Norton and MacFarlane: Nutritional dynamics of reproduction in Sebastes flavidus 



305 



somatic depletions were greatest in muscle. Muscle 

 loss occurs in other fish (e.g. capelin and sockeye 

 salmon) as well, but unlike yellowtail rockfish, these 

 species often have high metabolic demands for mi- 

 gration in addition to reproduction (Idler and Bitners, 

 1960; Henderson et al., 1984). 



Although muscle was the site of greatest net deple- 

 tion of somatic tissue, mesenteric fat contributed 

 more energy than muscle for female-specific costs of 

 reproduction. Previous studies have demonstrated 

 the importance of mesenteric fat as an energy source 

 in yellowtail rockfish (Guillemot et al., 1985; 

 MacFarlane et al., 1993). Lipid stored in mesenter- 

 ies seems to be readily mobilized for reproduction in 

 this live-bearing species as well as other oviparous 

 fishes (Idler and Bitners, 1960; Ince and Thorpe, 

 1976; Jezierska et al., 1982). 



In yellowtail rockfish, lipid was the main source of 

 energy for female reproduction. About one-third of 

 total lipid depleted from female soma was available 

 for reproduction. Lipid lost from all the major reserve 

 tissues equalled 74% of the total somatic energy 

 mobilized for female-specific reproductive develop- 

 ment. Lipid is typically the primary source of energy 

 for reproduction in oviparous teleosts (Sargent, 1976; 

 Sargent et al., 1989). Data from yellowtail rockfish 

 suggest the importance of lipid for reproduction ex- 

 tends to marine viviparous fishes. 



Female-specific protein loss from yellowtail rock- 

 fish somatic tissues was approximately half that of 

 lipid. The utilization of protein from muscle as a 

 supplemental source of energy for reproduction has 

 been reported in some oviparous fishes (Niimi, 1972; 

 Medford and Mackay, 1978; Jobling, 1980). But this 

 contrasts with herring, where lies (1984) and 

 Bradford (1993) suggested that somatic protein was 

 the primary fuel for gonad development whereas stor- 

 age lipid supported nonreproductive metabolic 

 processes. 



Determining the partitioning of somatic reserves 

 between reproduction and adult metabolism is very 

 difficult in most teleosts. Reproductive strategies 

 involving factors such as sex differences in activity, 

 simultaneous development of testes and ovaries, 

 migration, and somatic energy accumulation concur- 

 rent with gonadal development obscure fractional 

 distribution. Because the yellowtail rockfish repro- 

 ductive strategy, including physiological processes 

 and behavior, does not include these factors (Carlson 

 and Barr, 1977; Eldridge et al., 1991; Pearcy, 1992), 

 we were able to estimate the nutritional energetic 

 costs directed toward oocyte and embryo develop- 

 ment. Forty-three percent (43%) of female-specific 

 somatic lipid depletion was incorporated into ova- 

 ries, leaving 57% for reproductive metabolism. 



Henderson et al. (1984) employed an analytical 

 design well-suited to determining somatic lipid par- 

 titioning among adult maintenance, reproductive 

 metabolism, and ovarian accretion in capelin, 

 Mallotus villosus. Although ovaries accumulated 38% 

 of mobilized somatic lipid and testes gained none, 

 both sexes mobilized essentially the same quantity 

 of somatic lipids. The absence of a difference between 

 sexes in lipid mobilization precluded estimation of 

 allocations between gonadal metabolism and adult 

 maintenance. 



Significant increase in ovarian protein during 

 maturation was expected because de novo synthesis 

 is required for oocyte and embryonic proliferation. 

 However, the net increase in ovarian protein was 

 220% of female-specific somatic loss and indicated a 

 dietary source during late vitellogenesis and gesta- 

 tion. Although there is a general paucity of prey in 

 the California Current ecosystem during the winter 

 (Hobson and Chess, 1988; Ainley, 1990) and stom- 

 ach contents of yellowtail rockfish samples were mini- 

 mal at this time (Whipple 3 ), feeding remains the most 

 likely source for the excess protein accumulated in 

 the ovary. Data from yellowtail rockfish off the Wash- 

 ington and Oregon coast showed that they may feed 

 over winter (Brodeur and Pearcy, 1984). Since we 

 observed frequent regurgitation during capture, it 

 is possible that expulsion of stomach contents con- 

 tributed to imprecise estimation of feeding intensity 

 in the yellowtail rockfish of the present study. 



There are limited data on female-specific nutri- 

 tional dynamics in other species. Thus, it may be 

 beneficial to compare allocations from soma to go- 

 nadal tissue, uncorrected for sex differences, for yel- 

 lowtail rockfish to those of other fishes. Such com- 

 parisons do not provide information on the partition- 

 ing of nutrients for various female metabolic and 

 reproductive processes, only the net transfer to ova- 

 ries. For yellowtail rockfish, the gain of lipid and 

 protein in ovaries during reproductive development 

 was 14% and 52% of somatic depletions, respectively. 

 This net transfer of lipids into ovaries was mid-range 

 in comparison with values in oviparous species. Net 

 lipid transfers of 38% in capelin (Henderson et al., 

 1984), 22% in plaice, Pleuronectes platessa (Dawson 

 and Grimm, 1980), 8% in sockeye salmon, Oncorhyn- 

 chus nerka (Idler and Bitners, 1960), and 5% in En- 

 glish sole, Pleuronectes vetulus (Dygert, 1990) have 

 been reported. Protein transfers in yellowtail rock- 

 fish are comparable to English sole, 55% (Dygert, 

 1990). In plaice 48% more protein accumulated in 

 ovaries than was lost from soma during oocyte 



3 Whipple, J. A. 1988. National Marine Fisheries Service, South- 

 west Fisheries Science Center, Tiburon Laboratory, 3150 Para- 

 dise Drive, Tiburon, CA 94920. Unpubl. data. 



