Lakecaster Online

Fish Habitat in Southeast Texas Reservoirs: A Management Perspective
By James Parks


Habitat has been defined as the physical, chemical, and biological features of the environment where an organism lives. Fish basically occupy habitat for food, shelter, reproductive activities and comfort and ambush zones. Anglers typically refer to habitat as cover/structure or any object fish associate with (i.e. hydrilla mat edges, inundated timber, rocky points and humps). In a broad sense, the fisheries biologist considers fish habitat as the environment that surrounds the fish - physical and chemical characteristics of water, structural habitat (i.e. inundated timber, brush, and substrate) and aquatic vegetation. Biologists are interested not only in the littoral (< 15 feet) habitat that species such as largemouth bass, sunfish and crappie primarily inhabit but also the limnetic or deep-water habitat used by sport fish such as white bass, striped bass and hybrid striped bass. Habitat is an integral component to the establishment and maintenance of viable freshwater fisheries. Therefore habitat surveys are necessary to identify and quantify (measure by length or surface acreage) the habitat in a reservoir. Habitat surveys provide critical information that is useful for describing fish populations (preferred habitat and spawning areas), determining the need for habitat enhancement or control and evaluating angler access. Physical/chemical surveys are typically conducted concurrent with fish population surveys and only the most basic water quality parameters are assessed. Other agencies (TNRCC, Texas Water Development Board and Texas Department of Health) have greater resources and expertise for monitoring the parameters that can affect the health of fish as well as humans. Lake wide structural habitat surveys on a given reservoir are conducted at least every 4 years and provide an estimation of visible structural habitat over the entire waterbody. Surveys are conducted by boat and each habitat type is drawn as encountered on a scaled geo-referenced map. A GPS unit also may be used to aid in the measurement of habitat coverage in some situations. Other means of efficiently delineating visible habitat are being investigated (i.e. remote sensing). A TPWD study conducted at public reservoirs in 1998-99 assessed fish habitat at fish survey sample sites. Findings from this study may ultimately be used to alter sampling protocol somewhat to improve fish sampling accuracy thus providing the agency and public year-to-year data more representative of the actual population. Vegetation surveys may also be coupled with lake-wide structural habitat surveys. Vegetation surveys on the larger reservoirs that require more manpower and effort are typically conducted annually by the TPWD Habitat Enhancement and Control Team. Vegetation survey results provide coverage estimates of native and exotic plant species during the growing season and are necessary for identifying existing or potentially problematic vegetation (usually exotic). While surveys are important for detecting potentially harmful vegetation, the agency also relies on the public to inform if any potentially harmful plant (ie. giant salvinia) is discovered in public reservoirs. Vegetation coverage, both in variety and amount, on most Southeast Texas public waters is probably optimal for providing the nursery cover essential for productive largemouth bass/sunfish populations. While exotic plants are typically characterized as unwanted species that tend to be problematic, in some reservoirs the presence of hydrilla, by providing cover, has improved bass populations and fishing success. However, if vegetation (typically exotic) coverage is excessive (>30%) and either affects reservoir operation, restricts adequate access to the reservoir or diminishes the quality of fish populations, chemical or biological control may be required. The choice between chemical or biological control of problematic vegetation on public water bodies is dictated by a number of factors including type and amount of vegetation present, cost, and personal preferences of controlling authority and the public. TPWD may assist the controlling authority on chemical treatment efforts in certain situations but only by providing manpower. Triploid grass carp, typically used by private pond owners (by permit) to control vegetation, have increasingly been stocked in public reservoirs as the sole method of problematic vegetation control. Since these fish can efficiently control only specific vegetation and stocking rates are not well founded at this point, results can be unpredictable. Also, in situations where largemouth bass management is a priority, their stocking is discouraged due to the possibility of significant loss or elimination of the nursery cover essential for productive bass populations.

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