朱曉芳, 曹 瀟, 鞏建華, 徐善良, 郭春陽(yáng)

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投喂頻率對(duì)珍珠龍膽石斑魚幼魚生長(zhǎng)及系統(tǒng)水質(zhì)指標(biāo)的影響

朱曉芳1, 曹 瀟2, 鞏建華2, 徐善良1, 郭春陽(yáng)2

(1. 寧波大學(xué) 海洋學(xué)院, 浙江 寧波 315211; 2. 應(yīng)用海洋生物技術(shù)教育部重點(diǎn)實(shí)驗(yàn)室, 浙江 寧波 315211)

通過(guò)自制小型循環(huán)水系統(tǒng)養(yǎng)殖實(shí)驗(yàn), 研究不同投喂頻率對(duì)珍珠龍膽石斑魚(♀× ♂)幼魚(35.50 g±4.58 g)生長(zhǎng)及系統(tǒng)水質(zhì)指標(biāo)的影響。實(shí)驗(yàn)設(shè)1、2和4次/d 3個(gè)投喂頻率實(shí)驗(yàn)組, 每組3個(gè)重復(fù)。水溫控制在25℃±2℃, 每15 d取樣測(cè)魚體質(zhì)量, 每天取水樣測(cè)定水質(zhì)指標(biāo), 實(shí)驗(yàn)周期為45 d。結(jié)果表明: 不同投喂頻率條件下, 珍珠龍膽石斑魚幼魚的增質(zhì)量率、飼料轉(zhuǎn)化率差異顯著(<0.05); 隨著投喂頻率的增加, 增質(zhì)量率呈現(xiàn)顯著升高趨勢(shì), 飼料轉(zhuǎn)化率呈現(xiàn)先顯著升高后又顯著降低趨勢(shì); 特定生長(zhǎng)率也呈上升趨勢(shì), 2次/d和4次/d組顯著高于1次/d組(<0.05), 2次/d和4次/d組之間差異不顯著(0.05); 隨著養(yǎng)殖時(shí)間的延長(zhǎng), 增質(zhì)量率、餌料轉(zhuǎn)化率和特定生長(zhǎng)率都呈現(xiàn)顯著降低趨勢(shì)(<0.05)。在0~15 d, 4次/d組增質(zhì)量率最高, 其值為46.30%, 分別是1次/d和2次/d組的1.31倍和1.11倍, 2次/d組的飼料轉(zhuǎn)化率最高, 其值為158.95%, 分別是1次/d和4次/d組的1.30倍和1.13倍, 氨氮、亞硝酸鹽含量和pH變化差異不顯著(>0.05)。同時(shí)氨氮隨投喂頻率增加而升高, 而pH隨投喂頻率增加而降低。綜合認(rèn)為, 在循環(huán)水養(yǎng)殖模式下, 珍珠龍膽石斑魚幼魚適宜投喂頻率為2次/d。

珍珠龍膽石斑魚(♀×♂); 投喂頻率; 生長(zhǎng); 水質(zhì)

1 材料與方法

1.1 實(shí)驗(yàn)材料與裝置

珍珠龍膽石斑魚幼魚: 由象山魚得水水產(chǎn)有限公司提供, 挑選體質(zhì)健康、規(guī)格均勻的幼魚用于實(shí)驗(yàn), 體質(zhì)量35.50 g±4.58 g。

實(shí)驗(yàn)用水: 養(yǎng)殖用水為天然海水, 經(jīng)自然沉淀及300網(wǎng)目網(wǎng)袋過(guò)濾。

過(guò)濾器: 水處理過(guò)濾器為創(chuàng)星牌魚缸過(guò)濾器, 功率32 W。

生物填料: 所用生物填料為聚丙烯鮑爾環(huán)填料。

養(yǎng)魚桶: 養(yǎng)魚桶容積為600 L, 底部直徑950 mm, 頂部直徑1 000 mm, 高750 mm。

實(shí)驗(yàn)飼料: 山東青島七好牌石斑魚配合飼料: 粗蛋白含量50.00%, 粗脂肪含量10.00%, 水分8.12%, 灰分14.21%。

循環(huán)水養(yǎng)魚系統(tǒng)實(shí)驗(yàn)裝置自行設(shè)計(jì)組裝如圖1, 養(yǎng)魚桶經(jīng)出水管與生物過(guò)濾器相連, 經(jīng)過(guò)生物過(guò)濾器處理后, 由進(jìn)水管流入養(yǎng)魚桶。

圖1 實(shí)驗(yàn)裝置示意圖

A、B、C分別表示養(yǎng)魚桶、生物過(guò)濾處理裝置、生物填料, 箭頭表示管道水流方向

A, B and C respectively represent fish buckets, biofiltration and biological fillings, and the arrows indicate the direction of the flow of the pipe

1.2 實(shí)驗(yàn)設(shè)計(jì)及飼養(yǎng)管理

每桶加入實(shí)驗(yàn)用水300 L, 隨機(jī)選取暫養(yǎng)一周后實(shí)驗(yàn)魚30尾放入實(shí)驗(yàn)桶。共設(shè)置3個(gè)實(shí)驗(yàn)組, 每個(gè)實(shí)驗(yàn)組設(shè)置3個(gè)重復(fù)。第一組每天投喂1次(8: 00), 第二組每天投喂2次(8: 00和14: 00), 第三組每天投喂4次(8: 00、11: 00、14: 00、17: 00), 每次飽食投喂; 每桶布置一個(gè)充氣石, 溫度25℃±2℃, 鹽度20~28, 流量為24 L/h; 每天早上第一次投喂前分別取水樣測(cè)定氨氮、亞硝酸鹽和pH; 分別在0、15、30、45 d稱量魚體質(zhì)量(精確到0.01 g)。

每天用虹吸管吸底, 記錄水溫, 實(shí)際攝食量; 根據(jù)系統(tǒng)蒸發(fā)量不定期補(bǔ)充海水, 實(shí)驗(yàn)周期45 d。

1.3 水質(zhì)測(cè)定及計(jì)算公式

氨氮、亞硝酸鹽和pH水質(zhì)指標(biāo)均用杭州陸恒生物公司水質(zhì)監(jiān)測(cè)分析儀測(cè)定。

增質(zhì)量率=100%×(t–0)/0;

飼料轉(zhuǎn)化率=100%×(t–0)/;

特定生長(zhǎng)率=100%×(lnt– ln0)/。

其中,t和0分別為終末和初始均質(zhì)量(g),為累計(jì)攝食量(g),為實(shí)驗(yàn)時(shí)間(d)。

1.4 數(shù)據(jù)處理與統(tǒng)計(jì)分析

實(shí)驗(yàn)所得數(shù)據(jù)均采用SPSS Statistics17.0 軟件進(jìn)行單因素方差(ONEANOVA)分析處理, 以0.05作為差異顯著水平。

2 結(jié)果

2.1 不同投喂頻率對(duì)珍珠龍膽石斑魚幼魚增質(zhì)量率、飼料轉(zhuǎn)化率和特定生長(zhǎng)率的影響

不同投喂頻率對(duì)珍珠龍膽石斑魚幼魚增質(zhì)量率、飼料轉(zhuǎn)化率和特定生長(zhǎng)率的影響見表1。

表1 不同投喂頻率對(duì)珍珠龍膽石斑魚幼魚生長(zhǎng)的影響

Tab.1 The effects of different different feeding frequencyon growth in juvenile of pearl gentian grouper

注: 表中數(shù)據(jù)為平均值±標(biāo)準(zhǔn)誤; 同行數(shù)值上標(biāo)英文字母不同, 表明組間差異顯著(<0.05); 同列數(shù)值下標(biāo)羅馬字母不同, 表明組內(nèi)不同時(shí)段差異顯著(<0.05)

從增質(zhì)量率上比較: 隨著養(yǎng)殖時(shí)間的延長(zhǎng), 各投喂頻率下增質(zhì)量率呈顯著降低趨勢(shì)(0.05); 各養(yǎng)殖時(shí)間段內(nèi), 增質(zhì)量率隨著投喂頻率的增加而顯著升高(0.05), 在第0~15天, 各投喂頻率的增質(zhì)量率達(dá)到最大值, 4次/d組最大, 其值為46.30%, 分別是1次/d組和2次/d組的1.31倍和1.11倍。

從飼料轉(zhuǎn)化率上看, 隨著養(yǎng)殖時(shí)間的延長(zhǎng), 各投喂頻率下飼料轉(zhuǎn)化率呈顯著降低趨勢(shì)(0.05); 各養(yǎng)殖時(shí)間段內(nèi), 飼料轉(zhuǎn)化率隨著投喂頻率的增加先顯著升高后顯著降低(0.05), 在第0~15天, 各投喂頻率的飼料轉(zhuǎn)化率達(dá)到最大值, 2次/d組最大, 其值為158.94%, 分別是1次/d組和4次/d組的1.30倍和1.13倍。

從特定生長(zhǎng)率上比較: 隨著養(yǎng)殖時(shí)間的延長(zhǎng), 各投喂頻率下特定生長(zhǎng)率呈顯著降低趨勢(shì)(0.05); 各養(yǎng)殖時(shí)間段內(nèi), 特定生長(zhǎng)率隨著投喂頻率的增加先顯著升高(0.05), 后不顯著增加(0.05), 2次/d和4次/d組顯著高于1次/d組, 2次/d和4次/d組之間差異不顯著(0.05)。

2.2 不同投喂頻率對(duì)小型循環(huán)水系統(tǒng)水質(zhì)指標(biāo)的影響

2.2.1 不同投喂頻率對(duì)小型循環(huán)水系統(tǒng)氨氮濃度的影響

小型循環(huán)水系統(tǒng)氨氮濃度變化情況如圖2, 不同投喂頻率下, 系統(tǒng)氨氮濃度隨著投喂頻率的增加而升高, 隨著養(yǎng)殖時(shí)間的延長(zhǎng), 系統(tǒng)氨氮濃度系統(tǒng)氨氮濃度變化規(guī)律一致, 呈先增加后降低趨勢(shì), 均在10 d左右達(dá)到峰值, 1、2和4次/d組最大值分別為0.27、0.47和0.58 mg/L; 8~15 d組間差異較大, 此后各組趨于穩(wěn)定, 差異不顯著, 3組的氨氮濃度分別為0.02、0.05和0.08 mg/L。

圖2 不同投喂頻率下系統(tǒng)氨氮濃度變化情況

2.2.2 不同投喂頻率對(duì)小型循環(huán)水系統(tǒng)亞硝酸鹽濃度的影響

小型循環(huán)水系統(tǒng)亞硝酸鹽濃度變化情況如圖3, 在不同投喂頻率下, 系統(tǒng)亞硝酸鹽濃度總體上呈現(xiàn)先迅速升高后小幅波動(dòng)的變化, 峰值出現(xiàn)在5 d左右; 亞硝酸鹽濃度與投喂頻率不存在明顯的正相關(guān), 25 d以后1次/d投喂組明顯低于其他兩組; 最終系統(tǒng)亞硝酸鹽濃度趨于穩(wěn)定, 1、2和4次/d組分別為0.08、0.10和0.12 mg/L。

圖3 不同投喂頻率下系統(tǒng)亞硝酸鹽濃度變化情況

2.2.3 不同投喂頻率對(duì)小型循環(huán)水系統(tǒng)pH的影響

小型循環(huán)水系統(tǒng)pH變化情況如圖4, 不同投喂頻率下, 投喂頻率對(duì)系統(tǒng)pH的影響與氨氮相反, 系統(tǒng)pH隨投喂頻率的增加而降低, 25 d后愈加顯著; 隨著養(yǎng)殖時(shí)間的延長(zhǎng), 3個(gè)實(shí)驗(yàn)組的pH持續(xù)降低1、2和4次/d組的pH在第45天分別降低到8.20、7.21和6.56。

圖4 不同投喂頻率下系統(tǒng)pH值變化情況

3 討論

3.1 不同投喂頻率對(duì)珍珠龍膽石斑魚幼魚生長(zhǎng)的影響

對(duì)虹鱒()、鞍帶石斑魚()的研究指出, 飼料轉(zhuǎn)化率隨投喂頻率的增加而下降[28-29]。在本研究中, 2和4次/d的結(jié)果與上述一致, 當(dāng)投喂頻率過(guò)高時(shí), 魚類攝食活動(dòng)等行為頻繁, 魚體能量消耗過(guò)多, 導(dǎo)致用于生長(zhǎng)的能量貯存減少, 從而導(dǎo)致飼料轉(zhuǎn)化率降低[30], 還有可能是由于過(guò)高的投喂頻率條件下, 兩次投喂的時(shí)間間隔縮短, 導(dǎo)致攝入的飼料快速的通過(guò)消化道, 使得飼料沒有得到及時(shí)充分的吸收利用, 從而使飼料轉(zhuǎn)化率降低[31]; 而從1次/d到2次/d的結(jié)果則與上述結(jié)論相反, 這可能是由于1次/d投喂頻率下, 石斑魚攝入的總飼料量大部分用于基礎(chǔ)代謝和活動(dòng)代謝, 而僅有小部分用于生長(zhǎng), 2次/d投喂頻率下, 其大部分用于生長(zhǎng), 而僅有小部分用于基礎(chǔ)代謝和活動(dòng)代謝。隨著養(yǎng)殖時(shí)間的延長(zhǎng), 各投喂頻率下飼料轉(zhuǎn)化率呈顯著降低趨勢(shì), 這是由于隨著珍珠龍膽幼魚日齡的增加, 腸胃內(nèi)某些消化酶的活性降低, 進(jìn)而導(dǎo)致其對(duì)飼料的吸收利用率降低[32]。

在本研究中, 2次/d和4次/d組特定生長(zhǎng)率顯著高于1次/d組, 王武等[5]研究了瓦氏黃顙魚()幼魚的特定生長(zhǎng)率也隨投喂頻率增加而顯著升高。2次/d和4次/d組之間無(wú)顯著差異, 這是由于魚類攝食活動(dòng)等行為頻繁, 魚體能量消耗過(guò)多, 從而特定生長(zhǎng)率差異不明顯[30]; 隨著養(yǎng)殖時(shí)間的延長(zhǎng), 各投喂頻率下特定生長(zhǎng)率呈顯著降低趨勢(shì), 這與飼料轉(zhuǎn)化率結(jié)果一致[32]。

3.2 不同投喂頻率對(duì)小型循環(huán)水系統(tǒng)水質(zhì)指標(biāo)的影響

魚類排泄物與攝食物相關(guān), 而養(yǎng)殖水體中氨氮濃度與排泄物和殘餌密切相關(guān)[33], 在本研究中, 系統(tǒng)氨氮濃度隨著投喂頻率的增加而升高, 這是由于高投喂頻率下, 攝食量增加, 魚體排泄物以及水體中殘餌也增多, 導(dǎo)致系統(tǒng)氨氮濃度升高; 有研究表明[34], 一定范圍投喂頻率下水體氨氮差異不顯著(0.05), 本研究結(jié)果與以上結(jié)論相一致; 隨著養(yǎng)殖時(shí)間的延長(zhǎng), 系統(tǒng)氨氮濃度呈先增加后降低趨勢(shì), 這可能是由于系統(tǒng)的聚丙烯鮑爾環(huán)生物填料需要一段適應(yīng)的時(shí)間, 所以開始一周多的時(shí)間里氨氮含量保持上升趨勢(shì), 在第10天前后3個(gè)投喂頻率組均達(dá)到最大值, 生物包對(duì)氨氮未響應(yīng), 處理效果不佳, 氨氮含量持續(xù)上升, 但經(jīng)過(guò)一個(gè)多星期的培養(yǎng)調(diào)整后, 生物包成熟, 對(duì)氨氮的去除能力大大提高, 氨氮的去除量大于生成量, 氨氮逐漸下降, 最后趨于穩(wěn)定, 3組含量降至0.02~0.08 mg/L。此時(shí), 生物包對(duì)氨氮的處理和系統(tǒng)產(chǎn)生的氨氮達(dá)到一個(gè)動(dòng)態(tài)平衡狀態(tài)[35]。

養(yǎng)殖水體中過(guò)高的氨氮, 一部分在亞硝化細(xì)菌的作用下生成亞硝酸鹽, 也有一部分在硝化細(xì)菌的作用下生成硝酸鹽[35]。據(jù)報(bào)道, 養(yǎng)殖水體中過(guò)高的亞硝酸鹽會(huì)使魚體血液里的二價(jià)鐵變?yōu)槿齼r(jià)鐵, 而三價(jià)鐵血紅蛋白沒有運(yùn)輸氧的能力, 會(huì)造成魚體組織缺氧, 甚至導(dǎo)致死亡[36]。在本研究中, 亞硝酸鹽濃度與投喂頻率不存在明顯的正相關(guān), 系統(tǒng)亞硝酸鹽濃度變化存在小幅波動(dòng)。1次/d組的系統(tǒng)亞硝酸鹽濃度低于2和4次/d組, 這與各組的氨氮水平相關(guān), 較低的氨氮水平經(jīng)亞硝化菌分解后產(chǎn)生的亞硝酸鹽也相對(duì)較低。后期隨著生物包成熟, 系統(tǒng)亞硝化和硝化系統(tǒng)趨于穩(wěn)定, 亞硝酸鹽濃度趨于回落。而在第18天和第33天出現(xiàn)的小幅度升高而后降低的現(xiàn)象, 是由于在第17天和第32天對(duì)系統(tǒng)進(jìn)行簡(jiǎn)單的清洗緣故。

養(yǎng)殖水環(huán)境中穩(wěn)定適宜的pH對(duì)魚體生存和生長(zhǎng)至關(guān)重要, 而養(yǎng)殖水體中pH會(huì)隨著養(yǎng)殖時(shí)間的延長(zhǎng)持續(xù)降低, 特別是在封閉式循環(huán)水系統(tǒng)中[37]; 造成循環(huán)水水體pH持續(xù)降低的原因主要有以下3點(diǎn): (1)生物池處理系統(tǒng)的硝化作用過(guò)程本身是一個(gè)耗堿產(chǎn)酸的過(guò)程; (2)魚體自身呼吸作用產(chǎn)生大量的二氧化碳; (3)水體中殘餌和糞便中未被消化利用的有機(jī)物的氧化分解產(chǎn)生的二氧化碳[38]; 本研究結(jié)果顯示, 與氨氮相反, 系統(tǒng)pH隨投喂頻率的增加而降低, 由于高投喂頻率下, 每天的總攝食量大, 殘餌、糞便更多, 其氧化分解產(chǎn)生的二氧化碳也就較多, 從而導(dǎo)致pH下降更快; 高投喂頻率下, 也會(huì)導(dǎo)致魚體活動(dòng)增多, 呼吸作用增強(qiáng), 產(chǎn)生的二氧化碳較多。針對(duì)循環(huán)水系統(tǒng)pH持續(xù)降低問(wèn)題, 往往通過(guò)掛石灰袋或采用脫二氧化碳的裝置加以解決, 從而達(dá)到調(diào)節(jié)水體pH的目的。

4 小結(jié)

本研究結(jié)果顯示, 投喂頻率由1次/d增加至4次/d時(shí), 增質(zhì)量率顯著提高, 而飼料轉(zhuǎn)化率2次/d組顯著高于1次/d和4次/d組; 同時(shí)氨氮隨投喂頻率增加而升高, 而pH隨投喂頻率增加而降低。綜合珍珠龍膽石斑魚幼魚的增質(zhì)量、飼料利用和水質(zhì)指標(biāo), 研究認(rèn)為, 珍珠龍膽石斑魚幼魚循環(huán)水養(yǎng)殖中適宜投喂頻率為2次/d。

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(本文編輯: 譚雪靜)

Effects of different feeding frequencies on the growth of juvenile ♀× ♂and on water quality index

ZHU Xiao-fang1, CAO Xiao2, GONG Jian-hua2, XU Shan-liang1, GUO Chun-yang2

(1. School of Marine Sciences, Ningbo University, Ningbo 315211, China; 2. The Key Laboratory of Applied Marine Biotechnology Ministry of Education, Ningbo 315211, China)

Effects of different feeding frequencies on the growth of juvenile pearl gentian grouper (♀×) (35.5 g ± 4.58 g) and on water quality index were studied in a breeding experiment using a self-made small-scale circulating water system. Fishes were divided into three groups with three replicates in each group; groups were fed 1, 2 and 4 times per day. Body weight of the fishes was measured every 15 days, and water quality index was measured every day. The experimental period was 45 days and water temperature was 25°C ± 2°C. Results showed that weight gain and feeding conversion rates of juvenile fishes were significantly different under different feeding frequencies (0.05). As feeding frequency increases, weight gain rate significantly increased (0.05), and feed conversion rate showed a significant initial increase and then a decrease (0.05). Specific growth rate showed increased, and the growth rate of the groups that were fed two and four times per day was significantly higher than that of the group that was fed once a day group, whereas there was no significant difference between the groups that were fed two and four times per day (0.05). With the increased feeding time, weight gain, feeding conversion, and specific growth rates significantly decreased (0.05). In the first 15 days, weight gain rate in the group that was fed four times per day was the highest with a value of 46.30%, which was 1.31 and 1.11 times higher than those of the groups that were fed once and two times per day, respectively. The feeding conversion rate was the highest in the group that was fed two times per day with a value of 158.95%, which was 1.30 and 1.13 times higher than those of the groups fed once and four times per day, respectively. There were no significant differences in the contents of ammonia and nitrite and the variation of pH value (0.05). Meanwhile, nitrate content increased, whereas pH value decreased with increased feeding frequency. Results of the present study suggest that the optimal feeding frequency of pearl spotted grouper juvenile fish was two times per day under the recirculating aquaculture system.

♀× ♂; feeding frequency; growth; water quality index

[State Oceanic Administration Regional Symposium on Marine Economic Innovation in 2013, No.F01521145300; Zhejiang Province Science and Technology Project, No. 2017C32015]

Nov. 18, 2016

S913

A

1000-3096(2017)08-0032-08

10.11759//hykx 20161118001

2016-11-18;

2017-05-19

國(guó)家海洋局2013年海洋經(jīng)濟(jì)創(chuàng)新區(qū)域示范項(xiàng)目(F01521145300); 浙江省科技計(jì)劃項(xiàng)目(2017C32015)

朱曉芳(1991-), 女, 碩士研究生, 從事魚類繁殖生物學(xué), E-mail: 2366405841@qq.com; 徐善良,通信作者, 教授, E-mail: xushanliang@nbu.edu.cn