The Effect Of Feeding And Starvation On Fast-Start Performance And Shelter Occupation Competition In Silurus Meridionalis

The objective of this study was to investigate the effect of feeding and starvation onfast-start and shelter occupation competition in ambush-foraging fish, and explore theadaptive mechanism of feeding and starvation in these fish. The sit-and-wait foraging fish,Silurus meridionalis, which is endemic to China, was selected as experimental animal(N=240,10.32±0.05cm). Two experiments including fast-start test and shelter occupationcompetition were conducted at25.0±0.5oC. In the fast-start experiment,50fish wererandomly assigned into three treatment groups: starvation group (N=24, n=8;10,20,30d),feeding group (N=16, n=8; meal size12.5%,25%) and control group (N=10). The entirefast-start course initiated by electric stimulation was captured by high speed camera. Therelative parameters (V_max,A_max,S_120ms,RT,EK_max) were calculated and analyzed by TpsDigsoftware. In the shelter occupation experiment, fish were also distributed into threetreatment groups: starvation group (N=80;15d), feeding group (N=55; meal size25%) andcontrol group (N=55). The successful shelter occupation of fish from these treatmentgroups was observed and documented; the occupancy of these treatment groups wascalculated as well.The results are as follows:1. The RT, V_max, A_max, S_120msat25.0±0.5oC were21ms,1.41m s^-1,91.23m s^-2,100.4mm,respectively. The V_maxwas13.75times the length of the body.2. By comparing feeding group (meal size25%) with control group, V_maxand S_120mssignificantly decreased approximately36.2%and41.7%, separately (P<0.05); Bycomparing starvation group (25d) with control group, V_maxand S_120mssignificantlydecreased19.4%and28.3%, respectively (P<0.05).3. The major fast-start pattern that applied by fish from feeding group and control groupwas double-C bend; meanwhile, fish in starvation group mainly chose single C-bandpattern. 4. Despite a moderate increase of A_maxand EK_maxwas found by comparing feeding group(meal size12.5%) with control group, there was no significant difference in A_maxand EK_maxbetween these two groups. Nevertheless, the values of A_maxand EK_maxin these two groupswere decidedly higher than the feeding group's (meal size25%)(P<0.05).5. The shelter occupancy of feeding groups was significantly lower than that of starvationgroups and control group (P<0.05). There was no significant difference in shelteroccupancy between starvation group and control group (P>0.05).In conclusion:1. Feeding and starvation both negatively affected the fast-start ability in juvenile Silurusmeridionalis, resulted in different extent of decrease. Feeding is considered to be morepowerful than starvation. Such phenomenon may be in accordance with its strongendurance against starvation.2. Starvation has apparently altered the fast-start pattern of Silurus meridionalis, suchalteration may be an adaptive mechanism applied by fish with limited energy storageduring starvation period.3. The shelter occupancy of starvation groups is higher than that of feeding group. Thisresult implies that shelter competition may be the presentation of the natural characteristic(ambush-foraging living style) of this species. The social hierarchy status may be irrelevantto this phenomenon.