Effects Of Rearing Density Research Articles

Effects of Rearing Density, Substrate Height, and Feeding Frequency on Growth and Biomass Production of Hediste diversicolor

The polychaete Hediste diversicolor is a suitable species for industrial aquaculture; however, cost-effective culture techniques need to be developed for its intensive production. The aim of this study is to evaluate the effects of worm density and substrate height and their interaction, as well as feeding frequency, on the rearing performance of H. diversicolor. Two trials were conducted. In trial 1, the effects of two substrate heights—6 and 12 cm—and two rearing densities—1000 and 4000 individuals m−2—were assessed in terms of worm growth and biomass production. Worm initial wet weight was 48 mg, and specimens were fed with commercial fish feed during a 70-day assay. The results show no interaction between rearing density and substrate height, and confirm density as a key factor in growth; however, a density of 4000 individuals m−2 results in a significant increase in production (final biomass three times higher for the highest rearing density) without affecting survival. In trial 2, the effect of three levels of feeding frequency—seven days a week; three times a week; and once a week—on growth in individuals of three weight classes—small (25–50 mg); medium (100–150 mg); large (250–350 mg)—was evaluated in a 15-day growing assay. Feeding frequency showed a major influence on the smallest size class, with the best growth indicators obtained at the highest feeding frequency. This study shows that Hediste diversicolor can be reared at a high stocking density to obtain a higher biomass production, and that feeding frequency must be considered as an important factor and adapted to the culture phase.

Effects of Rearing Density on Developmental Traits of Two Different Biotypes of the Gypsy Moth, Lymantria Dispar L., from China and the USA.

Simple SummaryThe gypsy moth, Lymantria dispar, is a forest pest that is grouped into two biotypes: the European gypsy moth (EGM), found in Europe and North America; and the Asian gypsy moth (AGM), found in China, Russia, Korea, and Japan. Outbreaks of this pest result in high-density populations of larvae that can cause enormous damage to trees and forests. Studies have identified an influence of larval population density on gypsy moth development, but it is not known how EGM and AGM populations differ in their response to changing larval densities. We examined the effects of varying larval density on three colonies established from one EGM population and two AGM populations. All three colonies exhibited an optimal degree of larval survival and optimal rates of pupation and adult emergence at an intermediate density of five larvae/rearing container. The duration of larval development was fastest at the same intermediate density for all three colonies. Although differences in larval development time, survival, pupation and emergence were observed among the three colonies under the conditions of our study, our findings indicate that density-dependent effects on the development of different gypsy moth biotypes follow the same trends.The life-history traits of the gypsy moth, Lymantria dispar L. (Lepidoptera: Erebidae), have been observed to vary with larval population density, which can increase significantly during an outbreak of this pest. Laboratory studies on density-dependent variation in gypsy moth development have focused on single populations and were limited to comparing solitary larvae with groups of larvae reared at a single density. To evaluate how density-dependent impacts on development vary with different populations and subspecies of L. dispar, we compared the effects of rearing larvae of a European gypsy moth (L. dispar dispar L.) population from Connecticut, USA; and larvae of two populations of the Asian gypsy moth (L. dispar asiatica Vnukovskij) from Guizhou and Hebei provinces in China. Larvae were reared on an artificial diet at densities of one, three, five, seven, and nine larvae per 115 mL container, and the duration of larval development, percentage of surviving larvae, and the rates of pupation and emergence were measured at each density. A two-tailed response to density variation with values falling away on both sides from a peak or climbing from a base was observed for all three populations tested, with the most rapid larval development and the highest values of survival, pupation, and emergence observed at a density of five larvae/container. Although differences in larval development time, survival, pupation and emergence were observed among the different populations under the conditions of our study, our findings indicate that density-dependent effects on the development of different gypsy moth subspecies and populations follow the same trends.

Effect of Rearing Density on Life Table Parameters of the Laboratory Population of Galleria mellonella L.

Effect of Rearing Density on Life Table Parameters of the Laboratory Population of Galleria mellonella L.

Effects of Rearing Density on Return to Creel of Hatchery Catchable Rainbow Trout Stocked in Idaho Lentic Waters

AbstractEvaluating rearing techniques that maximize angler returns to creel of hatchery trout is an essential tool in shaping hatchery management practices and maximizing the public use of hatchery products. The goal of this study was to determine the effects of raceway rearing density on return to creel of catchable-sized (mean TL ≈ 252 mm) hatchery Rainbow Trout Oncorhynchus mykiss. In 2011 and 2012, Idaho Department of Fish and Game reared catchable-sized trout targeting three maximum density indices (0.15, 0.25, and 0.30 lb·ft−3·in−1) at three different state fish hatcheries. Each hatchery stocked fish into the same 11 lakes and reservoirs to evaluate return-to-creel rates by rearing density. Although there was a trend of lower angler catch for fish reared at a higher raceway density, the relationship was not statistically significant. Instead, angler catch was significantly influenced by fish size at stocking and the surface area of the water being stocked, whereby larger fish and smaller waters had ...

The Effects of Rearing Density on Growth, Fin Erosion, Survival, and Migration Behavior of Hatchery Winter Steelhead

AbstractJuvenile winter steelhead Oncorhynchus mykiss at Eagle Creek National Fish Hatchery in Estacada, Oregon, were reared for three brood years (2004–2006) at raceway densities of 7,500 (214 fish/m3), 15,000 (429 fish/m3), and 22,500 fish (643 fish/m3) to determine the effects of rearing density on growth, fin erosion, survival, adult yield, and migration behavior. Coded wire tags were used to evaluate adult survival, and fish were radio‐tagged to monitor migration times from the hatchery to the mouth of Eagle Creek following volitional release from the hatchery. We found rearing density had a significant effect (P < 0.05) on steelhead growth, fin erosion, and adult survival. Winter steelhead reared in low‐density raceways (13.6 kg/m3 at release) were significantly larger at release, larger at return, had significantly better dorsal fin condition, and had significantly greater smolt‐to‐adult survival rates than did those reared in medium (23.4 kg/m3) and high (35.2 kg/m3) density raceways. No significant relationship between smolt size at release and migration timing was detected; however, the effect of rearing density on fish migration was noticeable in brood year 2004. In that year (2004), smolts from the medium‐ and high‐density groups took from 6 to15 d longer to out‐migrate than those from the low‐density group.

The Effects of Rearing Density, Salt Concentration, and Incubation Temperature on Japanese Medaka (Oryzias latipes) Embryo Development

Environmental stressors are often present when an aquatic species, such as the Japanese medaka (Oryzias latipes) fish, are developing. This study examined the effects of some of these environmental stressors (variation in rearing density, salinity, and incubation temperature) on medaka embryo development. The hypotheses are if rearing density is increased, then hatching success will also be improved, while having no effect on embryo development; if the salt concentration is increased to 20 parts per thousand (ppt), then the rate of development will also be increased; if temperature is increased to 32°C, then the rate of development will also be increased. To determine the effects of variations in rearing density (1, 2, 3, and 4 eggs per well), the time of hatch was observed and noted. When testing variations in temperature (24°, 28°, and 32°C) and salinity (0.3, 10, 15, and 20 ppt), the onset of heartbeat and onset of retina pigmentation were observed. The original hypotheses were not all supported: as rearing density increased, success of hatch decreased; as salinity increased, only the rate of development for heartbeat increased; as temperature increased, the rate of development for both onset of the heartbeat and retina pigmentation also increased.

Effects of Rearing Density, Age, Sex, and Food Deprivation on Flight Initiation of the Red Flour Beetle (Coleoptera: Tenebrionidae)

Effects of rearing density, adult density and sex ratio in the flight chamber, adult age, sex, presence or absence of food, and duration of food deprivation on rate of and time to flight initiation of the red flour beetle, Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae), were studied in the laboratory. Rates of flight initiation were slightly lower at lower rearing densities, but they did not differ with age or sex of adults, presence or absence of food in the flight chamber, or duration of food deprivation. Focal adults were less likely to fly when individuals of the opposite sex were present in flight chambers. Presence of the same sex or mixed sexes and numbers of individuals in flight chambers did not affect tendency to fly of focal individuals. Mean time to flight of older beetles (7-20 d old) was less than that of younger beetles (1-4 d old). No young beetles flew during the first 24 h of flight tests. Mean time to flight did not differ with rearing density, sex, presence or absence of food, or duration of food deprivation. Our results indicate that this species is highly dispersive during the adult stage and that flight does not seem to be associated with just prereproductive or postreproductive dispersal phases, high rearing density, or short to medium periods of food deprivation. Therefore, T. castaneum level of flight activity does not seem to be associated with factors that have been shown in the literature to increase dispersal by walking for this species and to increase flight initiation in other stored-product species.

Effect of Rearing Density and Feeding Regimes on Growth and Survival of African Catfish, Heterobranchus longifilis (Valenceinnes, 1840) Larvae in a Closed Recirculating Aquaculture System

Heterobranchus longifilis larvae were reared over a 35 d period to evaluate the effects of stocking densities and feeding regimes on growth and survival. In experiment 1, larvae (12.3 ± 2.1 mg) were stocked into glass aquaria at densities of 1, 2, 5, 10, 15, 20, and 25 larvae L−1. Larvae were fed on Artemia nauplii ad libitum. Significant variations in terms of growth performance and feed utilization occurred at all levels of density treatments. Specific growth rate (SGR), body weight gain (BWG), and feed efficiency (FE) of the larvae decreased significantly as density increased. However, survival rate increased with the increase of stocking density. In experiment 2, larvae (13.4 ± 1.1 mg) stocked at a density of 15 larvae L−1, in the same conditions as experiment 1, were fed on three different regimes: Artemia nauplii; 35% protein beef brain; and 35% protein commercial catfish feed (CN+). SGR, BWG, and coefficient of variation (CV) of larvae fed on Artemia nauplii were significantly higher than those fed on beef brain and CN+. The survival rate of larvae fed on beef brain was significantly higher (88.40 ± 9.75%) than those of Artemia (69.21 ± 6.69%) and CN+ (40.40 ± 6.22%). The results of this study suggest that the optimum stocking density is 15 larvae L−1 and the beef brain can be used as alternative feed to Artemia in rearing H. longifilis larvae.

The effects of Rearing Density on Growth Perfor mance and Food Conversion Ratio of Siberian Sturgeon (Acipenser baeri Brandt)

The effects of Rearing Density on Growth Perfor mance and Food Conversion Ratio of Siberian Sturgeon (Acipenser baeri Brandt)

The Effect of Rearing Density on Growth and Survival of Cobia, Rachycentron canadum, Larvae in a Closed Recirculating Aquaculture System

The Effect of Rearing Density on Growth and Survival of Cobia, <i>Rachycentron canadum</i>, Larvae in a Closed Recirculating Aquaculture System

Effects of Rearing Density and Raceway Conformation on Growth, Food Conversion, and Survival of Juvenile Spring Chinook Salmon

Abstract Four brood years of juvenile spring chinook salmon Oncorhynchus tshawytscha were reared in conventional and baffled raceways at various rearing densities and loads at Willamette Hatchery, Oregon. A period of rapid linear growth occurred from August to November, but there was little or no growth from November to March when the fish were released. Both fall and winter growth rates were inversely related to rearing density. Final weight and length were also inversely related to rearing density. No significant relationship between load and any growth variable was observed. Fish reared at lower densities in conventional raceways tended to develop bimodal length distributions in winter and early spring. Fish reared in conventional raceways showed significantly larger growth rates and final lengths and weights than those reared in baffled raceways. Food conversions and average delivery times for feed were significantly greater in baffled than in conventional raceways. No significant relationships were o...

Effects of Rearing Density upon Cutthroat Trout Hematology, Hatchery Performance, Fin Erosion, and General Health and Condition

Abstract Ahstract.—Cutthroat trout of the Bear Lake Bonneville strain, Oncorhynchus clarki utah, were used in two separate density experiments. In the first, fish were reared for 212 d in outdoor raceways at four densities; fish were allowed to grow into their final rearing density and were fed 7 d/week. Final rearing densities averaged 768, 1,597, 2,073, and 2,998 fish/m3, and corresponding density indices (DI = fish weight, Ib/[fish length, in ×water volume, ft3]) were 0,40, 0.90, 1.10, and 1,46. In experiment 2, crowding screens were adjusted monthly, and fish were fed 5 d/week: final rearing densities were 338, 739, and 1,634 fish/m3 (DIs of 0.19, 0.39, 0.75). Feed conversion and mortality did not significantly differ among densities for either experiment, Final mean weights did not differ among the four densities of experiment 1, but mean total length was significantly longer in fish reared at the lower densities. In experiment 2, final mean weight was significantly reduced in the highest density and...

Effects of Rearing Density on the Growth Response of Juvenile Fathead Minnow (Pimephales promelas) under Toxicant-Induced Stress

The effects of rearing density on the apparent toxicity of pentachlorophenol and 2,4,5-trichlorophenol were investigated using 28-d growth and survival tests with larval fathead minnow (Pimephales promelas). The fish were held at rearing densities of 1, 5, or 10 fish per 1-L cage. Among individual fish, those held at the lowest density showed three times less variability in wet weight at 28 d than those at the highest density. Two-way analysis of variance of the growth data showed a significant interaction between concentration and density for both toxicants, suggesting that density affected the nature of the relationship between exposure concentration and response. The change in the concentration–response relationship was most dramatic for 2,4,5-trichlorophenol; a quadratic function for fish reared at low and medium densities changed to a linear function at the highest density. The estimated thresholds of toxicant impact on growth were twofold lower for low- versus high-density fish for both chemicals. Testwater volumes and replenishment were high enough in these experiments that decreased toxicant loading at higher densities did not appear to be a factor contributing to these results.

Effects of Rearing Density on the Stress Response and Growth of Rainbow Trout

One-year-old rainbow trout Oncorhynchus mykiss were reared for 8 weeks at a density of either 56 or 267 g fish/L (based on the volume of net-pens), equivalent to density indexes of 2.3 and 11.1 g fish/L-cm total fish length), respectively. The fish were held in 0.6 × 0.3-m netpens submerged to a depth of 0.15 m. Two net-pens for each fish density were suspended in each of three 3,040-L circular tanks provided with sufficient flow to maintain loading rates in the tanks at less than 800 g/(L-min). The fish were then subjected to an acute handling stress by being removed from the water for 60 s. No differences in the time course of changes in serum cortisol levels or hematocrits were observed over a 12-h period between fish in the two density groups. There were also no differences between the two groups of fish in weight, length, body condition factor (weight/length3), interrenal nuclear diameter, or the percentage of the anterior stomach that was mucosa. These results indicate that if high water quality is maintained, 1-year-old rainbow trout can be reared at a density index as high as 11. 1 g/(L-cm) without impairing their growth or causing overt chronic stress.

Effects of Rearing Density on Meristics and Developmental Stability of Rainbow Trout

We investigated the effects of a four-fold difference in incubation and rearing density on developmental rate, counts of eight meristic characters, and fluctuating asymmetry of rainbow trout, Oncorhynchus mykiss. Fish from the high density group had significantly more vertebrae and rays in the pelvic fins. The overall magnitude of morphological divergence between treatment groups, however, was small compared to that associated with genetic and temperature-induced alterations of developmental rate. Fish from the high density treatment had greater mean fluctuating asymmetry than those in the low density group, but this difference is not statistically significant. Hatching time did not differ significantly between treatment groups. The effects of density on meristic counts, therefore, appear to be independent of developmental rate.

Effect of Rearing Density on Poststocking Survival of Lake Trout in Lake Ontario

Abstract Six paired lots of yearling lake trout (Salvelinus namaycush) reared at densities of 41,000 and 51,000 fish per raceway during their last 9 months in the hatchery were stocked in Lake Ontario. Poststocking survival of the high-density (HD) and low-density (LD) fish was not different for the 1982 year-class. However, for the 1983 year-class, mean survival was significantly different between HD and LD fish (P < 0.01). Mean survival of HD fish was only 76% that of LD fish (P < 0.01), and most of the mortality attributable to rearing conditions had apparently occurred within 2 months after stocking. Mean size at stocking was not different for HD and LD fish of the 1982 year-class, but for the 1983 year-class, the LD fish were 6% longer and 22% heavier than the HD fish. Mean lengths and weights of LD and HD fish were not different in samples collected in Lake Ontario at age 2 and older. Size at stocking was not likely the factor that caused the difference in survival. Rather, the rearing conditions (p...

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.

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.

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.