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Fish full of fishes

By: Sally Reader, Mark McGrouther, Category: Science, Date: 30 Apr 2014

The 'fish folk' recently teamed up with James King from Photography to take x-rays of two predatory fish.  What we saw surprised us!

Checkered Snapper x-ray

James King © Australian Museum

The two fish x-rayed were Checkered Snappers, Lutjanus decussatus, and what was surprising was that their 'bellies' were full of smaller fishes (see link above for 'fish and fishes').

The Checkered Snapper had obviously been feeding shortly before they were caught. Given the completeness of the specimens in their stomachs some careful dissection could potentially increase our knowledge of the diet of this species.

The family Lutjanidae collectively known as tropical snappers (different family to the ‘Snapper’) comprises 21 genera and 123 species. They are mainly reef-dwelling marine fishes that live in tropical and subtropical waters.

Lutjanids are active predators feeding mainly at night on a variety of items including crabs, shrimps, various other crustaceans, gastropods, cephalopods and planktonic organisms.  Fishes, however, are the main component of the diet of most species. As seen in the bottom x-ray on the right, they are equipped with large canine teeth adapted for seizing and holding their prey.

Although tropical snappers are seldom the focus of major commercial fisheries, they are an important component of the local artisanal catch throughout their geographical range. The Checkered Snapper occurs in the Western Pacific and Eastern Indian Ocean from North-western Australia through to Eastern India and the Ryukyu Islands of Japan.

The fish in the x-ray are both about 20 cm long and were collected by hand over sand and coral at a depth of 3 meters from around the Mentawei Islands in Indonesia during a 1963 voyage by the research vessel R/V Te Vega, which at the time operated out of the Hopkins Marine Laboratory, California.

We often take x-rays of fish specimens as a non-invasive way of revealing the skeletal morphology of fishes for taxonomic research. This x-ray was taken for a colleague in New Zealand.

Reference:

  1. Allen, G.R. 1985. Snappers of the World. An Annotated and Illustrated Catalogue of Lutjanid Species Known to Date. FAO Species Catalogue. Vol. 6. FAO. Rome. Pp. 208, Pl. I-XXVII.
  2. Hoese, D.F., Bray, D.J., Paxton, J.R. & G.R. Allen. 2006. Fishes. In Beesley, P.L. & A. Wells. (eds) Zoological Catalogue of Australia. Volume 35. ABRS & CSIRO Publishing: Australia. parts 1-3, pages 1-2178.

Tags Lutjanus decussatus, Checkered Snapper, Lutjanidae, x-ray, gut contents, prey, fishes, ichthyology,