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วันจันทร์ที่ 8 ตุลาคม พ.ศ. 2550

Bluestripe snapper

The bluestripe snapper, Lutjanus kasmira, (also known as the bluestripe sea perch) is a common species of marine fish of the snapper family Lutjanidae. The bluestripe snapper is one of the most widespread of the snappers, occupying a range from the Red Sea south to Madagascar and east to India, Asia, Indonesia, Australia and a number of Pacific Islands including Hawaii. The species is not native to Hawaii, having been introduced in the 1950s to be used as a food and sport fish; a plan that failed. Concerns have since been raised on the long term effects of this new species on the Hawaiian native species and the marine ecology in general, as the bluestripe snapper has spread throughout the islands, becoming abundant in numbers.
The species is so named due to its distinctive colouration, which consists of a bright yellow body overlain by narrow horizontal electric blue stripes. The bluestripe snapper is primarily a reef dweller living in shallow coastal areas to reefs up to 265 m deep, consuming a range of fish, cephalopods and crustaceans. Often schooling while juveniles, the adults tend to be solitary and reach a maximum known length of 40 cm.

Taxonomy

The bluestripe snapper is classified in the genus Lutjanus, which is part of the snapper family Lutjanidae. The Lutjanidae is further divided into four subfamilies, with the genus Lutjanus falling into the subfamily Lutjaninae. The Lutjanidae are Perciformes in the suborder Percoidei.[1]
The species was first scientifically described by Swedish naturalist Peter Forsskål in 1775 under the name Sciaena kasmira, with the holotype specimen taken from "Arabia", possibly the Persian Gulf. Forsskål re examined the fish and determined that he had initially misassigned it, and put it in the genus Lutjanus, creating the new combination Lutjanus kasmira, which is still the valid name in use today.[2] After Forsskål, a number of naturalists tried to reclassify the species, with Cuvier applying Diacope octolineata , Lesson Mesoprion etaape and Bleeker applied Mesoprion pomacanthus to the species. These are all considered junior synonyms and therefore invalid under the ICZN naming rules.[3]
The common names of Lutjanus kasmira are descriptive in nature, with adjectives such as bluestripe, blue-banded and blouband commonly used in front of generic names such as 'snapper' and 'sea perch'. There are a large number of local names used for the species, with the wide range of the fish the cause of so many names.[3]


Description

The body of the bluestripe snapper is moderately deep in profile, with the dorsal profile of the head steeply sloped, having a well developed preopercular notch and knob. Identifying morphological features include the number of gill rakers on lower limb of the first arch, which number 13 or 14, with the total rakers on the first arch numbering 20 to 22. The dorsal fin consists of 10 spines anterior to 14 or 15 soft rays, while the anal fin has 3 spines and 7 or 8 soft rays. The pectoral fins have 15 or 16 rays, with the caudal fin being slightly emarginate. The row of scales on the back rise obliquely above the lateral line, which contains 48 to 51 scales.[2] The species reaches a maximum length of 40 cm.[3]
The color is probably the most diagnostic feature of the fish, especially when alive or fresh from the water. The back and sides of the fish are bright yellow, with the lower sides and underside of head fading to white. Four bright blue stripes run longitudinally on the side of the fish, with several faint greyish stripes on lowermost part of sides. All fins are yellow in colour.[2]


Range and habitat

The bluestripe snapper is one of the most widespread species of the Lutjanidae, ranging from the coast of Egypt bordering the Red Sea, south to Madagascar and east to India, China, South East Asia, Australia and a number of Pacific Islands.[4] The species has also been introduced to the waters of Hawaii, causing concerns for aspects of the areas ecology.
Like many snappers, it inhabits coral reefs, occurring in both shallow lagoons and on outer reef slopes to depths of at least 60 m, but has been recorded at depths of 180 and 265 m at the Marquesas Islands and the Red Sea respectively. In Hawaii they have been reported to spend some time over seagrass and sandy substrates also.[5] They are frequently found in large aggregations around coral formations, caves or wrecks during daylight hours.[2]