Short Paper. Development of Food Selectivity of Striped. Mullet Mugil cephalus during the. Larval Stage*1. Yoshioki Oozeki, *2 Atsushi Hagiwara. *3. Hiroki Eda ...
Nippon Suisan Gakkaishi
58(7), 1381 (1992)
Short Paper Development of Food Selectivity of Striped Mullet Mugil cephalus during the Larval Stage* 1 Yoshioki Oozeki, * Atsushi Hagiwara. * Hiroki Eda, 03 and C. S. Lee* 4 (Received November, 20, 1991) 2
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Designing a feeding schedule for fish larvae accord0.25 ing to their food preference will improve their survival and growth in the hatchery. The feeding schedule is currently determined speculatively by the development 0 of the mout parto and actually as a results of mass re3 5 10 15 aring trials at seed production stations. 2> A model Days after hatching feeding schedule should take into consideration the Fig. 1. Changes in the Chesson's index for various food preference of the recipient fish. This study defood organisms (4/m/) with the development of scribes the changing food preference of striped mullet striped mullet larvae. The broken line indicates Mugill cephalus larvae three (first feeding) to 17 days the theoretical threshold between negative and after hatching. positive preference for food. Fertilized eggs were obtained from hormonally induced spawns of mullet broodstocks at The Oceanic organism did not change markedly at samplings during Institute, following the method described by Lee et the six-hour experimental period. Food selectivity changed as a result of the development of the fish larvae al. 3> Subsequent to the hatching of fertilized eggs, the mullet larvae were reared in a 5000-liter indoor (Fig. 1). No significant differences in food preference tank at a temperature of 24.0-26.0°C and were fed on were observed between the high and low food-density S-type4 • 11> rotifer Brachionus plicati/is. 6> On days 3, 6, conditions. Chesson's index for S-type rotifers was 9, 13 and 17 post hatching, 600 to 1200 larvae were transferred, according to larval size, into 30-liter below 0.25 in all trials. L-type rotifers were obviously the preferred food organsim from Day 3 (3.3 mm in polycarbonate tanks for the study. Each tank contotal ength), and Chesson 's index for L-type rotifers tained 25-liter filtered seawater at 26°C. Each of the five trials was conducted in six tanks, containing two was above 0.25 up to age Day 13 (TL 5.2 mm). Chesdifferent food densities: 2/m/ (as the low food-density son's index for Artemia spp. nauplii increased steadily group) and 4/m/ (as the high food-density group). No from the beginning of feeding and was above 0.25 larvae were present in one of the three tanks in each when the fish larvae were 13 days old. Artemia spp. group which was stocked with only food organisms nauplii were highly preferred by 17-day old larvae (TL and served as the control. Four types of food or6.3 mm). An increased preference for rotifer eggs ganisms, i.e., S-type and L-type rotifers, Artemia spp. day 13 was also observed. This might relate to a nauplii and rotifer amictic eggs (S- and L-types) were after behavioral change from the larval stage {pelagic feeder) tested in this study. The density of each food orto the juvenile stage (demersal feeder). ganism was examined at one-hour intervals throughIn conclusion. this study suggests that L-type rot ifers out the six-hour duration of each trial. Sixteen larvae should be the main food for mullet larvae from three were randomly sampled from one of the tanks in each days of age, equal to the start of feeding, up to 5.0 mm group 1, 2, 4 and 6 hours after the food organisms in total length. Artemia spp. nauplii should be added were added into the tanks. These specimens were to the diet as fish reach 4.3 mm in TL (9 days old) and dissected and analyzed under a microscope for gutbecome the main food after 5.0 mm in TL. Considercontent. Chesson's index7> was adopted to address ing the selectivity of rotifer eggs as food, formulated the food selectivity of the mullet larvae, because the food could be added after the fish are 6.3 mm in TL. value of the selectivity index is not affected by the relative density of each food organism. 8> Chesson's index (a,) was calculated according to the following References formula: 1) A. Shirota: Nippon Sulsan Gakkalshl, 36, 3!58-368 (1970). a,=(r,/P,)/I:,(r,/P,) (i=l, 2, ... , n) 2) Y. Tsukashima, N. Yoshida/,C. Kitajima, S. Matsumura, and C. L. Besch Ill: Sulsan Zos oku, 30, 202-210 (1983). where r, and P, are the proportions of food type; in 3) c. s. Lee. C. s. Tamaru. G. T. Miyamoto, and C. D. Kelly: the digestive tract of fish larvae'" and in the tank. This Aquaculture, 62, 327-336 (1987). · d · d' .. 4) Y. Fu, K. Hirayama, and Y. Natsukari: J. Exp. Mar. Biol. m ex m 1cates a pos1t1ve pre1erence, if greater than Ecol., 151, 29-41, (1991). 0.25 and, conversely, a negative preference if less than S) Y. Fu. K. Hirayama, and Y. Natsukari: J. Exp. Mar. Biol. O 25 Ecol., 151, 43-56, (1991). • ' 6) H. Eda, R. Murashige, Y. Oozeki, A. Hagiwara, B. Eastham. The relative densities of food organisms did not P. Bass, C. S. Tamaru, and C. S. Lee: Aquaculture, 91, 281significantly change in the six tanks during the five7) j~H~~g~: Ecology, 64, ll97-1304 (198 3). trial experiments. Chesson's index for each food 8) M. J. Lechowicz: Oecologla (Berl). 52, 22-30 (1982). • 1 This is a contribution No. 485 from the Tohoku National Fisheries Research Institute. *2 Tohoku National Fisheries Research Institute, Shinhama-cho, Shiogama-city, Miyagi 985, Japan
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