300 



Fishery Bulletin 93(2), 1995 



Fisheries Management Council 2 ). Distinctive char- 

 acteristics of the reproductive strategy of yellowtail 

 rockfish (e.g. small testes, copulation months before 

 fertilization, quiescent testes during period of ova- 

 rian development [Eldridge et al., 1991], and 

 nonmigratory behavior [Pearcy, 1992]) allow male 

 nutrient dynamics to serve as adult metabolic con- 

 trols. Consequently, nutritional energy expenditures 

 specific to female reproduction can be estimated by 

 the difference between female and male dynamics. 



Knowledge of the nutritional dynamics specific to 

 female reproduction may contribute understanding 

 to the causes of interannual variability of larval pro- 

 duction and health (Moser and Boehlert, 1991). The 

 typical nutrient dynamic pattern may be altered by 

 episodic environmental perturbations that impact 

 reproductive output. Phenomena such as El Ninos 

 modulate the duration and intensity of upwelling, 

 thus lowering oceanic productivity and subsequent 

 energy flow (Boje and Tomczak, 1978; Ainley, 1990). 

 In fact, Lenarz and Wyllie Echeverria (1986) sug- 

 gested that the 1983 El Nino adversely influenced fat 

 accumulation and reproduction in yellowtail rockfish. 



The purpose of the present study was to determine 

 the temporal dynamics of tissue components in so- 

 matic and ovarian tissues in relation to the annual 

 reproductive cycle for yellowtail rockfish. Our objec- 

 tive was to determine the allocation of tissue compo- 

 nents for nutrition and energy committed to female 

 reproductive development. This report presents the 

 first comprehensive nutritional dynamics study on 

 a marine viviparous species. 



Materials and methods 



Adult yellowtail rockfish were collected by hook-and- 

 line at depths of 50 to 150 m from Cordell Bank, a 

 marine bank located approximately 20 nautical miles 

 west of Point Reyes, California (38°01'N, 123°25'W ). 

 Specimens were obtained monthly during one repro- 

 ductive cycle from May 1987 to April 1988. Fish were 

 immediately placed on ice and returned to the labo- 

 ratory for analyses. 



Within 24 hours of capture, ovarian or testicular 

 stage and morphometries were recorded and tissues 

 were excised for proximate and chemical analysis. 

 Tissues removed included liver, gonad, and a section 

 of muscle from the epaxial portion of the fish just 



2 Pacific Fishery Management Council. 1992. Status of the Pa- 

 cific coast groundfish fishery through 1990 and recommended 

 acceptable biological catches for 1993: stock assessment and 

 fishery evaluation. Document prepared for the council and its 

 advisory entities. Pacific Fishery Management Council, Port- 

 land, OR. 



below the spinous dorsal fin. In addition, mesenteric 

 fat deposits attached to the viscera were dissected 

 and weighed. 



Muscle mass for individual fish was estimated by 

 a regression equation. We regressed muscle weight 

 on body weight minus gonad weight from represen- 

 tative fish spanning the typical total body weight 

 range (800 to 1600 g) for yellowtail rockfish from 

 Cordell Bank. Muscle mass was determined by 



muscle (g) = 24.51 + 0.433 [body weight (g) 

 - gonad weight (g)]. (r=0.994, P<0.0005) 



Determinations of water, ash, and protein content 

 were performed on fresh tissues. Samples analyzed 

 for water content were dried at 80°C to a constant 

 weight and cooled in a desiccator prior to weighing. 

 Dried tissues were incinerated for 4 hours at 550°C 

 to measure ash content. Protein concentration was 

 assayed by the Lowrey method (Lowrey et al., 1951) 

 with bovine serum albumin (Sigma Chemical Co., St. 

 Louis, MO) as a standard. 



Tissue samples for lipid and glycogen determina- 

 tions were stored at -70°C and analyzed within one 

 month of collection. Lipid was extracted in duplicate 

 from 1 to 2 g of liver, gonad, and muscle by the 

 biphasic method of Bligh and Dyer (1959) following 

 homogenization with a Polytron homogenizer 

 (Brinkman Inc., Westbury, NY). Total lipid was quan- 

 tified by automated thin layer chromatography/flame 

 ionization detection (TLC/FID), by using an Iatroscan 

 TH-10 Mark III (Iatron Laboratories Inc., Tokyo, 

 Japan) with T Datascan software (RSS Inc., Bemis, 

 TN). Triplicates of 1 ul were spotted on Chromarods 

 S-III, dried, and scanned by the FID at 3.1 mm/sec, 

 0.95 kg/cm 2 hydrogen pressure and air flow of 2000 

 mL/min. Peak areas were converted to total lipid 

 weight by using external standards prepared gravi- 

 metrically from lipid extracts of S. flavidus livers. 

 Standard concentrations were attained by evaporat- 

 ing the organic layer to dryness and reconstituting 

 with chloroform to known concentrations ranging 

 from 2 to 70 ug lipid/uL. Chromarods were cleaned 

 with 9N sulfuric acid, rinsed in Milli-Q water and 

 stored in a desiccator between analytical runs. 



Glycogen content was measured by the anthrone 

 method (Carroll et al., 1956). Values wer^ standard- 

 ized with glycogen from rabbit liver (Sigma Chemi- 

 cal Co., St. Louis, MO). 



To evaluate variation in tissues and their compo- 

 nents over the reproductive cycle, tissue component 

 concentrations were converted to component masses 

 by determining the product of tissue mass and com- 

 ponent concentration. Since tissue and component 

 masses are a function of fish size, we adjusted the 



