JF M S E, 30(1), pp. 354~364, 2018. 수산해양교육연구, 제30권제1호, 통권91호, 2018. www.ksfme.or.kr https://doi.org/10.13000/jfmse.2018.02.30.1.354 사육수의수온과염분및부유물질농도변화에의한넙치 (Paralichthys olivaceus) 에관한생리활성변화연구 진병선 ( 안양대학교 ) Stress Response of Flounder, Paralichthys olivaceus to Changes in Salinity, Temperature and Suspended Solid Byung-Sun CHIN (Anyang University) Abstract One year old flounder were exposed to different conditions in temperature, salinity and suspended solid (SS). Three experiments were conducted separately on each condition and concentration (level) was continuously changed. In temperature experiment (Exp1), temperature was set to 15 and decreased 2 in every two days to 13, 11 and 9. In salinity experiment (Exp2), salinity was set to 30 psu and decreased to 15 psu, 7.5 psu, and 3.75 psu in every two days. In SS experiment (Exp3), SS concentrations was set to 30 mg/l, and increased to 60 mg/l, 120 mg/l, and 240 mg/l in every two days. Blood was extracted to measure hematocrit (Ht) and cortisol level in every 2 days. In all three experiments, Ht concentrations tend to increase when the condition gradient changed. In Exp1, cortisol concentration of plasma was decreased when water temperature decreased. In Exp2, cortisol concentration was increased as salinity decreased. In Exp3, cortisol concentrations tend to increase as the SS concentration increased. Among concentration of Ht and cortisol there were positive corelation. Results indicate that SS is the most stressful condition to flounder among levels set in these experiment. Key words : Physiological response, Cortisol, Salinity, Cooling water, Suspended solid Ⅰ. 서론 일반적으로생물은스트레스강도에비례하여 혈액내의생리대사활성이변화한다 (Davis et al., 1990; Parihar et al., 1996). 어류는스트레스에의 해서혈액중코티졸농도가증가하기에코티졸 은스트레스에의한결과를알아보는데좋은지 표가된다 (Kang et al., 2007). 코티졸농도의상승 Corresponding author : 032-930-6029, hkhachin@anyang.ac.kr. 이후에발생하는혈당치의상승은스트레스에대 항하기위하여어체에서에너지이용하는현상으 로알려져있고, 어류의전해질, 삼투압조절에서 도중요한역할을하며, 어류의해수적응에관여 하고아가미에작용하여해수형염류세포의분화 를촉진함과동시에 Na +, K + -ATPase 이온배출을 촉진하고장에서이온및물의흡수를증가시킨 다 (Kang el al., 2007). 어류의혈액내적혈구는 - 354 -
몸전체로산소운반능력을평가하는척도로사용되며, 스트레스로인하여혈액산성화현상에의한적혈구의산소운반능력이저하된다고보고되었다 (Perry and Reid, 1993). 어류에게스트레스로작용하는환경변화요인으로는수온, 염분, 용존산소, 부유물질, 양식밀도, 먹이제한등이있다 (Bolasina et al., 2006; Chang et al., 2001; Hur et al., 2002; Min et al., 2013; Myeong et al., 2011; Yoon & Park, 2011). 수온변화는어류의성비, 번식, 영양대사, 성장등과같은생리적인요인에영향을주며, 급격한수온변화는어류의생리조건을변화시키거나체내항상성을붕괴할수있다 (Barton & Iwama, 1991; Pickering, 1992). 부유물질은어류의아가미조직을변형시키고산소공급을방해하여사망하게하거나먹이에대한섭식행동이나무리를짓는행동, 회유및이동패턴등에영향을준다 (Baba et al., 2006; Berry et al., 2003; Kjelland et al., 2015; Ohata et al., 2011; 2013; Shin et al., 2006; 2008). 해양생물의경우, 이동범위가넓은종은외부로부터의급작스런외부의스트레스에의한반응으로서식처를회피하는행동을보이지만이동범위가좁은저서생물이나양식생물의경우회피반응보다는일정시간서식처에머물거나갇힌환경에서직접적인스트레스를받게되어생태-생리적으로영향을받을수있다고판단된다. 넙치 (Paralichthys olivaceus) 는한국, 일본, 중국에분포하고우리나라전연안역에서식하는정착성어종으로스트레스에대한내성이강한종으로알려져있는유용수산종이다. 또한광염성어류이고양식대상종으로어병치료, 양식기술, 이화학적체성분, 배합사료관련성장등의연구가활발하고광범위하게연구되고있다 (Hur et al., 2006; Jung & Seo, 2016; Kim et al., 2010; Kim et al., 2014; Kim et al., 2016; Yoon et al., 2016a). 연안해역의대규모산업시설인조력발전소, 제 철공장, LNG 저장기지로부터냉 온배수의연안해역방류, 저수온배출수방출, 주기적인갑문개폐에의해서방류또는홍수시방류를위한조력발전소가동정지등으로해양환경변동주기의급격한변화에의한스트레스가해양생물에미치는영향을검토할필요가있다 (Chang et al., 1999; Yoon et al., 2016b). 또한여름철의냉수대출현, 저염분지하수의이용등에의한스트레스가해양생물에미치는영향도고려할필요가있다 (Hur et al., 2002). 본연구에서는넙치를이용하여수온과염분및부유물질의농도 ( 정도 ) 를단기간에급격하게변화하는실험을수행하여생리적반응에관한기초적자료를확보하고자한다. Ⅱ. 재료및방법 1. 실험생물 본연구에서는태안지역의육상수조에서양식하는넙치를구입하여실험실로운반한후 14일간실험실환경에적응시킨후실험을수행하였다. 실험에사용한넙치는체장이 29.6±1.1 cm( 체중 250.1±40.2 g) 으로미성숙된한살개체들이었다. 넙치는 500 L 원형수조에서 15.0±1.0 수온, 30.0±1.0 psu 염분, ph 8.0±0.5, 용존산소는포화율 (%) 기준으로 90% 이상을유지하였고, 실험실내조도는실험실환경에따라 12시간 Light : 12 시간 Darkness 조건을유지하였으며, 넙치상업용먹이를 1일 2회공급하였다. 먹이잔여물은순환여과방식에의하여제거하였고유지에필요한사육용수의회수및교환은 1 2주간격으로실시하였으며, Ammonia Alert(Seachem) 를이용하여암모니아농도를측정한후고농도일경우 (>0.2ppm) 수시로교환하였다. 수온, 염분, 부유물질의농도에관련된실험을수행하였고실험기간중먹이급이에따른생물의대사활동변화를최소화시키기위해실험 48시간전부터절식시켰으 - 355 -
며, 실험중에는먹이를공급하지않았다. 모든실험에서수온, 염분, 수소이온농도 (ph), 용존산소는매일측정하였다. 2. 수온하강실험 (Exp.1) 수온변화에따른넙치의대사활동변화실험은 400 L 원형수조에서 9 15 수온범위로실시하였다. 수온변화실험은 15 에서시작하여 2일째에 2 씩단계적 (15, 13, 11, 9 ) 으로수온을하강시키면서넙치의대사활동을관찰하였다. 실험생물은 400 L 수조에서 29.6~30.6 psu 염분범위, ph 7.1~7.6, 용존산소 8.5~10.3 mg/l 범위에서실시하였으며, 실험실내조도는실험실환경에따라 12시간 Light : 12시간 Darkness 조건을유지하였다. 3. 염분하강실험 (Exp.2) 염분변화에따른넙치의대사활동변화실험은 400 L 원형수조에서 3.8 30.0 psu 염분범위로실시하였다. 염분실험은넙치를염분 30.0 psu(15 ) 를대조구로설정하여시작하여 2일째에기존염분농도의절반으로희석하여염분농도 (30.00, 15.00, 7.50, 3.75 psu) 를단계적으로하강시키면서실험생물의대사활동을관찰하였다. 염분은천일염을구입하여염분을조절하였고넙치는 500 L 원형수조에서 ph 7.5 8.0, 용존산소 8.03 9.57 mg/l 범위에서실시하였다. 4. 부유물질농도증강실험 (Exp.3) 부유물질은강화갯벌의퇴적물을이용하여부유물질농도변화에따른넙치대사활동변화실험은 30 240 mg/l 부유물질농도범위에서실시하였다. 부유물질실험은넙치를여과해수 (15 ) 에서 2주이상적응시킨후, 최초농도 30 mg/l에노출시키고 2일째에 2배의부유물질농도를단계적으로증가시키면서부유물질농도를 4구간 (30, 60, 120, 240 mg/l) 으로대사활동을관찰하였다. 실험에설정된부유물질농도는인천강화갯벌에서채취한퇴적물을 60 μm의체로여과하고건중량을측정하여실험수조에투입하였다. 부유물질농도는해수공정시험기준 (Ministry of Oceans and Fisheries, 2013) 에의하여부유물질농도를측정하였다. 실험생물인넙치는 2단수조로된순환수조에서실험하였다. 상단 200 L 수조에는부유물질을혼합하였고넙치는하단 400 L 수조에는수용하여실험하였다. 부유물질실험은 400 L 수조에서수온 15.0 15.6, 염분 29.9 30.7 psu, 수소이온농도 (ph) 7.6 8.9, 용존산소 7.4 8.4 mg/l 범위에서실시하였다. 5. 시료채취모든실험을위한모든생물은실험전최소 14일동안최초환경조건에적응시켰으며, 이후실험체계에맞추어농도변화직전에각각의농도에서넙치의생리활성분석을위한시료를채취하였다. 시료채취및분석은모든실험에서동일한항목으로수행하였고실험에사용된모든넙치개체는어체의크기 (mm) 및중량 (WWt) 을측정하여기록하였다. 시료채취시분석에사용한넙치의개체수는각각의실험에서 3~4개체를취하여분석시료로사용하였고넙치의혈액은페녹시에탄올 (phenoxy ethanol) 을해수와 1%(V/V) 이내로혼합한용액에넙치를마취시킨후, 미부의동맥에서헤파린을처리한주사기를사용하여 1분이내에개체별로채취하였다. 채취한혈액은즉시헤파린처리가된튜브에분주한후, 적혈구용적을측정하기위하여 4,000 rpm으로 30분간원심분리한후적혈구와혈장부분의길이에대한적혈구부분의비율을산출하였고추출한혈장은 -70 에서동결보관한후코티졸농도분석에사용하였다. 코티졸농도분석은 cortisol EIA kit(adi-901-071, Enzo Life Science, 미국 ) 를사용하여항원 항체반응을유도한다음 405 nm 파장 - 356 -
에서흡광도를측정하였으며, 제조사에서제공하는매뉴얼에따라코티졸농도로환산하였다. 6. 자료분석본연구에서는수행한넙치의수온별과염분별및부유물질농도별생리활성물질농도 ( 코티졸 ) 와적혈구용적률을이용하여일원분산분석 (one factor ANOVA) 을실시하여, 각각의실험수온별대상생물의생리반응에대한유의성을 α =0.05 유의수준에서검증하였다. 분산분석은자료의정규분포 (normal distribution) 와등분산성 (equal variance) 을가정하므로각각의조건이만족하는지여부를 Shaprio-Wilk W test(p>0.05) 로검증하였고코티졸은대수변환을하여분석을실시하였다. 코티졸의농도와적혈구용적률은상관관계분석을수행하였다. 전체 3개의실험에서분석된코티졸의농도와적혈구용적률을이용하여집괴분석을수행하였다. Primer v.6를이용하여자료는제곱근변환 (square-root transformation) 을실시하였고이후각실험구에서자료를바탕으로 Bray-Curtis similarity를계산하였으며, 이로부터산출된유사도행렬로부터각실험구를연결하는방법으로는 group average method를이용하였다. Ⅲ. 결과 실험수행기간중사망한개체는없었고, 각실험구당실험기간중의체중이나체장에서의변동은없었다. 넙치수온실험 (Exp.1) 에서 48시간간격으로수온을하강하여실험한결과수온하강에따른적혈구용적 (%) 은 15 와 13 수온구간에서각각 32.5±3.4%, 32.1±2.8% 로유사한수준으로나타났고, 수온 11, 9 에서는 43.9±2.0% 39.1±2.9% 로다소증가하였다 (<Table 1>). 수온하강에따른넙치의혈중코티졸농도변화를관찰한결과, 11 수온에서가장낮은농도 341.3 pg/ml를나타냈고통계적으로유의하였다 (P<0.01)([Fig. 1]). 다른수온구간 (13, 9 ) 에서는 15 실험구와통계적으로유의하지않았다 (P>0.05). 염분농도를 48시간간격마다절반의염분농도로하강하는실험 (Exp.2) 을수행한결과넙치의적혈구용적 (%) 은염분농도 30.00 psu에서 28.2±5.3% 이었고염분농도 15.00 psu로감소함에따라서 47.1±5.1% 로증가하는경향을보이다가낮은염분농도로이동할수록 7.50 psu와 3.75 psu 에서는각각 36.2±0.7% 와 34.5±5.8% 로감소하는경향을나타냈다 (<Table 1>). <Table 1> Hematocrit of flounder in three experiments Elapsed time (hr) Exp.1 Water temperature ( ) Level Hematocrit (%) Level Exp.2 Salinity (psu) Hematocrit (%) Exp.3 Suspend solid (mg/l) Level Hematocrit (%) 0 15 32.5±3.4 a 30.00 psu 28.2±5.3 30 mg/l 41.3±4.1 48 13 32.1±2.8 a 15.00 psu 47.1±5.1* 60 mg/l 40.2±2.9 96 11 43.9±2.0 b 7.50 psu 36.2±0.7 120 mg/l 52.9±1.0* 144 9 39.1±2.8 b 3.75 psu 34.5±5.8 240 mg/l 39.8±5.1 Mean within each column followed by same alphabetic letter are not significantly different(p>0.05) Asterisk is significantly different(p<0.05) - 357 -
[Fig. 1] Variation of cortisol levels in flounder by different temperature(exp.1). Asterisk is significantly different(p>0.05) 염분하강에따른넙치의코티졸농도는 30.00 psu 에서가장낮았고 (520 pg/ml) 염분이낮아짐 에따라서 30.00 psu 보다는증가하였고 15.00 psu 3.75 psu 는통계적으로유의하지않았다 (P>0.05)([Fig. 2]). 와 60 mg/l 에서는낮은값 (833.4~988.0 pg/ml) 을 나타냈고 120 mg/l 에서는농도 (2,307.3±639.0 pg/ml) 가가장높게증가하였고 240 mg/l 에서는 낮은농도와높은농도의중간농도 (1,597.9±478.0 pg/ml) 를나타냈다 (P<0.05)([Fig. 3]). 모든실험에 서측정된코티졸농도와적혈구용적률과의상 관관계를분석한결과양의상관관계를나타냈다 ([Fig.4]). [Fig. 3] Variation of cortisol levels in flounder by different suspended solid concentration (Exp.3). Same alphabetic letter are not significantly different(p>0.05) [Fig. 2] Variation of cortisol levels in flounder by different salinity(exp.2). Same alphabetic letter are not significantly different(p>0.05) 투명한해수 (0 mg/l) 에서 48시간간격으로농도를증강하면서수행한부유물질농도변화실험 (Exp.3) 에서넙치의적혈구용적 (%) 은부유물질농도 30 mg/l과 60 mg/l 및 240 mg/l에서각각 41.3±4.1%, 40.2±2.9%, 39.8±5.1로상대적으로낮게나타났고 120 mg/l에서는 52.9±1.0% 로높게나타났다 (<Table 1>). 부유물질농도 120 mg/l에서만통계적으로유의하게높았다 (P<0.05). 부유물질농도변화에따른코티졸농도는 30 mg/l [Fig. 4] Corelation between cortisol concentration and hematocrit of flounder in all the experiment. Ⅳ. 고찰 어류는주변환경변화에내성한계이하의환경 에서는체내적응과정을거쳐변화된환경에순 치되기때문에생리생태적영향이없다는보고 - 358 -
가있다 (Kim et al., 2002; Kim et al., 2006; Yoon et al., 2003). 그러나급작스런수질악화로인한임계수준을넘는자극에는생물들이심한스트레스를받게되고일시적으로본래의서식처를떠나회피하는행동을보이지만, 일부종들은생리활성도가떨어져건강도를악화시키고사망에이르기도한다 (Batton & Iwama, 1991; Popper et al., 2004). 개체의크기가 280 mm이상의양식넙치를대상으로수온급하강 (20 에서 10 로하강 ) 의생리적영향을분석한연구결과에의하면혈액내적혈구용적은수온이하강시변화가없고수온이상승시증가하였다가 26시간이후에는감소하여원래대로회복되었다 (Chang et al., 2001). 또한연속적인수온급하강실험에서는수온이하강함에따라서적혈구용적량과총단백질량이감소하는현상을보였다 (Chang et al., 1999; Park et al., 1999). 스트레스에대하여어류는생리적으로 1차, 2차반응을보인다. 1차반응에서코티졸의농도가증가하고스트레스가지속되면 2차반응에서는글루코스, 총단백질량, 젖산등이증가하여이들을스트레스에관련된지표로사용된다 (Chang et al., 2001; Hur et al., 2006). 일반적으로스트레스에의하여코티졸의농도와글루코스의농도는동시에증가한다. 돌돔 (Oplegnathus fasciantus) 의경우에는 15 9 수온구간에서수온이하강함에따라코티졸의농도가증가하고저수온에서생리적인영향을받는다고보고되었다 (Yoon et al., 2016b). 한편감성돔 (Acanthopagrus schlegeli) 은수온및염분변화에따른스트레스반응을관찰한결과, 24시간간격으로수온을 2 0 에서 30 로상승시킨경우코티졸농도는증가하여수온상승에따른어류의스트레스반응을보고하였다 (An et al., 2010). 본연구의 Exp.1에서는수온을하강하고 48시간이후에혈액을채취하여코티졸농도를측정하였고 13 이외에는같은농도를유지하여 48시간내에원래의상태로회복이된다고판단되었다. 그러나적혈구용적 률은 11 와 9 에서증가하였는데이결과는 1 5 에서순치한넙치가수온하강에의한스트레스로부터항상성유지를위하여활성을높였다고판단되었다. 수온이하강하는시기에넙치는 1 0 이하에서는매일먹이를급이하여도체중이감소하는경향을보이고 9 이하에서는먹이를공급하여도섭이하지못한다는보고가있다 (Chang, 2002). 넙치의적정사육염분은 27.7~35.7 psu로알려져있지만, 염분조절을가능하게하는염류세포를가지고있고유어기에천해의연안에서서식하는생태적특성으로일시적인저염분변화에적응할수있다고판단된다 (Hiroi et al., 1997; Minami, 1982). 넙치전장 176 mm의경우, 염분 30 psu에서 0 psu와 15 psu으로염분을하강한결과적혈구용적률은 24시간후에도증가한상태를유지하고코티졸의농도는염분 15 psu에서는한시간이내로적응하여염분 0 psu에서만증가하였다고보고되었다 (Hur et al., 2002). 또한염분 0 psu에서는총단백질농도증가, 글루코스, Na + 및 Cl - 농도감소로고삼투압조절능력에문제가일어나고 48시간부터는사망하는개체가있었고 144시간에는전량폐사하였다. 본연구의 Exp.2에서적혈구용적률은염분이 15.00 psu로하강할때, 증가하였고이후에는감소하는경향을나타냈다. 종묘로육상수조에서사육한넙치는자연에서와는다르게염분의변화를경험하지못한다. 본실험에서나타난결과는넙치가경험해보지못한염분변화에적응하는데시간이많이소요되어서 15.00 psu에서는적혈구용적률이높게나타났고이후에는염분변화에적응하는데시간이적게소요되어서적혈구용적률이낮게나타났다고판단된다. 코티졸의농도도염분 15.00 psu로하강할때증가하고이후에는감소하는경향을나타내어염분에대하여적응이되었다고판단된다. 넙치의자치어는염류세포가생성된이후에는 5 psu까지염분조절이가능하고 Exp.3의염분 3.75 psu에서코티졸의증 - 359 -
가와사망이없는결과로염분 3.75 5.00 psu가넙치에게는임계수준의경계로판단된다 (Daniels & Watanabe, 2010; Kim et al., 2004). Hur et al.(2003) 은넙치전장 176 mm의경우, 염분 15 psu의저염분에 30일동안사육한결과염분 35 psu 보다생존율이나성장률이다소낮았으나코티졸, 글루코오즈, Na +, Cl - 및삼투질농도등은대조구와실험수사이에차이가없었다고보고하였다. 넙치전장 208 mm를이용하여 15 psu에서 0 psu로염분을변화한후 120시간동간관찰한결과글루코스와코티졸의농도가높은값을유지하였고높은농도를계속유지하면생체에악영향을미친다고하였다 (Hur et al., 2006). 감성돔의경우, 염분 35 psu, 10 psu 및 0 psu에서의코티졸농도는염분농도가감소함에따라감성돔의스트레스가증가함을보고하였다 (An et al., 2010). 농어 (Lateolabrax japonicus) 유어의염분변화에따른생리반응을관찰한결과 30 psu에서 2 psu로하강하여 1시간동안노출된농어의코티졸농도는증가하였으며, 24시간후에는더욱증가하여저염분노출에따라코티졸농도가증가하는것으로보고하였다 (Han et al., 2003). 이와같이염분변화에의한스트레스는해양생물의혈액성상내의코티졸분비를증가시키고코티졸농도의회복시간은어종, 스트레스요인및강도에따라다르게나타난다 (Braton & Iwama, 1991). 연안역의어류들에서부유물질에노출이되면적혈구용적률, 헤모글로빈농도, 삼투조절액등이증가한다 (Sherk et al., 1975). 넙치치어 ( 체장 32 mm) 에대한부유물질의 7일반치사농도 (7d-LC50) 는 156.9 mg/l이고넙치치어 ( 전장 81.7 mm) 에대한연안역에많은부유물질인점토광물질스멕타이트 (smectite) 의 96시간반치사농도 (96h-LC50) 는 37,000 mg/l이었다 (Baba et al., 2006; Yoon & Park 2011). 여러종류의점토광물질 ( 중간입자크기 16.1 μm ) 을담수에부유시켜이용한부유물질실험에서넙치치어 ( 전장 81.7 mm) 에대한파이로필라이트 (pyrophyllite) 의 96h-LC50 은 78,000 mg/l이였고세리사이트 (sericite) 는 79,000 mg/l이였으며, 스멕타이트 (smectite) 4,000 mg/l이었다 (Iwata et al., 2011). 스멕타이트 (smectite) 는서로상이한결과를나타냈는데부유물질을실험에첨가하는방법이나점토광물질의종류에따라서영향농도가달라진다고보고하였고, 아가미손상에의한산소여과의실패가원인으로개체들이사망하였다 (Baba et al., 2006; Iwata et al., 2011). 감성돔 (Acanthopagrus schlegelii) 을 10일동안부유물질 1,000 mg/l의농도에서노출시켰을때, 염류세포의변화및 Na + -K + -ATPase의활성저해와아가미손상이발생하였다 (Lee, 2015; Li & Shen, 2012). 무지개송어 (Oncorhynchus mykiss) 는부유물질에노출되면적혈구용적률이증가한다고보고되었다 (Reid et al., 2003). 은연어 (Onchorhynchus kisutch) 는부유물질에노출되면혈중코티졸농도가증가하였다 (Redding et al., 1987). 넙치 ( 체장 398 mm) 에대한부유물질농도 4,500 mg/l와 10,000 mg/l에서는혈중글루코스농도가증가하여고갈이되고그로인한 ATP의부족으로혈중암모니아농도가상승하고혈장이온들이증가하여아가미가파손되고산소여과실패에의한산소결핍으로개체들이사망하였다 (Kawana et al., 2011). 이러한결과로부터어류는부유물질의종류나부유상태그리고어종이나어체의크기에따라스트레스에대한반응이다르게나타난다고판단된다. 본연구의 Exp.3에서설정된농도구간은넙치의몸을바닥기질에파묻는습성과타연구의반치사농도를고려할때낮은농도구간으로판단된다. Exp.3에서적혈구용적률과코티졸의농도는부유물질농도 120 mg/l에서증가였다가부유물질농도 240 mg/l에서코티졸의농도와적혈구용적률이감소하는경향을나타내어낮은농도의부유물질에서는 48시간동안에적응을하였지만, 120 mg/l에서는적응하는데 48시간이상소요되어서높게나타났다고판단되었다. 생물들은환경변화요인에순치될경우, 환경변화가급성변 - 360 -
화가아니면임계수준보다넓은범위에적응이 가능해진다 (Kim et al., 2011; Townsend et al., 2011). 본연구에나타난스트레스에대한넙치의생 리반응인코티졸의농도와적혈구용적률은양의 상관관계를나타냈다. 이결과로부터집괴분석을 수행한결과, 모든실험구가유사도 87.8% 에서 3 개그룹으로나누어졌다 ([Fig. 5]). [Fig. 5] A diagram illustrating the classification of sampling periods by analysis of cortisol concentration and hematocrit. T: Exp.1 (temperature); Sal: Exp.2(salinity); SS: Exp.3 (suspended solid); Number is level of each environment. 그룹 1 은수온실험구 (Exp.1) 과염분실험구 (Exp.2) 의 30 psu 실험구 (Sal30) 로묶였고그룹 2 는유사 도 90.7% 로부유물질실험구 (Exp.3) 의부유물질농 도 120 mg/l 실험구 (SS120) 를제외한나머지그룹 으로묶였다. 집괴분석의결과를고려하면과거 에경험한수온변화에는적응하는시간이짧고 경험이없는환경변화인염분변화나부유물질농 도변화에는적응하는데시간이상대적으로많이 소요된다고판단된다. 특히스트레스를받은부 유물질 120 mg/l 실험구에서는적응하는데많은 시간이소요되었다고판단된다. 본연구결과저 수온에서사육한넙치는순치가된수온보다는 경험하지못한환경변화염분과부유물질에더욱 스트레스를받는다고판단되고염류세포가있어 서염분조절이가능한환경변화보다는부유물질 에대하여더욱스트레스를받는다고판단된다. References An, K. W. Shin, H. S. Min, B. H. Kil, G. S. and Choi, C. Y.(2010). Profiles of glucocorticoid receptor mrna expression and physiological changes in response to osmotic and thermal stress conditions in black porgy (Acanthopagrus schlegeli). Korean Journal of Ichthyology, 22(1), 1 7 24. Baba, Y. Kawana, K. Handa, T. Iwata, N. and Namba, K.(2006). Eco-physiological effects of suspended solids on fish-effects of smectite on the survival of Japanese flounder Paralichthys olivaceus. Nippon Suisan Gakkaishi, 72(3), 408~413. Barton, B. A. and Iwama, G. K.(1991). Physiological changes in fish from stress in aquaculture with emphasis on the response and effects of corticosteroids. Annual Review of Fish Diseases, 1, 3~26. Berry, W. Rubinstein, N. Melzian, B. and Hill, B.(2003). The biological effects of suspended and bedded sediment (sabs) in aquatic systems: A review. Rhode Island, USA: US Environment Protection Agency, National Health and Environmental Health Effects Laboratory. Bolasina, S. Tagawa, M. Yamashita, Y. and Tanaka, M.(2006). Effect of stocking density on growth, digestive enzyme activity and cortisol level in larvae and juveniles of Japanese flounder. Paralichthys olivaceus, Aquaculture, 259, 432~443. Chang, K. N.(2002). Fish culture, Seoul, Samkwang Publish. Chang, Y. J. Hur, J. W. Lim, H. K. and Lee, J. K.(2001). Stress in olive flounder (Paralichthys olivaceus) and fat cod (Hexagrammos otakii) by the sudden drop and rise of water temperature. Journal of the Korean Fisheries Society, 34(2), 91~97. Chang, Y. J. Park, M. R. Kang, D. Y. and Lee, B. K.(1999). Physiological responses of cultured olive flounder (Paralichthys olivaceus) on series of lowering seawater temperature sharply and continuously. Korean Journal of Fisheries and - 361 -
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