Broodstock of Gulf killifish Fundulus grandis (initial mean [6SD] weight ¼ 8.2 6 1.6 g) were held in static outdoor tanks at a 2:1 (female : male) sex ratio and at densities of 15, 30, or 45 fish/m 3 . Eggs were collected twice per week from spawning mats suspended 8 cm below the water surface. Collected eggs were measured volumetrically and assessed for total number, egg size, and embryo viability. Significantly more eggs were collected from tanks with manufactured (Spawntex) spawning mats than from tanks with cured Spanish moss spawning mats. Significant differences in the mean number of eggs collected were present among density treatments in April, June, and July. Stocking density was also associated with mortality; the greatest mortality was observed in tanks at the highest density (45 fish/m 3 ). There was a clear pattern in egg production in relation to lunar phase, with egg production peaks occurring between full and new moon phases for all three stocking densities. Mean gonadosomatic index values differed significantly among sampling months for both females and males. Analysis of ovaries via histological sections indicated trends in oocyte stages that correlated to continued egg production for this fractionally spawning species. Peak egg production occurred between April and mid-May, when mean (6SD) weekly water temperatures ranged from 23.8 6 1.78C to 28.2 6 1.28C. During April, the mean daily number of eggs collected translated to a reproductive output of approximately 0.90, 0.72, and 0.76 eggs/g of female for stocking densities of 15, 30, and 45 fish/m 3 , respectively. Based on egg output and mortality over the 5-month spawning period, the intermediate density (30 fish/m 3 ) appeared to provide the optimum number of eggs per individual over time for Gulf killifish broodstock held in static outdoor tanks at a 2:1 female : male sex ratio.

Gulf killifish Fundulus grandis have evolved the ability to utilize air incubation in marsh grass to protect embryos from aquatic predators and allow for synchronous hatching during the following diurnal peak tide. This incubation strategy provides a humid, oxygen‐rich environment for the embryos to develop. The current project investigated practical materials that could be used in an aquaculture setting to mimic the air incubation strategy at different salinities, and determined the effect of substrate (moistened with 7.5‐g/L salinity water) on embryo size after an extended incubation period (19 d) at 22°C. Air‐incubated embryos were placed on synthetic foam, bamboo batting, or burlap cloth substrates. Substrates were moistened with 3.5‐, 7.5‐, 14‐, 20‐, or 27‐g/L‐salinity water, and hatching was induced by submersion in water after 19 d of incubation. Embryos incubated in water (3.5‐ and 7.5‐g/L salinity) at the same temperature began hatching at 8 d and continued intermittently until 14 d. These water‐incubated embryos had a hatch rate (mean ± SE) of 44.2 ± 1.1% in 3.5‐g/L‐salinity water and 49.1 ± 0.5% in 7.5‐g/L‐salinity water. The percentage of air‐incubated embryos that hatched was significantly affected by both substrate and salinity. For all air incubation substrates, the 7.5‐g/L salinity treatment provided the numerically highest overall percentage of hatched embryos, 69.9 ± 3.6%, 69.9 ± 6.5%, and 73.8 ± 4.6% hatching on foam, bamboo, and burlap, respectively. Overall, the foam substrate had the highest hatch rate among salinity treatments. Embryo size at hatch was assessed at the 7.5‐g/L salinity for water and all air incubation substrates. The air‐incubated larvae were found to be significantly larger than their water‐incubated counterparts, and foam‐incubated larvae had the smallest abdominal area. Air incubation of Gulf killifish eggs on foam substrate can be used as a production tool to produce larvae that can be synchronously hatched after an extended incubation period.

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Gulf killifish Fundulus grandis broodstock (7.3 ± 0.2 g [mean ± SE]) were held in static outdoor tanks at a 4:1 (female : male) sex ratio and a density of 20 fish/m3. Shade cloth was used to cover 0, 40, or 80% of the surface area of 12 randomly selected outdoor tanks. Eggs were collected from all tanks twice per week by using spawning mats suspended 15 cm below the water surface. Collected eggs were measured volumetrically and assessed for total number and embryo viability. The use of shade cloth had a significant effect on water temperature, the number of eggs collected, and embryo viability. Specifically, shading affected mean weekly water temperature, and the 80% treatment had significantly lower temperatures than both the 0% and 40% treatments during the months of June through August and than the 0% treatment in September. There was a clear cyclical reproductive pattern across all treatments, in which peaks in egg production occurred between the full and new moon phases for the majority of collection dates. Significant differences in the mean number of eggs collected among shade cloth treatments were present only for the month of September, when the 80% treatment produced significantly fewer eggs. The proportion of viable embryos was significantly higher for the 80% treatment than for the other treatments for the months of June, July, and August. The use of shade cloth during the summer months can increase the number of viable embryos produced during the summer depression of the protracted, bimodal spawning season of cultured Gulf killifish.