Due to stock declines there is a growing interest in farming of European hake Merluccius merluccius. Thus, knowledge of its sperm biology is of importance not only for purposes of broodstock management, but also for the development of sperm preservation techniques. Hake sperm were collected from mature males caught during the summer-early autumn waters off western Norway and during the winter-early spring in the Bay of Biscay (France). Sperm quality characteristics were assessed after storage at 4 degrees C for 25 +/- 14 h. Average (+/- SD) values for Norwegian and French samples respectively were (i) sperm volume: 3.9 +/- 4.0 and 2.6 +/- 4.0 ml; (ii) spermatozoa concentration: 6.6 +/- 3.2 and 13.9 +/- 5.1 x 10(9) spermatozoa/ml; (iii) spermatocrit: 80.2 +/- 3.3 and 81.8 +/- 10.7%; and (iv) total number of spermatozoa: 23.5 +/- 30.0 and 35.1 +/- 36.2 x 10(9). Average osmolality and pH (+/- SD) of French samples were 349 +/- 28 mOsmol/kg and 7.6 +/- 0.1, respectively. Activation by transfer into full sea water (100 SW) or 10% ovarian fluid in sea water (10 OF) occurred synchronously for virtually all spermatozoa and the percent sperm motile decreased with post activation time. When transferred into 50% sea water diluted with distilled water (50 SW) only a few spermatozoa were activated initially but subsequently reached a maximum percentage of motility followed by a decline. Hake sperm motility declined rapidly to 50% of motility 70 s after activation with 100 SW. Sperm were motile for longer when activated with 50 SW (1570 +/- 295 s) or 10 OF (718 +/- 71 s) compared to 100 SW (317 +/- 121 s). Undiluted hake sperm stored at 4 degrees C up to 10 days retained 10% motility when activated with 100 SW. When cryopreserved, the motility recovery index of the cells at thawing ranged from 0 to 76.4%. These results describe for the first time the sperm traits of European hake following successful cryopreservation, and also show the importance of activation medium on sperm motility. (C) 2010 Elsevier B.V. All rights reserved.