Color Preference And Gender Differences In Physiological Responses Of Yellow Perch Perca Flavescens Under Different Light-Emitting Diode (LED) Spectra

As an important environmental factor,light plays an important role in regulating behavior,growth,sexual maturity,and stress responses of fish.Photoreceptors in the retina of fish can distinguish the specific wavelength spectrum or light color,and fish can show the relevant response in behavior and physiology.Therefore,the scientific issue we concerned is how to use different light colors to regulate the growth performance,feeding behavior and gonadal development and to alleviate the stress response induced by intensive stocking in cultured fish.In this study,we explored color preferences of yellow perch?Perca flavescens?to different light environment including dark,white light?fluorescent bulb?as well as three LED monochromatic lights?629 nm red light,527 nm green light,and 400 nm violet light?based on the specific absorption peak of spectra in its retina by behavioral experiment.Furthermore,we determined the effects of the four light colors on the growth preference,gonadal development and stress state,especially focusing on the gender differences of those responds.The main results are as follow:?1?The light color preference of yellow perch to dark,white,violet,green,and red light was performed by phototaxis rate,and circadian rhythm and the influence of water flow were considered.The results showed that yellow perch showed a preference to dark and red light environment at daytime?P<0.05?,and to dark,white and red light environment at nightime?P<0.05?.In addition,the water flow had a positive effect on the phototaxis of perch under dark or red light environment at nightime?P<0.05?.?2?There was a significant gender difference on the effects of different LED spectra on the growth performance of yellow perch.There were no significant differences in survival rate?SR?,weight gain rate?BWG?,body weight specific growth rate?SGRW?,body length specific growth rate?SGR_L?and condition factor?CF?among different groups of yellow perch?P>0.05?without sex distinction.However,the male perch BWG under red LED was significantly higher than the white light?P<0.05?,and significantly higher than the same group of the females?P<0.05?.The males SGR_W significantly higher under red and violet LED compared with white light?P<0.05?,and male perch SGR_W and SGR_L were significantly higher than the females under red LED?P<0.05?.There was no siginificant difference in the growth performance of female yellow perch under different light groups?P>0.05?,but the CF was significantly higher than the males under green and red LED and white light?P<0.05?.These results suggest that the growth performance of male perch is more sensitive to light color than the females.?3?Different LED spectra had no significant effect on the gonadal development of yellow perch.Although the female perch gonadosomatic index?GSI?was higher under white light than other groups,there was no siginificnt difference among different light groups?P>0.05?;and there was no significant difference in the male GSI under each spectrum?P>0.05?.There was no significant difference in the oocyte proportion of female perch at different stages under different light colors?P>0.05?.?4?Gender difference was found in the stress state of yellow perch under different LED spectra.There were no significant differences in hydrogen peroxide?H₂O₂?content and total antioxidant capacity?T-AOC?in serum,and in malondialdehyde?MDA?content and superoxide dismutase?SOD?activity in liver of perch among different light color groups?P>0.05?.Only catalase?CAT?activity in liver was significantly higher under green LED compared with white group?P<0.05?.The cortisol content in serum of male perch was significantly increased under red light compared with other groups?P<0.05?,glucose level in serum was significantly increased compared with green LED and white groups?P<0.05?,and the hepatic SOD activity was significantly increased than white group?P<0.05?,but the hepatic SOD activity of the females was higher than that of the males under most light colors?P<0.05?.In summary,yellow perch prefers dark and red LED environment,and the water flow also has a positive influence on this preference.There are gender differences in growth performance and physiological stress under differdent LED spectra,and it seems that male perch are more sensitive to light color than the females.The results of this study can provide a theoretical and practical guidance for the selection of light source for yellow perch factory aquaculture and improving cultured fish welfare.