1. Introduction
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