Reproductive Output of Gulf Killifish at Different Stocking Densities in Static Outdoor Tanks

Abstract

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.

Contaminants reduce male contribution to reproduction at the population scale

“…The finding of no direct impact of male physical characteristics was unexpected. A positive relationship has been shown between body size, GSI and reproductive output (number of eggs or sperm produced) in several fish species (Kang et al 2003, Green et al 2010). In most fish, an exponential increase in reproductive output is expected as fish mass increases (Tarnada and Iwata 2005).…”

Diet-Induced Fatty Acid Variation in Critical Tissues of a Spawning Estuarine Fish and Consequences for Larval Fitness

“…Rates of lipid mobilization for vitellogenesis are assumed to be high during reproduction in F. grandis. Fractional spawning events produce small groups of relatively large eggs (Patterson et al 2013) over a protracted spawning season (Green et al 2010), with vitellogenic periods as short as 2 d for individual oocytes (Hsiao and Meier 1988). As a consequence, variations in lipid composition of food consumed immediately before and during spawning have the potential to greatly influence larval physiology.…”

Metabolic and embryonic responses to terrestrial incubation of Fundulus grandis embryos across a temperature gradient

“…The number of terrestrially incubated viable L. tenuis embryos decreased over time as treatment temperature increased (Smyder & Martin, ). At temperatures exceeding 28° C, the quantity and viability of F. grandis embryos decreased under aquatic incubation conditions (Green et al , ). Greeley & MacGregor () observed increasing gonado‐somatic index values in Alabama populations of F. grandis when temperatures warmed from 9 to 19° C, with a decline in reproductive activity when temperatures in the summer months exceeded 25° C. The temperature‐driven decline in viability would negatively affect embryos incubating at 30° C in this study, as their extent of incubation was c .…”

“…Broodstock were held in 12 outdoor tanks at the Louisiana State University Agricultural Center Aquaculture Research Station at 28·3 ± 0·1° C (mean ± s.e .). Twelve spawning mats as described by Green et al (; Spawntex, Blocksom and Co.; http://www.blocksom.com) were placed overnight in tanks containing brood stock to obtain embryos. Embryos were manually removed and dead and pigmented embryos were discarded.…”