Ecological Survey of Guadalupe River at Wagon's Ford, Guadalupe River, Comal County, TX

On 1/13/18, I made limited biological observations from the Guadalupe River in the vicinity of the Wagon's Ford camping area (Project Locality E, 29.871053, -98.482327).

I was notified upon entering the park that TPWD had released rainbow trout in the river at the park that day, and that many anglers were present.

Conditions were sunny with little or no wind all day, and temps during sampling were in the low to mid 50's. Sampling took place from around 2:00 pm to 4:00 pm.

Two general localities were sampled: E-1 (a fast, shallow riffle, just downhill from the Wagon's Ford Campground), and E-2 (long, slow pool immediately downstream of locality of E-1)

Aquatic Sampling in Riffle (Locality E-1): ~ 2 minutes of kicking rocks in fast riffle, roughly 12 inches deep, into macro net, positioned immediately downstream. Flipping rocks by hand produced abundant Isonychiid mayflies and several dobsonfly larvae, but no fish or crayfish. Time was spent looking for darters, but none were observed, despite perfectly clear water and seemingly favorable water/environmental conditions. Some small fish were seen, but appeared to either be Cyprinids or Poeciliids.

Notable observations from riffle samples:

• By in large, predominant macroinvertebrate taxa present was Isonychiidae (Brush-Legged Mayflies). Specimens were impressively abundant. Estimated percentage of total collection comprised of this taxa is roughly 80-90%.
• Corydalus (dobsonfly) larvae were present. 3 specimens were roughly 25-30 mm in length, but one specimen was over 80 mm.
• Hydropsychidae (net-spinning caddisflies) abundance was high relative to collections made in Boerne area localities. Approximately 10-15 specimens were collected and observed.
• Chironomids (non-biting midges) were present, but relatively sparse.
• A small number of Heptageniids (stream mayflies) and other non-Isonychiid mayflies were observed and collected, but the samples were misplaced. Non-Isonychiids comprised an estimated 10% of mayflies observed.

-Small number of apparent Corbicula juveniles were collected. One small gastropod was collected, but sample was lost and specimen was not analysed. No other mollusks were noted.

Aerial Sampling (Locality E-1): A few minutes were dedicated to collecting flying insects along the bank adjacent to the riffle mentioned above. The sample consisted of roughly a dozen Chironomid adults.

Aquatic Sampling (Locality E-2): roughly 10 minutes was devoted to collecting from benthos and submerged roots in long, slow pool , approx 3'-4' deep, which was immediately donwstream of riffle described above. Submerged leafpacks were stirred and then netted. Samples were not analyzed or sorted carefully, but only one specimen was apparent when sample was observed: a single Macromiid (cruiser dragonfly) nymph. Submerged roots were scraped with net, but produced no immediately apparent macroinvertebrates.

Aerial Sampling (Locality E-2): Around 3:30 pm, a mayfly hatch was observed at the surface of the long, slow pool described above. imagos and subimagos were abundant, but only a short time was dedicated to collecting these adult specimens, and only two were captured and observed.

Publicado el enero 15, 2018 03:29 MAÑANA por mattgeo1990