Gila Trout

Diet and feeding

The FishTraits compilation records these diet categories for this species: invertebrates or larval fish. These are broad categories, not a claim that every individual consumes every example in a category.

Reported feeding positions include surface or water-column feeding. The compilation combines published observations; diets can vary with age, locality, and available food.

Habitat preferences

Reported habitat associations include streams and small rivers, creeks.

The source records associations with gravel, cobble. An association indicates reported use, rather than an exclusive requirement.

Reproduction and parental care

The compilation reports a representative maturity age of 4 years. Its maturity field summarizes mean, median, or modal estimates, usually for females; male estimates can be used when female data are unavailable. It is not a fixed age at which every fish first breeds.

Recorded spawning months are Mar, Apr, May, Jun for the source’s reporting region (NM). This is a regional calendar, not a range-wide schedule.

The reproductive-guild classification includes hiding a brood without subsequent guarding.

Size and recorded longevity

FishTraits reports a maximum total length of 55 centimetres. Some entries use an estimated asymptotic length; this value should not be treated as a certified record catch.

Recorded longevity in the compilation is 7 years. Wild observations were preferred, but captive records were accepted where wild records were unavailable, and unspecified records were assumed wild. The value is not a guaranteed wild lifespan or an aquarium life expectancy.

Identification and appearance

Gila trout and Apache trout are similar in coloration however the Gila Trout have smaller, more profuse spots compared to the Apache Trout (Oncorhynchus apache). Parr marks along the sides can be present but fade in large Gila trout adults while parr marks are absent or very rare in Apache trout (Behnke 2002). Mature Gila Trout have a faint rose or pink coloration along the lateral line, which is missing from all life stages of Apache Trout (Behnke 2002, Minckley and Marsh 2009). In comparison to other western trouts, the Gila trout has a longer adipose fin.

Native range

Gila River system, New Mexico and Arizona, including the San Francisco drainage in Arizona and New Mexico, and the Verde and Agua Fria drainages in Arizona (Page and Burr 1991; U.S. Fish and Wildlife Service 1993).

Habitat and ecology

Gila Trout typically live four years, but the maximum known is six years (Behnke 2002). Males are sexually mature at age 1 or 2, and females mature around 172 mm total length at age 3 (Minckley and Marsh 2009). Spawning occurs in the spring or early summer (April -June). Females lay between 143-686 eggs based on body size (Nankervis 1988) and require clean coarse gravel substrates and continuous stream flow for redds (i.e., nests) (Arizona Game and Fish Department 2009).

Stocking and naturalization of non-native trout (Rainbow Trout, Oncorhynchus mykiss and Brown Trout, Salmo trutta) species in the native range of Gila Trout have impacted the species through predation and competition (Arizona Game and Fish Department 2003). Gila trout readily hybridize with rainbow trout (O. mykiss) and therefore have lost some of its genetic integrity at some populations (U.S. Fish and Wildlife Service 1993).

Introduction history

This endangered species was intentionally stocked to increase its distribution. McKnight Creek was stocked in November 1970 with 307 fish from Main Diamond Creek. The creek was restocked in April 1972 with 110 fish from Main Diamond Creek to supplement the population stocked in 1970 after a severe drought in 1971 that reduced its numbers to less than 20. Flooding in 1988 resulted in a loss of greater than 90 percent of the population. The creek was restocked in October 1989 with 200 trout from Main Diamond Creek (U.S. Fish and Wildlife Service 1993).