Fin Condition Research Articles

Interactions between individual feeding behaviour, growth, and swimming performance in juvenile rainbow trout (<i>Oncorhynchus mykiss</i>) fed different rations

Aerobic swimming performance (critical swimming speed, Ucrit), food consumption per meal (by X-ray radiography), specific growth rate (SGR), haematocrit, and fin condition were monitored in individual juvenile rainbow trout (Oncorhynchus mykiss). The fish were held in groups over a 9-week period and fed daily group rations (dry food) of 2.0, 1.5, 1.0, and 0.5% wet body mass (BM)·day-1. SGR declined and competition increased at lower ration levels, as reflected by greater fin damage, reduced haematocrits and condition factors, and, at 0.5% BM·day-1, a substantial increase in the coefficient of variation among individual meals. Absolute Ucrit also declined at lower ration levels. However, there was no relationship between Ucrit and haematocrit, fin damage, or condition factor in any of the ration groups. A negative correlation was found between Ucrit and SGR in individual trout fed a group ration of 2.0% BM·day-1, but a positive correlation was seen at 0.5% BM·day-1 and no relationship at 1.0 and 1.5% BM·da...

The effect of diet on dorsal fin erosion in steelhead trout ( Oncorhynchus mykiss)

A 2 × 2 factorial experiment of diet type (krill vs. fish meal) and steroid supplementation (0 vs. 30 μg 17α-methyltestosterone kg −) was conducted to determine the effects on dorsal fin erosion in steelhead trout. Triplicate tanks of 250 fry were fed one of the four diets at a rate calculated to produce 115 g fish in 34 weeks. Fish were transferred to larger tanks when mean density index reached 0.40. Dorsal fin index (DFI, measured as mean dorsal fin height × 100/total fish length) was greater ( P < 0.001) among fish fed krill-based diets than for fish fed fish-based diets at weeks 12, 22, and 34 of the trial. Added testosterone decreased ( P = 0.04) DPI among fish fed the krill diet at week 12 but otherwise had no effect on fin condition. Addition of testosterone to either diet type decreased ( P = 0.02) critical thermal maximum, which is a measure of fish resistance to thermal stress. The results suggest that diet composition can influence the rate of dorsal fin erosion in steelhead trout through a metabolic, behavioral, or combined change.

The Effects of Fry Rearing Density on Hatchery Performance, Fin Condition, and Agonistic Behavior of Rainbow Trout Oncorhynchus mykiss Fry

AbstractRainbow trout Oncorhynchus mykiss fry were reared at four densities ranging from 10,800 to 43,926 fish/m3 (9.91 to 37.60 kg/m3) during an initial feeding period of 35 d. Each of the four initial density treatments were then split into high (3,780 fish/m3) and low (1,890 fish/m3) density groups and reared in outdoor raceways for an additional 74 d. A necropsy‐based general health and condition assessment indicated that hematocrit, plasma protein, and the thymus index were significantly elevated in the outdoor high density group. Changes in these variables were unrelated to the initial rearing density, except for plasma protein which decreased as the initial density increased at low densities. Other necropsy variables indicated normal, healthy fish. Agonistic behavior was assessed at 4, 9 and 13 wk of age by observing the number of aggressive chases in paired and group (five fish) trials. The number of chases generally increased with age, although the difference between 9 and 13 wk was variable. Feeding did not elicit more chases in this study except for 9‐wk‐old fry. Initial rearing density did not have any impact on the number of chases at 4 or 13 wk, but at 9 wk the number of chases increased with initial density for the group tests. Relative fin length measurements of all fins except the adipose indicated no combination of initial density and outdoor density was superior to another for reducing fin erosion. This study indicated that rainbow trout fry may be reared at initial densities approaching 44,000 fish/m3 (Piper density index of 1.1) without negatively affecting growth and fin condition or inducing higher levels of agonistic behavior later on.

Effects of Intermittent Exposure to Therapeutic Levels of Formalin on Growth Characteristics and Body Condition of Juvenile Rainbow Trout

Abstract The effects of twice weekly exposure to formalin (200 mg/L in a 1-h static bath) on juvenile rainbow trout Oncorhynchus mykiss (57.4 g initial weight) were assessed in a completely random, matched-pairs, 12-week growth trial. Growth rates, appetite, feed conversion, and body condition index of the fish were not significantly affected by formalin treatment after 6 and 12 weeks. There was also no evidence of a cumulative effect of formalin treatments over time, because the similarities between treated and untreated groups of fish persisted over the 12-week trial. Formalin-treated fish had significantly better fin condition and a lower incidence of corneal opacity than did untreated fish. This study showed that formalin, in a 1-h static bath at 200 mg/L repeated twice weekly, can be used as a disease prophylaxis regime with no negative effects on growth.

Assessment of Demand Feeder Spacing on Hatchery Performance, Fin Condition, and Size Variation of Rainbow Trout Oncorhynchus mykiss

Abstract.— Fingerling rainbow trout, Oncorhynchus mykiss, were fed for 133 d by one of three feeding methods: one demand feeder per 5.5 m of raceway, 2 demand feeders per 5.5 m of raceway, and hand‐fed controls. Mean weight, total length, mortality, and feed conversion were not influenced by the method of feeding. Size variation did not differ among treatment groups, as assessed by comparing the coefficient of variation of total length. Necropsy‐based health and condition profiles were conducted three times during the rearing period, and results indicated that fish were generally normal and healthy in all treatments. Several parameters differed significantly over time, but no trends were observed except for the fin index and hematocrit. Over time, hematocrit decreased from 48.6 to 45.0%, and the fin index increased from 0.80 to 1.57. Fin index values did not differ among the feeding methods. Fin condition assessed by measuring relative fin length was better in the single feeder treatment than controls for caudal and ventral fins in the last sample. However, since fish from the two‐feeder treatment did not differ from controls, demand feeding per se did not improve fin condition relative to fish that were fed by hand, four to six times per day. The lack of significant improvements in growth or health with the addition of another demand feeder indicated that using more than one feeder per 5.5 m of raceway length is unnecessary for culture of juvenile rainbow trout.

Fin Condition and Health Profiles of Albino Rainbow Trout Reared in Concrete Raceways with and without a Cobble Substrate

Abstract Fingerlings of albino rainbow trout Oncorhynchus mykiss were reared for 200 d in concrete raceways with either concrete (controls) or cobblestone bottoms. Health and condition profiles were performed on 20 fish/treatment on four occasions. For fish in cobble-bottom raceways, there was no fin erosion as measured by fin indices (ranked from 0 to 2) applied to the fish as a whole or relative fin lengths (% of body length) of individual fins. For control fish, however, considerable erosion was evident for caudal, dorsal, anal, both pectoral, and both ventral fins. Condition factor, fat levels, and total length were reduced in cobbled raceways. Results are compared with previous experiments with normally pigmented rainbow and cutthroat trout O. clarki. Overall, cobble substrates markedly reduced fin erosion, which suggests that cobble-bottom raceways are especially suitable for rearing albino rainbow trout, if a slight reduction in growth is acceptable.

Performance and behavior of cutthroat trout ( Oncorhynchus clarki) reared in covered raceways or demand fed

Cutthroat trout ( Oncorhynchus clarki Utah) were reared in outdoor raceways with or without plywood covers. The same hand-fed controls for this experiment were also used to test the effects of demand feeding. Growth, feed conversion, and mortality did not differ ( P > 0.05) among the hand-fed covered, hand-fed uncovered (control), and demand-fed groups after 256 days. Autopsy-based parameters were generally not significantly different among groups. However, hematocrit and the fat index were significantly higher in covered raceways after 166 days. The fin index was significantly lower in covered raceways on both Day 166 and 225. Pectoral fin erosion was significantly reduced in covered raceways relative to controls by Day 166, but did not differ by Day 225. Demand feeding did not improve fin condition. Observations of cover preference were made for four fish groups over a 45 min period, either in the presence of a stuffed eagle or without it. All groups significantly preferred cover, but there were no differences related to rearing under cover or the presence of a predator model. Covers did improve fin condition and fat levels of fish during early rearing, but the benefits were not sustained throughout the rearing period. Use of demand feeders did not produce tangible health or growth benefits, but did not negatively impact the fish either. Demand feeding reduced the labor required to feed the fish, but increased cleaning time.

A Survey of Trout Fin Erosion, Water Quality, and Rearing Conditions at State Fish Hatcheries in Utah

AbstractA total of 600 hatchery trout were examined for signs of fin erosion including rainbow trout Oncorhynchus mykiss, cutthroat trout O. clarki, brook trout Salvelinus fontinalis and brown trout Salmo trutta. A scoring system was used to evaluate erosion on all fins from 20 fish samples. Water quality and hatchery rearing variables were also determined for corresponding raceways or ponds. For rainbow trout groups (N= 24), stepwise multiple linear regression was used to interpret the relationship between fin erosion and the other variables. These fish groups averaged between 92 and 243 mm in total length and no significant correlation was observed between length and a fin erosion index (r = 0.045). The best‐fit regression model (adjusted R2= 0.689) suggested that fin erosion was correlated with lower alkalinities, unnatural bottom substrates (concrete or steel), higher unionized ammonia levels, and higher fish densities. Despite significant variation between hatcheries, fin condition was significantly better in rainbow trout than in cutthroat trout in three of four hatcheries containing both species and the same substrate. Fin erosion in rainbow trout occurred primarily on dorsal fins, followed in order of decreasing severity, by pectoral, caudal, anal, and ventral fins.

Performance and Oxygen Consumption of Snake River Cutthroat Trout Reared at Four Densities with Supplemental Oxygen

Abstract Snake River cutthroat trout (Oncorhynchus clarki) of the Bar BC strain were reared at four densities in triplicate for 18 weeks. Supplemental oxygen was required in the rearing units holding the three highest densities to maintain adequate dissolved oxygen (DO) levels of 6–7 ppm (61–71% of saturation) after the last feeding in the afternoon. Density indices (lb!ft3 per inch of fish length) achieved for each treatment averaged 0.48, 1.40, 2.12, and 2.30, and fish density averaged 3.43, 10.56, 15.56, and 15.42 lb/ft3, respectively, at the conclusion of the study. Survival, weight gain, feed conversion, and fish health were adversely effected by increased density; however, dorsal and pectoral fin condition, total length, length variation, and water quality were not adversely effected. Neither un-ionized ammonia (maximum, 0.0051 ppm) nor total carbon dioxide (maximum, 24.2 ppm, pH 7.5) concentrations reached detrimental levels. Over a 24-h period at the end of the study, daily DO consumption averaged...

Fin Condition of Atlantic Salmon Reared at High Densities in Heated Water

We assessed the condition of dorsal and pectoral fins of parr of Atlantic salmon Salmo salar that were reared for 70 d at 17.5°C to final densities of 14–55 kg/M2 (rearing-unit bottom area) or 80–310 kg/m3 (rearing-unit volume). Pectoral fins were not significantly affected by rearing density, but dorsal fins were more eroded in fish reared at the highest density than in fish checked before the rearing experiments or in those reared at lower densities. Densities as great as 41 kg/m2 (229 kg/m3) did not affect fin quality of Atlantic salmon reared at 17.5°C.

Performance of Two Strains of Rainbow Trout Reared at Four Densities with Supplemental Oxygen

Abstract Wild and domesticated strains of rainbow trout (Oncorhynchus mykiss) were reared in triplicate groups at four fish densities in two separate studies. Fish weight gain, survival, length increase, length variability, feed conversion (weight fed/weight gain), dorsal fin condition, fish health, and water quality were monitored during each 4-month test. Dissolved oxygen was supplemented to maintain afternoon effluent oxygen levels at 6–7 ppm (61–71% saturation). Survival decreased with increasing density for both strains: wild strain survival was reduced because of cannibalism, and domesticated strain survival was reduced because of mechanical failures that reduced dissolved oxygen. Weight gain and total length increased with increasing densities for the wild strain, but the opposite occurred for the domesticated strain. Length coefficient of variation (SD/mean) increased directly with increasing fish density. Feed conversions of both strains were adversely affected by increased densities, but dorsal ...

Effects of baffles and isolation on dorsal fin erosion in steelhead trout, Oncorhynchus mykiss (Walbaum)

Abstract. Dorsal fin condition was evaluated in two groups of hatchery-reared steelhead trout, Oncorhynchus mykiss(Walbaum), and compared to wild fish. Hatchery fish were reared either in nursery tanks with baffles or in isolation (1 fish/rearing space). Evaluations were conducted to determine differences in dorsal fin condition between these groups and to monitor the progression and severity of fin damage. Isolated hatchery and wild steelhead trout maintained perfect dorsal fins with characteristic white margins. Hatchery fish reared in nursery tanks with baffles experienced dorsal fin erosion that started when the fish were about 40mm total length (30 days after being on feed). This erosion continued until dorsal fin length averaged only 2·3 mm in fish 161–200 mm total length in contrast to an average dorsal fin length of 20·9mm in wild fish of the same size.

Effects of Rearing Density on Growth, Survival, and Fin Condition of Atlantic Salmon

Abstract Parr of Atlantic salmon (Salmo salar) were reared to final densities of 0.53-4.29 lb/ft2 of rearing container bottom area under conditions of constant temperature, water quality, and diet. Growth and survival were not affected by density. After 171 d, the condition of pectoral and dorsal fins had not changed from that initially recorded and did not differ among treatments. We conclude that rearing density alone does not affect growth, survival, or fin condition of Atlantic salmon reared at densities likely to occur at production hatcheries.

Fin condition of lake trout, Salvelinus namaycush Walbaum, reared at different densities

Fin condition of lake trout, <i>Salvelinus namaycush</i> Walbaum, reared at different densities

The Response of Coho Salmon and Guppies to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in Water

Abstract TCDD exposure for 96 hours at 0.54 ng/g (amount of TCDD in test container per gram of wet body weight) had no effect on food consumption, weight gain, or survival of young coho salmon (Oncorhynchus kisutch) during a 60-day postexposure period in a static-water toxicity test. Growth and survival 114 days after exposure to 5.4 ng/g TCDD were reduced, and the reductions were greater after 24 hours than after 12 hours exposure to TCDD. These effects were first observed 56 days after exposure. The body burden of TCDD in young coho salmon 114 days after exposure increased with both the level and duration of exposure. The half-life of the whole-body TCDD residues was at least 109 days after fish were placed in clean water. Guppies (Poecilia reticulata) exposed to 0.8 ng TCDD/g developed fin disease 42 days after exposure. There was a significant decrease in the diseased fin condition between 42 to 69 days after exposure. Guppies had no increase in fin disease after exposure to 0.08 ng/g TCDD.

Effect of Amount of Food on Fin Condition of Fingerling Trout

(1938). Effect of Amount of Food on Fin Condition of Fingerling Trout. The Progressive Fish-Culturist: Vol. 5, No. 39, pp. 16-18.