Locomotory Activity Patterns of Cottus poecilopus Heckel and C. gobio L. (Pisces)

Abstract

The locomotory activity of the closely related freshwater sculpins Cottus poecilopus Heckel and C. gobio L. was investigated in South Sweden (55? 35'N, 130 30'E). Three physical factors were considered: light intensity, day-length and temperature. 1. The activity of both species was lower in winter than in summer. Short-time variations in activity followed variations in temperature at low temperature. The annual cycle of level of activity seemed to be correlated to temperature as far as influenced by exogenous factors. 2. In natural light conditions the diel activity of both species was synchronized to light throughout the year with a maximum peak after sunset. On overcast days in winter C. poecilopus began its activity earlier than C. gobio, being also active in the afternoon. 3. Spawning caused a temporary desynchronization for some days. 4. In artificial light low intensity released a phase shift in C. poecilopus which became lightactive, while C. gobio remained dark-active. Seasonal phase shifts are known for C. poecilopus in North Sweden (at the Arctic Circle), where the species is light-active in winter but darkactive in summer. 5. Feeding of the fishes did not affect the diel activity pattern. 6. The different response to low light intensity may diminish competition between the two species, as they utilize different periods of the day for activity. Pe3IoMe PerrcTpaLisI aKTHBHOCTH HnepeABH)KeHHS HCcnIeAOBanacb y 6RH3Ko CTOSHLAX BHAOB npecHOBOAHbIX IaOgKamHMMHKOBMX Cottuspoecilopus HecKel y C. gobio B IO)KHOl fIBeMHH (550 35'N, 130 30'E) Y'ITbIBaJIOCb TPH 4H3H'IeCKHx 4?aKTopa: CHna cBeTa, npOAOJIXHTejJIbHOCTb HSA H TeMnepaTypa. 1. AKTHBHOCTIb y o6oIx BHAOB 6ibIa MeHbme 3HMOI 'eM JIeTOM. KpaTlKOBpeMeHHmIe H3MeHeHeHHS aKTHBHOCTH cneXoBaJU xojie6aHHsM TeMnePaTYPbI HPH HH3KOr TeMiaepaType. rooBOA iHKji aKTHBHOCTH TOxKe 3aBHCHT OT TemilepaTypbL, KorAa oHa KOHTPOJIHPYeTC.I 3K3oreHH6IMMH aKTopaMH. 2. fipH IIpHPOAHbIX CBeTOB]I.X YCJIOBHIIX o6a BIAa HMeIOT llO'ITH TOT-)Ke KpyrJIOCyTO'IHbIA o6pa3 )KH3HH. OHH 6miJm CHHXPOHH3OBaHM C CHJIOft cBeTa Ha HPOTADKeHHH ieJIoro roxRa c MaKCHMajibHOA aKTHBHOCTB6O nociie 3axoxa COJIHija. 3amoft, B naCMypHbIe AHH HaIHaJI C. poecilopus paHime CBOIO aKTHBHOCTb, 'leM C. gobic H 6ibJI aKTIIBHbIM TaKwe B nocneo6exeHHoe BpeMI. 3. HepeCT BbI3bIBaJi BpeMeHHyio xeCHHXpOHH3a]EkHIO B Te'IeHHe HeCKOJIBKO CYTOK. 4. IlpH HCKYCCTBeHHOM CBeTe BbI33IBJIia cJia6aA CHJIa CBeTa cMeuieHHe 4am y C. poecilopus KOTOpbIlA CTaHOBHJICA CBeToaKTHBHbIM Tor~a, Korxa C. gobio OCTaBanIcA TeMHOaKTHBHbIM. CMeL1eHRS 4)a3 CBA3aHHbI C BpeMeHaMH roa BCTpe'IaIOTCS y C. poecilopus B CeBepHOA EE[BeLXHH (B6JuI3H flOnsIpHoro Kpyra), rxe BHA ABjiSeTCS CBeToaKTHBH]6M 3HMOk H TeMHoaKTHBHM6M jieTOM. 5. KopmiIeHie pmI6 He OKa3bIBaJIO HHKaKOrO BJIHAHHS Ha CyTO'IHyio aKTHBHOCTB. 6. Pa3Has peasKLHA Ha cJIa6bItk CBeT no-BHAIHMOMY yMeHbUiaeT KOHKypeHLIHIO MexAy BHXIaMH, TaK KaK OHH HCIIOJlb3yIOT pa3Hoe BpeMs CYTOK AR CBOeft aKTHBHOCTH. Manuscript accepted January 1969.