Lake Tahoe Nearshore Community Structure Pilot Monitoring

No Project associated with this Finding

Finding Details

The 2014-2015 monitoring efforts provided important baseline information about the composition, distribution, and abundance of nearshore biological indicators in Lake Tahoe.

Baseline collections and observations of biological indicators in the nearshore are useful in assessing nearshore condition changes at Lake Tahoe. It is evident from comparisons of the recently-collected and previously-collected data summarized in the project report that changes to biological communities in the nearshore are occurring. However, the researchers could not identify trends or provide an integrated evaluation of ecosystem health because too few data points exist across all categories.

Evaluation of the Chironomidae in Lake Tahoe has been useful in determining lake-wide trophic status for comparison to other oligotrophic lakes (see Hayford et al., 2015). This analysis can link to the water quality indicators and be useful for identifying changes to diversity.

Fish surveys in 2014 showed that the most common and widespread species in the nearshore of Lake Tahoe were Lahontan redside shiner and speckled dace. The 2014 survey showed that the distribution and abundance of native fish species has declined since historical surveys.

Over the past seven years, crayfish abundance was found to be consistently greatest in the northern part of Lake Tahoe. It is likely that crayfish abundance and distribution is driven by substrate type. Fall and summer minnow trapping yielded greater abundances of crayfish than did spring and winter trapping, confirming the importance of seasonal monitoring as outlined in the current monitoring protocol.

The distribution and composition of macrophytes during the 2014 survey differed greatly from macrophyte distribution and composition in previous years. Previous surveys found non-native macrophytes (Eurasian watermilfoil and curlyleaf pondweed) at various locations around the lake, but the recent survey at 2 and 5 m contours detected macrophytes only in the southern part of the lake. Such a change in the distribution and composition of macrophytes could be a result of decreased water levels from drought conditions, which have separated many marinas from the main lake. Marinas were not surveyed in 2014 and it is possible that marinas contain source populations of non-native macrophytes.