Sources of age determination errors for sablefish (Anoplopoma fimbria)

This study was undertaken to resolve problems in age determination of sablefish (Anoplopoma fimbria). Aging of this species has been hampered by poor agreement (averaging less than 45%) among age readers and by differences in assigned ages of as much as 15 years. Otoliths from fish that had been injected with oxytetracycline (OTC) and that had been at liberty for known durations were used to determine why age determinations were so difficult and to help determine the correct aging procedure. All fish were sampled from Oregon southwards, which represents the southern part of their range. The otoliths were examined with the aid of image processing. Some fish showed little or no growth on the otolith after eight months at liberty, whereas otoliths from other fish grew substantially. Some fish lay down two prominent hyaline zones within a single year, one in the summer and one in the winter. We classified the otoliths by morphological type and found that certain types are more likely to lay down multiple hyaline zones and other types are likely to lay down little or no zones. This finding suggests that some improvement could be achieved by detailed knowledge of the growth characteristics of the different types. This study suggests that it may not be possible to obtain reliable ages from sablefish otoliths. At the very least, more studies will be required to under-stand the growth of sablefish otoliths.

Studies on the possible sources of microbial contaminations of processed fishery products

An attempt has been made in the present study to estimate and describe in detail the nature and extent of contamination of processed fishery products. In large scale prawn processing when the preprocess preparation is elaborate, the industry in India has found it advantageous to establish the primary processing centers away from the processing factories. The data collected have clearly indicated that if such processing centers are not properly organized there is a possibility of greater contamination of the products at this stage. The data collected during the course of this investigation have given the basis for the measures to be taken for the maintenance of bacterial quality of prawn during different stages of processing.

Sources of the deep water masses in the northern Red Sea

The hydrographic structure of the northern Red Sea indicated that, the surface waters of temperature around 22°C, salinity of 40.1OO%o and dt = 28.1 might sink to depths between 400-500 m by convective overturn, contributing to the formation of the mid-deep Red Sea waters. Below the 500 db depth down to the bottom the water column is stable. The geostrophic circulation clearly indicated an inflow of water from the Red Sea towards NNW, along the main axis of the sea. Arriving at the northern edge of the sea, it sends a branch in the Gulf of Aqaba, turns to the west, and sends another branch to the Gulf of Suez, but its main mass reaches the African coast where it sets southward along this coast. A large cyclonic gyre centered near 27 deg 30'N and 34 deg l0'E is detected at the head of the Red Sea deep waters. The effect of the outflow of the bottom water of the Gulf of Suez on the formation of the deep water of the Red Sea is limited.

On computing the physical sources of jet noise

We derive a closed system of equations that relates the acoustically radiating flow variables to the sources of sound for homentropic flows. We use radiating density, momentum density and modified pressure as the dependent variables which leads to simple source terms for the momentum equations. The source terms involve the non-radiating parts of the density and momentum density fields. These non-radiating components are obtained by removing the radiating wavenumbers in the Fourier domain. We demonstrate the usefulness of this new technique on an axi-symmetric jet solution of the Navier-Stokes equations, obtained by direct numerical simulation (DNS). The dominant source term is proportional to the square of the non-radiating part of the axial momentum density. We compare the sound sources to that obtained by an acoustic analogy and find that they have more realistic physical properties. Their frequency content and amplitudes are consistent with. We validate the sources by computing the radiating sound field and comparing it to the DNS solution. © 2010 by S. Sinayoko, A. Agarwal.

Reprint of: Flow filtering and the physical sources of aerodynamic sound

The physical sources of sound are expressed in terms of the non-radiating part of the flow. The non-radiating part of the flow can be obtained from convolution filtering, as we demonstrate numerically by using an axi-symmetric jet satisfying the Navier-Stokes equations. Based on the frequency spectrum of the source, we show that the sound sources exhibit more physical behaviour than sound sources based on acoustic analogies. To validate the sources of sound, one needs to let them radiate within the non-radiating flow field. However, our results suggest that the traditional Euler operator linearized about the time-averaged part of the flow should be sufficient to compute the sound field. © 2010 Published by Elsevier Ltd.

Studies on the probable sources of fungal infection and the control measures in a fish seed farm

The causes of mortality of fry of cultivable fishes in a fish seed farm were investigated. The mortality was due to fungal infection and the pathogen was Saprolegnia sp. The sources of infection were unhygienic breeding hapas, spawnery hapas in the cemented ponds, hatching jars and excess feeding. Application of one kg slaked lime followed by 75g of CuSo sub(4)(l-0.5 p.p.m.) and 150g of KMno sub(4)(2-1 p.p.m.) per each nursery (158m³ water) controlled the pathogen.

A preliminary study on the evaluation of casein, shrimp meal, squid meal and spirulina as protein sources of Penaeus monodon (Fabricius) postlarvae

P. monodon postlarvae were fed with fresh brown mussel (Modiolus metcalfei ) meat, and artificial diets containing casein, shrimp (Metapenaeus ensis ) meal, squid (Loligo ) meal, and Spirulina as protein sources at a rate of 20% of their biomass per day for a period of 10 days. No statistical difference was found among the weight gains of shrimp fed on various experimental diets. However, shrimp fed squid meal diet had highest weight gain followed by shrimp meal, fresh brown mussel meat, casein and Spirulina . Shrimp fed squid meal diet had a significantly better feed conversion and those receiving other experimental diets. Poorest fed conversion was observed in shrimp fed Spirulina . The protein efficiency ratio was statistically highest for the squid meal diet, with the lowest value again for Spirulina diets. Survival rate was significantly highest for shrimp fed the shrimp meal diet. No statistical differences were found among shrimp fed other experimental diets. Appropriate data are tabulated.

Transient ventilation dynamics induced by heat sources of unequal strength

We examine theoretically the transient displacement flow and density stratification that develops within a ventilated box after two localized floor-level heat sources of unequal strengths are activated. The heat input is represented by two non-interacting turbulent axisymmetric plumes of constant buoyancy fluxes B1 and B2 > B1. The box connects to an unbounded quiescent external environment of uniform density via openings at the top and base. A theoretical model is developed to predict the time evolution of the dimensionless depths λj and mean buoyancies δj of the 'intermediate' (j = 1) and 'top' (j = 2) layers leading to steady state. The flow behaviour is classified in terms of a stratification parameter S, a dimensionless measure of the relative forcing strengths of the two buoyant layers that drive the flow. We find that dδ1/dτ α 1/λ1 and dδ2/dτ α 1/λ2, where τ is a dimensionless time. When S 1, the intermediate layer is shallow (small λ1), whereas the top layer is relatively deep (large λ2) and, in this limit, δ1 and δ2 evolve on two characteristically different time scales. This produces a time lag and gives rise to a 'thermal overshoot', during which δ1 exceeds its steady value and attains a maximum during the transients; a flow feature we refer to, in the context of a ventilated room, as 'localized overheating'. For a given source strength ratio ψ = B1/B2, we show that thermal overshoots are realized for dimensionless opening areas A < Aoh and are strongly dependent on the time history of the flow. We establish the region of {A, ψ} space where rapid development of δ1 results in δ1 > δ2, giving rise to a bulk overturning of the buoyant layers. Finally, some implications of these results, specifically to the ventilation of a room, are discussed. © Cambridge University Press 2013.

Discharges and sediments as sources of extracellular alkaline phosphatase in a shallow Chinese eutrophic lake

Total alkaline phosphatase activity (APA) and soluble reactive phosphorus (SRP) concentrations were measured in municipal wastewater, and a shallow Chinese freshwater lake receiving it. Activities of Dissolved alkaline phosphatase ( ADAP) in overlying and interstitial water were also analyzed monthly at three sites for several years. The lake was enriched with SRP and alkaline phosphatase by discharge of the wastewater, indicating that the inclusion of APA for estimating water pollution was reasonable. Annual data showed that APA in coarser fraction was significantly higher at the site receiving more wastewaters, both in surface and overlying water, suggesting that resuspension of enzyme most likely occurred in the basin heavily discharged. ADAP was an order of magnitude higher in the wastewater than those in lake waters, and was generally higher in interstitial water, a feature more striking at the site receiving more discharges. Besides, it was irrespectively inhibited by Na2WO4, L-cysteine and EDTA-Na, but stimulated by Cu2+, Zn2+, CTAB and Triton X-100 in interstitial, overlying and surface waters. This similarity of responding patterns to the stressors indicated an analogy between dissolved alkaline phosphatase in water column and that in interstitial water, supporting the hypothesis that the polluted sediments act as source of dissolved alkaline phosphatase in eutrophic lakes.

Macrozoobenthos in 2 shallow mesotrophic Chinese lakes with contrasting sources of primary production

Comparative studies on macrozoobenthos were done in 2 shallow mesotrophic lakes in the middle basins of the Yangtze River, China: Lake Biandantang where macrophytes were abundant, and Lake Houhu where macrophytes were scarce Samples were taken monthly at 4 stations in each lake from April 1997 to March 1999, and a total of 67 and 31 tara of macrozoobenthos were recorded in Lake Biandantang and Lake Houhu, respectively. Both annual mean density and biomass of macrozoobenthos were higher in Lake Biandantang than in Lake Houhu: 780 vs 532 indivials/m(2) and 37.1 vs 25.9 g wet mass/m(2), respectively. Abundance of functional feeding groups followed the order: scraper > collector > predator > shredder in Lake Biandantang, and collector > predator > scraper > shredder in Lake Houhu. Only 1 density peak occurred from winter to early spring in Lake Houhu; however, in Lake Biandantang, there were 2 peaks, the winter peak and spring peak. K-dominance curves and Shannon-Wiener, Simpson, and Margelef indices indicated that macrozoobenthos were more diverse in Lake Biandantang than in Lake Houhu Our study suggests that, in shallow lakes, submerged macrophytes are essential for the maintenance of biodiversity of macrozoobenthos mainly because the macrophytes increase habit heterogeneity and availability of suitable food, and may also decrease predation by fish on the macrozoobenthos.

A comparative study of benthic nematodes in two Chinese lakes with contrasting sources of primary production

Ecological studies on benthic nematodes were conducted in two small, shallow lakes in the middle Yangtze basin, China; Lake Houhu, where the main source of primary production is phytoplankton and Lake Biandantang where it is predominantly macrophytic in origin. Monthly sampling was carried out from April 1996 to March 1997. A total of 36 species of nematodes was found in Lake Houhu and 51 species in Lake Biandantang. The dominant trophic groups of nematodes were algophages in Lake Houhu and bacteriophages associated with omniphages and phytophages in Lake Biandantang. Community analyses based on K-dominance curves, Shannon-Wiener and Simpson diversity indices, demonstrate that the benthic nematodes are more diverse in Lake Biandantang than in Lake Houhu. The results suggest that the abundance of submerged vegetation is essential for maintenance of habitat heterogeneity and biodiversity of nematodes in shallow lakes.