Photo: Cara, Tally, Maya, Gus, and Oso on the Gambusia Road Trip
Day four had a great start. The second heater made the camper toasty warm all night. Even Gus had a comfortable night. Also, we had camped adjacent to the spring and its outflow, so getting to the habitat of G. nobilis and the introduced G. geiseri was a short stroll.
After breakfast we leashed the dogs and headed for an underwater viewing port I had used to view both species of Gambusia on earlier trips. I expected to would be simple through it to take photos of both species. I especially wanted photos of the endangered G. nobilis. As is often the case, things that should be simple aren’t. Arriving at the viewing port we found it completely algae encrusted, preventing any viewing or photography. That called for invoking plan B. Hoping the park might have an aquarium housing some G. nobilis, we trekked the short distance to the ranger station. No luck; plan B bombed. The park had no aquaria at all, so no fish to photograph. The park ranger explained the viewing port’s poor (non-existent) maintenance. The Texas Parks and Wildlife Department’s budget had been repeatedly cut to the bone by our cut-services-and-lower-taxes-on-the-wealthy-and-businesses-in-the-vain-hope-a-charitable-company-would-fund-the-parks Legislature. The department had insufficient resources to keep up with anything but bare necessities. In fact, a lot of the upkeep in the park was being done by unpaid volunteers. I might have to go back and volunteer to clean the viewing ports in return for being allowed to photograph the fish.
We were reduced to taking photos of the habitat, not realizing until later in day the camera’s flash card had ceased to work. Sometimes, bad luck is all you have. If I’d had an underwater camera, the park has a very large outdoor swimming pool made by damming San Salomon Spring. According the park ranger, numerous G. nobilis swam there. Furthermore, I was assured by the ranger that I wouldn’t be harassing them by swimming with them and taking photos. Unfortunately, Toyahvale is hundreds of miles from a store offering an underwater camera. So, there would be no G. nobilis photos on this trip.
G. nobilis, the Pecos Gambusia, while endangered has a significantly larger range than most of the other rare species. It is still, however, threatened by the introduction of G. affinis and predatory fish.
G. geiseri since its introduction into San Salomon Spring has undoubtedly had a negative impact on the population of its close relative and congener. The vast majority of Gambusia seen consist of the surface dwelling G. geiseri. Only a few G. nobilis were visible near the bottom and close to cover in the form of a species of hornwort and leaf litter from nearby cottonwood trees.
Disappointed, we broke camp late mid-morning to rush to Presidio, TX on the Mexican border to view G. speciosa and its habitat. At Presidio we turned downstream, paralleling the Rio Grande, stopping periodically to look for G. speciosa. We saw fish that were likely this species and tried to get photos of it and its habitat. We finally discovered the camera was malfunctioning at our last stop on the Rio Grande.
G. speciosa was only recently split out of G. affinis. The range of this species includes the Rio Concho of Mexico and the Rio Grande near the two rivers’ confluence. It’s very possible the Gambusia we saw were G. affinis instead of G. speciosa.
We were running out of daylight and still planned to visit the G. gaigei pool in Big Bend National Park before nightfall and then checking into an RV park in Marathon, TX. We were also trying to outrun a cold front, but were unsuccessful at that. Driving a Suburban pulling a camper in high winds isn’t a pleasant experience. We arrived at Rio Grande Village on the far side of the national park with about 45 minutes of daylight remaining. It was a fair hike to the hidden pool, but we made it in time to some photos with our IPhones. We saw only a few fish hiding among the cattails. The last time I’d visited the pond in 1991, it was teeming with thousands of G. gaigei. I don’t know what has changed, but I’m glad Dexter has a backup population.
As an aside, despite a very high coefficient of inbreeding, I saw no deformities in the fish in 1991 or in the population kept by Dexter. Remember, all of these fish are descended from a single female. Readers of my column have seen me discuss the issue of inbreeding depression many times.
We made Marathon well after dark and set up camp without problems, except for a rather long walk to and from the showers.