Male reproductive biology of European hake Merluccius merluccius

The reproductive biology of European hake (Merluccius merluccius) has been studied extensively in the field, but mainly focusing on fecundity regulation in females and its implications for the fishery. The European hake is highly important commercially throughout its geographical range. Because catches have been decreasing since the 1960s, interest in hake as a potential aquaculture species has recently increased. However, for successful domestication of hake, a better understanding of its reproductive biology, including sperm biology, is needed for purposes of broodstock management and also for the development of sperm storage techniques, including cryopreservation. The objectives of this thesis were to assess hake sperm quality, including sperm production characteristics and energetics, and to characterize sperm movement parameters such as the percentage of motile cells, sperm velocity and flagellar beats. Changes of these parameters over time following activation were evaluated qualitatively for fresh hake sperm. The effects of i) salinity of the activation medium, ii) survival in relation to short term storage duration at 4°C, and iii) sperm cryopreservation on sperm motility characteristics, as well as the reliance on the sperm’s energetic content, were evaluated. In many other Gadoid species, drumming muscles are an important component of reproductive behaviour in spawning males: the contraction of these muscles associated to the swim-bladder results in an audible ‘drumming’ sound during the courtship of the females. However, the presence of drumming muscles has never been reported for hake. Mature hake collected for the sperm analyses, as well as mature females and immature individuals were thus dissected to investigate the presence of drumming muscles and the existence in mature males of potential correlations between their morphological characteristics and the sperm motility parameters.