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Cultured Senegalese sole (Solea senegalensis) breeders fail to spawn fertilized eggs. The implantation of large-scale in vitro fertilization protocols, to solve this problem, has been frustrated by low production of poor quality sperm. Cultured females were induced to ovulate with a 5 µg kg−1 single injection of gonadotropin-releasing hormone agonist (GnRHa) and viable eggs (82.6 ± 9.2% fertilization) were stripped 41:57 ± 1:46 h after the injection. Sperm was collected from cultured males, diluted in modified Leibovitz and used fresh to fertilize the eggs. Males were not treated with hormones. A nonlinear regression, an exponential rise to a maximum (R = 0.93, p < 0.0001) described the number of motile spermatozoa required to fertilize a viable egg and 1617 motile spermatozoa were sufficient to fertilize 99 ± 12% (±95% CI) of viable eggs. Similar, spermatozoa egg−1 ratios of 592 ± 611 motile spermatozoa egg−1 were used in large-scale in vitro fertilizations (190 512 ± 38 471 eggs). The sperm from a single male (145 ± 50 µl or 8.0 ± 6.8 × 108 spermatozoa) was used to fertilize the eggs. The mean hatching rate was 70 ± 14% to provide 131 540 ± 34 448 larvae per fertilization. The viability of unfertilized eggs stored at room temperature decreased gradually, and the sooner eggs were fertilized after stripping, the higher the viability of the eggs. The collection of sperm directly into a syringe containing modified Leibovitz significantly increased the percentage of motile spermatozoa (33.4 ± 12.2%) compared with other collection methods. The spz egg−1 ratios for Senegalese sole were at the lower end of ratios required for fish. Senegalese sole have a pair-spawning reproductive behaviour characterized by gamete fertilization in close proximity with no sperm competition. The provision of a large-scale in vitro fertilization protocol (200 µl of sperm per 100 ml of eggs) will enable the industry to operate sustainably and implement breeding programmes to improve production.

Anisotremus scapularis is a marine fish distributed along the Peruvian coast that is commercially important in local markets. IMARPE started research on this species aimed to condition breeders and control reproduction in captivity and avoid dependence on wild broodstock. Therefore, the present study characterized and compared the reproductive performance, quality of eggs and larvae between a first generation domesticated broodstock (F1B) and a wild broodstock (WB). The F1B and WB broodstocks were conditioned in recirculation systems (RAS) to spawn naturally from August 2021 to August 2022. The following parameters were recorded for each spawn, the total number of eggs, percentages of viable eggs and fertilization, and hatching, and biochemical analyses on each spawn were performed. Progeny from each spawning were assessed for survival activity index (SAI), and at 20 days’ post-hatch (DPH), the temperature tolerance index (TTI) was analyzed. WB had significantly higher (P