Physiological Responses

Portner and Farrell

The California Golden Trout are found in high elevation, shallow streams that have lots of stream-side vegetation. This habitat however, is quickly changing for the Golden Trout. Their streams, which are already shallow, are being widened by grazing cattle and in combination with rising temperatures creates concern for the health and success of the trout (Knapp 1998). Rising air temperatures quickly raise the water temperature because the shallow waters are more sensitive to temperature change. An increase in water temperature can lead to physiological, developmental, and reproductive problems for the Golden Trout.

Warming temperatures do not bode well for the success of the species. The thermal window of the California Golden Trout changes throughout its lifetime like most fish, as noted in the figure to the right. The bottom axis increases from cold (blue) to warm (red) temperatures and the left axis represents the lifespan of a fish and starts from birth at the bottom to death at the top with a typical lifespan of about 7 years (Musky Trout). This means that when warming air temperatures change the water temperatures to extremes outside of the thermal window the fish are not able to perform essential life functions. This affects fish at all stages of life. According to "Physiology and Climate Change" by Portner and Farrell, "Beyond low and high critical temperatures, only a passive, anaerobic existence is possible". A fish is in an anaerobic state when there is no oxygen available or it cannot process the oxygen that it receives.

Scientists are concerned for Golden Trout and the lack of oxygen availability because it is usually coupled with lowered ph, also know as an increase in acidity. A study done by Peuranen et al., tested the affects of low ph on the gills and physiology of Brown trout, a close relative to the California Golden Trout.

Peuranen et al., 1994

In their study, trout were exposed to water with a ph of 5 and 6 for two days. Oxygen intake was measured through gill and blood samples to note the affects of a change in ph on the the trout. The results are shown in the figure to the left. The top most picture are gills from a fish exposed to a ph of 5 and the bottom picture is a fish exposed to a ph of 6. It was found that at a ph of 5, the cells in a fish's gills were fused together. This significantly decreased the ability to intake oxygen. In fact, half of the fish in the tank with a ph of 5 died after the first day. The fish that were exposed to a ph of 6 did not show total fusion of cells but had a decreased ability of oxygen intake due small changes in their gills from decreased ph levels. There were other chemicals used in this study such as iron and humic acid but results from the data showed that fish exposed to a low ph showed significant signs of reduced oxygen intake.

This is troubling because the shallow streams that the California Golden Trout live in are very sensitive to temperature and chemical changes. For example, a change in a ph of 1 will have detrimental affects on the life of a Golden Trout. Oxygen supplies the energy needed for moving, eating, and reproducing. A change in chemical composition of the water due to climate change will have serious repercussions on the physiology of the Golden Trout and its ability to survive.