Changes in Mesopotamian spiny eel, Mastacembelus mastacembelus (Bank & Solender in Russell, 1794) (Mastacembelidae) milt quality during a spawning period E. S ¸ahino ¨z a , F. Aral b, * , Z. Dog ˘u a a Harran University, Bozova Vocational School Department of Fisheries, Bozova, Sanliurfa, Turkey b Department of Reproduction and Artificial Insemination, Faculty of Veterinary Medicine, Harran University, 63300 Yenisehir, Sanliurfa, Turkey Received 28 February 2006; received in revised form 30 October 2006; accepted 5 November 2006 Abstract This study was carried out to determine the milt quality in male Mesopotamian spiny eel (Mastacembelus mastacembelus; Bank & Solender in Russell, 1794) during spawning season. Review was performed using 58 M. mastecembulus males captured from Atatu ¨rk Dam Lake in Turkey. Milt samples were collected and evaluated daily during sampling period. In collected milt, volume of milt, sperm motility percentage, the duration of forward motility, sperm concentration, milt production and milt pH were evaluated. On June 10, 2005, 72% of the males were spermiating, which increased to 100% in the middle of June and dropped to 72% by late June. Sperm motility percentage showed a significant improvement after beginning of spermiation (P < 0.001). Sperm concentration changed significantly (P < 0.001) in milt collected during sampling period. Duration of sperm motility increased significantly (P < 0.001) from beginning (8.22 min) through end (37.33 min) of spermiation. Milt production was maximal on June 15th, decreasing from a mean value of 3.12–0.46 Â 10 9 /ml. The high pH in milt was observed during the week of spermiation (P < 0.001). In conclusion, the results show that season has a significant influence on semen quality in male M. mastecembulus corresponding to spawning season in hot arid. Milt of good quality was especially collected in the middle of June. Spawning season in this fish species was found to be short. # 2006 Elsevier Inc. All rights reserved. Keywords: Mesopotamian spiny eel; Mastacembelus mastacembelus; Milt 1. Introduction The Mastacembelus mastecembulus (M. mastacem- belus, Bank & Solender in Russell, 1794), which is a demersal fish species of economic importance for aquaculture, inhabits the Atatu ¨rk Dam Lake, Euphrates River System. There are a few studies on M. mastacembelus and its subspecies, which belong to Mastacembelidae. Few studies have been carried out on the biology of M. mastacembelus and its subspecies, which belong to Mastacembelidae, including systematic [1], feeding habits and carbohydrate accumulation in mucus cells [2] and age estimation and growth rate [3]. Milt production of fishes is influenced by many factors, such as species, age, environment (daylight length, water temperature), which result in great variations of milt characteristics [4,5]. Additionally, www.theriojournal.com Theriogenology 67 (2007) 848–854 * Corresponding author. Tel.: +90 414 312 84 56; fax: +90 414 314 41 58. E-mail addresses: faral@harran.edu.tr, faral6@hotmail.com (F. Aral). 0093-691X/$ – see front matter # 2006 Elsevier Inc. All rights reserved. doi:10.1016/j.theriogenology.2006.11.001