REPRODUCTIVE HORMONE PROFILING IN BALLAN WRASSE Labrus bergylta DURING NATURAL CYCLES AND SPAWNING INDUCTION
Ballan wrasse is a candidate cleaner fish for controlling sea lice in salmon aquaculture. But to realise this potential, a degree of control is required over its sustainable production. Amongst the many challenges associated with this goal is a requirement for improved control over wrasse reproduction (it has a single discrete annual spawning event) and more knowledge about manipulation of natural spawning physiology (wrasse is a protogynous sex-changing species i.e. female first). An extended study was carried out into sex steroids during the natural hormonal cycle of female ballan wrasse at Carna Research Station, in the west of Ireland. Monthly profiles of sex steroids (estradiol, testosterone, progesterone and cortisol) from 10 randomly selected captured fish each month were examined using ELISA from April 2010 to October 2011 in addition to microscopic evaluation of gonado-somatic and hepato-somatic indices. A hormonal induction trial also took place in April and May 2011 during which spawning was induced using gonadotropins and their analogues (LHRHa, hCG, Ovaprim and control injections). Sex steroids were again examined, this time before and after induction. In total, 190 fish of monthly sex steroid profiles including 96 fish captured in 2010 and 64 fish captured in April and May 2011 for spawning induction were randomly selected and examined in three size categories. Spawning induction on various treatment groups showed hCG to have very significant results over LHRHa and Ovaprim in producing viable eggs and larvae. Egg quality was relatively higher in hCG treatments compared to Ovaprim treatments. Cortisol levels were relatively high compared to estradiol, testosterone and progesterone regardless of body size and type of hormonal treatments and stress in captivity as well as body condition were also important factors influencing spawning. The results showed that injection of hCG and Ovaprim can induce spawning in ballan wrasse without negative effects on egg and larval quality. The results will be discussed in the context of sex steroids profiles before and after spawning induction as well as during the natural hormonal cycle.