When the Rio is “on” it is fantastic!! At other times it is known locally as a “stingy river.” Thunderstorm activity and irrigation upstream make summer on the Rio unpredictable. From mid September through October flows reach their natural level and water clarity improves. Fish are very active and accessible during this period. Fish dry flies in pocket water and nymphs in deeper runs. Best fishing here is in the upper gorge, above the confluence with the Red River, a one mile hike into the 800 vertical foot gorge. Fish here are mostly Browns with some good size Cuttbows in the deeper runs.
In the box on the Rio Grande*Spring Caddis on the Rio Grande*
The spring Caddis hatch is an annual event that begins in mid-April in the Pilar area and progresses slowly upstream. April is also the start of spring run-off and in most years the two events are simultaneous. In years when the run-off is late due to cooler than normal weather, or when lack of high mountain snow pack makes for minimal runoff, some excellent dry fly fishing can be had.
This is a “blanket” hatch with millions of bugs literally blanketing the water. The key is to stay on the leading edge of the hatch as it works it’s way upstream into the Taos box.
Fishing can be feast or famine depending on where you are on the river. Too many bugs? Move upstream.
*Fall: Generous Time on a Stingy River*
Besides the spring Caddis hatch, the Rio Grande is very unpredictable. When flows normalize in mid-September (300 to 400cfs at the New Mexico – Colorado State line) through October the fishing in “The Box” can be excellent. Browns love the shallow pockets and can be taken on large dries, Caddis and Stones. In deeper runs, a large peacock bodied nymph fished through the deepest spots often yield large Cuttbows.
The aquatic insect populations varies depending on the section of the river you are fishing but those listed below are plentiful throughout most of the stream from its headwaters to its lower section.
Prior to the runoff, the main hatches consist of Western March Browns and Blue-winged Olives. The March Browns can get caught up in the high runoff water depending on the exact time it occurs. The BWOs can start as early as late February and early March but April usually is the most consistent time for the hatches to begin. About six different species, mostly Baetis, species make up what is called BWOs. There’s also a Fall hatch of the Blue-winged Olives. It usually takes place from late September through the month of October.
Midges are very plentiful in the Rio Grande. Imitations will work well anytime and become more important when the water is too cold for most other insects. Small black winter stoneflies hatch in the early season, even when there’s snow on the ground. These are mostly found in the fast pocket water.
Salmonflies are present in some sections of the river and begin to emerge in early June. They are often caught up in the Spring runoff. You will find some hatches of Golden Stoneflies become to come off in late June to early July. The hatches can last into the first of August. Little Yellow Stoneflies are plentiful in fast water sections in late July and early August.
The first caddisflies to hatch are the Little Black Caddis, called the Mothers Day hatch in most places in the West. This hatch starts in mid April and last about a month. In is a sparse hatch but can be important.
In late June and early July, there’s several different species of caddisflies called Spotted Sedges that begin to hatch. These are the most plentiful of the caddisflies and the different species hatch throughout most of the Summer and on into the early Fall. There are also some Green Sedges that hatch from May to September.
In late June, usually before the runoff ends, Pale Morning Duns will start hatching. The PMD hatch will last most of the summer and other than BWOs is the most consistent mayfly hatch.
In some areas of the fast water you will find a few Pink Ladies that hatch in August and September. Many anglers call these mayflies Yellow Quills.
In the late Summer, August and September, terrestrials can play an important role in the trout’s diet. Imitations of grasshoppers, ants and beetles will become important flies.
Sculpin are very plentiful throughout the river. There are some other types of baitfish and minnows but sculpin are by far the most important in the food supply for the trout.