Short communication On the record of pug-headedness in cultured Atlantic salmon, Salmo salar Linnaeus, 1758 (Salmoniformes, Salmonidae) from Norway By L. A. Jawad 1 , A. Kousha 2 , F. Sambraus 3 and P. G. Fjelldal 3 1 Flat Bush, Auckland, New Zealand; 2 Norwegian College of Fisheries Science, The Arctic University of Norway, Tromsø, Norway; 3 Institute of Marine Research (IMR), Matre Research Station, Matredal, Norway Introduction Fish developmental anomalies occur in hatchery-raised and wild fish populations. Dawson (1964, 1966, 1971) prepared comprehensive bibliographies of reported abnormalities. Pug- headedness is an anomalous condition in fish that has been reported in a broad variety of fish groups (Manusueti, 1960; Dawson, 1964, 1966, 1971; Warlen, 1969; Dawson and Heal, 1971; Nakamura, 1977; Shariff et al., 1986; Al-Hassan and Na’ama, 1988; Jawad and Hosie, 2007). The condition affects the skeletal formation of the head, particularly that of the upper jaw, resulting in an abnormally shorter upper jaw in relation to the lower jaw. In 1553, the French naturalist Pierre Belon (in Gudger, 1930) published the first figure of a pug-headed female sal- monid, and Buckland (1877) is considered to have published the earliest account on pug-headedness in salmonids. Since 1553, just over 120 published works have reported on this condition in different species of fish, mostly from Europe and North America (Dawson, 1964, 1966, 1971; Dawson and Heal, 1971). This is the first report of pug-headedness in a cultured salmonid, Salmo salar from Norway. Materials and methods The pug-headed salmon, S. salar (age 3) in the present study is a triploid Atlantic salmon that originated from a popula- tion of diploid and triploid siblings fertililized on 3 December 2008 at the Institute of Marine Research, Matre, Norway. A mixture of eggs from three females was fertilized with a mix- ture of the milt from three males (Aquagen strain; Aqua Gen AS, Trondheim, Norway). The eggs were incubated at a natu- ral water temperature (~6°C), first-fed at an elevated tempera- ture (~11°C), and then switched to a natural temperature in June 2009. These fish were produced as under-yearling smolts and transferred to seawater on 1 October 2009. Reared in tanks with 15°C seawater (34 ppt) until 21 January 2010, they (n = 400 per ploidy) were then pit-tagged (Trovan transpond- ers ID 101; BTS Scandinavia AB, Åhus, Sweden) and trans- ferred to one 5 9 5 9 7 m sea-cage under natural light for common rearing. The sea-cage temperature was stable at ca. 8°C until early March 2010, when it decreased to 4°C over a 14-day period. Thereafter the water temperature increased gradually to 18°C in early September 2010, and then decreased gradually to 5°C until sampled on 1 March 2011, when the stocking density was 12 kg/m 3 . The fish were fed commercial Skretting (Skretting AS, Stavanger, Norway) diets throughout the study. An abnormal and a normal sal- mon specimen were obtained from the same stock for com- parison and deposited in the fish collection of the Institute of Marine Research (IMR), Matre Research Station, Matredal, Norway. When the fish were screened for occurrence of the studied deformity on 1 March 2011, 0.3% (n = 1) of the dip- loids and 1.3% (n = 5) of the diploids had this phenotype. They were all classified clearly as pug-headed when they were pit-tagged on 21 January 2010 (~270 g). Results The pug-headed specimen had a 546 mm total length, 503 mm standard length, 13 mm preorbital length and 26 mm postorbital length. This specimen is compared to nor- mal fish having 490 mm total length, 460 mm standard length, 23 mm preorbital length and 36 mm postorbital length. The abnormal specimens were shown to have short neu- rocranium and upper jaw, and a normal lower jaw (Fig. 1) with a nearly absent snout and asymmetrical upper and lower jaws. The mouth was virtually closed by a flap of skin, leaving only a small opening. On the right side of the head, the pre-maxilla was deformed, twisted downward and for- ward. The left side of the premaxilla was normal. The lower jaw was slightly distorted to the left. The shortening of the snout had brought the steep forehead close to the eye and moved the anterior nostril ventrally towards the mouth. The osteological deformity was compared with the normal specimen. Internally, the vomer, parasphenoid, and maxillar- ies were shortened, and displacement and/or curvature of the nasals, frontals, vomer, and palatines were observed. The teeth in the upper jaw curved backward and stuck together instead of being projected downward. For these reasons, the forehead is upraised and steep in the pug-headed specimen (Fig. 1a,b). U.S. Copyright Clearance Centre Code Statement: 0175-8659/2014/3003–537$15.00/0 J. Appl. Ichthyol. 30 (2014), 537–539 © 2014 Blackwell Verlag GmbH ISSN 0175–8659 Received: October 6, 2013 Accepted: October 28, 2013 doi: 10.1111/jai.12403 Applied Ichthyology Journal of