Tree cluster - Kitsukimure

…Tunas often swim in schools on the surface of ocean currents, and sometimes they swim with other creatures or drifting objects, each of which is given a special name. For example, a school that follows whale sharks is called a "shark-attached school," one that follows whales is called a "whale-attached school," one that follows drifting timber is called a "tree-attached school," and one that follows a flock of birds is called a "bird-attached school." Also, a school that chases prey is called a "prey-bearing school," and a school of tuna swimming by itself is called a "sunamura" (spontaneous school). …

*Some of the terminology that refers to "tree-attached groups" is listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

…カツオはよく海流の表層を群れて泳ぐが，その際他の生物や漂流物といっしょに泳ぐことがあり，それぞれ特別な名称がつけられている。例えば，ジンベイザメにつく群れを〈サメ付き群〉，クジラにつくものを〈クジラ付き群〉，漂流木材につくものを〈木付き群〉，鳥の群れについているものを〈鳥付き群〉といったりする。また，餌生物を追いかけるものを〈餌持ち群〉といい，カツオだけで群泳するものを〈素群（すなむら）〉という。…

※「木付き群」について言及している用語解説の一部を掲載しています。

出典｜株式会社平凡社世界大百科事典 第２版について | 情報