Ikeda Energy budget of Maurolicus muellen 



51 



Gonads (ovaries and testes) were removed from 

 frozen specimens >36 mm TL and weighed (WW). 

 Prior to freeze-drying and grinding, the diameter of 

 oocytes was measured by using a microscope, and 

 ovaries with oocytes >0.5 mm diameter were defined 

 as "mature" (Ikeda, 1994). For some mature ovaries, 

 the individual oocytes were dissected after freeze- 

 drying. These gonads and isolated oocytes were used 

 in subsequent analyses. 



Carbon (C), hydrogen (H), and nitrogen (N) were 

 analyzed with an elemental analyzer (Yanaco CHN 

 Corder MT-5, Yanagimoto Co., Ltd., Kyoto) with an- 

 tipyrine as a standard. A weighed fraction of each 

 sample was incinerated at 480°C for 5 hours and re- 

 weighed for ash determination. All measurements 

 were made in duplicate for each sample. From repli- 

 cated determinations (rc = 10) on the same sample, the 

 precision of these analyses, as expressed by the coef- 

 ficient of variations (SD/mean, %), were 1% for C and 

 H, 2% for N, and 7% for ash. The elemental composi- 

 tion data were expressed as the percentage of DW, 

 or as the percentage of ash-free dry weight (AFDW). 

 The caloric content was calculated by using a for- 

 mula given by Gnaiger ( 1983), amended by Gnaiger 

 and Shick ( 1985): (4.436^ + 66.265W. - 11.2)/4.18, 

 where W N and W c are fractions of N and C, respec- 

 tively, on an AFDW basis. 



Energy budget 



Calculation of the energy budget is based on the ba- 

 sic balanced equation of Winberg ( 1956), i.e. 



0.8 xF = M + G, 



and 



K 2 = 100 x GAG + M), 



where 0.8 is the generalized assimilation efficiency, 

 F is the daily food ingestion, M is the daily metabo- 

 lism, G is the daily growth, and K 2 is the net growth 

 efficiency ( note that some symbols were changed from 

 those used by Winberg [1956]). Energy associated 

 with loss in scales, mucus secretion, excretion, etc. 

 were considered to be negligible and were omitted. 

 Energy use for reproduction was estimated from calo- 

 rific data of isolated gonads. F is often expressed as 

 the percentage of body energy (=daily ration, F'). 



The growth in length ofM. muelleri has been shown 

 to fit well to the von Bertalanffy curve (Gjosaeter, 

 1981;Yuuki, 1984; Ikeda, 1994): TL = TLjl-e^'-'»% 

 where TL^ is the theoretical maximum size, A" is a 

 growth factor, and t Q is the time (yr) at which growth 

 starts. In the calculation of the energy budget, the 

 curve of M. muelleri in Toyama Bay, southern Sea of 

 Japan, established by Ikeda (1994) was used: i.e. 

 TLj= 59.5 mm, K = 1.19, and * = 0.65 (yr). On the 

 basis of the hatching size (ca. 3 mm) of M. muelleri, 

 t=0.1 (TL=3.6 mm) was assumed as the start of 

 growth for this fish, and the growth calculation was 

 made in 0.1 yr (=36.5 d) increments. Total length at 

 a given age of the fish was converted to wet weight 

 (WW in mg) by using the allometric equation estab- 

 lished in the present study ( WW=0.00211TL 3346 

 [r=0.997, /!=312|), then to caloric units by multiply- 

 ing with the appropriate conversion factor (Kcal/g 

 WW) obtained from chemical composition analyses. 

 For the calculation of between-age metabolic expen- 

 diture, a mean value, multiplied by 36.5 d, was used. 

 Between-age values thus obtained were also used to 

 compute age-specific net growth efficiency (K 2 ) and 

 daily ration (F'). 



