Effects Of Initial Stocking Density Research Articles

Влияние плотности посадки на личиночное развитие камышовой жабы (Epidalea calamita) (по результатам лабораторных исследований)

The Natterjack toad (Epidalea calamita) is widespread in Europe, but it is reducing in numbers, especially in the north and east of its range. The paper presents the results of studying the effect of initial stocking density on survival, development duration and body length of E. calamita larvae in laboratory conditions. The experiments used containers with the same bottom area (1092 cm2), but with different water levels (14 and 28 cm). Larvae were grown at different stocking densities per unit volume (1–3 larvae/L) of water and per unit area of the bottom (82.4–494.5 larvae/m2). The studied larvae have very high survival rate (90.7–100.0%) and show no differences in this parameter in groups in all variants of cultivation. Animals from the lowest density groups were characterized by the shortest developmental duration. With an increase in the stocking density per unit volume of water and bottom area the larval development duration increased. There was a negative correlation of body length with the initial stocking density per unit volume of water (r=-0.52) and bottom area (r=-0.62). The stocking density per the bottom area affected greater the larval developmental duration and body length of juvenile toads, than the stocking density per unit water volume. The authors note that it is advisable to grow E. calamita larvae in laboratory conditions at maximum stocking density (3 larvae/L and 494.5 larvae/m2), as this allows for a greater number of juvenile toads.

Nursery culture of sandfish Holothuria scabra in sea-based floating hapa nets: Effects of initial stocking density, size grading and net replacement frequency

Sea-based culture of early juvenile sandfish Holothuria scabra up to fingerling size (>2 g) using floating hapa nets has been confirmed as a viable nursery system in tropical countries such as the Philippines. However, production can be further optimized through more efficient rearing practices. In this study, we demonstrate the effects of initial stocking density, size grading and net replacement frequency during the culture of early juvenile sandfish in sea-based floating hapa nets (2 × 1 × 1 m). Testing different initial stocking density treatments ranging from 150 to 2000 early juveniles (4–10 mm; 0.02–0.06 g) per hapa net, we confirmed significantly faster growth (0.06–0.08 g d−1) and higher survival (72–97%) in low densities (≤500 hapa−1), compared to high densities (≥700 hapa−1: 0.02–0.04 g d−1; 67–80%). Low density culture can produce 2 g sandfish in about a month, while higher densities will require a 2–3 mo culture period to reach this size. Culture performance following size grading was also compared using three initial size classes (small, 0.05–0.99 g; medium, 1–1.99 g; and large, 2–3 g) and a mixed group (0.05–3.00 g). At 45 d, juveniles in pooled size-graded groups grew significantly faster (0.11–0.13 g d−1) than those in the mixed group (0.01 g d−1). Survival was significantly higher in the medium (85.3%) and large (84.7%) groups, than those in the small (54.4%) and mixed (45.6%) groups. However, size variation was not significantly mitigated by grading during the 45-d culture. Culture performance of sandfish was not significantly enhanced by more frequent net replacement for short-term rearing (30–45 d). Optimal results were gained from an initial stocking density of ≤500 early juveniles (5–10 mm) per floating hapa net which may be cultured in a month, without requiring net replacement and size grading to produce ≥2 g sandfish. However, in cases of high hatchery production, it is also feasible to adopt higher density stocking (e.g. >1000 hapa−1), but will require longer culture duration (60–85 d), monthly net replacement and size-grading to attain the same size. Results of this study can help fine-tune management practices for nursery culture of sandfish in sea-based floating hapa net nurseries in order to boost production of fingerlings needed for aquaculture and restocking.

Effect of stocking density and feeding regime on larval growth, survival, and larval development of Japanese flounder, Paralichthys olivaceus, using live feeds

This research examined the effect of initial stocking density and feeding regime on larval growth and survival of Japanese flounder, Paralichthys olivaceus. Larval rearing trials were conducted in nine 50‐L tanks with different initial stocking densities combined with different feed rations (20 larvae/L with standard feed ration [LD], 80 larvae/L with standard feed ration [HD], and 80 larvae/L with four times the standard feed ration [HD+]). Larvae were stocked on 0 days posthatch (DPH) following hatching of the fertilized embryos. Larval total length (TL), survival rates, and final densities were observed on larval settlement (32 DPH) to evaluate larval rearing performance. At 32 DPH, there were no significant differences (p > .05) in TL or survival rates between the LD (46.5 ± 17.0%) and HD+ (40.3 ± 9.4%). The TL and survival rate of HD (23.1 ± 3.5%) were significantly lower than that of LD and HD+ (p < .05). However, the larval density of HD was significantly higher than that of LD (p < .05). HD+ achieved the best larvae production (32.27 ± 7.51 larvae/L), supported by sufficient food source, high water exchange, and proper water quality management (routine siphoning, surface skimming). The larval‐rearing protocols and larval development from hatching to metamorphosis is described in detail, with corresponding photographs taken during the experiment.

The effects of stocking density on key biological parameters influencing culture productivity of the calanoid copepod, Parvocalanus crassirostris

Copepods are the most common metazoans in the marine environment and are considered to be ideal live prey for fish larvae. However, the difficulty in their culture, particularly at high culture density, hinders their use in aquaculture hatcheries. The aim of this study was to evaluate the effects of initial stocking density on a range of biological parameters affecting the culture productivity of the calanoid copepod Parvocalanus crassirostris. Five initial stocking densities of 1000, 3000, 5000, 7000 and 9000 adults L− 1 were evaluated. Among the treatment differences on both daily and total egg production, the egg hatching rate and mortality rate were all highly significant (p < 0.001). Egg production was monitored over seven consecutive days, and the density of 5000 adults L− 1 produced significantly (p < 0.001) more eggs daily than did the other treatments. Egg hatching success was very high at 91.8–92.3% at the lower initial stocking density of ≤ 5000 adults L− 1; however, as density increased to ≥ 7000 adults L− 1, it dropped sharply to only 55–73%. Similarly, significantly higher adult mortality rates were recorded for densities ≥ 7000 adults L− 1. Moreover, population growth was evaluated for a 15-day culture period. It showed that the initial stocking density of 5000 adults L− 1 produced the highest final population (6429.4 ± 202.2 individuals L− 1) at the end of the culture period. However, in terms of percentage population growth over the initial population, it was the lowest density of 1000 adults L− 1 that achieved the highest growth (319.4 ± 20.0%), while high density treatments of 7000 and 9000 adults L− 1 suffered negative percentage growth. Interestingly, the sex ratio was also significantly affected by initial stocking densities as the male to female ratio increased significantly at a density of ≥ 7000 adults L− 1. Our results demonstrated that P. crassirostris is a highly promising species for culture as live prey for aquaculture hatcheries, and it can be stocked at a high initial density of 5000 adults L− 1 without negatively impacting culture productivity.

Interactive Effects of Stocking Density and Algal Feed Ration on Growth, Survival, and Ingestion Rate of Larval Geoduck Clams

AbstractThe combined effects of initial stocking density (2, 5, 10 individuals [inds]/mL) and feed ration (5×103, 20×103, 40×103, 100×103 cells·ind−1·d−1) on growth, survival, and ingestion rate of larval geoduck clams Panopea generosa fed Isochrysis sp. (Tahitian strain, TISO clone) were assessed. All three measurements were significantly affected by stocking density, ration, and their interaction. Growth rate ranged from 2.15 to 3.85 μm/d in the various treatments. It increased with stocking density at 5×103 cells·ind−1·d−1, was significantly higher at 5 than at 2 inds/mL at 20×103 cells·ind−1·d−1, and was significantly higher at 2 and 5 than at 10 inds/mL at 40×103 and 100×103 cells·ind−1·d−1. Growth rate increased with increasing ration up to 40×103 cells·ind−1·d−1 at 2 and 5 inds/mL, but decreased with increasing ration at 10 inds/mL. Percent survival over the experiment duration (23 d) ranged from 7% to 56% in the various treatments and generally decreased with increasing stocking density. There was no significant effect of ration on percent survival at 2 and 5 inds/mL, but survival decreased with increasing ration at 10 inds/mL. Ingestion rate ranged from 2×103 to 29×103 cells·ind−1·d−1 in the various treatments. It was not significantly affected by stocking density at 5×103 and 20×103 cells·ind−1·d−1, but larvae held at 2 and 5 inds/mL had significantly higher ingestion rates than those stocked at 10 inds/mL at 40×103 and 100×103 cells·ind−1·d−1. Ingestion rate increased with ration at 2 and 5 inds/mL but was not significantly affected by ration at 10 inds/mL. Due to the significant interaction of the treatment factors, stocking density‐specific ration levels must be selected in order to maximize growth and survival.

Quantification of Quercus petraea Liebl. forking based on a 23-year-long longitudinal survey

For Quercus petraea (sessile oak), the origin of forks is either traumatic or related to crown base formation (“metamorphosis”). The objectives of this study were to quantify forking, distinguish the two origins and test the effect of initial stocking density and tree attributes on the number of forks and height to the lowest one.The experiment took place in a 23-year-old sessile oak plantation in Normandy, France, where three initial planting densities were compared (1333, 2667 and 5333seedlings per ha). The forks were observed every 3years after the plantation. Fork number was modelled with a system of simultaneous linear equations that respectively predicted tree girth, height and the log-transformed fork frequency, with age and initial stocking density as explanatory variables. This model 1 was fitted as a seemingly unrelated regression with random effects to account for the tree and plot clustering. For trees having at least one fork, lowest fork height was quantified using a linear mixed model including predictors compatible with the response variables of model 1, age and stocking.The results showed that the number of forks can be predicted using the expected explanatory variables and it is significantly correlated with height and girth as well. Traumatic and metamorphosis-related origins were not clearly distinguished, but significant differences between the initial seedling densities were found, with the lowest density showing the highest number of forks. Lowest fork height depended on response variables of model 1, age and stocking. The stocking effect was significant but small.This study presents the first statistical quantification of tree forking ever made. From this quantification, it seemed obvious that the initial density of 2667 seedlings per ha could be a relevant initial density to avoid the emergence of too many forks and the insertion of the lowest forks too low down.

Effects of stocking density, algal density, and temperature on growth and survival of larvae of the basket cockle, Clinocardium nuttallii

This study determined optimal rearing conditions – stocking density, algal density, and temperature – for hatchery production of the basket cockle, Clinocardium nuttallii, from newly-hatched D-larvae to pediveligers using static rearing systems and discontinuous feeding. The combined effect of initial stocking density (2, 4, and 8 larvae ml − 1 ) and algal density (10, 25, and 50 × 10 3 cells ml − 1 ) on larval growth and survival was examined using a bi-algal diet of Chaetoceros muelleri (CM) and Isochrysis sp. (Tahitian strain, TISO). The effect of algal density (0, 2.5, 5, 10, 20, 40, 60, and 80 × 10 3 cells ml − 1 ) as a single factor was assessed using a single-algal diet of TISO and a fixed stocking density (2 larvae ml − 1 ) held constant throughout the experiment. The effect of temperature (5.9, 10.2, 14.2, 18.2, 21.9, and 26.3 °C) on larval growth and survival was also evaluated. The results showed that, when feeding the bi-algal diet of CM and TISO, an initial stocking density of 2 larvae ml − 1 combined with an algal density of 25 or 50 × 10 3 cells ml − 1 or an initial stocking density of 4 larvae ml − 1 combined with an algal density of 50 × 10 3 cells ml − 1 were optimal conditions for larval growth, and survival rate was significantly better in the treatment with 4 larvae ml − 1 . When feeding the single-algal diet of TISO, optimal larval growth was observed at algal densities of ≥ 40 × 10 3 cells ml − 1 . These optimal rearing conditions translated into minimum food rations of 18.4 and 20 × 10 3 algal cells larva − 1 day − 1 using the bi-algal and single-algal diets, respectively, to support maximum larval growth from newly-hatched D-larvae to pediveligers. Within the tested temperature range of 5.9 to 21.9 °C, larval growth was greater with increasing temperature but survival to settlement stage was not affected by temperature. The larvae failed to survive at the highest tested temperature of 26.3 °C.

Effect of Initial Stocking Density on Larviculture Performance of the Ocellate Puffer, Takifugu rubripes

Abstract Depending on the initial stocking density, ocellate puffer larvae exhibit the cannibalism that resulted in high mortality. We aimed to clarify the relationship between stocking density of larvae, mortality, and the effect of density on cannibalism. Ocellate puffer larvae were reared at five different stocking densities between 5 and 25 larvae/L with duplicate 1‐m3 tank for each treatment. Larvae were stocked at 0 d after hatch (d.a.h.), and the experimental cultures lasted for 55 d. In larvae stocked initially at more than 10 larvae/L, cannibalism was evident from 11 to 17 d.a.h., and the survival rate at 55 d.a.h. was less than 15%. The survival rate was 25.5% at 5 larvae/L, and cannibalism was observed from 31 to 32 d.a.h. Consequently, an initial density of 5 larvae/L was the most efficient in terms of survival and the prevention of cannibalism. On the other hand, when cannibalism is still observed at 5 larvae/L, it is necessary to lower the stocking density before the onset of cannibalism.

The Effect of Initial Stocking Density on Growth and Survival of Pike-perch Fingerlings Reared under Intensive Conditions

Pond-nursed pike-perch (Sander lucioperca) fry were trained to artificial diet and reared under controlled conditions maintained in aquaria using three stocking densities (1.25, 1.66 and 2.08 g/l). Two replicates per treatment were applied. The survival during the 4-week period of the experiment ranged from 44.2 to 49.6%. The majority of the losses were caused by cannibalism; only 8–14% could be attributed to natural mortality. Both cannibalism and natural mortality occurred in the first 2–3 weeks of rearing. The differences in the rate of cannibalism were independent of the stocking density. Natural mortality decreased with increasing density, consequently the highest survival was observed under the highest stocking density. Stocking density did not significantly influence growth, feed consumption and feed conversion ratio of the pike-perch fingerlings (p < 0.05).

Effect of Stocking Density on the Yield of Larval Mass Production of Kuruma Prawn.

The effect of initial stocking density (8-47 thousand indiv./m3) on larval mass production of kuruma prawn was studied in ten trials. The larvae were reared for 24 days from the nauplius stage to the 15-16th day of the postlarval stage. The survival rates ranged from 0.29 to 0.84, and were above 0.5 in eight trials. The daily declining pattern of survival numbers in these eight trials colud be expressed by a logarithmic linear regression throughout the rearing period, thus the population decreased in a constant proportion. By a negative correlation between initial stocking density and survival rate, 24-day rearing obtains a survival rate of more than 0.5 with an initial stocking density of less than 30 thousand indiv./m3. Relationship between initial stocking density and harvested biomass per initially stocked individual (final individual fresh body weight×survival rate) showed a more significant negative correlation. The maximum yield was estimated as approximately 80g/m3 at an initial stocking density of 30 thousand indiv./m3. The actual value of the largest yield among these trials was 87g/m3 at an initial stocking density of 25 thousand indiv./m3.

Food concentration and stocking density effects on survival and growth of laboratory-reared larvae of bay anchovy Anchoa mitchilli and lined sole Achirus lineatus

Bay anchovy (Anchoa mitchilli) eggs were stocked at densities from 0.5 to 32.0 l-1 and larvae were fed on wild plankton (copepod nauplii) in concentrations that ranged from 50 to 5000 prey l-1. Lined sole (Achirus lineatus) eggs were stocked at 0.5 to 16.0 l-1 and larvae were fed wild plankton at concentrations from 50 to 1000 prey l-1. Some larvae of each species survived at all stock and food levels to the transformation stage at 16 days after hatching. Survival rates for both species exceeded 40% when food concentration was 1000 l-1 or higher. Growth and dry weight yields also increased significantly at the higher food concentrations. Effects of initial stocking density were not well defined, but both survival and growth decreased at the highest stocking rates. Standardized culture of bay anchovy and lined sole larvae can be based on a food concentration of 1000 copepod nauplii l-1 to routinely produce healthy larvae.