Oncorhynchus gilae apache
An Apache trout from the White Mountains of Arizona.
The Apache trout are considered subspecies of Gila Trout, Oncorhynchus gilae apache and are native streams draining the White Mountains of Arizona. Although originally thought to be most closely aligned with cutthroat, studies have shown that both Gila and Apache trout are in fact more closely related to rainbow trout. While Apache trout have been reduced to a mere fraction of their historic abundance, recovery efforts have been largely successful and Apache trout now support a popular fishery in the White Mountains.
The Apache trout does not appear to possess any unique life history traits and historically occurred as stream resident and fluvial populations. Today the predominate life history displayed by the Apache trout is the stream resident form, as virtually all remain Apache trout population have been pushed back to high altitude headwater streams. Native Apache trout are not thought to have gotten very large historically, with the average adult size in streams today ranging from five to nine inches. However when stocked into fertile lakes, these fish are known to reach sizes up to five pounds (AGFD 2001). Apache trout are generalists, and their primary diet of consists of aquatic and terrestrial invertebrates. Although adult Apache trout may live up to six years, the average life span is typically four years old (Behnke 2002).
Like other western trout, Apache trout are iteroparous and spawn during the spring. Apache trout typically spawn for the first time at an age of two to three years old, with males making up the bulk of the two year old fish. The timing of spawning is largely controlled by the water temperature and typically occurs between April and May when stream temperatures rise to between 46 and 47 degrees Fahrenheit (Behnke 2002). Females tend to seek out the downstream end of pools containing moderate sized cobble to construct their redds and Rinne (2001) showed that a 25% or greater amount of fine sediments greatly impacts successful emergence by fry. The average female will lay between 200 and 500 eggs with fry generally hatching after 30 days and emerging at around 60 days (AGFD 2001). After emerging, juvenile Apache trout orient to sections of the stream with cover and tend to seek out areas of streams with some sort of surfaces disturbance, or overhanging vegetation for protection from predators (Cantrell et al. 2005). Cantrell et al. (2005) showed that adult Apache trout tend to seek out pool habitat and areas with slower moving water, with suitable cover.
Over the past century, the Apache trout populations have been reduced to faction of their former abundance and this decline can be attributed to a number of factors. As with many other isolated species of trout, the Apache trout do not deal with introduced species well and non-native trout have played the largest role in their decline. Hybridization with both rainbow and cutthroat trout has been the largest problem and a 1993 study showed that out of 31 wild Apache trout populations only 11 showed no sign of hybridization (Carmichael et al. 1993). Due to the earlier emergence the fry of fall spawning brook and brown trout, these two introduced species typically out-compete Apache trout, since there fry are able to establish territories before the Apache trout have even spawned. Beyond the issues caused by non-native trout, Apache trout are also threatened by logging and overgrazing by livestock. These practices eliminate stream cover and also increase sedimentation, run-off, and stream temperatures due to a loss of riparian vegetation. As the preferred habitat for Apache trout is deep pools with ample cover, these practices can be especially problematic. The increased sedimentation causes pools to fill in and lose for riparian habitat leads to a poor rate of regeneration of instream cover. Due to their coloration are easily spotted when out in the open and the availability of stream cover is thought to be very important for Apache trout to be able to successfully avoid predators (Mesick 1988). All of the Apache trout that I accounted on my 2009 trip were very found in the deepest pools and were typically in very close proximity to an undercut bank or some other form of cover, the very habitat that is most impacted by these practices.
Apache trout were historically believed to be native to around 600 miles of stream habitat, they have suffered large scale declines over the last century. In fact prior to the start of recovery efforts their populations had been reduced to around 30 miles of small headwater streams (Behnke 1992). This vast reduction in their range resulted in the Apache trout being listed on the Endangered Species Act (ESA) along with the Gila trout in 1973. However restoration efforts were already underway by the time that they were listed and by 1975 they were downlisted to threatened, to better facilitate the restoration plan. Today only 35 populations of wild Apache trout remain and the bulk of these are isolated in small headwater streams above barriers (TU 2009). While there has been a lot of progress in the restoration of the Apache trout over the past half of a century, their abundance today is still a far cry from what it once was.
The Apache trout is most closely related to the Gila trout and as such displays many similarities. Like Gila trout the bodies on the Apache trout tend to be deeper and more compressed when compared to other trout (Miller 1972). Generally the coloration of the Apache trout is a brownish-olive to a bronze color on the back and transitions to a golden-yellow on the sides, with the color of the Apache trout typically being brighter than that of the Gila. Like the Gila trout, Apaches have relatively large fins and the dorsal fin on Apache trout in particular is longer than that of any other western trout (Behnke 1992). The pelvic, anal and dorsal fins on the Apache trout are all typically tipped with white, although the dorsal may be tipped with orange. The spots on Apaches are moderately sized, fairly sparse and typically evenly distributed across the body. A distinctive trait in wild Apache trout is a horizontal dark band of pigmentation across their iris, that gives them a "bandit" look. Typically this trait is absent in hatchery reared Apache trout.
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