Take a look at fishbase info below. They could be gams (cant tell from pic) . Usually gams don't have large broods like that.

http://fishbase.org/Reproduction/FishRep...;StockCode=3411


Reproduction of Gambusia affinis
Document source: http://fishbase.org/Reproduction/FishRep...;StockCode=3411

Main Ref. Seale, A., 1917

Mode dioecism
Fertilization internal (oviduct)
Spawning frequency No obvious seasonal peak
Batch spawner Ref.
Reproductive guild bearers
internal live bearers
Description of life cycle and mating behavior The species is viviparous (Ref. 5258). Internal fertilization is possible because the anal fin of the male is modified into a copulatory organ. The females carries about 30 alevins and gestation lasts for a period of 24 days (Ref. 6348) to a month (Ref. 30578).
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http://fishbase.org/Reproduction/FishRep...;StockCode=5109

Reproduction of Gambusia holbrooki
Document source: http://fishbase.org/Reproduction/FishRep...;StockCode=5109

Main Ref. Wischnath, L., 1993

Mode dioecism
Fertilization internal (oviduct)
Spawning frequency
Batch spawner Ref.
Reproductive guild bearers
internal live bearers
Description of life cycle and mating behavior Matures at 4-6 weeks; 3 generations can be produced in one year. Gestation lasts 3-4 weeks. Brood may reach up to 354 young, but is generally around 40-60 (Ref. 1672, 59043).
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