Fishes as Indicators of Environmental Quality

Flowing waters integrate the landscape. As water flows from mountain tops to valleys and ultimately to lakes and oceans, it collects runoff, sediments, nutrients, and pollutants. Point and nonpoint sources of pollution are synergized and often form complex and lethal compounds as they accumulate downstream. Fishes, as the best-known species of the aquatic world, reflect the health status of the aquatic habitats.

Certain fish or fish guilds may be utilized as indicators of environmental degradation. The presence of certain introduced fishes, such as carp and mosquito fish, may indicate poor-quality habitats because of their broad tolerance to degraded environmental condition. Increasing incidence of hybridization, diseases, and parasites also often indicate degraded habitat conditions.

The use of single fish a species as indicator can be misleading. For that reason, broader measures of fish community diversity have been developed to more clearly qualify and quantify habitat degradation.

For example, the Index of Biotic Integrity (IBI) combines attributes of communities, population and species to assess biological integrity by making comparisons between disturbed and relatively undisturbed habitats of the same region.

Factors considered in determining the IBI in a particular stream might include fish species richness and community composition, ratios of native versus nonnative species, trophic composition, and overall fish abundance and condition. However, in situations whereby natural fish diversity is relatively low, aquatic macro invertebrates can also be used as partial or total substitutes for fish community data.

Fish Conservation Strategies

 Fishes as Indicators of Environmental Quality

The development of sound and measurable goals is critical to conservation work. However, the right approach to designing what level of management that should be adopted is diverse and may depend on the nature of the issue itself, geography and may be other factors.

1. Species Based Conservation Effort

For many species of fish, it is important to maintain the diversity both within population and among population. It is known that for desert fishes, the genetic diversity of one population may differ greatly from another population of the same species. This is the situation with fishes
of the Pacific and Atlantic salmon.

Striped bass and many anadromous fishes are organised into discrete stocks as a result of homing instincts that lead adults to return to the streams from which they were spawned. Each stock may have distinct genetic qualities worthy of preservation.

Many recovery efforts for fish focus on the species level and include plans for habitat protection and reintroduction. Recovery plans are mandated for each species once identified as threatened or endangered pursuant to the Endangered Species Act. Typically, the plan details specific needs for habitat protection, research, reintroductions, monitoring, and public education.

2. Ecosystem-Based Conservation Efforts

The increasing rate of endangerment among species has recently led conservationists and the public to question the efficacy of traditional species-based approaches to management. As a result, ecosystem based approaches to management are being developed that focus on critical ecosystem processes and functions that maintain communities.

For example, floods often serve to control riparian plant succession, maintain aquatic habitat complexity, and remove nonnative fishes from stream systems. In this way, floods are becoming viewed as beneficial, much like the role of firs in maintaining the vigour of terrestrial ecosystems.

For fish conservation, fundamental areas of focus for ecosystem-based management are riparian areas and watersheds. Riparian areas are the interface between terrestrial and aquatic habitats, and as such, they are one of the most dynamic and critical components of the landscape.

Healthy riparian zones dissipate flood flows, moderate drought, store surface waters, and reduce erosion. Riparian areas also directly influence the quality of aquatic habitats by reducing sediments, modifying water temperature, and contributing woody materials that are critical for maintaining habitat complexity and for pool development.

Watersheds are considered to be a logical focus for ecosystem-based management for both terrestrial and aquatic species because:

(i) Their boundaries can be easily determined on topological maps and in the field,

(ii) They possess a hierarchical organization by aggregating into larger basins or subdividing into smaller watersheds, and

(iii) Their rivers provide focal points for cumulative effects analyses.

3. Improving Aquatic Resource Management

Implementation of the following management principles would substantially improve the status of fish conservation and would help ensure a sustainable supply of fish resources for future generations.

(i) Fishery management practices such as harvest quotas and artificial manipulation should be cautious and conservative in the face of uncertainty.

(ii) Remaining aquatic habitats of high environmental quality should be preserved to conserve fish diversity and demonstrate the components of healthy ecosystem.

(iii) Management efforts should focus on maintaining biodiversity, which provides stability and resilience to communities.

(iv) Genetic studies need to be integrated into management programmes to ensure that the full array of fish diversity is identified and maintained.

(v) Although efforts should continue for species-based conservation, new efforts should focus on community conservation, including the restoration and maintenance of ecosystem processes and functions, such as natural flow regimes, that maintain healthy communities.

(vi) Fishery conservation should include a focus on entire watersheds, particularly riparian zones, which provide the interface between actions on land and quality of aquatic habitats.

(vii) Artificial management tools, such as hatcheries, barging fish past dams, Lake Fertilisation, and so on should be considered as methods of last resort and should not be substitute for habitat restoration.

Read Also: Fishery Biodiversity Conservation

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Benadine Nonye is an agricultural consultant and a writer with over 12 years of professional experience in the agriculture industry. - National Diploma in Agricultural Technology - Bachelor's Degree in Agricultural Science - Master's Degree in Science Education...  Visit My Websites On: 1. - Your Comprehensive Practical Agricultural Knowledge and Farmer’s Guide Website! 2. - For Proper Waste Management and Recycling Practices. 3. - Your Reliable Agriculture and Waste Management Online Community Forum! 4. - The Agriculture and Waste Management Practices On Your Screen! 5. - Your Reliable Agriculture Job Board! Join Me On:  Twitter: @benadinenonye - Instagram: benadinenonye - LinkedIn: benadinenonye - YouTube: TheAgriPedia TV - Pinterest: BenadineNonye4u - Facebook: BenadineNonye

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