Biology ETDs

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Ten tissues from each of four species of fish-large­mouth bass (Micropterus salmoides), black crappie (Pomoxis nigromaculatus), walleye (Stizostedion vitreum) and rainbow trout (Salmo gairdneri) from Lake Powell were analyzed and compared for the concentrations of ten heavy metals: Fe, Ca, Mg, Cu, Cr, Cd, Zn, As, Se, and Pb.

Samples were digested with nitric and perchloric acids, and analyses were performed by atomic absorption spectro­photometry. Concentrations were expressed on a dry weight basis for all tissues, and were not corrected for percent recovery.

As expected, high levels of iron were observed in the blood tissues, with low concentrations being observed in the flesh, skin, and bone. Concentrations ranged from 0.01 mg/g to 1.24 mg/g.

Calcium and magnesium displayed parallel patterns with high concentrations of both elements in the bone and skin with scales. Differences in scale structure between fishes were evident.

Copper concentrations ranged from 0.02 mg/kg to 170.79 mg/kg with the liver being the organ of copper localization. Data was presented which indicated that copper uptake is via the food chain.

Highest chromium concentrations were observed in the brain tissue of three species; however, the pattern of chromium accumulation was not consistent between species. Chromium concentrations ranged from 0.1 mg/kg to 38 mg/kg.

Cadmium levels in flesh and skin with scales (0.02 mg/kg and 0.04 mg/kg respectively), were comparable to values reported in fish from other areas. Cadmium content did not appear to be dependent upon fish size.

Zinc concentrations ranged from 0.02 mg/g to 1.25 mg/g. Trout were unique in having the highest zinc concentrations of all species in eight tissue types, while having the lowest levels of all species in flesh and skin.

No consistent pattern of arsenic accumulation was observed in that the tissue of highest arsenic concentration was different for each species. In general, trout had lower arsenic concentrations than the other species.

High selenium concentrations were observed in fish tissues, which reflected the high levels known to exist in the plankton and sediments in the lake. Levels in flesh ranged from 6.4 mg/kg to 16.8 mg/kg. Selenium levels in bass appeared to be dependent upon fish size.

Lead levels in the flesh and skin of Lake Powell fish were comparable to concentrations in fish from other areas. High lead levels were observed in the gills of three species. Lead levels in the gills of fish netted from a region of extensive recreational use were compared to levels in the gills of fish from an area of limited use. Data indicated that recreational activity and the use of outboard motors may introduce significant amounts of lead into the aquatic system, and may account for the high lead levels observed.

Cadmium, lead, arsenic, and selenium are toxic to humans. The concentrations of these heavy metals in the edible portions of Lake Powell fish were compared to the maximum safety threshold levels established in several independent studies. At this time, none of the metals, aside from selenium, appear in concentrations high enough to pose a health hazard, and should not be cause for concern. However, the high selenium levels in fish flesh may con­stitute a possible health hazard, although little is known of the factors influencing selenium assimilation in humans.

Project Sponsors

National Science Foundation, Lake Powell Research Project



Document Type


Degree Name


Level of Degree


Department Name

UNM Biology Department

First Committee Member (Chair)

David Eugene Kidd

Second Committee Member

Leonard Patter

Third Committee Member

James P. Gerz

Fourth Committee Member

Manuel C. Molles Jr.

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Biology Commons