Diario de mattgeo1990

On Wednesday, January 3rd, I took a limited sampling of aquatic invertebrates, several fish, and flying insects. I will expand on this in the near future.

Aerial net was swept at a height of 1-8 feet above the surface of the water over an area of roughly 1000 square feet for a total of about 10 minutes.

Dip net used with kick method in very shallow riffle below water ford at Jacob's Crossing for roughly 10 minutes. Incidentally captured one male Orangethroat Darter.

Dip net was used to sweep through aquatic vegetation in slower, deeper pools and kicked-up leafpacks for total of roughly 10 minutes.

Samples collected from riffle and from pools were kept separate.

Preliminary observations:

Midge larvae were present in both riffle and pools, but were remarkably abundant in pools. Midges seemed to be the predominant taxa, followed closely by small mayflies.

Amphipods were notably absent.

Two apparently different net-spinning caddisfly taxa were abundant in the riffle, more so than in other localities in the Boerne area sampled so far.

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.

GRTU conducted a study in from Aug 2006 to July 2007 on the diet of stocked rainbow trout in the Guadalupe River downstream of Canyon Dam (Canyon Tailrace). The study found that macroinvertebrates were abundant in the river, but that overall, the fish fed primarily on algae, detritus, and gastropoda. The further downstream the fish were captured, the higher the percentage of their diet that consisted of macroinvertebrates. At site #1 (river bend roughly 1/2 mile upstream from Rio Raft), the diet consisted of roughly 25% gastropoda, and 30% LEAVES. At site 2, (deep pool in bend near island downstream of GRTU access site old #5), the diets consisted of roughly 35% isopods (sowbugs). At site 3, (Rocky Beach), the diet consisted of roughly 15% detritus, 10% ephemeropterans, 20% gastropoda, and 20% unidentified insect parts. At site 4 (near Riverbank Outfitters), the trouts' diets consisted of 40% ephemeropterans and 20% unidentified insect parts. Algae made up roughly 20-25% of the stomach contents of the fish at three of four localities, but only 15% of the diet at site 4.

Macroinvertebrate samples were collected from the river by various methods. Predominant taxa collected in drift nets at sites 1-3 included: Chironomidae, Baetidae, Simuliidae, Isonychia, Stenonema, with the former 3 being the most prominent. Chironomidae were the most abundant taxa at all three sites. Site 3 produced significantly more macroinvertebrates than sites 1 and 2. This could be related to favorable stream conditions further downstream of the dam?

Temporally, the macroinvertebrate community varied. In summer, diptera and hemiptera dominated. In fall, ephemeroptera and diptera dominated. In winter, ephemeroptera comprised almost 50% of the community, with diptera representing roughly 25%. In the spring, diptera comprised over 50% of the community.

Heptagenia flavescens

Leucrocuta maculipennis

Maccaffertium exiguum
Maccaffertium mediopunctatum mediopunctatum
Maccaffertium mexicanum integrum
Maccaffertium mexicanum mexicanum?
Maccaffertium modestum
Maccaffertium terminatum terminatum

Stenacron interpunctatum

Stenonema femoratum

(flyfishingentomology.com)