李秀梅， 葉振江??， 李增光， 胡海生， 鄒　全, 于洪亮

(1.中國海洋大學水產(chǎn)學院，山東 青島 266003; 2.威海市文登區(qū)海洋與漁業(yè)局，山東 威海 264400)

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技術(shù)報告

黃海中部近岸產(chǎn)卵場日本鳀卵子大小的時空變化?

李秀梅1， 葉振江1??， 李增光1， 胡海生1， 鄒全1, 于洪亮2

(1.中國海洋大學水產(chǎn)學院，山東 青島 266003; 2.威海市文登區(qū)海洋與漁業(yè)局，山東 威海 264400)

摘要：2013年4月下旬至7月上旬，在黃海中部近岸產(chǎn)卵場20 m以淺水域進行6個航次的魚類浮游生物調(diào)查，對日本鳀(Engraulis japonicus)卵子形態(tài)及大小的時空變化進行研究。結(jié)果表明：調(diào)查海區(qū)日本鳀卵子形態(tài)呈橢球形，卵子大小在不同發(fā)育階段無顯著性差異，但其時空變化差異顯著。從5月上旬至7月上旬，卵子大小整體上呈逐漸減小的趨勢，且與水溫呈顯著負相關(guān)。日本鳀卵子在調(diào)查海區(qū)最早出現(xiàn)于5月上旬，卵子最大，長徑(1.57±0.09)mm，短徑(0.77±0.04)mm，縱切面積(0.95±0.07)mm2；6月下旬卵子最小，長徑(1.20±0.07)mm，短徑(0.64±0.03)mm，縱切面積(0.61±0.43)mm2。同歷史數(shù)據(jù)相比，調(diào)查海區(qū)的日本鳀卵子5月上旬顯著大于東海海域，6月下旬顯著小于山東半島南部。

關(guān)鍵詞：黃海中部；海州灣；日本鳀；卵子大小；時空變化

LI Xiu-Mei, YE Zhen-Jiang, LI Zeng-Guang, et al. Spatial and temporal changes of the egg size of Japanese anchovy (Engraulis japonicus) inhabiting the near shore spawning ground of central Yellow Sea [J]. Periodical of Ocean University of China, 2016, 46(2)： 54-60.

卵子大小與繁殖力是魚類生活史上的2個重要生殖習性特征，其研究對解析漁業(yè)資源數(shù)量變動及對環(huán)境變動的應(yīng)答機制具有重要意義[1]。生物廣布種的形態(tài)、生理、行為和生態(tài)特征往往在不同地區(qū)存在顯著的差異[2]，魚類繁殖力、產(chǎn)卵期等生殖習性特征可因海域與棲息環(huán)境而異[3-4]。魚類卵子體積是體現(xiàn)魚類遺傳屬性及環(huán)境適應(yīng)性特征的重要生物學參數(shù)，對后代存活率、產(chǎn)卵場環(huán)境狀況、魚類群體劃分等具有重要指示意義，相關(guān)研究有較多報道[5-6]。

日本鳀(Engraulisjaponicus)廣泛分布于中國東海的西北部、黃海、日本海、日本九州島西部近海、瀨戶內(nèi)海和日本群島的太平洋近海[7]，作為主要餌料魚種在海洋生態(tài)系統(tǒng)中起重要作用[8]，為高資源量的小型中上層魚類[9]。黃海日本鳀產(chǎn)卵期為5—10月，產(chǎn)卵期長[10]。有關(guān)中國近海日本鳀的研究，主要集中在產(chǎn)卵親魚的生殖生態(tài)學特征、群體結(jié)構(gòu)以及卵子分布與環(huán)境的關(guān)系等，而關(guān)于其卵子大小僅零星報道中有所提及[11]，缺乏深入系統(tǒng)的研究。黃海中部近岸海域是黃海主要產(chǎn)卵場之一，也是黃海日本鳀產(chǎn)卵場的重要組成部分，本文以黃海中部近岸水域為研究海域，對春夏季日本鳀卵子大小及時空分布做了初步研究，為該魚種生殖習性現(xiàn)狀及資源變動機制的研究提供依據(jù)。

1材料和方法

1.1 調(diào)查海域、站位與航次

以黃海中部海州灣近岸20m以淺水域(34.5°N～35.5°N,119.0°E～120.5°E)為調(diào)查海域，分別于2013年4月23—24日、5月10—12日、5月23—25日、6月6—8日、6月21—23日和7月6—8日(下簡稱4月下旬、5月上旬、5月下旬、6月上旬、6月下旬和7月上旬)開展了6個航次的調(diào)查，每半月大潮調(diào)查1次，共設(shè)置了75個調(diào)查站位(見圖1)，租用50～180馬力調(diào)查漁船，采用淺水Ⅰ型網(wǎng)進行魚類浮游生物斜拖采樣(網(wǎng)長145cm,網(wǎng)口直徑50cm，網(wǎng)口面積0.2m2)，網(wǎng)口設(shè)置流量計以校正每網(wǎng)濾水量，每站位拖網(wǎng)時間為10min，拖速2kn左右。各站位以XR-420型CTD進行溫度、鹽度、水深等環(huán)境要素的測定。

圖1　調(diào)查海域及站位分布

1.2 樣品處理與圖像采集

樣品以5%海水甲醛溶液固定保存，樣品的室內(nèi)分析處理均按照《海洋調(diào)查規(guī)范》[12]中規(guī)定方法進行。實驗室內(nèi)以形態(tài)學方法，參考《中國近海魚卵與仔魚》[13]和《臺灣海域魚卵圖鑒》[14]，利用JSZ5型體視顯微鏡(20X)對魚類浮游生物樣品進行分類鑒定，依據(jù)Thompson &Riley魚卵ⅴ期發(fā)育標準[15]對樣品進行發(fā)育分期鑒定。利用浮游生物計數(shù)框和醫(yī)用計數(shù)器，對各站位樣品進行取樣計數(shù)。已有研究表明日本鳀魚卵和秘魯鳀魚卵在甲醛溶液中不會收縮，形狀不會改變[16-17]，因此，本文卵子大小量度指標的測量系直接對甲醛固定樣品進行。

6個航次調(diào)查共采集到日本鳀的魚卵747411粒。根據(jù)魚卵密度分布特征，各航次分別在調(diào)查區(qū)域內(nèi)選取主要魚卵密集區(qū)，并兼顧其空間分布，確認4～6個圖像采集站位(見圖2)，在各站位隨機選取50粒卵子，在10×放大倍數(shù)下，使用SMZ800體視顯微鏡及圖像采集系統(tǒng)進行卵子圖像的采集，個別站位不足50粒卵的全取。6個航次中除4月下旬外，其余5個航次皆有鳀魚魚卵出現(xiàn)。實驗共采集24個站位、1123粒的日本鳀卵子圖像(見表1，圖2)。

表1　各航次測量站位及魚卵樣品數(shù)量

圖2　各航次采樣站位位置及卵子總數(shù)

1.3 形態(tài)測量指標篩選及數(shù)據(jù)分析

日本鳀卵子呈橢球形。選取卵子長徑、短徑、長徑/短徑比及最大縱切面積(下簡稱面積)做為卵子大小量度指標，以Image-Pro Plus軟件對卵子圖像進行量度指標的測量。

通過單因素方差分析one-way ANOVA(滿足方差齊性)或非參數(shù)檢驗Kruskal-Wallis test(不滿足方差齊性)，利用SPSS 20.0件對各航次日本鳀大小量度指標進行分析[4,11,18-20]。

2結(jié)果

2.1 日本鳀不同發(fā)育時期卵子大小變化

為比較不同發(fā)育階段的卵子大小差異，對同一航次同一站位的樣品進行分析。5月上旬站位13處于Ⅰ-Ⅴ期的卵子總共4011粒，隨機選取270粒，分析不同分期的卵子大小。方差分析表明，處于不同發(fā)育期的卵子大小量度指標無顯著性差異(面積，P>0.05，F(xiàn)4,265=1.780；長徑，P>0.05，F(xiàn)4,265=0.534；短徑，P>0.05，F(xiàn)4,265=0.129；長徑/短徑，P>0.05，F(xiàn)4,265=0.265)，因此處于不同發(fā)育期的卵子可以合并分析(見表2)。

表2　不同發(fā)育期日本鳀卵子長徑、短徑、面積和長徑/短徑

Note: ①Developmental stage; ②Longer axis; ③Shorter axis; ④Area; ⑤Ratio of longer axis to shorter axis

2.2 日本鳀卵子大小的空間分布

對各航次的取樣站位日本鳀卵子的面積、長徑/短徑進行分析，結(jié)果表明各航次的取樣站位間，日本鳀卵子的面積、長徑/短徑均存在顯著性差異(見表3)。

2.3 日本鳀卵子大小隨時間的變化

從5月上旬至7月上旬，卵子平均長徑為(1.32±0.16)mm，平均短徑為(0.68±0.06)mm，平均面積為(0.71±0.14)mm2，長徑/短徑平均值為1.94±1.15。各航次卵子平均長徑范圍為1.57～1.22mm，平均短徑范圍為0.77～0.65mm，平均面積范圍為0.95～0.62mm2，長徑/短徑平均值范圍為2.03～1.89，(見表4)。5月上旬至7月上旬，日本鳀卵子長徑、短徑、面積及長徑/短徑總體上呈逐漸減小的趨勢(見圖3)。方差分析結(jié)果表明長徑(H=764.16，P<0.05)、短徑(H=682.61，P<0.05)、面積(H=810.55，P<0.05)及長徑/短徑(H=196.23，P<0.05)各航次間差異顯著，變化趨勢見圖3。

表3　日本鳀卵子面積和長徑/短徑

注：各航次的同一列中標有不同字母上標的數(shù)值相互之間差異顯著(P<0.05)。

Note: Values sharing the same letters in the same column of each cruise indicate insignificant difference among groups (P<0.05).

①Cruise；②Sampling station；③Date of survey；④Ratio of longer axis to shorter axis；⑤Area

表4　水溫與日本鳀卵子長徑、短徑、面積和長徑/短徑

圖3　各航次卵子長徑、短徑、長徑/短徑及面積

山東半島南部產(chǎn)卵場日本鳀胚胎發(fā)育的閾溫度為10.26℃[21]，本研究海區(qū)各航次取樣站位的水溫均高于10.26℃，卵子可進行胚胎發(fā)育。通過對各航次取樣站位的水溫分析發(fā)現(xiàn)，5月上旬至7月上旬的水溫逐漸上升，各航次卵子面積與其對應(yīng)水溫呈顯著負相關(guān)，其線性回歸方程為：

y=1.37-0.035x，(r2=0.90，P<0.01)。

3討論

本文研究結(jié)果表明，從5月上旬至7月上旬，隨著水溫的升高，日本鳀卵子的所有量度指標均呈逐漸減小的趨勢，各航次間卵子各量度指標均存在顯著差異。這與其他魚類的相關(guān)研究結(jié)果，如加拿大東南部沿海大西洋鱈魚(Gadusmorhua)[5,22]和智利中北部沿海秘魯鳀(Engraulisringens)[20,23]等類似。

海洋魚類的卵徑變化受很多因素制約，包括水溫、年齡結(jié)構(gòu)、種群棲息地、緯度、產(chǎn)卵期時間、產(chǎn)卵批次和不同批次間的影響等[24]。隨著溫度升高，魚類卵子體積(卵徑)與溫度往往呈負相關(guān)關(guān)系[19,22]，造成上述現(xiàn)象的原因可能與親魚繁殖期的推移，儲備能量減少有關(guān)[25]。黃海區(qū)日本鳀親魚脂肪儲備從5—7月持續(xù)下降[26]，這可能是造成日本鳀卵徑逐漸減小的一個原因。關(guān)于卵徑隨著產(chǎn)卵期推進而減小的這種季節(jié)趨勢的另一個原因可能是產(chǎn)卵群體年齡結(jié)構(gòu)的變化[27]。在山東半島南部產(chǎn)卵場，產(chǎn)卵前期以2、3齡日本鳀剩余產(chǎn)卵群體為主，產(chǎn)卵中期則以1齡早生產(chǎn)卵群體和2齡產(chǎn)卵群體為主，而產(chǎn)卵后期及末期主要為1齡晚生補充產(chǎn)卵群體[28]。研究表明，對銀大麻哈魚(Oncorhynchuskisutch)[4]和大麻哈魚(Oncorhynchusketa)[29]的同批次卵子而言，產(chǎn)卵親魚個體體長值越大，卵子卵徑就越大；在產(chǎn)卵期的不同階段，進入山東半島南部海域產(chǎn)卵場中心產(chǎn)卵的鳀魚生殖群體全長優(yōu)勢組成存在明顯的結(jié)構(gòu)差異，日本鳀生殖個體在產(chǎn)卵前期、中期及后期的平均全長逐漸減小，產(chǎn)卵前期的生殖個體平均全長12.51cm，產(chǎn)卵中期平均全長為11.93cm，產(chǎn)卵后期平均全長為10.84cm[28]，因而對日本鳀而言，繁殖季節(jié)中日本鳀生殖個體的全長變化亦可能是卵子大小變動的潛在原因。

日本鳀作為廣布種，不同海區(qū)、不同產(chǎn)卵群體和不同批次的卵子卵徑可能存在差異。采用單樣本t檢驗對本次研究結(jié)果與以往的研究結(jié)果[11]比較，5月上旬日本鳀樣品卵子面積顯著大于2007年5月7—14日中國東海沿海的日本鳀卵子面積(t=62.73，df=209，檢測值testvalue=0.633，P<0.01)，也顯著大于閩南-臺灣淺灘漁場1973年4月—1977年3月采集的日本鳀卵子面積(t=61.75，df=209，檢測值testvalue=0.638，P<0.01)，略小于1958年日本近海采集的日本鳀卵子面積；5月下旬樣品卵子面積顯著大于1963年5月14日—6月3日黃海膠州灣的日本鳀卵子面積(t=9.551，df=162，檢測值testvalue=0.705，P<0.01)；6月下旬樣品卵子面積顯著小于2003年6月16—29日山東半島南部產(chǎn)卵場中的日本鳀卵子面積(t=-13.51，df=249，檢測值testvalue=0.643，P<0.01)(見表5)。這與其它魚種的類似研究中，卵子大小隨空間環(huán)境變化的一般趨勢相符，筆者認為其反映了魚種對高強度捕撈壓力及不同產(chǎn)卵場環(huán)境的生物學適應(yīng)[33]。

表5　其他海域日本鳀卵子的大小比較

Note: ①Coastal waters of the East China Sea; ②Fishing ground of the south Fujian-Taiwan Bank; ③Jiaozhou Bay in Yellow Sea; ④Japanese coastal waters; ⑤Spawning grounds off south Shandong Peninsula

隨著緯度的升高，成魚必須要抵抗更短的生長季和更長的冬季，與低緯度相比，體型可能偏小[34]。生長率和體長的差異與緯度的相關(guān)性在生活史第一年尤其明顯，仔魚體長的增加通常會提高其第一年冬季的成活率，最終影響到種群的補充情況[35]。研究表明，鳀科魚類卵子卵徑的變化原因包括親魚生殖能量的變化、生殖群體年齡組成的變化以及雌性卵細胞的形成過程等[24,36]。卵子大小在本研究海域相對較小的空間尺度范圍內(nèi)亦呈現(xiàn)出一定的時空異質(zhì)性特征，其具體成因,以及不同海區(qū)、環(huán)境和季節(jié)下日本鳀卵子大小的變動規(guī)律、其對環(huán)境的響應(yīng)機制和對種群資源動態(tài)的影響等尚需以后進一步深入研究。

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責任編輯朱寶象

Spatial and Temporal Changes of the Egg Size of Japanese Anchovy (Engraulisjaponicus)Inhabiting the Near Shore Spawning Ground of Central Yellow Sea

LI Xiu-Mei1, YE Zhen-Jiang1, LI Zeng-Guang1, HU Hai-Sheng1, ZOU Quan1, YU Hong-Liang2

(1.College of Fisheries, Ocean University of China, Qingdao 266003, China; 2.Bureau of Oceanic and Fishery of Wendeng District, Weihai 264400, China)

Abstract：The Japanese anchovy Engraulis japonicas is widely distributed along the western North Pacific, such as eastern China Sea, Yellow Sea, Japan Sea, etc. and it has also supported one of the largest fisheries in China over the last three decades with the peak yield of more than 1 million tons in 1990s. However, there are few studies for the early life stages of this species in North Pacific, especially in near shore spawning ground of central Yellow Sea. Egg size of fish is not only easy to quantify, but also often reflects the amount of resources mothers invest in individual offspring. It is treated as one structural element with which to characterize a species’ ontogeny regardless of causal relationships between the species and its habitat. It is therefore that egg size often highly varies both between different species and between stocks of a species, even between clutches of the same individual. As shown by numerous publications dealing with conditions of life and reproduction of fishes, egg size of fish is an important biologi cal parameter characterizing the environment of spawning ground and fish reproductive traits. This study were aimed to as follows: 1) report changes in egg size throughout the Japanese anchovy spring and summer spawning season as well as the spatial characteristic of egg size in near shore waters of central Yellow Sea; 2) evaluate whether egg size varies with respect to space and time, and 3)provide data for studies on its reproductive traits and resources variation mechanism. Six ichthyoplankton cruise surveys were conducted in < 20m depth waters of central Yellow Sea from late April to early July, 2013 with the time interval of half a month. We collected Japanese anchovy eggs from 75 stations along the coastal zone(34.5°N～35.5°N, 119.0°E～120.5°E). This area is one important part of the spawning waters of Japanese anchovy. Eggs were collected with a plankton net(500μm mesh). Upon collection, all eggs were preserved in 5% buffered formalin and then transferred to the lab after the survey. Egg size(length, width, area) was measured by software Image-Pro Plus 6.0 based on the images captured on a dissecting microscope and camera(Nikon SMZ1500). Based on data from the six cruise surveys conducted, the temporal and spatial changes in the morphology and size of Japanese anchovy eggs were investigated. The results indicated that the morphology of elliptical anchovy eggs was similar among anchovy eggs at different developmental stages. However, egg size varied temporally and spatially. Egg size decreased generally from early May to early July, which was negatively correlated with water temperature. The eggs began to occur in the study area in early May with largest longitudinal section area of (0.95±0.07)mm2(longer axis (1.57±0.09)mm and shorter axis (0.77±0.04)mm). Minimum egg size occurred in late June (longitudinal section area (0.61±0.43)mm2, longer axis (1.20±0.07)mm and shorter axis (0.64±0.03)mm). Compared with the documented previously, Japanese anchovy eggs from early May in the currently studied area were significantly larger than those collected in coastal waters of East China Sea, and anchovy eggs from late June were significantly smaller than those collected at the spawning grounds off south Shandong Peninsula. These results is consist with the popular science regularity that egg size varies among different spawning grounds and decreases during the whole spawning season. In the meanwhile, the phenomenon that there were some spatial egg size varies to be founded between positions in so small areas would be paid more attention to it.

Key words:Central Yellow Sea; Haizhou Bay; Japanese anchovy; egg size; temporal and spatial variation

DOI：10.16441/j.cnki.hdxb.20140331

中圖法分類號：Q948.3

文獻標志碼：A

文章編號：1672-5174(2016)02-054-07

作者簡介：李秀梅(1989-)，女，碩士，主要從事魚類早期發(fā)育研究。E-mail：xiuxiu12345@126.com??通訊作者： E-mail:yechen@ouc.edu.cn

收稿日期：2014-10-16；

修訂日期：2015-05-07

基金項目：? 海洋公益性行業(yè)科研專項經(jīng)費項目(201305030)；高等學校博士學科點專項科研基金項目(20120132130001)；中央高校基本科研業(yè)務(wù)費專項(201262004)資助

引用格式：李秀梅，葉振江，李增光，等. 黃海中部近岸產(chǎn)卵場日本鳀卵子大小的時空變化[J].中國海洋大學學報(自然科學版)， 2016, 46(2)： 54-60.

Supported by Public Science and Technology Research Funds Projects of Ocean (201305030); Specialized Research Fund for the Doctoral Program of Higher Education (20120132130001); Fundamental Research Funds for the Central Universities (201262004)