Water in the Little Colorado River within Grand Canyon is naturally high in salt (NaCl), which is known to prohibit development of external fish parasites such as Ich (Ichthyophthirius multifiliis). The naturally high salinity (>0.3%) of the Little Colorado River at baseflow may be one factor allowing survival and persistence of larval and juvenile humpback chub (Gila cypha) and other native fishes in Grand Canyon. We compared salinity readings from the Little Colorado River to those reported in the literature as being effective at removing protozoan parasites from fish. In laboratory tests, 10 juvenile roundtail chub (Gila robusta; 61–90 mm TL) were randomly placed into each of 12, 37-L aquaria filled with freshwater, water obtained from the Little Colorado River (0.3% salinity), or freshwater with table salt added until the salinity reached 0.3%. Roundtail chub was used as a surrogate for humpback chub in this study because the species is not listed as endangered but is morphologically and ecologically similar to humpback chub. All roundtail chub infected with Ich recovered and survived when placed in water from the Little Colorado River or water with 0.3% salinity, but all experimental fish placed in freshwater died because of Ich infection. The naturally high salinity of the Little Colorado River at baseflow (0.22%–0.36%), appears sufficiently high to interrupt the life cycle of Ich and may allow increased survival of larval and juvenile humpback chub relative to other areas within Grand Canyon.
You have requested a machine translation of selected content from our databases. This functionality is provided solely for your convenience and is in no way intended to replace human translation. Neither BioOne nor the owners and publishers of the content make, and they explicitly disclaim, any express or implied representations or warranties of any kind, including, without limitation, representations and warranties as to the functionality of the translation feature or the accuracy or completeness of the translations.
Translations are not retained in our system. Your use of this feature and the translations is subject to all use restrictions contained in the Terms and Conditions of Use of the BioOne website.