Richard J. Strange

Physiological Stress Responses in Wild and Hatchery-Reared Rainbow Trout

Abstract Stress-induced changes in plasma cortisol, glucose, and chloride were more extreme in wild rainbow trout Salmo gairdneri than in hatchery-reared fish subjected to confinement in a net and to electroshock. During 12 h of net confinement, plasma cortisol increased from resting levels of 10 ng/mL to 480 ng/mL in wild fish, and from 2 ng/mL to 155 ng/mL in hatchery fish. Plasma glucose was also higher in wild fish, increasing from 55 to 284 mg/dL, versus an increase from 58 to 196 mg/dL in hatchery fish. Plasma chloride decreased from resting levels of 132–135 meq/L to 53 meq/L in wild fish (and it continued a decline to 33 meq/L during the first 24 h after confinement), but only to 102 meq/L in hatchery fish. Both wild and hatchery-reared fish required more than 24 h after they were removed from the net to recover resting levels of plasma constituents. Plasma concentrations of cortisol, glucose, and chloride were less altered in response to electroshock than they were in response to net confinement....

Acclimation Temperature Influences Cortisol and Glucose Concentrations in Stressed Channel Catfish

Abstract Basal concentrations of plasma cortisol (near 50 ng/ml) and plasma glucose (near 0.50 mg/ml) were significantly greater in yearling channel catfish (Ictalurus punctatus) acclimated to 10 C than in fish adapted to 20 or 30 C; the latter groups had similar basal levels of cortisol (near 25 ng/ml) and glucose (near 0.30 mg/ml). Fish at 10 C had a slower and less marked increase in cortisol and glucose over minutes, hours, and days in response to the stress of severe confinement than fish at 20 or 30 C which were again similar. No mortality occurred in the fish stressed at 10 C during 3 days of confinement, while 89% died in the 20 C group by day 3 and all fish at 30 C were dead by day 2. Glucose concentrations initially rose more slowly than those of cortisol, but continued to increase between 3 and 12 hours after confinement. Also, glucose returned to near basal levels in dying fish while cortisol was at its highest then. Channel catfish, even at warm temperatures, have a slower and less extensive ...

Summer food limitation reduces brook and rainbow trout biomass in a southern Appalachian stream

Abstract We assessed salmonid production in summer in a second- and third-order montane stream in eastern Tennessee in 1987. We sampled three stream sections, one containing exclusively brook trout Salvelinus fontinalis, one containing exclusively rainbow trout Oncorhynchus mykiss, and a third with a mixture of both species. Population estimates for July and October 1987 revealed reductions in biomass over the 4-month period that ranged from 31 to 49%, whereas population densities declined by 32–46% during the same period. Total net production during the 4-month period was low and ranged from 0.38 to 0.45 g/m2. From June through September, the mean number of prey items per stomach ranged from 4.2 to 29.9, whereas the mean relative weight of stomach contents ranged from 0.12 to 1.34 mg dry weight per gram wet weight offish flesh. There was a strong positive correlation between the mean relative weight of stomach contents and the mean condition factor for a given date. Calculated energy intake was below the...

Growth and Production of Sympatric Brook and Rainbow Trout in an Appalachian Stream

Abstract A small, second-order stream in the southern Appalachians was sampled every 2 months from September 1978 to October 1979. The 1.5-km study segment was divided into 50, 30-m sections grouped into three areas: A downstream area with only rainbow trout Salmo gairdneri; a middle, mixed-trout area; an upstream area with predominantly brook trout Salvelinus fontinalis. Although a few fish of both species exhibited substantial movements, the majority of fish moved less than 30 m either upstream or downstream. Growth rates of both species were approximately equal until the spring of their second year, when rainbow trout outgrew brook trout and thereafter maintained a size-at-age advantage. Rainbow trout, particularly the 1978 cohort, dominated trout production in the stream. Even in the brook trout area, where the density of 1978 cohort brook trout was twice that of 1978 cohort rainbow trout, rainbow trout outproduced brook trout by 1.20 g/m2 to 1.14 g/m2. Declining mean biomass of older fish of both spe...

Protein Digestibility Coefficients for Yearling Channel Catfish Fed High Protein Feedstuffs

Abstract Yearling (1 +) channel catfish (Ictalurus punctatus) were held in a regulated environment and fed high protein feedstuffs to determine apparent crude protein digestibility coefficients (ACPD). ACPD was determined by feeding semi-purified diets containing a sufficient non-protein energy source and substituting the test feedstuff at an isonitrogenous level. Feedstuffs tested were corn gluten meal, peanut meal, poultry by-product meal, soybean meal, menhaden fish meal, blood meal, and meat and bone meal. ACPD values ranged from 92% for corn gluten meal to 65% for poultry by-product meal. Mean ACPD from plant sources was higher than the mean ACPD from animal sources but may be an artifact of the feedstuffs tested.

No Net Loss of Brook Trout Distribution in Areas of Sympatry with Rainbow Trout in Tennessee Streams

Abstract Lowest distributional elevations for brook trout Salvelinus fontinalis in 25 streams in east Tennessee were determined during 1991–1995 to evaluate changes related to encroachment and possible replacement by rainbow trout Oncorhynchus mykiss since surveys conducted during 1978–1984. No efforts to remove rainbow trout or enhance brook trout populations were made in these streams during the 7–16-year intervals between surveys. Compared with the earlier surveys, brook trout distributions receded (lower elevation increased) in nine streams (36%), advanced (lower elevation decreased) in eight streams (32%), and did not change in eight streams (32%). The average total change in stream length occupied by brook trout was a 109-m downstream increase (SE = 82) with a mean annual increase of 8 m (SE = 6). Neither average total change nor annual change was significant (P > 0.19). Additionally, the highest elevations at which rainbow trout were present (determined in 10 streams) increased in four streams but ...

Distribution of cortisol among its free and protein-bound fractions in rainbow trout (Orhynchus mykiss): Evidence of control by sexual maturation

1. Total cortisol concentrations did not differ in sexually matured female, male, and immature rainbow trout. 2. The per cent cortisol bound to a corticosteroid binding protein was greater in mature female fish (48.2%) than in mature male (16.0%) and immature fish (19.5%). 3. The mature female fish exhibited a lower percentage of free cortisol (21.8%) compared to mature males (44.8%) and immature fish (43.2%). 4. Parallel aspects of the teleostean cortisol binding-protein and the mammalian counterpart are compared and commented upon.

Nutrient Content of Clupeid Forage Fishes

Abstract Gizzard shad Dorosoma cepedianum, threadfin shad D. petenense, hybrid gizzard shad x threadfin shad, and alewives Alosa pseudoharengus were collected from Cherokee, Dale Hollow, and Old Hickory reservoirs, Tennessee, from January 1984 through December 1984. Samples were analyzed for proximate composition (moisture, ash, protein, and fat) and gross energy content. Overall ranges of nutrients for all collections were determined: Moisture, 69.7–84.9%; ash, 12.0–32.5%; protein, 45.4–79.1%; fat, 3.3–31.5%; and gross energy, 3.92–6.06 kcal˙g−1. Changes in protein, ash, and moisture percentages within an age-class of a species were primarily the result of changes in fat percentage. In general, fat content increased through summer, peaked during fall, and declined during winter. Seasonal variations in reproductive condition, as well as differences in age and sex, were causes of variations in body composition within a species. Proximate composition and gross energy content of the clupeids examined were si...

Hematology of Striped Bass in Fresh Water

Abstract Eight hematological characteristics were measured on a total of 40 adult striped bass (Morone saxatilis) taken during four collections from three freshwater reservoirs. The range of mena hematological values from the four samples was as follows: hematocrit 31-38%, hemoglobin 7-11 g/100 mL, plasmaosmolality 321-381 mOs, plasma chloride 129-156 meq/L, plasma glucose 77-118 mg/100 mL, plasma cortisol 0.77 -6.33 µg/100 mL, total plasma protein 4.3 -4.9 g/100 mL, and total plasma cholesterol 322-499 mg/100 mL. These means generally fell within the range of means reported for apparently healthy striped bass from salt water. The variability within our samples was comparable to the variability associated with same measurements or fish held under controlled laboratory conditions. We attribute this to the rapid collection and preparation technique we employed in the field. No consistent pattern in the differences between collections was discerned and they may be attributed to normal variations due to seaso...

Effects of Tricaine Methanesulfonate, Hypno, Metomidate, Quinaldine, and Salt on Plasma Cortisol Levels following Acute Stress in Threespot Gourami Trichogaster trichopterus

Abstract Blood plasma cortisol concentration is an indicator of stress in fish, and anesthetics may serve to ameliorate stress and reduce the cortisol response. Previous studies have concentrated on cold- and warmwater species; little information exists for tropical fishes. Mortalities are increased after handling stress of threespot gourami Trichogaster trichopterus (Osphronemidae), a commonly cultured tropical ornamental fish. Plasma cortisol levels were evaluated in threespot gourami after a handling stressor and treatment with one of four anesthetics—tricaine methanesulfonate (TMS; 60 mg/L), metomidate (0.8 mg/L), quinaldine (5 mg/L), and Hypno (0.14 mg/L)—or salt (NaCl; 3 g/L). Fish in all anesthetic treatments had significantly lower cortisol levels than either salt-treated fish or the untreated controls. Therefore, the use of such anesthetics should be beneficial in reducing handling stress. Based on our data, further studies refining the use of anesthetics, particularly metomidate and quinaldine, ...