¶ … Fish Speciation: Brazos River and Lake Bryan The sample areas of the Brazos River and Lake Bryan showed clear differences, but also shared a few similarities. The primary difference was the size of the species, which is based on factors including the style of gear used that can tend to skew size of collected populations and the available macroinvertebrates for food. In the Brazos River, there were much smaller diameters of fish recorded, based on the potential for seine and gill net methods do tend to catch smaller species and high presence of the smaller caddis fly. On the other hand, Lake Bryan showed much larger species of fish, possibly based on the increased presence of the mayfly larvae and the environmental conditions of the lake that provide better for larger, predatory fish. Still, since both locations had fewer mosquito larvae, they both showed low levels in mosquito fish. Ultimately, it was the available food source present that tended to define the number of populations seen in the samples collected.

The Brazos River saw larger number of smaller fish species. Reports from the river show a high number of red shiners, or Cyprinella lutrensis, and the Pimpephales vigilax, or the bullhead minnow. These species are relatively small in size compared to other freshwater species. A number of factors can lead to this higher population reading of such small freshwater species. This research used gill nets and...

Typical designs include a hauled net that swoops through the water. However, the "configuration of nets currently used do not exhibit optimum selectivity, often retaining large numbers of small fish, including juveniles of the targeted species" (Gray, Larsen, & Kennelly, 2000). Prior studies using similar methods generally show a much smaller fish population collected, typically from midsize of the target to juvenile. Moreover, there was a higher recording of the caddisfly present in the river, which was the primary macroinvertebrate. This tends to be a popular food source for smaller species, such as the ones found in the current sample (Wiggins, 2015). As the larvae are smaller, they are a primary food source for smaller fish species throughout the growth cycle. Ultimately, both the primary food source and gear methods used in the collection of species may have resulted in the higher presence of smaller species compared to those seen at Lake Bryan. Still, there were still a high number of mayflies collected as well, suggesting that the conditions of the river itself may be an impact on the smaller species more prevalent compared to Lake Bryan (Wetzel, 2001).
In fact, Lake Bryan saw a much larger number of larger species. The reports from Lake Bryan show a much higher ratio of larger fish. The primary species present in the sample included Lepomis macrochirus, or Bluegill, and…