Masters Theses

Date of Award

5-1998

Degree Type

Thesis

Degree Name

Master of Science

Major

Wildlife and Fisheries Science

Major Professor

Richard J. Strange

Committee Members

James W. Habera, Mary Sue Younger

Abstract

A multiple mark-recapture study was performed on a wild population of brown trout (Salmo trutta) and brook trout (Salvelinus fontinalis) in Laurel Fork, a second order stream in Carter County, Tennessee. The 1.5 km study area was divided into 37 contiguous sections and was surveyed every three months from July 29, 1996 to October 31, 1997 with two AC backpack electrofishing units. Large fish (≥130 mm) were marked using Visible Implant Tags (VITs) while small fish were cold branded. All fish were marked with an adipose fin clip. Length, weight, and section of capture were recorded for each fish and scales were taken from all fish for age determination and verification.

Total salmonid densities ranged from 163 to 311 fish/ha (147 - 252 fish/ha for brown trout and 16 - 67 fish/ha for brook trout) and were significantly lower in January 1997. Young of the year (YOY or age-0) and age-1 fish made up the majority of the catch. No brook trout were over age 3 and only two age-4 brown trout were collected. Total salmonid standing crop ranged from 7.99 to 13.85 kg/ha and was highest in the spring and summer of 1997. Fish distribution throughout the study area differed significantly with higher trout numbers in lower stream reaches and more brook trout, relative to brown trout, in upper stream reaches.

Fish were found to be quite sedentary, with only 12% of brown trout moving more than one section (~40 m) from where they were first captured. No seasonal movement trends or spawning migrations were observed, except that fish moved least between October 1996 and January 1997, with no fish moving more than one section. Overall movement averaged 15 m upstream for brown trout and 27 m upstream for brook trout and was not significant from zero. Older fish (≥age 1) tended to move farther but less often than YOY. Adult fish remained in the same section 56% of the time compared to 49% for YOY.

Annual brown trout production was 10.35 kg/ha. The highest three-month production interval was February through April 1997 (3.83 kg/ha) and the lowest was November through January 1997 (0.81 kg/ha). Age-1 fish accounted for the majority of annual production, at 5.34 kg/ha (51.5%), followed by age-2 (27.4%), YOY (17.4%), age-3 (8.3%), and age-4 fish (2.3%). Instantaneous growth rates were positive and significantly greater than zero over all periods. Growth rates were lowest from November 1996 to January 1997 (0.13) and highest from August to October (0.77 in 1996; 0.45 in 1997). Growth rates were primarily influenced by fast growing YOY. Mean annual survival for all trout was 0.45 with near zero mortality for February through April, while survival ranged from 0.76 to 0.78 for other three-month intervals.

Brown trout scale annuli formed between mid-January and mid-February, with 44% of age-0 and age-1 fish having 2-3 widely-spaced circuli near the scale margin on January 27, 1997. Effective three-month VIT retention was 73%. Fish size and experience of the fish tagger were associated with higher tag retentions. Overall cold brand retention was 78%, with better readabilities over intervals of slower growth.

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