| Popis: |
The introduction of a forage fish into a reservoir to enhance the growth of sport fish(es) has been popular in recent years. In 1982, the Texas Parks and Wildlife Department stocked 140 adult blueback herring (Alosa aestivalis) into Lake Thee, a 30-ha reservoir in Caprock Canyon State Park, Quitaque, Texas in Briscoe County. The purpose of this stocking was to experiment with a new forage fish possibly suitable for largemouth bass (Micropterus salmoides salmoides). This study addressed the suitability of blueback herring as a forage fish for black crappie (Pomoxis nigromaculatus) and white crappie (P. annularis) in that same reservoir. This was achieved by establishing the following three objectives: (1) to determine if black crappie and white crappie included blueback herring in their diet, (2) to determine diet overlap of the three species, and (3) to determine if the growth rates of black crappie or white crappie were influenced by the presence of blueback herring. Fish were collected with_experimental gill nets and electrofishing. All fish collected were divided into three size classes. Size class 1 included those fish 201 mm. Benthic and zooplankton samples were taken to determine what forage base existed for the fish to feed upon and to determine feeding selectivity. The first objective was accomplished by conducting stomach content analysis on the three fish species. Results indicated that blueback herring constituted less than 0.3% of the black crappie diet and less than 0.5% of the white crappie diet. Objective 2 was achieved by determining diet selectivity and diet similarity among the three species. Results indicated that there was significant similarity between certain size classes of herring and certain size classes of both crappie species, especially in August and September. Objective 3 was accomplished by determining if the growth rates of crappie collected in 1987 (in the presence of herring) were different from crappie collected in 1988 (in the absence of herring). Whole view otoliths were used to determine the age of all fish. Blueback herring were also aged using whole otoliths. Results indicate neither black crappie nor white crappie utilized blueback herring as forage, therefore it would serve no purpose for the enhancement of crappie growth. Due to the slow growth, short life span,and tendency of blueback herring in Lake Thee to form weak year classes, they should be stocked only assuming it would be possible to follow up with periodic maintenance stocking. |
