A Laboratory Study of the Bioenergetics of Larval 

 Walleye Pollock, Theragra chalcogramma 



Yoh Yamashita and Kevin M. Bailev 



ABSTRACT: Rates of growth, oxygen consump- 

 tion, and ingestion were measured for lanal wall- 

 eye pollock, Theragra chalcogramma, in the lab- 

 oratory. These measurements were used to relate 

 assimilation and growih efficiencies to larval age 

 (and size) and prey ration level. Larval growth was 

 0.06 mm/d during the transition from endogenous 

 to exogenous food (days 4-16), and increased to 0.16 

 mm/d (days 19-21). Ingestion ranged from 24 to .58% 

 body dry weight/d. Oxygen consumption rates were 

 measured and used to partition total daily meta- 

 bolic expenditures into four components: resting 

 metabolism; SDA; lights-on generated nonfeeding 

 activity; and active (feeding) metabolism, which 

 accounted for 45.7, 13.3, 11.1, and 29.9% of the total 

 daily metabolic rate, respectively. Net assimilation 

 efficiency ranged from 24 to 64% and gross growth 

 efficiency ranged from 9 to 35%, depending on lar- 

 val age and size. Little difference was observed in 

 efficiencies at low and high ration levels. The daily 

 caloric requirement to support metabolism and 

 growth of first-feeding larvae was calculated at 0.16 

 calories, which is equivalent to 76 copepod nauplii. 

 This value is higher than ingestion estimates from 

 field studies. 



Capture and transformation of energy into body 

 mass is especially critical dming the larval stage 

 of marine fishes. Specific growth rate is highest 

 during this stage and weight may increase by 

 three orders of magnitude (Smith 1985; Houde 

 1987). Furthermore, duration of the larval stage, 

 as regulated by growth rate, is recognized as a 

 crucial factor in determining year class strength 

 (Houde 1987; Miller et al. 1988). Growth effi- 

 ciency, the proportion of ingested energy used in 

 growth, depends on a number of factors includ- 

 ing envu-onmental conditions, prey quahty, prey 

 abundance, and larval size and age. 

 Walleye pollock, Theragra chalcogramma, is 



Yoh Yamashita, Ocean Research Institute, The University 

 of Toliyo, Tokyo 164, Japan; present address: Tohoku Re- 

 gional Fisheries Research Laboratory, Shinhama-cho 3-27-5, 

 Shiogama 985, Japan. 



Kevin M. Bailey, Northwest and Alaska Fisheries Center, 

 National Marine Fisheries Service, NOAA, 7600 Sand Point 

 Way, N.E., Building 4, BIN C15700, Seattle, WA 98115. 



Manu.tcript Accepted April 1989. 

 Fishery Bulletin. U.S. 87: 525-536. 



the most abundant commercial species in the 

 northeastern Pacific Ocean, comprising 80% of 

 the total gi-oundfish catch (Bakkala et al. 1986). 

 Several studies have evaluated the bioenergetics 

 of late larvae, juveniles, and adults (Fukuchi 

 1976; Nishiyama 1981; Hams 1985; Smith and 

 Paul 1986; Dwyer et al. 1987; Smith et al. 1988) 

 but there are relatively few studies of bioener- 

 getics of early larvae, and their gi-owth effi- 

 ciency is unknown. Incze et al. (1984) reviewed 

 the early life history of this species and calcu- 

 lated daily ration based on literature-derived 

 values of growth and respiration. Clarke (1984) 

 made a similar estimate. Early studies of larval 

 walleye pollock respii-ation were limited because 

 larvae were not successfully grown in the labora- 

 tory. Likewise, estimation of larval growth, 

 determined from otolith ageing, was limited by 

 the lack of daily increment validation. Recently, 

 walleye pollock larvae have been successfully 

 reared in the laboratory (Bailey and Stehr 1986), 

 and daily growth increments on otohths have 

 been validated (Nishimura and Yamada 1984; 

 Bailey and Stehr 1988). 



In the present study we estimate components 

 of the energy budget of larval walleye pollock 

 reared in the laboratory. These components in- 

 clude rates of ingestion, growth, and metabo- 

 hsm. Oxygen consumption was measured at dif- 

 ferent levels of activity in order to model daily 

 metabolic costs. We also calculated efficiencies of 

 assimilation and growth for larvae as influenced 

 by ration and age. 



MATERIALS AND METHODS 

 Rearing of Larvae 



Experiments were carried out from March to 

 May 1988. Eggs from ripe females, collected in 

 Puget Sound, were fertilized and reared accord- 

 ing to methods described by Bailey and Stehr 

 (1986). Yolk-sac larvae were transfen-ed to 120 

 L black fiberglass tanks set in a water bath. 

 Initial stocking density was 1,200 larvae per 

 tank. Overhead fluorescent lights, on a 14 h 



525 



