The historic range of Rio Grande silvery minnow includes the Rio Grande and Pecos rivers in New Mexico and Texas, down to the Gulf of Mexico. Rio Grande silvery minnow are the last of five species with similar life histories as pelagic spawners that still exist in the Rio Grande.
Rio Grande silvery minnow prefer large streams with slow to moderate current flowing over silt or silt/sand substrate. Rio Grande silvery minnow typically occupy stream habitats where water depths are less than 15.75 inches and have low to moderate velocity. Such habitats include eddies formed by debris piles, pools, backwaters, embayments, shoreline, and submerged vegetation.
Rio Grande silvery minnow are considered herbivores based on its anatomy, an elongated intestinal tract. Its diet consists of algae, but may include macroinvertebrates indirectly eaten while foraging on plant material.
The maximum total length for the Rio Grande silvery minnow is about 4.6 inches.
Rio Grande silvery minnow are pelagic spawners, which means they release semi-buoyant eggs that drift in the river’s current just below the surface. Reproduction normally consists of several spawning episodes over a 12-hour period by an individual, with the spawning season lasting one to two months.
Spawning behavior includes male Rio Grande silvery minnow pursuing a single female. If a female minnow is ready to spawn, a single male will nudge her abdominal region and then wrap himself around the female. Usually, around this time, eggs and milt are released simultaneously by the female and male Rio Grande silvery minnow.
Rio Grande silvery minnow eggs hatch within 24 to 48 hours of being fertilized, depending on water temperature. The warmer the water, the quicker the eggs develop. Water temperature also influences how quickly the Rio Grande silvery minnow go from passively drifting larvae to actively swimming larvae, which can be four to seven days after hatching. The larvae are mature and ready to spawn by the following spring.
Most Rio Grande silvery minnows live only about 18 months in the wild, but some can live up to 3 years.
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