Rainbow trout responses to water temperature and dissolved oxygen stress in two southern California stream pools

Abstract

Habitat use by rainbow trout Oncorhynchus mykiss is described for a southern California stream where the summer water temperatures typically exceed the lethal limits for trout (>25°C). During August 1994, water temperature, dissolved oxygen (DO), and trout distribution were monitored in two adjacent pools in Sespe Creek, Ventura County, where summer water temperature reached 28.9° C. Water temperature was an important factor in trout distribution in the two pools. During 1–11 August 1994, water temperatures in pool 1 ranged from 21.5°C at the bottom (4.1 m) to 28.9° C at the surface. After 5 August, trout were no longer found in this pool, suggesting that trout had moved out of the high temperature water or died. In the adjacent, shallower (1.5m) pool 2, surface water temperatures were as high as 27.9° C, but temperatures on the bottom remained cooler (17.5–21° C) than pool 1, presumably due to groundwater seeps. Consistent aggregations of trout were observed in pool 2 throughout the study period. During the day when water temperature was highest, most trout were found in a region of the pool with the lowest water temperature (mean=18.3° C). Conversely, regions with the highest water temperatures had the fewest trout during the day. The seeps may have introduced water with low dissolved oxygen into pool 2, as the DO in many locations on the bottom ranged from <1 mg 1−1 to 5 mg 1−1 over 24 h, while the surface DO ranged from 4.1 to 10.0mg 1−1. Lowest DO occurred from 2400 to 0600 hours. During August, water temperature and DO were positively related. Thus, rainbow trout faced a trade‐off between the relatively cool water temperature with low, possibly lethal levels of DO (e.g. 1.7 to 3.4 mg 1−1 in region 3), and lethally high water temperature but high DO. Seeps may serve as important thermal refugia for trout, and an increased understanding of their role as potential critical refugia in Southern California is necessary.

Abiotic habitat thresholds for salmonid over‐summer survival in intermittent streams

“…Exposure to lethal DO levels (<2 ppm) kills juvenile salmonids quickly (Herrmann et al 1962), while exposure to sublethal DO levels (3-5 ppm) can cause metabolic problems (Whitmore et al 1960, Brett and Blackburn 1981, Carter 2005, Barnes et al 2011. Salmonids may survive low-DO periods in DO refugia, perhaps in the saturated zone at the pool surface (Matthews and Berg 1997) or in areas of hyporheic inflow. During late-summer snorkel surveys in low-DO pools, we often observed salmonids clustered near areas of hyporheic inflow (i.e., at the head of a pool below a dry riffle) and at the pool surface, and on one occasion observed a 1+ steelhead parr apparently air breathing at the surface of an anoxic pool.…”

Diet and capture of Hypostomus strigaticeps (Siluriformes, Loricariidae) in a small brazilian stream: relationship with limnological aspects

“…The microscopic analysis of the gut contents confirmed that the most important food items -diatoms, fungi hyphae and unidentified material -were, in fact, associated with the sediment. Matthews & Berg (1997) stated that low oxygen rates would be expected to have a negative effect on fish, inducing them to migrate in search of other places with better oxygen concentration. Although this may be discussed in the case of H. strigaticeps, which is an alternative breathing species that uses its stomach to carry out gaseous exchanges (Val & Almeida-Val, 1995;Armbruster, 1998), a fewer individuals were caught at site B.…”

Effects of the “Run-of-River” Hydro Scheme on Macroinvertebrate Communities and Habitat Conditions in a Mountain River of Northeastern China

“…The DO concentration in rivers is influenced by many biological, chemical, and physical interactions, and in terms of the physical process, it is heavily controlled by water temperature, water pressure and flow velocity [25,26]. In this case, with little water temperature difference, the lower velocities and induced relatively weak disturbances in downstream reaches are likely to decrease oxygen aeration and, hence, reduce DO levels.…”