Effects of Water Temperature on Feeding and Growth of the Amphidromous Sculpin, Cottus Pollux Middle-Egg (ME) Type, Reared in the Laboratory

Aquaculture Sci. 62（4），407－414（2014）

Effects of Water Temperature on Feeding and Growth of the Amphidromous Sculpin, Cottus pollux Middle-egg (ME) Type, Reared in the Laboratory

1, 2 3 4 Naohiko TAKESHITA ＊, Itaru IKEDA , Kunimasa AOKI , Yukiya NISHIMURA , 5 6 7 Takumi HASEGAWA , Kazuhiro SAKATA , Shingo NAGATA , 6 6 Takuya KONDOU and Makoto SHIMADA

Abstract: Effects of water temperature on feeding and growth of the amphidromous sculpin Cottus pollux ME were studied using 9 different temperatures from 10 to 26℃ for 30 days. At each of the 9 temperatures, five males and females were reared in aquaria and the rearing examination was repeated 3 times (n = 270). Results indicate that water temperatures ranging from 18 to 20℃ were optimal for daily feeding rate, temperatures ranging from 14 to 17℃ were optimal for daily growth rate, and feeding efficiency temperatures ranging from 11 to 16℃ were optimal among males and females. The optimal water temperatures for daily growth rate and feeding efficiency were slightly lower than those for daily feeding rate. Also, the values by the polynomial equation of daily growth rate and feeding efficiency for 26℃ had lower or negative values. These results indicate that the optimal water temperature range is from 14 to 20℃, and that a water temperature of 10℃ is too low and 26℃ is too high for C. pollux ME to feed and grow.

Key words: Cottus pollux middle-egg (ME) type; Effect of water temperature; Feeding; Growth

Three types of Cottus pollux: the small-egg and habitat of this species have been reported (SE), middle-egg (ME) and large-egg (LE) (Nagoshi and Murakami 1980; Natsumeda et types, are thought to be distributed in the al. 1997; Natsumeda 1998a, 1998b, 1999, 2001, Japanese Archipelago (Goto 2002). C. pollux 2003, 2005, 2007a, 2007b, 2007c; Yamamoto and SE (including C. reinii from Lake Biwa) is Sawamoto 1998). However, little is known about amphidromous and lacustrine, C. pollux ME is the ecology of amphidromous C. pollux SE or amphidromous, and C. pollux LE is fluvial (Goto ME, except for the morphology and early life and Arai 2003). These fishes are target spe- history of these fish (Mizuno and Niwa 1961; cies of river fisheries (Nakamura 1963; Miyadi Kurawaka 1976; Shimizu et al. 1994; Shinagawa et al. 1976). There are many ecological stud- et al. 2002). C. pollux ME inhabits cool limpid ies on fluvial C. pollux LE, the growth, matu- streams (Ehime Prefecture 2003), and is dis- rity, movement, feeding habit, reproduction tributed in rivers flowing into the Japan Sea

Received 21 January 2014; Accepted 25 September 2014. 1 Graduate School of Fisheries Science, National Fisheries University, Shimonoseki, Yamaguchi 759-6595, Japan. 2 Department of Applied Aquabiology, National Fisheries University, Shimonoseki, Yamaguchi 759-6595, Japan. 3 Department of Fisheries Distribution and Management, National Fisheries University, Shimonoseki, Yamaguchi 759- 6595, Japan. 4 Tokyo Metropolitan Harumi-Sogo High School, Harumi, Tokyo 101-0053, Japan. 5 Oriental Techno Co., Ltd., Tatsuno, Hyogo 671-1321, Japan. 6 West Japan Engineering Consultants, Co., Ltd., Watanabe-dori, Fukuoka 810-0004, Japan. 7 F-TREK Co., Ltd., Kengun, Kumamoto 862-0991, Japan. ＊Corresponding author: Tel, (+81) 83-86-5111; E-mail, [email protected] (N. Takeshita). 408 N. Takeshita, I. Ikeda, K. Aoki, Y. Nishimura, T. Hasegawa, K. Sakata, S. Nagata, T. Kondou and M. Shimada in Hokkaido and Honshu Islands, those flow- Hakko Kogyo Co., Ltd.), respectively. A paste ing into the Seto Inland Sea in Shikoku Island, diet for eel (Unagi High Step, Hayashikane and those in the northwestern Kyushu Island Sangyo Co., Ltd.), prepared by blending 100 g (Goto and Arai 2003). In Kyushu Island, C. dry weight of diet with 90 ml of water, was given pollux ME has been designated as an “extinct from 100 days after hatching. species in the wild” in Fukuoka Prefecture, a Seventeen months after hatching, 138 males “critically endangered and endangered spe- and 234 females survived. Sex was determined cies” in Saga and Kumamoto Prefectures, an from the external sexual characteristics, males “endangered species” in Nagasaki Prefecture, having a genital papilla (Mizuno and Gose and a “data deficient species” in Oita 1972). The males and females were kept sepa- Prefecture, respectively (Oita Prefecture 2000; rately in FRP tanks (150 l), in a running water Fukuoka Prefecture 2001; Saga Prefecture system with a flow rate of 200 ml/min, aerated 2003; Kumamoto Prefecture 2009; Nagasaki (600 ml/min) and filtered with 2 sets of Tetra Prefecture 2011). Therefore, the abundance of Brillant Filter (Tetra Co., Ltd.), after measur- this fish is considered to be declining in almost ing TL to the nearest 0.1 mm. Rearing water all rivers in northwestern Kyushu Island. For temperature was controlled by using an air con- accumulation of basic ecological data and the ditioner at about 25℃ from July to September, future conservation of C. pollux ME, the effects considering the summer water temperature of water temperature on feeding and growth of where C. pollux ME were observed in the this species were examined in the laboratory. springs of the Hikawa River (Takeshita et al. unpubl. data). In the other months, rearing Materials and Methods water temperature was not controlled, it ranged from 6 to 9℃ in winter. Photoperiod was not Fish rearing and diet controlled during the fish rearing. It seemed Egg clusters guarded by a C. pollux ME male that both males and females matured 2 years of 104.2 mm in total length (TL) were collected after hatching in these FRP tanks, based on the at 6.9 km upstream from the river mouth of the appearance of the large white testes or matured Hikawa River (32°33’31”N, 130°40’55”E), west- eggs (ca. 1 mm in diameter) visible in bellies ern Kyushu Island, Japan, on 12 January 2009. from December to March 2011 (Takeshita et al. These eggs were reared in a 30 l polycarbonate unpubl. data). tank in a running freshwater system with a flow Rearing experiments over periods of 30 days rate of 100 ml/min and aeration (600 ml/min). for males and females were conducted 3 times, Hatching occurred mainly on 14 February respectively. Males at 17 (1st period), 20 (2nd 2009. Newly hatched pelagic larvae (about period) and 30 (3rd period) months after hatch- 1000 in total) were distributed to four poly- ing and females at 19 (1st period), 25 (2nd carbonate tanks (30 l) and kept in a running period) and 32 (3rd period) months after hatch- freshwater system with a flow rate of 200 ml/ ing were used for these experiments, which did min and aeration (600 ml/min). Artemia salina not include the maturity period in the labora- nauplii enriched by a commercial enrichment tory from December to March, that is 21 to 24 product (Power full brine, Miyako Kagaku months after hatching (Takeshita et al. unpubl. Co., Ltd.) was given every day at 8 : 00-9 : 00 data). and 16 : 00-17 : 00, until 40 days after hatching. After 2 days of fasting, 45 fish were randomly Artemia density was increased from 5 to 10 allocated to 9 groups (5 fish each). Body weight individuals/ml according to the fish growth. (BW) was measured to the nearest 0.01 g The juveniles (22 days after hatching) started (Tables 1, 2). Each fish was individually marked to settle in the tanks. From 20 to 80 days and by the removal of spines of the first dorsal fin from 60 to 120 days after hatching, they were and soft rays of the second dorsal fin in differ- fed with dry pellets, N-400 and N-700 (Kyowa ent combinations. Each group of 5 fish was kept Temperature Effect on Feeding of Cottus pollux ME 409 in a freshwater aquarium (60×30×36 cm), in a Cooler (RZ-150Y, Rei-Sea Co., Ltd.) with a 200 running water system with a flow rate of 50 ml/ W heater, respectively. Photoperiod was not min, aerated (600 ml/min) and filtered with one controlled during the experimental periods. set of Tetra Brillant Filter. Water temperature of The fish were fully fed the paste diet at the 9 aquaria was controlled at 10, 12, 14, 16, 18, 17 : 00-18 : 00 for a period of 30 days. The diet 20, 22, 24, and 26℃ (±0.5℃) using a Rei-Sea was pelletized to 0.060 g per piece during the

Table 1. Growth, total diet intake (TDI), daily feeding rate (DFR), and feeding efficiency (FE) of male Cottus pollux ME among the 9 groups reared in different water temperatures for 3 30-day periods WT (℃) 101214161820222426 1st period BW (g) Initial (n = 5) 10.23±2.31 9.92±2.35 9.99±2.15 10.12±1.94 9.92±1.67 9.72±1.85 9.70±1.62 9.23±1.41 9.88±1.62 Final (n = 5) 11.46±2.83 11.12±3.05 11.63±2.14 12.32±2.42 11.93±2.23 11.59±2.56 10.96±1.55 10.06±1.60 9.18±1.39 DGR (%, n = 5) 0.39±0.12 0.38±0.15 0.58±0.33 0.74±0.29 0.67±0.29 0.62±0.20 0.46±0.22 0.30±0.18 -0.23±0.20 TDI (g) 12.30 12.72 16.50 18.36 19.62 20.76 18.78 15.03 8.40 DFR (%, n = 30) 0.76±0.39 0.81±0.34 1.01±0.42 1.10±0.35 1.20±0.36 1.30±0.34 1.21±0.35 1.03±0.35 0.59±0.26 FE (%) 49.84 47.41 49.70 59.91 51.27 44.94 33.60 27.48 -41.91 2nd period BW (g) Initial (n = 5) 13.08±2.35 13.67±2.70 13.13±1.98 13.67±2.06 14.34±2.75 13.98±2.88 14.19±3.79 13.67±3.06 14.54±2.95 Final (n = 5) 14.80±2.32 16.08±3.03 15.32±3.01 16.92±2.24 16.72±2.95 15.92±4.08 15.36±3.87 14.00±2.51 15.30±3.11 DGR (%, n = 5) 0.45±0.13 0.60±0.11 0.53±0.22 1.08±0.50 0.57±0.24 0.43±0.21 0.28±0.11 0.11±0.20 -0.06±0.19 TDI (g) 15.12 20.56 21.20 27.36 27.52 25.84 23.92 22.92 19.16 DFR (%, n = 30) 0.73±0.71 0.93±0.59 1.00±0.60 1.21±0.62 1.19±0.44 1.16±0.38 1.08±0.32 1.11±0.42 0.89±0.24 FE (%) 56.61 58.71 51.65 59.43 43.28 37.42 24.46 7.24 -6.21 3rd period BW (g) Initial (n = 5) 19.81±3.84 19.50±3.29 19.68±3.48 20.97±2.92 21.78±5.04 21.16±3.73 21.81±3.52 21.80±5.67 22.22±5.15 Final (n = 5) 22.40±4.01 22.46±3.99 24.62±4.63 24.50±3.93 24.66±6.03 24.92±4.13 23.73±4.32 23.07±6.38 22.40±5.43 DGR (%, n = 5) 0.45±0.15 0.50±0.11 0.83±0.15 0.55±0.16 0.43±0.16 0.60±0.17 0.29±0.12 0.18±0.21 0.02±0.09 TDI (g) 22.12 26.70 35.98 31.61 32.41 35.09 29.45 32.18 23.00 DFR (%, n = 30) 0.70±0.30 0.85±0.46 1.09±0.39 0.94±0.46 0.93±0.34 1.02±0.38 0.86±0.36 0.95±0.31 0.69±0.29 FE (%) 58.64 55.54 68.62 55.81 44.37 53.61 32.60 19.70 3.91

Table 2. Growth, total diet intake (TDI), daily feeding rate (DFR), and feeding efficiency (FE) of female Cottus pollux ME among the 9 groups reared in different water temperatures for 3 30-day periods WT (℃ ) 101214161820222426 1st period BW (g) Initial (n = 5) 4.58±0.71 4.78±0.64 4.70±0.54 4.58±0.62 4.63±0.45 4.49±0.62 4.53±0.80 4.66±0.53 4.49±0.48 Final (n = 5) 5.10±0.90 5.43±0.64 5.32±0.50 5.86±0.95 5.77±0.78 5.44±0.73 5.28±0.66 5.00±0.74 4.63±0.57 DGR (%, n = 5) 0.37±0.18 0.47±0.12 0.45±0.11 0.92±0.34 0.80±0.19 0.71±0.22 0.59±0.28 0.23±0.20 0.09±0.18 TDI (g) 4.80 5.88 6.75 8.61 8.19 7.02 6.92 6.87 5.73 DFR (%, n = 30) 0.66±0.30 0.77±0.35 0.90±0.34 1.11±0.33 1.06±0.34 0.95±0.29 0.94±0.38 0.95±0.23 0.84±0.41 FE (%) 54.79 55.78 45.93 74.10 69.35 67.66 54.23 24.60 11.52 2nd period BW (g) Initial (n = 5) 11.02±1.58 10.80±1.20 11.05±1.48 11.03±1.48 11.09±1.34 10.92±1.08 11.08±1.11 10.92±1.50 10.33±1.31 Final (n = 5) 12.49±1.47 12.49±1.23 12.30±2.02 13.13±2.04 12.68±1.62 12.06±1.38 12.18±1.08 11.61±1.54 10.21±1.22 DGR (%, n = 5) 0.46±0.17 0.53±0.06 0.36±0.14 0.63±0.24 0.48±0.17 0.34±0.09 0.34±0.12 0.22±0.22 -0.03±0.15 TDI (g) 13.34 15.90 15.00 20.48 19.32 18.04 18.60 18.98 14.66 DFR (%, n = 30) 0.77±0.28 0.91±0.43 0.86±0.37 1.14±0.46 1.09±0.40 1.05±0.31 1.07±0.30 1.12±0.34 0.95±0.26 FE (%) 55.10 53.15 41.67 51.17 41.15 31.54 29.68 18.12 -4.16 3rd period BW (g) Initial (n = 5) 12.69±1.56 12.04±1.95 12.93±1.48 12.77±1.69 13.27±1.57 12.46±1.57 13.01±1.84 12.99±1.30 12.97±2.34 Final (n = 5) 14.28±1.51 14.01±2.19 15.75±1.83 15.37±2.02 14.92±2.11 13.75±1.79 13.29±1.43 12.88±1.46 12.18±2.22 DGR (%, n = 5) 0.43±0.12 0.55±0.08 0.73±0.10 0.68±0.21 0.41±0.12 0.34±0.13 0.09±0.16 -0.03±0.16 -0.20±0.21 TDI (g) 17.10 18.84 25.83 24.42 21.93 22.65 23.01 19.92 15.36 DFR (%, n = 30) 0.84±0.36 0.97±0.39 1.21±0.50 1.16±0.44 1.04±0.40 1.16±0.38 1.17±0.33 1.03±0.24 0.82±0.36 FE (%) 46.37 52.28 54.67 53.11 37.80 28.43 6.08 -2.66 -25.78 410 N. Takeshita, I. Ikeda, K. Aoki, Y. Nishimura, T. Hasegawa, K. Sakata, S. Nagata, T. Kondou and M. Shimada

1st period, 0.080 g per piece during the 2nd females reached 59.8-85.3 mm TL (Mean±SD = and 3rd periods for males, and 0.030 g per 72.1±6.6 mm TL, n = 234). Males were signifi- piece during the 1st period, 0.040 g per piece cantly larger than females (t-test, t = 28.87, in the 2nd period, 0.060 g in the 3rd period P < 0.001). for females. Daily diet intake (g, DDI) in each aquarium was calculated from the number of Effect of water temperature on feeding pieces eaten by the 5 fish in each aquarium for Mean values of DFR in 3rd period are lower a period of 30 days. After the completion of the than those in the other periods for males, and 30 days feeding period and 2 additional days of those of DFR in 1st period are higher than fasting, BW was measured to the nearest 0.01 g those in the other periods for females (Fig. 1). (Tables 1, 2). The relationship between water temperature Daily growth rate (DGR) was individually cal- and mean values of DFR among the 9 groups in culated as follows: each experimental period for males and females -1 -1 DGR (%) = 100 (W2 - W1) W1 T is given by the following equations, respec- where, W1 is the initial BW, W2 is the final BW tively: and T is the rearing interval (30 days). Daily Male in 1st period: feeding rate (DFR) in each aquarium was calcu- DFR = - 1.663 + 3.164 E-1 WT - 8.646 E-3 WT 2 lated as follows: (R2 = 0.833, P < 0.01) -1 DFRn (%) = 100 DDIn TWn Male in 2nd period: -1 -1 -3 2 where, DDIn is DDI on the n-th day, TWn is DFR = - 8.627 E + 2.173 E WT - 5.749 E WT total BW of all fish in each group on the n-th (R2 = 0.925, P < 0.001) day. TWn was calculated using the linear equa- Male in 3rd period: tion between the initial BW of all fish (n = 5) and DFR = - 3.870 E-1 + 1.561 E-1 WT - 4.363 E-3 WT 2 final BW of all fish (n = 5) of each group (Tables (R2 = 0.643, P < 0.05) 1, 2). Feeding efficiency (FE) in each aquarium Female in 1st period was calculated as follows: DFR = - 6.296 E-1 + 1.747 E-1 WT - 4.585 E-3 WT 2 -1 2 FE (%) = 100 TDI (TW2 - TW1) (R = 0.820, P < 0.01) where, TDI is the total diet intake for 30 Female in 2nd period: -1 -1 -3 2 days, TW1 and TW2 is the total of initial BW and DFR = - 2.60 4 E + 1.348 E WT - 3.343 E WT final BW of all fish in each group, respectively (R2 = 0.758, P < 0.05) (Tables 1, 2). Female in 3rd period: DFR = - 4.673 E-1 + 1.830 E-1 WT - 5.085 E-3 WT 2 Statistical analysis (R2 = 0.771, P < 0.05) Body size (TL) of male and female were ana- where, WT is the water temperature. These lyzed with parametric test (t-test) using JMP 9 equations indicate that approximately 18.3℃ in (SAS Institute Inc.). DFR, DGR and FE were 1st period, 18.9℃ in 2nd period and 17.9℃ in analyzed using the values at each experimental 3rd period had the highest values for DFR of period for males and females, respectively. DFR, males, 19.2℃ in 1st period, 20.2℃ in 2nd period DGR and FE were analyzed with parametric sta- and 18.0℃ in 3rd period had the highest values tistical tests (regression analysis). For all statis- for DFR of females, respectively (Fig. 1). tical tests, significance was assessed at P = 0.05. Effect of water temperature on growth Results Mean values of DGR are similar among the 3 periods for males, and those of DGR in Body size of male and female 1st period are higher than those in the other Seventeen months after hatching, males periods for females (Fig. 2). The relationship reached a size range of 74.3-105.4 mm TL between water temperature and mean values of (Mean±SD =92.3±6.4 mm TL, n = 138), and DGR among the 9 groups at each experimental Temperature Effect on Feeding of Cottus pollux ME 411 period for males and females is given by the fol- DGR = - 5.684 E-1 + 1.666 E-1 WT - 5.983 E-3 WT 2 lowing equations, respectively: (R 2 = 0.919, P < 0.001) Male in 1st period: where, WT is the water temperature. These DGR = - 1.966 + 3.205 E-1 WT - 9.609 E-3 WT 2 equations indicate that approximately 16.7℃ in (R 2 = 0.920, P < 0.01) 1st period, 15.4℃ in 2nd period and 15.0℃ in Male in 2nd period: 3rd period had the highest values for DGR of DGR = - 1.080 + 2.301 E-1 WT - 7.466 E-3 WT 2 males, 17.2℃ in 1st period, 14.6℃ in 2nd period (R 2 = 0.758, P < 0.05) and 13.9℃ in 3rd period had the highest values Male in 3rd period: for DGR of females, respectively (Fig. 2). DGR = - 5.495 E- 1 + 1.550 E-1 WT - 5.168 E-3 WT 2 (R 2 = 0.788, P < 0.01) Effect of water temperature on feeding efficiency Female in 1st period: Values of FE are similar among the 3 periods DGR = - 1.969 + 3.180 E-1 WT - 9.239 E-3 WT 2 for males, and those in 1st period are higher (R 2 = 0.819, P < 0.01) than those in the other periods for females Female in 2nd period: (Fig. 3). The relationship between water tem- DGR = - 3.006 E-1 + 1.114 E-1 WT - 3.813 E-3 WT 2 perature and FE among the 9 groups in each (R 2 = 0.839, P < 0.01) experimental period for males and females is Female in 3rd period: given by the following equations, respectively:

Fig. 1. Daily feeding rate (DFR) of male (A) and female Fig. 2. Daily growth rate (DGR) of male (A) and female (B) Cottus pollux ME at 9 different water temperatures (B) Cottus pollux ME at 9 different water temperatures for 30 days ( , male in 1st period; , male in 2nd for 30 days ( , male in 1st period; , male in 2nd period; , male in 3rd period; , female in 1st period; , male in 3rd period; , female in 1st period; , female in 2nd period; , female in 3rd period; , female in 2nd period; , female in 3rd period). period). 412 N. Takeshita, I. Ikeda, K. Aoki, Y. Nishimura, T. Hasegawa, K. Sakata, S. Nagata, T. Kondou and M. Shimada

Male in 1st period: where, WT is the water temperature. These FE = - 112.6 + 22.62 WT - 7.381 E-1 WT 2 (R 2 = equations indicate that approximately 15.3℃ 0.852, P < 0.01) in 1st period, 12.0℃ in 2nd period and 13.2℃ Male in 2nd period: in 3rd period had the highest values for FE of FE = 8.871 + 8.138 WT - 3.377 E-1 WT 2 (R 2 = males, 16.2℃ in 1st period, 11.2℃ in 2nd period 0.981, P < 0.0001) and 12.8℃ in 3rd period had the highest values Male in 3rd period: for EF of females, respectively (Fig. 3). FE = 8.457 E-1 + 9.120 WT - 3.461 E-1 WT 2 (R 2 = 0.930, P < 0.001) Discussion Female in 1st period: FE = - 85.93 + 19.09 WT - 5.895 E-1 WT 2 (R 2 = Little is known about the growth of C. pollux 0.808, P < 0.01) ME, the only available evidence is that males Female in 2nd period: reach a maximum of 160 mm TL (Shimizu et al. FE = 22.75 + 5.306 WT - 2.367 E-1 WT 2 (R 2 = 1994). Based on the TL measurements of this 0.939, P < 0.001) preliminary rearing, males reach a size range Female in 3rd period: of 74.3-105.4 mm TL, and females reach 59.8- FE = - 23.00 + 11.81 WT - 4.611 E-1 WT 2 (R 2 = 85.3 mm TL at seventeen months after hatch- 0.983, P < 0.0001) ing, thus males grew significantly larger than females. Sexual size dimorphism of the fluvial C. pollux LE was reported by the successive mark-and-recapture method in the Inabe River, central Honshu Island, Japan (Natsumeda et al. 1997). Considerable sexual size differences had already occurred at age 1, growth rates of immature males being significantly higher than those of females (Natsumeda et al. 1997). It seems that both the amphidromous C. pollux ME and fluvial C. pollux LE have similar growth patterns showing sexual size dimorphism. Feeding and growth patterns of C. pollux ME were different among the different con- ditions of water temperatures, in this study. This rearing examination indicates that water temperatures ranging from 18 to 19℃ for males and those from 18 to 20℃ for females were optimal in DFR, those ranging from 15 to 17℃ for males and those ranging from in 14 to 17℃ for females were optimal in DGR, those ranging from 12 to 15℃ for males and those ranging from 11 to 16℃ for females were optimal in FE, respectively (Figs. 1, 2, 3, Tables 1, 2). These results indicate that the Fig. 3. Feeding efficiency (FE) of male (A) and female optimal water temperatures in DGR and FE are (B) Cottus pollux ME at 9 different water temperatures slightly lower than those in DFR. It seems that for 30 days ( , male in 1st period; , male in 2nd the low values of DGR in the lower water tem- period; , male in 3rd period; , female in 1st period; , female in 2nd period; , female in 3rd peratures were affected by low values of DFR. period). Whereas, the low values of DGR in higher water Temperature Effect on Feeding of Cottus pollux ME 413 temperatures are affected by the low values of DFR and FE. The values from the polynomial References equation of DGR in 26℃ and value from the polynomial equation of FE in 26℃ had lower or Ehime Prefecture (2003) Cottus sp. In “Red Lists 2003 in negative values (Figs. 2, 3). It is supposed that Ehime Prefecture”, http://www.pref.ehime.jp/030ken- minkankyou/080shizenhogo/00004541040311/ these lower or negative values of DGR and FE detail/04_03_001100_1.html, accessed 14 Aug 2014 in high water temperatures are caused by high (in Japanese). utilization of energy except for growth, as well Fukuoka Prefecture (2001) Cottus pollux. In “Red Data as the low values of DFR. These results indicate Book in Fukuoka Prefecture in 2001”, Fukuoka, p. 290 (in Japanese). that the optimal water temperature ranges from Goto, A. (2002) Cottus pollux. In “Freshwater Fishes of 14 to 20℃, and a water temperature of 10℃ is Japan” (ed. by H. Kawanabe, N. Mizuno and K. too low, and 26℃ is too high for C. pollux ME to Hosoya), Yama-Kei Publishers, Tokyo, pp. 666-667 (in feed and grow. Japanese). Goto, A. and T. Arai (2003) Migratory histories of three Adults of C. pollux ME were mainly observed types of Cottus pollux (small-egg, middle-egg, and in the waters upstream 5.4 km from the river large-egg types) as revealed by otolith microchemis- mouth of Hikawa River (Takeshita et al. unpubl. try. Ichthyol. Res., 50, 67-72. data). The Hikawaoozeki Weir with a pool type Kumamoto Prefecture (2009) Cottus reinii. In “Red Data Book in Kumamoto Prefecture in 2009”, http://www. fish ladder was built 7.4 km upstream from pref.kumamoto.jp/uploaded/attachment/26059.pdf, the river mouth of Hikawa River. We could not accessed 24 Dec 2013 (in Japanese). observe C. pollux ME in the waters upstream Kurawaka, K. (1976) Study of speciation in fish. Doctor from this weir (Takeshita et al. unpubl. data). Dissertation, Kyoto University, 55 pp., 31pls. Miyadi, D., H. Kawanabe and N. Mizuno (1976) Cottus Therefore, it seems that the distribution range hilgendorfi. In “Colored Illustrations of the Freshwater of this fish in this river has been disrupted by Fishes of Japan”, Hoikusha, Osaka, pp. 306-309 (in the presence of the weir, which restricts any Japanese). upstream migration to the upper reaches. A Mizuno, N. and K. Gose (1972) Studies on growth of fishes. In “Ecology of Rivers”. Tsukiji Shokann, Tokyo, similar distribution of this fish was reported pp. 146-165 (in Japanese). in the Kamogawa River in Shikoku Island Mizuno, N. and H. Niwa (1961) Two ecological types of (Shimizu et al. 1994). the freshwater scorpion, Cottus pollux Günther. Zool. - In waters where C. pollux ME inhabit Mag., 70, 267 275 (in Japanese with English abstract). Nagasaki Prefecture (2011) Cottus sp. 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飼育水温がカジカ中卵型の摂餌と成長に及ぼす影響

竹下直彦・池田至・青木邦匡・西村幸也・長谷川匠阪田和弘・永田新悟・近藤卓哉・嶋田誠

熊本県氷川で採集したカジカ中卵型の卵塊を孵化させ飼育した個体を用い，水温が摂餌と成長に及ぼす影響について，水温を10 ～ 26℃の 9 段階に調整して調べた。雌雄別に 5 個体ずつ水槽に収容し， 30日間の給餌実験を 3 回ずつ行った。日間給餌率は18 ～ 20℃，日間増重率は14 ～ 17℃，餌料効率は 11 ～ 16℃で高く，それらが至適水温と考えられた。日間増重率と餌料効率の至適水温は，日間給餌率の至適水温より低い傾向があった。また，26℃における日間増重率と餌料効率の回帰式からの推定値は，ともに低い値を示した。以上の結果から，本種の摂餌と成長には水温14 ～ 20℃が適しており， 10℃は低過ぎ，26℃は高過ぎると考えられた。