The biological effects of artificial reefs in Smith Mountain Lake, Virginia
| Autor: | Prince, Eric D. |
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| Jazyk: | angličtina |
| Rok vydání: | 1976 |
| Předmět: | |
| Druh dokumentu: | Dissertation |
| Popis: | Artificial reefs were installed in Smith Mountain Lake, Virginia, during the summer and fall of 1973 to evaluate the biological effects on the aquatic ecosystem. Virtually all sport fishes were attracted to the reef areas. The frequency of sport fish on the reefs generally coincided with their overall abundance in the reservoir. Sunfishes (Lepomis spp.) and white catfish were the most common. Centrarchid basses were also well represented in the reef sport fish community. Sport fishes were significantly more abundant on the experimental reef sites during both years after reef construction than prior to reef installation. Fishes colonized the reef area on a seasonal basis. Fishes moved onto the reefs in the spring as water warmed and off reefs as temperature cooled in late fall. Centrarchid sunfishes preferred low profile reef units in shallow water (1.5 m) while centrarchid basses preferred high profile reef units in deeper water (4.6-6.1 m). Nest building centrarchid basses spawned adjacent to the reef units while centrarchid sunfishes spawned inshore of the shallowest reef units. Cavern seeking ictalurids were the only sport fish to utilize the reef substrate directly for spawning. They deposited their eggs between the sidewalls of the tire units. The tire reef units resulted in increased primary productivity and nutrient levels of the tire reef periphyton community as compared to the primary productivity and nutrient concentration of the littoral phytoplankton. Periphyton communities attached to the tire reefs were the major food and ultimate source of energy of the reef sport fish community. Installation of artificial tire reefs altered the availability of food to reef fishes and subsequently modified the typical lentic food web in isolated areas of the impoundment. Reef sport fishes utilized the tire reefs extensively as a feeding station during the growing season. Sunfishes converted periphyton and other reef associated food into increased body condition and growth (weight) when compared to fishes from other natural structure types in the reservoir. Therefore, artificial tire reefs in Smith Mountain Lake showed a potential for increasing fish production. Most Peterson disc tagged fishes indicated a strong home range tendency to specific parts (site of original capture) of the multi-component reef. Entanglement of Peterson discs in monofilament fishing line on the bottom of the reservoir caused an important source of tag loss. Seasonal climatic changes in temperature and morphometric features of the basin of Smith Mountain Lake influenced the movement of telemetry equipped largemouth bass. Non-reef largemouth bass showed increased summer movement and utilized uncleared offshore areas of the reservoir while reef bass were more sedentary confining the majority of their summer movement to littoral reef areas. After thermal destratification, behavior of reef and non-reef bass were essentially the same. Both groups of fish moved offshore into deeper water away from the reefs during winter. Underwater biotelemetry techniques were developed to successfully monitor the movement of bluegill for periods up to 30 days or more. Changes in water temperature and to a lesser extent morphometric features of the reservoir influenced bluegill movement. Non-reef bluegill showed increased summer activity and utilized offshore areas while reef bluegill were more sedentary on the reefs during the summer. After thermal destratification bluegill moved to offshore areas. Bass and bluegill moved primarily during daylight hours where periods of peak activity were likely associated with feeding. Internal implantation of transmitters into bass did not appear to affect bass behavior. Surgical effects of transmitter implantation on bluegill apparently had a minimal effect on bluegill behavior. The results of this study show a net beneficial biological effect of artificial reefs on the aquatic ecosystem of Smith Mountain Lake, Virginia, and indicate that artificial reefs placed in structure deficient freshwater lentic environments are a viable fisheries management tool. Ph. D. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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