Sensorische Bewertung, Mikrobiologie und chemische Kenngrößen von eisgelagertem Wittling (Merlangius merlangus)

During the 160th research cruise of the FRV "Walther Herwig III" in the North Sea in May 1995 an ice-storage experiment with whiting was performed. Gutted whiting with and without spleen was stored in melting water-ice. Freshness and/or spoilage were monitored by measuring sensory, chemical, physical and microbiological indicators. It was found that besides the classical sensory assessment on the cooked sample and the EU-quality grading scheme, the microbiological counts were of major importance for the determination of the degree of freshness or spoilage. The cfu (colony forming units) of spoilage bacteria on the skin correlated significantly with time in ice. A very good correlation was also found for the cfu of spoilage bacteria with the sensory assessed odour of the cooked fillet sample. The measurement of the fish tissue with the Intellectron Fischtester VI and the determination of the creatine content in fillet are both suitable freshness and spoilage indicators. The pH-value measured in different body compartments and in musele homogenate and the ammonia content are only of limited value for freshness determination. Removal of kidney did not influence the shelf life.

Determination of optimum stocking density of Macrobrachium rosenbergii larvae using multiple feed in a commercial hatchery at Cox’s Bazar, Bangladesh

Experimental stocking density of Macrobrachium rosenbergii in larval rearing was conducted in A.G. Aqua Hatchery, Chakaria, Bangladesh to study the effect of different stocking densities on growth, survival rate and diseases stress under hatchery condition. The research work was conducted using six cemented rectangular tanks having 3m3 capacity (1.5mX2mX1m) each. Stocking density were maintained in three experimental setup as 200, 150 and 100ind/L of the T1, T2 and T3 respectively with one replicate each. The larvae were fed with Artemia nauplii, Custard, Maxima and brine shrimp flakes. Water quality was maintained by exchanging 20-30% (12ppt saline water) daily. During the study period, temperature, pH, DO, salinity, nitrite-nitrogen, ammonia and alkalinity were maintained from 28.5-31.5ºC, 7.5-7.8, 5.8-5.9mg/L, 12-13ppt, 0.14-0.2 mg/L, 0.22-0.3mg/L, and 140-160mg/L respectively. The growth rates of larvae at 11th stage were recorded in terms of body length 0.115, 0.136, and 0.169 mm/day whereas body weight were observed 0.000115, 0.000180, and 0.000240g/day. The survival rate of larvae were found 21.8%, 30.4% and 51.3% in treatments T1, T2 and T3 respectively. PL was obtained as 43, 45, and 51PL/L and days required of 41, 38 and 34 days in stocking density of 200, 150, and 100ind/L respectively. It was found that the minimum of 34 days was required to attain the PL (12th stage) using the stocking density of 100 individuals/L. Cannibalism, Zoothamnium, Exuvia Entrapment Disease (EED), and Bacterial Necrosis (BN) were found to be the threat to the commercial hatchery operation that might responsible for potential larval damages which can be reduced by lowering the stocking densities in larval rearing tank that also increased the survival and growth rate.

Management of Biesboch reservoirs for quality control with special reference to eutrophication

The three Biesbosch Reservoirs are pumped storage reservoirs, fed with rather polluted and highly eutrophic water from the River Meuse. Air injection at the bottom of the reservoirs prevents thermal stratification, which would otherwise result in serious water quality deterioration. Reservoir mixing also serves as an economic algal control measure; mixing over sufficient depth causes light to play the role of limiting factor and this, combined with zooplankton grazing, keeps the biomass of phytoplankton at acceptable levels. Special problems are caused by benthic, geosmin-producing Oscillatoria species growing on the inner embankment. Rooting up the bottom with a harrow is used as the method of control, based on underwater observations by biological staff trained as SCUBA-divers. With regard to pollutant behaviour the three reservoirs act as a series of fully mixed reactors. This enables the application of kinetic models to describe their behaviour and allows the use of a selective intake policy, e.g. for suspended solids with associated contaminants, ammonia and polynuclear aromatic hydrocarbons. A combination of selective intake and self- purification processes - enhanced by the compartmentalisation of the storage volume in three reservoirs - leads to a striking improvement for many water-quality parameters.

Toxicité de l'ammoniaque chez le silure africain Heterobranchus longifilis

The acute toxicity of ammonia to the African catfish (Heterobranchus longifilis, Valenciennes 1840) was studied using static bioassay systems.

Production primaire, secondaire et régéneration des sels nutritifs dans l'upwelling de Mauritanie

Primary and secondary productions and nutrient regeneration in the Mauritanian upwelling area were studied by following a drogue for 9 days, from the point of upwelling till the water mass dives under offshore waters. The lag between phytoplanktonic bloom, zooplanktonic peak and bacterial activity is very short and may be explained by a well-settled biological cycle connected with an undercurrent. Organic production was estimated in two ways: (1) from chlorophyll 'a' values, considering a C/Chla ratio of 25 during the 5.5 day phytoplankton growth period, primary production computed by this method reaches 13.5 g C/m2; (2) from 14C values net primary production calculated for the same period reaches 10.5 g C/m2 and total organic production (net production + organic excretion) reaches 19.5 g C/m2. Organic production computed ratios, delta O/ delta C/ delta N/ delta Si/ delta P are equal to 130/43/11/7.4/1. Secondary production and 'grazing' are estimated from mesozooplankton respiration values and have a huge increase during the bloom. Net secondary production is assessed to be 1.0-4.2 g C/m2 for 6 days. Evidence of nutrient regeneration as ammonia, phosphate and silicate is given and regeneration rates are calculated. Zooplankton excretion plays an important part in nitrogen and phosphorus regeneration. Bacterial activity is induced by zooplankton organic excretion, then increased by phytoplankton decomposition at the end of the bloom.

Cheshire Meres 1995, May-June

This is the Cheshire Meres 1995, May – June Surveys Report from the National Rivers Authority, 1995. The report focuses on the surveys of ten Cheshire Meres in November 1994 and then again in May-June 1995 as part of a rolling program examining the water quality of this group of still waters. The ten meres surveyed were: Betley, Budworth, Combermere, Hatchmere, Oak mere, Pick mere, Redes, Rostheme, Tabley, and Tatton. This report discusses the results of the May-June survey before making a comparison between these and the November survey results. The section on results contains information about suspended solids (S.S.) and volatile suspended solids (V.S.S.); Nitrate and Nitrite; Ammonia; ortho-Phosphate; Silicate and Soluble reactive Silica; and total Phosphorus.

South Area still waters 1995 November surveys

This is the South Area still waters 1995 November surveys from the National Rivers Authority, 1996. The report focuses on the surveys of ten Cheshire Meres (Betley, Budworth, Combermere, Hatchmere, Oak mere, Pick mere, Redes, Rostherne, Tabley, and Tatton) previously surveyed in November 1994 and May 1995. Eight others (Chapel Mere, Little Mere, Marbury Mere, Mere Mere, Oss Mere, Petty Pool, Quoisley Big Mere and Tabley Moat) were surveyed for the first time. Two other lakes, Carr Mill Dam and Pennington Flash, were surveyed. Neither of these are considered to be part of the Cheshire meres group of lakes but are of a Regional interest. This report discusses the results of the November 1995 survey before making a comparison between these and the November 1994 survey results. The section on results contains information about water column profile; nutrients (chlorophyll a; Phaeophytin; Nitrate and Nitrite; Ammonia; ortho-Phosphate; Silicate; and total Phosphorus.

Cheshire stillwaters. Summary results of September 1998

This is the Cheshire stillwaters. Summary results of September 1998 from the Environment Agency, 1998. In May 1997, a Stillwaters meeting was held to discuss the way forward in stillwaters monitoring. It decided upon the establishment of a three year rolling programme, in which three stillwaters would be monitored three times a year, every third year. Oak Mere, Tatton Park Mere and Hatch Mere were surveyed between the 29th - 30th September as part of the three year rolling programme. Betley Mere, Petty Pool, Scotman's Flash and Pearson's Flash were also surveyed. Surveys also included algal and zooplankton samples, which are to be analysed by APEM and presented in the end of year report. The section on results contains information about water column profile; and nutrients (chlorophyll a; Phaeophytin; Nitrate and Nitrite; Ammonia; ortho-Phosphate; Silicate; and total Phosphorus).

Oak Mere continuous monitoring summary report, 1997 to 2000

This is the Oak Mere continuous monitoring summary report, 1997 to 2000 from the Environment Agency North West. This report focuses on the continuous monitoring programme made by a multi -parameter probe in Oak Mere since summer 1997. From 1999 nutrient and chlorophyll samples were taken when the water quality instrument was serviced. Water level measurements were made since 1998. Moreover, the report shows a summary Oak mere water quality of each year (1997-2000). The physico-chemical parameters and nutrient levels included are: temperature, specific conditions, dissolved oxygen, pH, Depth, secchi disc measurements, chlorophyll a, total Phosphorus, orto-Phosphate, Nitrate, Ammonia, and Silicate.

Kent estuary survey 8th July 1980

This is the Kent estuary survey 8th July 1980 produced by the North West Water Authority in 1980. This survey was carried out on the Kent Estuary on the 8th July, 1980 during the period 3h hours before to 1.5 hours after low water. The chemical water quality in the vicinity of Arnside was found, in general, to be good. The E. coli counts were found to be at or below the E E C mandatory value for bathing waters. Downstream of the Arnside outfall the E coli counts were generally above the E E C mandatory value, the counts getting higher at and after low water. B O D values also increased at low water though ammonia and phosphate (except for 1 sample) concentrations were low. The total coliform counts both at Arnside and below the outfall were always above the E E C mandatory level (except for 2 samples).

Kent estuary survey 18th August 1981

This is the Kent estuary survey 18th July 1981 produced by the North West Water Authority in 1981. The report focuses on a tidal cycle survey carried out on the Kent estuary on the 18th August, 1981. The chemical water quality at Arnside Pier and at New Barns was, on the whole, acceptable. However, samples taken downstream of the outfall at low water for total coliforms and E. coli were all above the EEC mandatory level whilst those for faecal streptococci were all above the guideline value. This document shows chemical and bacteriological data analysed at Kent estuary such chloride, dissolved oxygen, BOD, ammonia, nitrate, phosphate, total coliforms, E. coli and Faecal streptococci.

The Kent estuary 1992 surveys. Summary of results

This is the Kent estuary 1992 surveys: Summary of results produced by the National Rivers Authority in 1993. The report summarises routine and baseline water quality surveys carried out on the Kent estuary during 1992. Baseline surveys are designed to respond to regional, national, and European requirements. During 1992 baseline surveys were carried out in June and December. Unfortunately, in June, samples could only be taken from stations 3, 7 and 8. For ease of interpretation the results have been presented in graph form, including the maximum and minimum parameter concentration and the appropriate Environmental Quality Standards (EQS). The parameters measured in this survey were physical parameters (temperature, BOD, dissolved oxygen, Ph, salinity, conductivity); nutrients (ammonia, phosphate, and nitrate); metals (Mercury, Nickel, Arsenic, Cadmium, Chromium, Cooper, Boron, and Zinc) and organic compounds.

Role of microalgae in conditioning water in penaeid larval culture

Microalgae play an important role in conditioning water quality for penaeid larval culture. Recently it has been demonstrated that a modification of the green water larval culture system (Ling, 1969) for Macrobrachium allows the production of post larvae without any water change, despite extensive use of artificial feeds (Ang and Cheah, 1986). Increase of toxic metabolites such as ammonia and nitride are also common in penaeid larval culture, especially where excessive amounts of artifial feeds are employed. Present work examines the use of six marine microalgae at four cell concentrations as a "biological filter" system, to control and detoxify levels of ammonia and nitrite in P. monodon larval culture water whilst using artificial diet. Preliminary results indicate that amongst the six algal species tested, C. japonica at 1000 cell μlˉ¹ was most effective in reducing accumulated toxic metabolites from an unchanged culture water environment.

Effect of chloral hydrate on metabolic rate of Labeo rohita (Ham) and Poecilia reticulata (Peters)

Comparative impact of chloral hydrate anaesthesia on the metabolic rate of Indian major carp Labeo rohita and larvivorous fish Poecilia reticulata was assessed. Observation on the Oxygen Consumption Rate (OCR) revealed that in common guppies OCR was substantially low (1.105 and 1.097 mg/g/hr) at 0.1 and 0.25 g/l concentrations of chloral hydrate as against OCR of 1.487 mg/g/hr in the control. Fry of L. rohita in group showed lower metabolic rates in the control as well as treated conditions as compared to the individuals of this fish. This may be due to sympathetic psychophysiological reflex of grouped fish. Higher dose of chloral hydrate (0.25 g/l) also caused higher OCR probably due to distress. Application of chloral hydrate also favoured lesser release of metabolic wastes (ammonia and carbon dioxide). There was significant positive correlation between time and oxygen consumption, whereas, for time and OCR this relationship was negative. Regression of chloral hydrate doses for OCR and time has also been calculated.

Macrobenthos of intertidal zone of Versova along the coast of Mumbai

To assess the biodiversity of macro benthos in the changing environment along the coast of Mumbai, the intertidal zone of Versova was identified. The water quality in this intertidal region was poor with low pH, salinity and dissolved oxygen, and high nitrite, nitrate, phosphate and ammonia. The substratum was sandy with 1.29% organic matter in it. Mean faunal density of 2257 no./m² was recorded during the study which was mainly contributed by polychaetes (83.5%) followed by amphipods (14.5%), while other groups represented were isopods, crabs, hermit crabs, unidentified decapods, pelecypods and gastropods. Average biomass of 34.83 g/m² (93.7%) was contributed by polychaetes. Shannon and Wiener Index (0.4107) indicated heavy pollution in the intertidal area of Versova.