In nature, African catfish, Clarias gariepinus, has a
discontinuous annual reproductive cycle with alternate periods of resting, pre-spawning and breeding, regulated by cyclically active gonadotrophes [1]. The breeding season correlates with periods of maximal rainfall and a pre-spawning LH surge takes place at least once during this period [2]. Spawning occurs usually during the scotophase, after rain in recently inundated marginal areas.
In captivity, catfish are kept under constant environmental conditions. Throughout the year, their pituitaries contain large and densely granulated gonadotrophes, storing large amounts of LH [3].
Under laboratory and fish-farming conditions, the natural cues are difficult to mimic. Over the last few