Native Fish Community

Framework / Assessment
California Water Plan Update 2013: Pilot Statewide Assessment
Summary

Ratio of observed to expected native fish species in a waterbody or watershed. Fish indicators have been widely used and recognized as important tools to evaluate watershed and stream ecosystem health.

General Information
Sustainability Goal

Goal 5: Protect and enhance environmental conditions by improving watershed, floodplain, and aquatic condition and processes.

Domain

Ecosystem Health = The condition of natural system, including terrestrial systems interacting with aquatic systems through runoff pathways.

What is it?

An intact and healthy watershed and waterway network will tend to maintain most or all of the expected native aquatic fauna and flora over any one study period. As disturbance increases, fewer native species will be observed and this ratio will decline. Two types of aquatic animals that have been assessed in California are native (and non-native) fish and benthic macroinvertebrates (primarily early life stages of certain insects). Comparing the observed presence of native fish or other animals to what is expected gives an indication of environmental conditions and disturbance. The benthic macroinvertebrate indicator is represented by the California Stream Condition Index.

Fish indicators have been widely used and recognized as important tools to evaluate watershed and stream ecosystem health. A combination of native fish conservation status and the fish community composition will provide a complete evaluation of the fish condition in California watersheds.

NATIVE FISH STATUS

• Conservation status of freshwater fish: This is an evaluation of the threat status of the 129 freshwater fish native to California that follows a group-specific quantitative protocol detailed in Moyle et al 2011 (see scoring rubric in Appendix 1). Under this protocol there are seven metrics to assess fish threat: area occupied, estimated adult abundance, intervention dependence, tolerance, genetic risk, climate change and anthropogenic causes (including15 related categories). Each species is evaluated separately and then a summary report for the State is produced in terms of total species by threat category. The first specific assessment developed by Moyle et al (2011) would be use as the baseline evaluation to compare for long-term changes in fish conservation status. Evaluations are suggested to be carried out on a 5-year period.

• Status of key fish species: This metric is based on a species-specific assessment of conservation status. Some native species in California are of particular concern due to the rapid decline of their populations in the last decades. Examples include the Central Valley Chinook Spring-Run Salmon, Coho Salmon, Delta Smelt, Sacramento Perch. To consider few species (2-3) as state key indicators would not be the best approach due to the diverse and distinct biological regions across the state. Therefore, this metric will include 1-2 key fish species per each one of the 6 main zoogeographic regions in California . This metric will use the same threat status quantitative protocol by Moyle et al (2011) and will also include a species-specific distribution range analysis. Species-specific assessments are suggested to be carried out on a 5-year period basis.

FISH COMMUNITY COMPOSITION

• Percentage of native richness expected: This indicator compares the native species richness to the expected number of fish species by main zoogeographic/watershed region1. The expected native richness by main watershed region is obtained from Moyle (2002), which provides the historic (pre-1850) native fish diversity. Native richness would be evaluated periodically in a 5-year period.

• Proportion non-native species: This metric is the percentage of non-native fish diversity over total fish diversity (species richness) by main zoogeographic/watershed region1. Established non-native species will include species from outside California and also intra-state introductions. A baseline community composition data by main watershed region for long-term comparison and evaluation is provided by Marchetti et al (2004).

Why is it important?

California has 129 native inland fishes, of which 63% are endemic to the state (Moyle et al 2011). Diverse conditions in California have produced fish species that have evolved and adapted independently in isolated watersheds. Fish communities, therefore, are important elements of the state freshwater ecosystems and their status and composition represent good indicators to evaluate disturbances over time.

The fish conservation status indicators provide useful information on the threat categories native fish fall into and the causes of decline in ranking of importance. This information can be used to improve and adapt management decisions, especially to assign resources where is more needed. Also, it can be used to evaluate conservation management efforts directed to restore threatened species and the watersheds or streams where they live. Specific-species assessments complement the state-level status evaluation. Certain species are of great ecological, economic and cultural importance because they are strong indicators of habitat quality in specific watershed systems. Impacts of human activities and climate change have imposed challenges to the survival of these key species, which makes stronger the need of a long-term monitoring of their status to ensure their conservation.

Measures of fish community composition that assess how native diversity is doing in comparison to non-native diversity provide an indicator of biotic integrity. How different is the current fish native assemblage compared to the historical native richness indicates how well the watershed or streams are doing in supporting the natural functional diversity. Either low native species richness or high percentage of exotic species show that the system is departing from its natural balance and that the watershed ecological health is declining (Meador et al 2003). In the Sierra Nevada montane watersheds, for example, dominant salmonids are non-native, which indicates a considerable alteration of the historic fish fauna in these meadow systems (Purdy et al 2011). Moreover, the composition of fish fauna in watersheds can also be correlated to the composition and status of other fauna groups (native amphibians declines after the stocking of non-native trout for example, Knapp (2005)).

What can Influence or Stress Condition?

Stressors of native fish communities in California are several, including habitat conversion and degradation, impacts of anthropogenic activities and introduced species. A recent analysis on the conservation status of native fish in California (Moyle et al 2011) concluded that even though each imperiled species has its own combination of causes of decline, common stress factors are two: large-scale landscape changes (mainly invasive species, dams, agriculture and urbanization) and climate change. 62% of threatened fish in California are affected by climate change, especially those species that rely on flows of cool water (< 20C).

Target or Desired Condition

NATIVE FISH CONSERVATION STATUS

For the conservation status of native fish, the ideal condition is that none species become extinct or endangered and the ones in these categories recover over time and become assessed under a low extinction risk category. Based on the quantitative protocol used for the fish conservation status assessment (Moyle et al 2011), the desired target is that all native fish species reach a score of 5, indicating that there is no negative impact on status .

FISH COMMUNITY COMPOSITION

The desired condition is that native fish communities will be fully intact, that they will conserve or resemble the historical natural assemblage (100% similarity), and there are no invasive species. Each watershed is given a score dependent on the ratio of current richness over historic richness. Scores equaling 100 represent no loss in richness over time or even gains in richness. A score of 50 represents a loss of 50% richness between the historic and current species richness in each HUC12. A score of 0 represents no current range contributed to the richness in that particular HUC12.