 and its importance as an energy source are not un- 

 expected because both species feed heavily on eu- 

 phausiids (Brodeur and Pearcy, 1984), which contain 

 large amounts of TAG (Fricke and Oehlenschlager, 

 1982). 



Lipid class composition has been promoted as a 

 measure of nutritional condition for larvae of a vari- 

 ety of oviparous marine fish, including Atlantic cod 

 (Lochmann et al., 1995), Atlantic herring (Fraser et 

 al., 1987), and anchovy Engraul is mordax (Hakanson, 

 1989). Depending upon the species, the quantities of 

 TAG or PL, or both, related to the probability for 

 survival. Lochmann et al. ( 1995) suggested that sur- 

 vival was related to a condition index based on a dis- 

 criminant function of TAG, PL, and defatted dry 

 weight in laboratory and field-collected cod larvae. 

 Triacylglycerol (TAG) was regarded as the critical 

 variable in condition for herring (Fraser et al., 1987) 

 and anchovies (Hakanson, 1989). 



It is reasonable to apply this concept to the assess- 

 ment of larvae from viviparous species as well. The 

 nutritional status of larvae just prior to parturition 

 would represent their condition at the start of life in 

 the marine environment and would be related to their 

 ability to survive until adequate feeding occurs. The 

 presence of an oil globule in rockfish larvae during 

 the early days after birth argues for the importance 

 of lipids for energy. For rockfish, the amounts of TAG 

  at birth should be related to survival potential be- 

 cause this lipid class is the predominant component 



in oil globules of most fishes (Henderson and Tocher, 

 1987; Heming and Buddington, 1988) and has con- 

 sistently been shown to correlate with physiological 

 condition (Fraser, 1989). 



We analyzed embryos in pregnant female short- 

 belly rockfish from populations living in the proxim- 

 ity of three submarine canyons off the central Cali- 

 fornia coast. The purpose was to determine the vari- 

 ability in metabolism of lipid classes for specific popu- 

 lations and the estimated concentrations of each lipid 

 class at birth, thus providing a measure of nutritional 

 status and relative probability for survival. When 

 lipid class concentrations were assessed in embryos 

 from the separate populations, there were differences 

 in the amounts and rates of depletion during 

 intraovarian development (Table 2). Two-way ANOVA 

 determined there were significant differences among 

 populations at the three canyons, despite being lo- 

 cated within about a one-degree latitude span off the 

 central California coast. All lipid classes, except 

 NEFA, varied significantly by EMS (P<0.0001 ), popu- 

 lation (P<0.0001), and the interaction of population 

 and EMS (P<0.05). 



The changes in concentrations of lipid classes were 

 linearly related to EMS for embryos from each popu- 

 lation (Table 2). Parameter estimates from linear 

 regressions of each lipid class by stage of embryonic 

 maturation revealed that rates of metabolism dif- 

 fered among the populations (Table 2). The greatest 

 catabolic rates of TAG and PL were found in embryos 

 from the Pioneer Canyon population. Rates of pro- 

 tein depletion were also greater in embryos from Pio- 

 neer Canyon and lowest in those from Ascension 

 Canyon. 



In conjunction with initial concentrations of pro- 

 tein and lipid classes at fertilization, the rates of 

 nutrient metabolism can be used to estimate concen- 

 trations at parturition (EMS 33). The greater rates 

 of nutrient utilization for embryos in females from 

 the population at Pioneer Canyon resulted in the low- 

 est levels of nutritional stores at birth of the three 

 populations evaluated (Table 3). Conversely, newborn 

 larvae from females at Ascension Canyon contained 

 the greatest concentrations of lipids and protein, 

 suggesting that they have a greater likelihood of sur- 

 vival until suitable feeding conditions exist. 



The differential status of nutrient levels in larvae 

 at birth may contribute to differences in survival rate 

 among the populations and, thus, influence the di- 

 versity of the species year class. Parturition occurs 

 during the winter when oceanic conditions prevail 

 along the California coast. This is the period of low- 

 est primary and secondary productivity annually 

 (Ainley, 1990). Until marine conditions become fa- 

 vorable for biological productivity, usually in April 



