Study On Compensatory Growth In Crimson Snapper Lutjanus Erythopterus

Compensatory growth of Crimson Snapper (Lutjanus erythopterus), following 4 weeks of starvation, were studied at Nanao Marine Biology Station of Shantou University, from September to December, 2003. In the study, the control group was fed to satiation once a day during the 12-week experimental period, while the experimental group was starved for 4 weeks and then fed to satiation for 8 weeks. The blood, liver, and white muscle were sampled from six fish each time at weeks 0,1,2,4 in the period of starvation, and at weeks 1,2,4,8 in the period of re-feeding respectively.The body length, total length and coefficient of fat and fullness of Crimson Snapper in the experimental group decreased but there was no significant difference compared with control group. These results showed that body length, total length and coefficient of fat and fullness were not good indices for nutritious status of fishes. On the contrary, hepatosomatic index of the fish decreased significantly after 1-week starvation, which recovered to the level of the control only in 2-week re-feeding. The result showed that hepatosomatic index was relative sensitive compared with other body parameters of fishes. The body weight of the fish decreased during the period of starvation. And between 2-week and 4-week re-feeding, the body weight increment of the starved was significantly larger than the control. This result suggested that the fish showed compensatory growth during period of re-feeding. The SGR of Crimson Snapper was negative during starvation, indicating negative growth in the fish. After re-feeding, the SGR of starved group was higher than control, which indicated that the growth speed of starved was faster.Some of the blood biochemical indices in Crimson Snapper were sensitive to starvation and re-feeding. The content of plasma glucose decreased significantly after 1-week starvation. And the content of plasma lipid also decreased significantly after 2-week starvation. After 8-week re-feeding, the content of these two indices increasedto the control level. In contrast, the content of plasma protein kept stable throughout the experiment. These results indicated that during starvation, Crimson Snapper used plasma glucose at first, then plasma lipid and seldom or didn't use plasma protein. The results also suggested that plasma glucose and plasma lipid were good indices for nutritious status of fishes.After 1-week starvation, the glycogen content in liver decreased rapidly. So did the protein and lipid contents in white muscle after 2 and 4-week starvation respectively. The glycogen content in white muscle declined slightly and had no significant difference from control. In addition, the protein and lipid contents in liver increased to some extent and these phenomenon may be explained in this way: these two kinds of material were seldom or not utilized by Crimson Snapper during starvation while the other energy materials were mostly used. So the relative content of these two kinds of material increased. The result suggested that during starvation, Crimson Snapper took good advantage of glycogen in liver first, lipid in white muscle subsequently and then protein in white muscle as energy material.It could be seen from the change of body weight and SGR that Crimson Snapper showed completely compensatory growth after 8-week re-feeding, following 4-week starvation. After 1-week or 2-week refeeding, the feeding ratio and food conversion ratio of starved fish were significantly higher than the control. And these results suggested that the mechanism of compensatory growth in Crimson Snapper was due to the increase of both feeding ratio and food conversion ratio.