Snow crab - Zuwaigani (English spelling) snow crab

Japanese: ズワイガニ - ずわいがに（英語表記）snow crab

This crab belongs to the family Arthropoda, order Decapoda, class Crustacea. It is an important edible crab in the fishing industry. It has been closely related to people's lives since ancient times, so it has many local names. In consumption areas such as the Tokyo and Osaka regions, it is commonly called Echizen crab (Echizen crab), named after the main production area, or Matsubagani (pine needle crab), which is the name given in the San'in region. The origin of the word "snow crab" is unclear. Considering that the word "snow crab" is used in various regions to refer to large males, "zu" stands for head, and it is thought to mean king of crabs. In the Japan Sea side of the Tohoku region, snow crabs are called "taraba crab," and it is important to note that real king crabs are sometimes called "ibaragani." In many regions, females are called "seiko" or "seko," but they are also called "megani," "komochi," and "koubakugani." Adult females incubate eggs all year round, and resume incubating immediately after releasing the larvae. In other words, females are always incubating eggs, but "Seiko" or "Seko" is a general term for incubating females, and those with orange eggs in the early stages of development are sometimes called "Akako," while those with dark brown, eyed eggs are called "Kuroko." Young crabs whose abdomens have not yet fully expanded are called "Zenmaru," those with double carapaces close to shedding are called "Futakawagani," "Futayogagani," or "Nimaigani," and those that have molted and are soft are called "Watagani."

The outline of the shell is a rounded triangle, and the shell is not very hard. Males have a shell width of 18 cm, and when their walking legs are spread, it can reach 80 cm, but females reach sexual maturity at 7-8 cm and stop growing. They are distributed throughout the Sea of Japan, through the Sea of Okhotsk, and up to Alaska at depths of 70-500 meters, but it is said that the ratio of the length to width of the long segment of the first walking leg in those near Japan is 5.5-6.3, and in the northeastern Pacific it is 4.9-5.2. In other words, those in the northwestern Pacific have slightly longer walking legs, and so the scientific name of the subspecies Ch. opilio elongatus is sometimes used.

The red-colored Red Snow Crab Ch. japonicus is distributed in the waters off Japan. It lives deeper than the Snow Crab at depths of 400 to 2000 meters and is prolific, but its meat is inferior in quality. In recent years, hybrids of the two species have been obtained and are the subject of much discussion. Bristol Bay and its surrounding waters are home to large numbers of the Giant Snow Crab Ch. bairdi and the Northern Snow Crab Ch. tanneri , which are valuable resources for the North Pacific fishing industry.

[Masamichi Takeda]

Fisheries

Of the total crab catch in the world, which was about 1,340,432 tons (2007), crabs of the genus Snow crab are the second largest after crabs of the family Portunidae. In Japan, red snow crab and snow crab rank first and second, respectively, but their numbers are declining. The main fishing grounds are off the east coast of Canada, the Gulf of St. Lawrence, Hudson Bay, the eastern and western Bering Sea, off the west coast of Alaska, the Sea of Okhotsk, and the Sea of Japan. The depths are 70 to 200 meters. However, in the Sea of Japan, it is becoming common for snow crabs to be caught at depths of 200 to 450 meters, and for red snow crabs, 1,200 to 1,500 meters. The main fishing gear is a cage with a drop opening to prevent the crabs from escaping. Other fishing methods used include bottom trawling, which involves dragging a bag-shaped net along the seabed, as in the case of red snow crab in the Sea of Japan, and bottom gill nets, which involve entangling crabs in a net. Snow crabs are delicious, prone to overfishing, and grow slowly, so depleted stocks do not easily recover. Therefore, it is desirable to reduce the mortality of female and juvenile crabs by improving the traps and make effective use of the reproductive power of the stock.

[Yasuo Sasagawa and Teisuke Miura]

“FAOFAO Yearbook; Fishery and Aquaculture Statistics (2008)”

[References] | Crabs | Spider crabs

Snow crab [specimen drawing]
© Tadaaki Ohkata ">

Snow crab [specimen drawing]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

Japanese:

節足動物門甲殻綱十脚(じっきゃく)目クモガニ科に属するカニ。食用ガニで水産業上の重要種である。古くから人々との生活と密接な関係にあったため地方名が多い。東京地方や大阪地方などの消費地では主産地名をとったエチゼンガニ（越前蟹）、あるいは山陰地方の呼び名であるマツバガニ（松葉蟹）の名が通りがよい。ズワイガニの語源は明らかでない。各地でズワイとよぶのは大形雄に対してであることを考えると、「ズ」は頭で、カニの王者の意味ではないかとされる。東北地方の日本海側ではズワイガニのことをタラバガニとよび、本当のタラバガニをイバラガニとよぶことがあるので注意を要する。雌に対してはセイコとかセコという地方が多いが、メガニ、コモチ、コウバクガニなどともよばれる。成体になった雌は一年中抱卵し、幼生を放ったのちにふたたびすぐ抱卵する。すなわち、雌はつねに抱卵しているが、セイコまたはセコは抱卵雌の総称で、発生初期の橙(だいだい)色の卵をもつものをアカコ、黒褐色の発眼卵をもつものをクロコと呼び分けることもある。腹部がまだ完全には広がっていない幼ガニをゼンマル、脱皮間近の二重の甲をもつものをフタカワガニ、フタヨガニ、ニマイガニなどとよび、脱皮後の軟らかいものをワタガニとよぶ。

　甲の輪郭は丸みを帯びた三角形で、甲はあまり硬くない。雄は甲幅18センチメートル、歩脚を広げると80センチメートルに達するが、雌は7～8センチメートルになって性的に成熟すると成長が止まる。日本海全域、オホーツク海を経てアラスカまでの水深70～500メートルに分布するが、日本近海のものでは第1歩脚の長節の長さと幅の比が5.5～6.3、北東太平洋のものでは4.9～5.2といわれる。すなわち、北西太平洋のものは歩脚がやや長いということで亜種Ch. opilio elongatusの学名が使われることもある。

　日本近海には紅赤色のベニズワイガニCh. japonicusが分布している。ズワイガニより深い水深400～2000メートルにすみ、多産するが、肉質が劣る。近年、両種の雑種が得られ話題となっている。ブリストル湾とその近海にはオオズワイガニCh. bairdiやキタズワイガニCh. tanneriが多産し、北洋漁業の貴重な資源となっている。

［武田正倫］

漁業

世界のカニの漁獲量約134万0432トン（2007）のうち、ズワイガニ属のカニ類はワタリガニ科のカニ類に次いで多い。日本でもベニズワイガニとズワイガニがそれぞれ1、2位を占めているが、減少傾向にある。主漁場はカナダの東岸沖、セント・ローレンス湾、ハドソン湾、ベーリング海の東部・西部、アラスカ西岸沖、オホーツク海および日本海である。その深度は70～200メートルである。ただし、日本海ではズワイガニで200～450メートル、ベニズワイガニでは1200～1500メートルが普通になってきている。主漁具は籠(かご)で、それには入ったカニが出にくいように落とし口がつけてある。ほかに日本海のベニズワイガニのように袋状の網を海底沿いに引く底引網、あるいは網にカニを絡めて漁獲する底刺網類も用いられる。ズワイガニは美味で、乱獲されやすく、しかも成長が遅いために、減少した資源は容易に回復しない。したがって、籠の改良によって雌ガニ、子ガニの混獲死亡を軽減し、資源の再生産力を有効に利用することが望ましい。

［笹川康雄・三浦汀介］

『FAOFAO Yearbook；Fishery and Aquaculture Statistics（2008）』

[参照項目] | カニ | クモガニ

ズワイガニ〔標本画〕

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