緒 言 に する 臼 沿 における 10 (1994-2003 ) サケ( Oncorhynchus keta ) 獲 1,000 に し, 獲 を っている.これら サケに ,他 域に す る が まれている ,そ 多く に した に された によって維 されて いる えられる.これら 獲 を4 み し, 臼 沿 域に する に されたサケ から した 易 8.9 %に し,他 域 に 較して めて い を している. サケ ま に 沿 を し,そ ま オホーツク に する こ が られている( ら 1998; 浦 2000; Urawa et al. 2001 ).オホーツク 移 した サ ケ ,域 体 する えられ, 沿 域における 活 によりサ ケ に 域 が じる われる. 沿 域 い ,こ 域がサケ に って, い を維 するために が あるこ を している. サケ 活 を 右する 因 して,餌 が げられるが( 2005 ), 沿 域 サケ 態 そ 餌 に して ,笠 (1985 ) がみられるだけ ある. 沿 域 い 維 因を らかにするため, 1998 から5 にわたり 臼, 沿 において,サケ 態 , Bulletin of the National Salmon Resources Center,No. 8:37-46 March 2006 さけ・ます センター 第8 37-46 2006 3 根室海峡標津沿岸域における春季の動物プランクトンの鉛直分布 ・ ・ 太 〒062-0922 2-2 さけ・ます センター T emporal Changes of Vertical Distributionof ZooplanktonCommunities during Spring andEarly Summer inthe Nemuro Strait Coastal Waters Off Shibetsu, EasternHokkaido Seki Jiro, Toshihiko Saito, and Ikutaro Shimizu Research Division, National Salmon Resources Center 2-2 Nakanoshima, Toyohira-ku, Sapporo 062-0922, Japan ([email protected]) Abstract . - This paper reportedthetemporal changes of zooplanktonbiomass, characteristics of theirdistributionpatternandsuccessionofitemsinthecoastal watersoffShibetsu, eastern Hokkaido. Zooplanktons were collected with simultaneously horizontal townets form2-6 different layers fromMay to mid July in 2001 and 2002. The zooplankton wet weight (mg/m 3 ) in 2001 was 2 to 16 times higher than that in 2002. The number of zooplanktons in 2001 was always superior that in2002. The zooplanktoncompositions were categorizedclearlybetween2001and2002by principalcomponentanalysis.The cold living type zooplanktons( Acartia longiremisand Pseudocalanus spp.) were dominant fromMay to mid or late June, while they were replaced by the warmliving ones ( Evadne nordmanni and Fritillaria sp.) in late June to July. The change of these dominateditemsin2001was10dayslaterthanthat in2002. Threedominateditemsof A. longiremis , Pseudocalanus spp. and E. nordmanni haddifferent distributionpatternof vertically and horizontally. Key words: coastal waters, zooplankton, vertical distribution, Shibetsu, Hokkaido Contribution ANo. 45 fromthe National Salmon Resources Center. 賛 2006 National Salmon Resources Center
10
Embed
Temporal Changes of Vertical Distribution of …salmon.fra.affrc.go.jp/kankobutu/bulletin/BNSRC08-5.pdfAbstract.- This paper reported the temporal changes of zooplankton biomass,
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Abstract.- This paper reported the temporal changes of zooplankton biomass, characteristics of their distribution pattern and succession of items in the coastal waters off Shibetsu, eastern Hokkaido. Zooplanktons were collected with simultaneously horizontal tow nets form 2-6 different layers from May to mid July in 2001 and 2002. The zooplankton wet weight (mg/m3) in 2001 was 2 to 16 times higher than that in 2002. The number of zooplanktons in 2001 was always superior that in 2002. The zooplankton compositions were categorized clearly between 2001 and 2002 by principal component analysis. The cold living type zooplanktons (Acartia longiremis and Pseudocalanus spp.) were dominant from May to mid or late June, while they were replaced by the warm living ones (Evadne nordmanni and Fritillaria sp.) in late June to July. The change of these dominated items in 2001 was 10 days later than that in 2002. Three dominated items of A. longiremis, Pseudocalanus spp. and E. nordmanni had different distribution pattern of vertically and horizontally.
さけ・ます資源管理センター研報 Bull. Natl. Salmon Resources Center, No. 8, 200638
Fig. 1. Map of sampling stations in the Nemuro Strait near Shibetsu, eastern Hokkaido.
Fig. 2. Temporal changes of vertical distribution of tempera-ture (solid line) and salinity (broken line) along a survey line in the coastal waters off Shibetsu from May 23 to July19, 2001.
Fig. 3. Temporal changes of vertical distribution of tempera-ture (solid line) and salinity (broken line) along a survey line in the coastal waters off Shibetsu from May 8 to July18, 2002.
Fig. 4. Temporal changes in wet weight (mg/m3) of zoo-plankton in the coastal waters off Shibetsu, 2001 (solid line) and 2002 (dotted line).
さけ・ます資源管理センター研報 Bull. Natl. Salmon Resources Center, No. 8, 200640
Fig. 5. Temporal changes in number (103 inds./m3) of zoo-planktons in the coastal waters off Shibetsu, 2001 (solid line) and 2002 (dotted line).
Fig. 6. Temporal changes in zooplankton wet weight (mg) per one individual in the coastal waters off Shibetsu, 2001 (solid line) and 2002 (dotted line).
Fig. 7. Relationships between the first component score and the second component score determined by principal component analysis for zooplankton samples to collect in the same period from May to mid July, 2001 (circle) and 2002 (square).
さけ・ます資源管理センター研報 Bull. Natl. Salmon Resources Center, No. 8, 200642
Fig. 8. Composition of zooplankton items along the survey line in the coastal waters off Shibetsu sampled at 2-6 different layers from 27 May to 19 July in 2001.
クトン個体数が維持された.6月27日にはこれらのほとんどはPseudocalanus spp. によって構成され,距岸8 kmの定点の5 m層では冷水性のNeocalanus spp. (N. plumchrus と N. fermingeri)が7%を占めた.この定点の水深は18 mと浅く,下層部の水温が7℃ 台に上昇していたにもかかわらず冷水性のNeocalanus spp.が分布していたことから,これらの動物プランクトンは,低水温層に分布していたものが起源となっていると推察される.標津沿岸より北側の羅臼沿岸域は水深が深く,深層部にはNeocalanus spp.が高い割合で分布していることから,標津沿岸の沖側の下層部に分布した冷水性種を主体とする動物プランクトンは,この海域から海底に沿うように移動した可能性が考えられる.7月中旬になると,Pseudocalanus spp. が高い割合を維持したのは最下層部だけで,多くの採集層ではE. nordmanni, A. longiremisと魚卵が卓越した.特に,暖水性である枝角類のE. nordmanniが上中層に多かったことから,上層を暖水が覆い,下層には6月下旬から継続して冷水性のPseudocalanus spp.が残留していたと考えられる. 湿重量と個体数から求めた動物プランクトン1個
関ら-標津沿岸域の動物プランクトン鉛直分布 43
Fig. 9. Composition of zooplankton items along the survey line in the coastal waters off Shibetsu sampled at 3-6 different layers from 8 May to 19 July in 2002.
さけ・ます資源管理センター研報 Bull. Natl. Salmon Resources Center, No. 8, 200644
Fig. 10. Vertical distribution of three dominant zooplankton items of Acartia longiremis (solid line), Pseudocalanus spp. (dotted line) and Evadne nordmanii (dash-dotted line) along the survey line in the coastal waters off Shibetsu from 23 May to 19 July, 2001.
Brodskii, K. A. 1950. Calanoida of the Far Eastern Seas and Polar Basin of the USSR. Nauka, Leningrad, pp. 440 (Israel Program for Scientific translation, Jerusalem, 1967).平川和正. 1984. 噴火湾における浮游性橈脚類の季節分布並びにCalanus pacificus, Calanus plumchrusお
関ら-標津沿岸域の動物プランクトン鉛直分布 45
Fig. 11. Vertical distribution of three dominant zooplankton items of Acartia longiremis (solid line), Pseudocalanus spp. (dotted line) and Evadne nordmanii (dash-dotted line) along the survey line in the coastal waters off Shibetsu from May 8 to July 18, 2002.
よびEucalanus bungii bungiiの生活史に関する研究.日本海洋生物研究所,東京.48 p.入江隆彦. 1990. 海洋生活初期のサケ稚魚の回遊に関する生態学的研究, 西水研報, 68: 1-142.笠原恵介. 1985. 根室海峡沿岸域の1984年春におけるサケ稚魚の生態および環境調査. さけ・ますふ研報, 39: 91-111.Moulton, L. L. 1997. Early marine residence, growth, and feeding by juvenile salmon in northern Cook Inlet, Alaska. Alaska Fish. Res. Bull., 4: 154-177.
Urawa, S. Y. Ueno, Y. Ishida, L. W. Seeb, P. A. Crane, S. Abe, and N. D. Davis. 2001. A migration model of Japanese chum salmon during early ocean life. NPAFC Tech. Rep., 2: 1-2.