Spawning of captive Senegal sole (Solea senegalensis) under a naturally fluctuating temperature regime

Senegal sole aquaculture is at present limited due to poor reproduction of captive breeders in many facilities. Temperature seems to play an important role in controlling reproduction of Solea senegalensis, and differences in temperature regimes followed by various hatcheries are likely to be responsible for lack of success in some of them. This work describes the reproduction of captive soles, held in facilities that used water at ambient temperature, from a marshy environment where this species naturally breeds. Acclimated sole breeders were kept for two consecutive years. The main spawning period occurred from February to May, with a secondary spawning in autumn. Total yearly fecundity ranged from 1.15 x 10(6) to 1.65 x 10(6) eggs kg(-1) body weight. Of the total egg batches produced, only 5.4% corresponded to autumn spawns. The male population was found to produce sperm all year round, with a maximum proportion of 100% occurring in spring, and a minimum proportion of around 50% in summer. Females showed the more developed ovary stages from October to May, with partial regression in the summer months. During the main spawning period, eggs were produced between 46% and 69% of days. Spawning took place at temperatures from 13 to 23 degreesC, although higher fecundities (P<0.05) occurred between 15 and 21 degreesC. Within the range between 17 and 20 degreesC, the mean number of spawned eggs was 29,600+/-21,600 eggs day(-1) kg(-1). Most of the eggs (65-73%) were produced after temperature increased up to 2.5 degreesC within 3 days prior to spawning. Mean egg fertilization was 63.1+/-17% (year 2002) and 44.9+/-18% (year 2003), and hatching rates varied from 69.7+/-24% (2002) to 56.5 +/- 25% (2003). Weak correlations were found between either fertilization or hatching and fecundity, whereas a positive regression (P<0.05) indicated that higher hatching rates were achieved when fertilization increased. A weak, but significantly (P<0.05) positive correlation was found between egg fertilization and the spawning temperature. Present results indicate temperature is an important control factor for reproduction of S. senegalensis, and suggest it can be used to properly manage controlled captive reproduction of this species. (C) 2004 Elsevier B.V. All rights reserved.