Vitellogenesis, oocyte maturation pattern, spawning rhythm and spawning frequency in Otolithes rubber (Schneider, 1801) (Seiaenidae) in the Kuwaiti waters of the Arabian Gulf

Abstract

Vitellogenesis, occyte maturation pattern, spawning rhythm, spawning frequency, batch focundity and oocyte diameter-frequency distribution of the tigertooth croaker, Otolithes rubber (Shneider, 1801) in Kuwaiti waters investigated from Mrch, 1999 to February, 2000 and from January to May, 2005, using histological andmorphological methods. Oogenesis is described in four phases: vitellogenic, mature, spent and regressed. Vitellogenesis, in turn is described in three classes; early vitellogenic, mid-vitelloenicandlate vitellogenic. Development of the yolky oocyte is an asynchronous process resulting, by the time of oocyte maturation, in clear differentiation between a ready batch of oocytes (ready for spawning) and a reserve pool. Consequently, O. rubber is capable of a spawning multiple times during the reproductive seasons. Spawning frequency estimates, based on the final oocyte maturation (FOM) method indicated that the species spawns once every 2.8 days, while the estimates based on the post-ovulatory follicle (POF) method indicated a spawning every 2.2days, during a 5-month spawning seasons lasting from January to May. Batch fecundity (BF) was significantly positively correlation with both ovary-free body weight (OFBW) P < 0/05) and standard length (SL) (P < 0.05), but SL was a better predictor of BF (r2 = 33%) than as OFBW (r2 = 19.9%). Batch fecundity was also significantly different between March and April (P < 0.05) and March and May (P < 0.05), but not between April and May (P < 0.05). Relative batch fecundity was 716 eggs/g OFBW; thus, estimates for potential annual relative batch fecundity were 10024 eggs/g OFBW using the FOM method for spawning frequency estimation, and 7876 eggs/g OFBW using the POF method. The oocyte diameter-frequency distribution analysis revealed a multimodal distribution, confirming the evidence of multiple spawning.