Watauga River Trout Investigation

Executive Summary, Final Report to TWRA

Phillip W. Bettoli

  

1. The Watauga River was stocked in 1998 with catchable-sized rainbow trout Oncorhynchus mykiss (42,150), fingerling rainbow trout (50,000) and catchable-sized brown trout Salmo trutta (17,568). This study examined the fate of trout stocked in 1998, evaluated the habitat, and estimated the biomass of overwintering trout in the Watauga River. Cohorts of hatchery trout were microtagged, a roving creel survey was conducted, electrofishing samples were collected, and habitat was mapped using GPS and GIS technology. The Watauga River is one of only two Tennesse tailwaters that has a special regulations or "Quality Zone" reach, where anglers are prohibited from using any form of bait, the minimum size limit is 356 mm (14 inches) and only two fish per day can be harvested.

2. Fishing pressure between March and November 1998 (32 weeks) was 65,118 hours and represented 20,564 trips. There was a significant, but weak, negative relationship between instantaneous counts of anglers and river discharge. At any given level of discharge, twice as many anglers were observed on weekend days then weekdays. On a per-area basis, fishing pressure on the Watauga River was less than half what the South Fork of the Holston River received in 1997.

3. Most (90%) anglers interviewed on the Watauga River were Tennessee residents. Most (93%) Tennessee anglers were from the three counties adjacent to the river (Carter, Washington, and Sullivan), particularly Carter county. Anglers harvested 0.8 trout per trip and reported catching 4.6 fish per trip; most (68%) anglers used some form of bait. Hourly catch rates (1.40 fish/hour) were excellent and among the highest observed in a Tennessee tailwater.

4. Survival over 200 days of catchable rainbow trout stocked in the spring was excellent and ranged between 17% and 27%. Survival of fingerling rainbow trout was also good (27% over 200 days), as was brown trout survival (46%). Only the cohort of rainbow trout stocked in July suffered poor survival (1% over 200 days). Between 5 and 8% of the catchable rainbow trout stocked before July 1998 survived through April 1999, or about 3,500 fish. About 7,500 fingerlings stocked in 1998 survived through April 1999. About 5,200 of the brown trout stocked in 1998 survived through April 1999.

5. Catchable rainbow trout stocked into the Watauga River grew slowly (5-7 mm/month) compared to similar-sized fish stocked into other Tennessee tailwaters. Brown trout and fingerling rainbow trout also grew slowly relative to trout in other tailwaters. The robustness of stocked rainbow trout, large resident rainbow trout, stocked brown trout, and small brown trout presumed to be wild fish all declined significantly over time. Only large brown trout (300 - 450 mm total length) exhibited increased body condition over time.

6. Excellent populations of trout overwintered between 1998 and 1999. In March 1999, an estimated 55,231 trout (both species) were present, which represented a standing crop of 122 kg/hectare. Brown trout represented 60% of the density and 65% of the biomass of trout. Out of four other Tennessee tailwaters surveyed in the 1990s, only the South Fork of the Holston River boasted a higher standing crop of trout.

7. Rainbow trout longer than 400 mm were not common; the largest fish measured 526 mm (21 inches). Brown trout longer than 400 mm were common and the largest measured 710 mm (30 inches) and weighed 3.5 kg (7.8 pounds). Only limited natural reproduction by rainbow trout was observed. About 7% of the brown trout collected in March 1999 were wild fish hatched the previous year; an additional 9% were age-2 fish hatched in 1997.

8. High quality trout habitat existed in the Watauga River. Although spawning habitat was limited, the riffle:run:pool ratio was excellent (2.0 : 1.6 : 1.0) and conducive to good trout growth and survival.

9. The density of trophy trout (> 356 mm TL) was greater in the Quality Zone than elsewhere in the river; nearly all trophy rainbow trout in the Watauga River were in the Quality Zone. Brown trout in the Quality Zone were larger on average than elsewhere in the river and individuals of both species were significantly more robust in the Quality Zone. Dispersal into the Quality Zone by trout stocked upriver of the zone was very slow; thus, trout that were encountered in the Quality Zone were long-term survivors and showed fewer signs of domestication. Habitat in the 4-km Quality Zone was similar to other reaches of the river, but access and fishing pressure were much less. Therefore, it is prudent to conclude in the absence of any other data that the combination of low fishing pressure and special regulations has resulted in a high-quality trout community in the Quality Zone.

10. The Watauga River is comparable to the more-famous South Fork of the Holston River in terms of quality habitat and appropriate minimum flows, water temperatures, and dissolved oxygen concentrations to support healthy trout populations. The capacity of the Watauga River to overwinter trout is second only to the Holston River. However, the Watauga River would be classified as unproductive based on total dissolved solids and conductivity, and fishing pressure is not high enough to yield good return rates. If access and fishing pressure can not be increased, consideration should be given to reducing the number of catchable rainbow trout stocked. In addition to saving hatchery fish and money, reducing the number of trout stocked would reduce intraspecific competition for food resources and promote better growth and condition.




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