Rearing Density Research Articles

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.

Plasma Cortisol and Secondary Stress Responses of Red Drum to Handling, Transport, Rearing Density, and a Disease Outbreak

Abstract The effects of some common fish culture procedures on the biochemical stress responses of juvenile red drum (Sciaenops ocellatus) were examined in the present study. Plasma cortisol, glucose, and osmolality were measured in cultured red drum subjected to capture and handling, transportation, an outbreak of disease, and different rearing densities. Capture and handling elicited rapid, marked elevations of plasma cortisol and glucose in the fish. The responses were transient, however, and the plasma concentrations returned to initial values 1 d after handling. Similarly, transportation of red drum induced rapid but transient plasma cortisol, glucose, and osmolality responses and caused no mortality. An outbreak of disease evoked cortisol, glucose, and osmolality stress responses in red drum. As the disease progressed, the plasma cortisol and osmolality responses became more pronounced. Fish reared at different densities had similar plasma glucose levels. Cortisol titers were temporarily elevated in...

Effects of Rearing Density on Growth and Survival of Lake Trout

Abstract Lake trout (Salvelinus namaycush) were reared at density indices (allowable density in pounds/cubic foot divided by fish length in inches) of 0.25, 0.50, 1.0, and 2.0 in cages suspended in circular tanks. Water flow rates were such that dissolved oxygen remained above 8 ppm within all the cages. Thus treatment effects were attributed to density and not influenced by water quality. Growth and condition were not affected by density, but survival was lower at the higher density than at the three lower densities. We conclude that lake trout may be successfully reared at a density index of at least 1.0 if the water requirements for respiration and waste dilution are met.

Rearing of the Brown Citrus Aphid, Toxoptera citricidus (KIRKALDY), (Homoptera : Aphididae), on a Synthetic Diet with Reference to pH and Sucrose Concentration of Diet and Rearing Density

Rearing of the Brown Citrus Aphid, Toxoptera citricidus (KIRKALDY), (Homoptera : Aphididae), on a Synthetic Diet with Reference to pH and Sucrose Concentration of Diet and Rearing Density

An initial description of the quantitative genetics of growth and reproduction in the mosquitofish, Gambusia affinis

Three stocks of mosquitofish were reared under identical conditions through one complete life cycle to quantify phenotypic and genetic variability for traits of growth and reproduction. At 60 days of age females and males averaged 473 mg and 183 mg in weight and 26.2 mm and 20.9 mm in length, respectively. Significant differences were found among stocks for both sexes in both traits. Rearing density strongly affected female size; its effection male size was much less pronounced. Stage of maturity and male size were closely related, with maturing males being significantly larger than either mature or very immature fish. Heritability estimates for males were 0.25 for both length and weight, for females 0.72 for length and 0.77 for weight. Males averaged 55 days of age at sexual maturity. There were no significant differences among stocks, nor was there a significant effect of density on this trait. Heritability of age at maturity was estimated to be 0.41. Maturation of the first male to mature in a tank appeared to be under much weaker genetic control than maturation of subsequent males, suggesting a genotype-environment interaction. The size of first broods of virgin females averaged 23 fish. Significant differences between stocks for size of first brood were apparent only when female weight was considered. Heritability of brood size was estimated to be 0.16 without correction for female weight, and was impossible to estimate but presumably very low when corrections were made for female weight. Although female weight significantly affected brood size, it accounted for only 13% of the variation in the trait.

Stress-Related Effects of Hatchery Rearing Density on Coho Salmon

Juvenile coho salmon Oncorhynchus kisutch were reared for 12 months at four densities in rectangular concrete ponds. Increasing fish density was associated with significant decreases in weight, length, condition factor, and food conversion efficiency; elevated body water content; reduced fat and protein contents; and increased mortality (which did not exceed 3%). Skewness in length distribution changed from positive to negative with increasing fish density. At the time fish were released into the ocean, interrenal cell nuclear diameters in small fish held at the highest density were significantly greater than in large fish or in fish of either size held at the lowest density. This suggests that crowding stress particularly affects small fish.

Studies on Optimum Rearing Density in Layer House

Studies on Optimum Rearing Density in Layer House

Studies on Optimum Rearing Density in Layer House

Studies on Optimum Rearing Density in Layer House

Life History of the Central American Locust, Schistocerca sp. (Orthoptera: Acrididae), in the Laboratory1

Hopper (nymphal) life of the Central American locust, Schistocerca sp., averaged 45 days for both sexes; usually there were 6 instars, but occasional males had only 5. Rearing density greatly affected the coloration of the hoppers. Those reared in crowds invariably had a heavy black pattern on a pink or peach ground color; those reared in isolation had little or no black pattern, and the ground color was green, brown, pink, or straw. The type of food similarly affected the coloration of the isolated hoppers, but not that of the crowded specimens. When hoppers kept in crowds for the earlier part of their life were subsequently isolated, their coloration showed dependence on both the previous and the current density. The color of fledgling adults was not correlated with nymphal coloration; all had a rather somber, brown appearance. Sexually mature males kept in crowds became predominantly yellow, but crowded females developed only a little yellow coloration, and isolated adults developed none at all on maturity. Density affected the length of the pre-oviposition period also, which averaged 36 days from fledging to production of the first egg pod by females kept in crowds, 61 days for those that were isolated. Crowded adult females averaged 6 egg pods each, with 70 eggs per pod; isolated females, 8 pods with 62 eggs per pod. Pods were produced at 6–7 day intervals, regardless of density. The incubation period was 18–19 days at 32°C, 25 days at 28°C. Newly hatched hoppers from crowded parents were relatively dark colored and heavier, as compared with those from isolated parents. Morphometric data from the experimental locusts showed that the femur-caput ratio was correlated with previous rearing density, and, together with nymphal coloration, would provide criteria for estimating the potential danger of field populations. The similarity in life histories between the Central American locust and related locusts of the Old World is discussed.

Some Effects of Rearing Density on the Biology of the Elm Spanworm

AbstractThe elm spanworm, Ennomos subsignarius (Hübner), a defoliator of oaks and hickories in the Southern Appalachians, was reared under three population densities — one, two, and four larvae per cage. The size of the group influenced to a degree the time spent in the larval stage, but was even more significantly related to the duration of the hatch to adult period. Although male pupal weight was not related to group size, female weight and fecundity were. Females reared singly had significantly greater pupal weight and fecundity than those reared in groups.