Naso thynnoides (Cuvier 1829)

Body elongate-ovate. Dorsal and anal profiles nearly even. Forehead without rostral prominence when in adults. Peduncular plate single, with a semicircular, retrorsely curved keel. Reaches 35 cm SL.Description: Characterized further by overall pale grey body color; side of body with broad yellowish zone and numerous thin bluish-grey bars; greatest depth of body 2.8-3.2 in SL (Ref. 90102).

Dorsal spines (total): 4; Dorsal soft rays (total): 28 - 30; Analspines: 2; Analsoft rays: 27 - 29

Generally uncommon species found in steep outer lagoon and seaward reef slopes (Ref. 9710, 48637). Maximum depth reported at 40m (Ref. 37792) Occurs singly or in large schools (Ref. 9710, 48637). Usually seen swimming steadily along upper edges of drop-offs in pursuit of plankton (Ref. 48637). A semi-pelagic fish that feeds on zooplankton, but remains over or near reefs. Also feeds on algae (Ref. 30573). It is cleaned by Labroides and sleeps on reefs at night, taking on a disruptive mottled pattern (Ref. 10671). Caught with nets (Ref. 30573).

fisheries: commercial; aquarium: commercial

分布於印度-西太平洋區，由非洲東部至巴布新幾內亞，北可至日本南部。台灣發現於南部及東部離島海域。

一般以流刺網、延繩釣或潛水鏢魚法等捕獲。觀賞及食用兼具。剝皮後，煮薑絲湯，肉質鮮美。尾柄上骨質盾板非常銳利，易傷人，處理時需小心。

體呈長橢圓形而側扁；尾柄部僅有一個盾狀骨板，有一個龍骨突。頭小，頭背弧形，隨著成長，成魚在前頭部無角狀起，亦無瘤狀突起。口小，端位，上下頜各具一列齒，齒稍側扁且尖銳，兩側或有鋸狀齒。背鰭及臀鰭硬棘尖銳，分別具IV棘及II棘，各鰭條皆不延長；尾鰭彎月形，上下葉緣不延長如絲。體背側呈深褐色，腹側深色，體側具不顯且大小不一之垂直細紋；尾鰭一致為暗色，基部具白色斑塊。骨板基部同體色。

為半大洋性魚種，但一般活動於近岸。主要棲息於較深的潟湖或礁區斜坡海域，棲息深度在40公尺以內，較少見到。以浮游動物為食。

Naso thynnoides is a tropical fish found in coral reefs in the Pacific and Indian Oceans. It is commonly known as the oneknife unicornfish, oneknife unicorn, thunny unicornfish, singlespine unicornfish, one-spine unicorn, or barred unicornfish. It is of value in commercial fisheries, and is also used in aquaria.

Inhabits rocky areas and coral reefs.