Effect of treatment with LHRH analogue on oocyte maturation, plasma sex steroid levels and egg production in female striped trumpeter Latris lineata (Latrididae)

Striped trumpeter Latris lineata (Schneider, 1801) are currently being inve stigated for their aquaculture potential. Little is known of the reproducti ve physiology of this fish and a limited supply of eggs is hindering larval rearing trials. This study assessed the effect of hormone therapy to induc e ovulation in wild caught broodstock. Female striped trumpeter were implan ted with 0, 100 or 200 mu g kg(-1) body weight of a synthetic luteinizing h ormone releasing hormone analogue (LHRHa: des-Gly(10), [D-Ala(6)]-LH-RH eth ylamide), administered in a slow release cholesterol pellet (n = 12 per tre atment). Blood and ovarian samples were collected daily from each fish, and the volume of eggs produced was recorded. Plasma levels of testosterone (T ), 17 beta-oestradiol (E-2) and 17 alpha 20 beta-dihydroxy-4-pregnen-3-one (17,20 beta P) were measured by radioimmunoassay. Four, 11 and 12 fish trea ted with 0, 100 or 200 mu g kg-l LHRHa respectively, ovulated. When compare d to the control group, both LHRHa treatments resulted in significantly inc reased (P < 0.05) egg volumes overall and also on Day 4 post-implant in ter ms of daily volumes. Whilst there was no significant difference (P > 0.05) in egg volumes between the two LHRHa treatments, when combined, two groups could be defined; those fish that underwent only 'one or two ovulations' (O TO) and those that underwent 'three or more ovulations' (TMO). The OTO fish (n = II) had similar plasma steroid levels to the control fish whereas the TMO fish (rt = 12) had significantly increased (P < 0.05) plasma levels of T, E?(2)and 17,20 beta P, with peaks occurring on Day 1 for T (4.8 ng ml(- 1))and on Day 2 for E-2 and 17,20 beta P (2.2 and 1.3 ng ml(-1), respective ly). Twenty-one of the 24 LHRHa-treated fish first ovulated on Day 4 and, i n the TMO fish, subsequent clutches of eggs were produced approximately eve ry 3 days for up to 5 cycles. Oocyte recruitment appeared to originate from pre-vitellogenic oocytes from the third clutch onward. This work identifie d female striped trumpeter as multiple spawners with group synchronous oocy te development and showed LHRHa to be an effective stimulant for the induct ion and synchronization of ovulation. (C) 1998 Elsevier Science B.V. All ri ghts reserved.