Diurnal variation in a fish pond in Seoni,India

Summary The diurnal variation in the water chemistry and the plankton of Budhwari tank Seoni, India, which is a highly productive tank, has been studied after the monsoon. Not much variation from the other tropical waters in the chemistry has been noted. The plankton showed a little diversion from the normal behaviour in tropical fresh waters.     

Primary production in a tropical fish pond at Aligarh,India

Summary Seasonal fluctuations in gross and net primary production values were quite apparent in surface waters and showed a bimodal type of distribution. The values were generally high during post winter months (March to May) and low during winter (February) and monsoon months (July and August). At different depths the rate of primary production was always found decreasing from surface to bottom. The rate of photosynthesis was found to be highly variable from time to time and at different depths.Respiratory rate was found to be increasing from surface to bottom perhaps due to decomposition of organic matter and high bacterial growth at the increasing depths. A close relationship was found between the transparency and primary production values. Phosphate-phosphorus was found to be directly related with the gross primary production values. However, there was no relationship between nitrate-nitrogen and production values. An inverse relationship was shown between ammonia-nitrogen and the production values. Fluctuations in chlorophyll were also found significantly related with the gross primary production.     

Diurnal variations in two shallow ponds in Delhi,India

Summary Observations on the diurnal variations in water chemistry and plankton in two shallow ponds, show large fluctuations in oxygen, pH and correlated changes in carbonate concentrations. A dissolved oxygen concentration of 28.2 p.p.m. was recorded in one pond. Plankton counts suggest that the diurnal migration pattern is not similar to that often found in temperate waters. Nocturnal depletion of oxygen killed fish in one pond.Department of Zoology, University of Delhi.     

Studies on the bottom fauna in a tropical freshwater fish pond

Summary Quantitative samples of the bottom fauna obtained from a tropical freshwater fish pond during a period of two years were studied with regard to species composition, zonal variation and seasonal fluctuation. Two different zones with differences in faunal composition could be distinguished. The littoral zone was dominated by Mollusca, whereas Oligochaetes were predominant in the profundal zone. Most of the organisms showed their peaks in the months January to April. Breeding activities ofVivipara bengalensis, Digoniostoma cerameopoma, Melanoides granifera andPisidium clarkeanum as evidenced by presence of younger length groups in the populations were also observed during the same period (January to April). The influence of environmental factors as temperature, alkalinity and food were discussed as probable causes for the peaks in abundance. The average number of total organisms per square metre was found to be comparatively high indicating a high standing crop. Differences observed in the total number of organisms present have been attributed to inflow of water resulting in sudden alteration of the nutrient condition of the bottom mud. The seasonal variations of the standing crop of bottom fauna during both the years have been found to be influenced by fluctuations of the bivalve mollusc,Lamellidens corrianus. The availability of sufficient amount of benthic fauna for consumption by bottom feeding fishes has been indicated.This work formed part of a thesis submitted for the Degree of Doctor of Philosophy to the University of Calcutta, India in 1964.     

Interactions of fish,algae, and abiotic factors in a shallow,tropical pond

Protecting and restoring shallow tropical lakes and wetlands requires a knowledge of what shapes and controls algal dynamics and primary productivity in these systems. Algal community structure and composition can be regulated either through biotic or abiotic controls. Large-scale changes in fish populations can affect algal communities by altering food web dynamics and the physical and chemical properties of the aquatic environment. A reduction in fish biomass can lead to a reduction in algal biomass because of increased grazing by zooplankton and reduced availablity of nutrients. However, the omnivorous fish common in tropical systems often consume algae, and their reduction can increase algal biomass. There is a need for more information on the effect of fish removals/reductions in tropical systems. In a five-year study of a shallow, tropical pond in Hawaii, I investigated the water quality effects of tilapia removal following the occurrence of two natural fish die-offs. I describe the concurrent impacts of water-level fluctuations and the fish die-offs on the physical and chemical conditions of the pond and the subsequent changes in the algal community. Overall, nutrients, suspended sediment, organic matter, and algal biomass were significantly reduced and light availability significantly increased in the absence of tilapia.

     

Community metabolism in a tropical freshwater pond

Summary Apparatus and method to measure the soil biota respiration was described. Daily production rates of a tropical pond community were measured and classified into different types. High production rates of hydrophytes were associated with low amounts of plant biomass both in the field and under experimental conditions on bright and overcast days. Decrease in the production rates on overcast days was 2 to 3 fold up to 353.75 g/m³. Highly turbid pond water was twofold less productive than clear waters. Summer pulse in the production rates was recorded. Plankton as well as soil biota respiratory rates were higher during summer due to higher tropical temperatures. The efficiency ratios of individuals and trophic levels compared favourably with those reported earlier. The high respiration efficiency ratios for herbivores may be due to high temperatures. The input and output of energy of the tropical pond community were measured and the energy flow diagram was constructed. The community metabolism of the tropical pond community was much higher than the communities whose metabolism has been studied else where.Data formed part of Ph. D., thesis and published with the permission of the Syndicate of S. V. University, Tirupati.     

On the food of Chironomus costatus (Chironomidae: Diptera) from a shallow freshwater pond in South India

A study has been made of the feeding of Chironomus costatus in a temporary fresh-water pond in South India. It was found that, irrespective of the size of the larvae, the food composition was the same. The larvae were non-selective feeders in that the organisms enumerated in the water were also found in the gut.     

Fluctuations in the relative abundance of the weed fauna of a tropical freshwater fish pond

Summary The macrofauna present in the weed Eichhornia crassipes in a tropical fish pond have been studied for a two year period. Different groups of animals under the phyla Annelida, Arthropoda and Mollusca and their seasonal abundance have been recorded. The method of studying densities of organisms as related to a known volume of plant material was found to give satisfactory results. Aulophorus furcatus and Branchiodrilus hortensis were the two species of Oligochaeta which were associated with the weeds. The Ostracods Stenocypris malcolmsonii and Eucypris capensis showed almost similar seasonal trends. Larvae of the Ephemeropteran, Baetis, five species of Chironomidae and different nymphal instars of Zygoptera and Anisoptera were also encountered. Of the four species of Molluscs, three were pulmonates whose occurrence in the weeds is considered to be favourable for their growth and reproduction in view of their proximity to the water surface. The effect of nutrition on the populations of weed fauna has been discussed. Their maximum abundance during the months of November to March was found to be concurrent with the presence of other favourable environmental factors also.This work formed part of the thesis submitted for the award of the Degree of Doctor of Philosophy to the Calcutta University, in 1964.     

Seasonal and spatial variations of fish trophic guilds in a shallow,semi-enclosed tropical estuarine bay

A study on seasonal and spatial variations of feeding habits and trophic guilds of dominant fish species in Pattani Bay during March 2003 to February 2004 was aimed at classifying diet composition, identifying dominant food components of each species, categorizing trophic guilds of the community and evaluating effects of habitat characteristics and seasonality on guild organization. Most fishes showed high food intake, fed on a diverse range of food items but relied heavily on calanoid copepods and shrimps. All species, with the exception of Epinephelus coioides, were classified as specialist feeders. Four main dietary guilds were classified. Three of these were classified as the guilds dominated by at least two major food items. Significant variations in trophic guilds of 28 fish species based on habitat types and seasons were also identified. They could be divided into three seasonal groups and three site-groups and a single site. Trophic organization for each season and habitat ranged from two to four groups. This information identifies groups of fishes that seasonally and spatially utilize different food resources within a semi-enclosed estuarine bay ecosystem.     

Food selection by young Catla catla (Hamilton–Buchanan) in a tropical fish pond

Food selection by young Catla catla from a tropical fish pond was studied by computing the electivity indices for various types of planktonic food organisms. The fish was found to be a selective feeder. A positive selection was observed for cladocerans, copepods and nauplii larvae. Among the rotifers, however, Keratella and Brachionus were positively selected while Rotaria was completely avoided.
High electivity indices for some and low for the other genera were observed within each group of phytoplankton. Strict stenophagism seemed to occur for certain phytoplanktonic organisms.     

On the ionic composition of five tropical fish-ponds of Aligarh (U.P.), India

Summary The ionic composition offour very productive and one unproductive fishpond has been investigated. The concentration of various ions is typical of carbonate waters except in two ponds for reasons of pollution. Calcium and bicarbonate are the major cation and anion while inspite of high productivity potassium is not very abundant. Because of the geographical position the area enjoys, the carbonate content seems to be important in productivity evaluation. For the same, its equivalent ratio to calcium and bicarbonate is very significant.     

Diurnal and spatial (vertical) dynamics of nutrients (N, P, Si) in four sampling days (summer, fall, winter, and spring) in a tropical shallow reservoir and their relationships with the phytoplankton community.

The vertical and diurnal variation of nitrogen and phosphorus forms, as well as that of soluble reactive silica (SRS), were studied in four sampling days at Gar9as reservoir, a shallow tropical one located in the city of S?o Paulo, in southeastern Brazil. Except for N-NH4, all other inorganic forms of nitrogen (N-NO2, N-NO3, and total N) demonstrated decreased concentrations toward the bottom of reservoir. Similarly, all showed significant diurnal differences on every sampling day, with increased values during the night due to absence of photosynthetic assimilation during that period. In the sampling days, these forms decreased on the spring sampling day due to the bloom of Microcystis registered during this period of the year. All three forms of phosphorus (SRP, particulate P, and total P) showed significant vertical variation, except on the fall sampling day. On the summer sampling day there was an increase of both total P and particulate P, the latter because it constitutes more than 70% of the total P during all sampling days. Hourly phosphorus variation was significant during all sampling days, except for the summer one. The SRS vertical variation was significant during all sampling days, except for that in the spring. It was also different hourly on sampling days.     

Decomposition patterns of unprocessed and processed lignocellulosics in a freshwater fish pond

In an attempt to recycle the lignocellulosic wastes like Eichhornia crassipes, Salvinia cucullata and rice (Oryza sativa) straw as manurial inputs in freshwater fish pond ecosystem, a decomposition experiment was carried out in litter bags in an oligotrophic freshwater fish pond environment, with the above mentioned three substrates in unprocessed and microbially processed forms. The loss rates, associated microbial groups, oxygen consumption patterns and other related parameters like carbon, nitrogen, phosphorus, cellulose, hemicellulose and lignin were analysed. The mean daily dry matter loss rates (unprocessed: 10.44>6.97>1.97 and processed: 11.03>8.21>3.67) and oxygen uptake rate (unprocessed: 0.675>0.571>0.568 mg O₂ g^–1 h^–1 and processed: 0.592>0.424>0.407 mg O₂ g^–1 h^–1) in raw and processed substrates were in the sequence Eichhornia > rice straw > Salvinia. The oxygen consumption pattern almost covariated with variations in temperature of pond water, daily dry matter loss rates and fungal counts on substrates. During the decay, the percentage of N and P increased whereas that of C decreased, resulting in lowering of C/N and C/P ratios of the substrates. The structural polymeric fractions like cellulose and hemicellulose decreased along with dry matter whereas the lignin content increased after an initial decrease due to loss of other structural carbohydrates resulting in apparent per cent gain of lignin. A higher number of different heterotrophic bacterial groups was observed in the processed substrates as compared to their raw counterparts. However, cellulolytic bacterial numbers were found to fluctuate through the study period. The fungal load was found to be decreasing gradually as the decay progressed. In this study, bacteria were found to be the prominent microbial group responsible for the decay. The nitrogen-fixing, phosphatase-producing and phosphorus-solubilising bacterial groups were observed to play an important role in lowering the C/N and C/P ratios of the decomposing substrates during decay.     

Heavy metals in water,sediments, fish and plants of river Hindon,U.P., India

We analysed the concentrations of Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn in the water, sediments, fish and plants of the River Hindon, U.P., India, at seven sampling stations, in the year 1982. Considerable variation in concentration between water, sediments, fish and plants were noted. The concentration in the water was in the order Fe > Zn > Cr > Mn > Cu > Pb > Ni > Co > Cd, in the sediments, Fe > Mn > Zn > Ni > Cr > - Co > Cu > Pb > Cd; in a fish (Heteropnuestes fossilis) Fe > Zn > Mn > Pb > Ni > Co > Cu > Cd > Cr, and in a plant (Eicchornia crassipes) Fe > Mn > Zn > Ni > Cu > Cr > Pb > Co > Cd.     

Citogenetic characterization of the tropical freshwater fish Parachromis managuensis (Pisces: Cichlidae)

To describe the cytogenetics of the jaguar cichlid fish Parachromis managuensis, we collected eight males and 13 females in Villahermosa, Tabasco, México. The specimens were processed with standard cytogenetic techniques (slightly modified), and high quality fields of chromosomes in mitosis and meiosis were obtained; 14 of these fields were analyzed by meristics and statistics methods. The specimens presented a diploid modal number of 2n = 48 chromosomes, which is similar to the number reported for others Central American cichlids; five pairs were submetacentric-metacentrics (biarmed) and 19 were subtelocentric-telocentric (uni-armed), giving a fundamental number (NF) of 58. The haploid number was confirmed by counting meiotic fields in metaphase I. There was not evidence of heteromorphism: sexual chromosomes were not identifiable.     

Studies on species of fungi associated with mycotic infections of fish in a Nigerian freshwater fish pond

A survey was carried out on the species of fungi associated with mycotic infections of fish in a Nigerian freshwater fish pond. A total of 24 fungal species belonging to 6 genera of aquatic phycomycete were isolated from the infected fishes. Achlya racemosa, Aphanomyces laevis, Dictyuchus sterile, Saprolegnia ferax, S. litoralis and S. parasitica had 100% frequency of occurrence amongst the infected fishes. There were similarities in the species of fungi isolated from the infected fishes in the fish pond and those isolated from the hatchery. Of the infected fishes, Clarias lazera had the highest number of fungal isolates. It was followed by Tilapia zilli, then by Chanos chanos, Ethmalosa fimbriata and finally by Cyprinus carpio. The implications of the results obtained on the development of fish farming in Nigeria are discussed.     

Seasonal and diurnal changes in the water temperature of a temperate pond (England) and a tropical pond (Kenya)

Seasonal changes in water temperatures, embracing periods of low, rising, high and declining temperatures, were recorded in both a temperate and a tropical pond. In the course of a year, the range between the lowest and highest average weekly temperatures was greater in the temperate pond. The spans between the average minimum and the average maximum weekly water temperatures in the warmest months of the year in the tropical pond were greater than those found at any time of the year in the temperate pond. The average weekly air and water temperatures showed the same pattern of seasonal fluctuations; in the tropical pond the average weekly air temperatures were always less than the average minimum weekly water temperatures, whereas they were below, within or above the spans between the average minimum and average maximum weekly aquatic temperatures, according to the time of year, in the temperate pond.In both ponds, diurnal fluctuations were absent during the cooler months; the amplitudes of the fluctuations in the warmer months varied according to the time of year, and were greater, during the warmest months, in the tropical pond. In both ponds lowest temperatures were recorded sometime between 0200 and 1000 hours and highest between 1200 and 2000 hours.The influence of temperature on the life-cycles of invertebrates in both ponds is discussed briefly.

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Zusammenfassung Jahreszeitlich bedingte Schwankungen in der Wassertemperatur, welche Perioden mit niedriger, ansteigender, hoher und abfallender Temperatur einschlossen, wurden in einem gemäßigten und in einem tropischen Teich festgestellt. Im Laufe eines Jahres war der Unterschied zwischen den tiefsten und höchsten wöchentlichen Durchschnittstemperaturen im gemäßigten Teich größer. Hingegen war der Abstand zwischen Mindest- and Höchsttemperatur des Wassers im Wochendurchschnitt während der warmsten Monate des Jahres im tropischen Teich größer als zu irgendeiner Jahreszeit im gemäßigten Teich. Der Wochendurchschnitt der Luft- und Wassertemperaturen wies das gleiche jahreszeitlich bedingte Schwankungsmuster auf. In dem tropischen Teich war die wöchentliche Durchschnittstemperatur der Luft stets niedriger als die Mindestdurchschnittstemperatur des Wassers in einer Woche. Jedoch lag sie — je nach Jahreszeit — unterhalb, auf gleicher Höhe oder oberhalb der Spannweite der niedrigsten and der höchsten wöchentlichen Dutchschnittstemperaturen des Wassers im gemäßigten Teich.In beiden Teichen traten die taglichen Schwankungen während der kÜhleren Monate nicht auf. Der Umfang der Schwankungen in den wärmeren Monaten variierte je nach Jahreszeit and war in den wärmsten Monaten in dem tropischen Teich größer. In beiden Teichen wurden die tiefsten Temperaturen zwischen 2.00 and 10.00 Uhr and die höchsten zwischen 12.00 and 20.00 Uhr gemessen.

     

Seasonal variations in the diel vertical distribution of phytoplankton and zooplankton in a shallow pond

The seasonal succession of phytoplankton diversity, and the variations in the diel vertical distribution of phyto‐ and zooplankton were investigated in a small shallow pond (1.7 m water depth) in 2003. It was inferred that the water tended to stratify weakly in the daytime from February to June. In February and April, the green alga Golenkinia radiata Chodat dominated the phytoplankton assemblage. The cell density of G. radiata greatly decreased in April, when rotifers increased near the bottom. The vertical mixing was attenuated in June, large populations of the euglenoids (Lepocinclis salina Fritsch, Phacus acuminatus Stokes, Trachelomonas hispida (Perty) Stein et Deflandre) developed, and the cyanobacterium Aphanizomenon flos‐aquae var. klebahnii Elenk. appeared at low density. Euglenoids and A. flos‐aquae were mostly distributed in the bottom layer. In late September, when the water was mixed throughout the day, euglenoids and A. flos‐aquae were distributed evenly throughout the water column. The zooplankton (cyclopoid copepods and rotifers) densities in September were the lowest throughout the year. The vertical mixing increased in November, and the phytoplankton community was composed of A. flos‐aquae, P. acuminatus, T. hispida and the green alga Ankistrodesmus falcatus (Corda) Ralfs. In November, at the final stage of water bloom of A. flos‐aquae, its population density decreased with depth. The two euglenoids exhibited similar cell distributions at 0.8 m and 1.6 m during 1–3 November. A. falcatus was distributed evenly throughout the water column; however, when the vertical mixing lessened, the cells at the surface started to sink. Copepod nauplii and rotifers appeared at high densities in November. Seasonal variation in the phytoplankton community structure in the pond seemed to be related to the vertical mixing of the water. In addition, zooplankton, especially rotifers, might play an important role in initiating a spring clear‐water phase and in the bloom collapse of A. flos‐aquae.