Diurnal variations in a shallow tropical freshwater fish pond in Shahjahanpur,U.P. (India)

Summary Diurnal variations in water chemistry and plankton in this eutrophic tropical freshwater ponds were quite apparent. Large fluctuations were noted in dissolved oxygen, pH, carbonate and bicarbonate concentrations. The pond water gets oversaturated with oxygen during day (24.2 p.p.m.) and depleted in the night (1.2 p.p.m.). Diurnal migrations of plankton were not in conformity with temperate 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.     

Studies on the zooplankton of a tropical fish pond

Summary Seasonal abundance and the pattern of fluctuations in the zooplankton of a tropical fish pond has been studied at weekly intervals for a period of two years from September 1960 to August 1962. Except for a group of ciliates, protozoa were found only in limited numbers. Coleps, Tintinnus and Difflugia were recorded during both the years, whereas Arcella and Codonella were collected in the first year only. Other members as Centropyxis, Didinium, Paradileptus, Stentor and Bursaria were seen occasionally as few individuals. The total numbers of protozoa showed their peak from January to April and the prevailing phytoplankton abundance and temperature conditions are suggested as probable causative factors. More than thirty species of rotifers were recorded during this study, although many of them were only in limited numbers. Loricate forms showed their maximum density in summer months only, when total alkalinity values were also high. Nonloricate forms were found during September, October and December to February. The effect of temperature, total alkalinity and phytoplankton on these populations have been discussed. Five species of Copepoda were recorded. The most dominant copepod Mesocyclops hyalinus was present almost throughout the year and its fluctuation pattern closely resembled that of the copepodids and the nauplii. Definite peaks in naupliar populations were probably indicative of periods of active reproduction. Among the five species of cladocera, Diaphanosoma brachyurum was present during certain months only, in both the years. Moina brachiata was present during the first year only. The total abundance of these microcrustacea showed direct relationship with phytoplankton production. The importance of these investigations in fish cultural practices is suggested.This work formed part of a thesis submitted for the degree of Doctor of Philosophy to the University of Calcutta, India in 1964.     

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.     

Influence of the fish pond aquaculture effluent discharge on abiotic environmental factors of selected rivers in Northwest Poland

Pollution of rivers caused by human activity is a widely discussed problem, however there is not much attention paid to the changes of water quality that result from the inflow of effluent discharged from fish breeding ponds. The paper presents results of studies on changes of the abiotic parameters (hydrochemical and hydrological) of water observed in the yearly cycle between 2004 and 2008 in selected rivers of Northwest Poland. It was proved that the fastest reaction on the inflow of the effluent discharged from the fish ponds was reflected in changes of biogenic and organic compounds in the river water. The largest, i.e. threefold (rivers Krapiel and Tywa) or even fourfold (rivers Rurzyca and Stepnica) increase in nutrients and organic matter was recorded during the pond effluent discharge into the rivers. At that time values of the organic matter ranged from 8.9 to 18.3 mgO₂/dm³ (BOD₅), the nitrogen compounds from 16.868 to 26.930 mgN/dm³, while the phosphorus from 1.928 to 6.353 mgP/dm³. Interestingly, an additional dry mass of seston was recorded no earlier than the activity of the harmful element had been stopped and the river had resumed to the “initial” state (i.e. before the effluent discharge); that period varied from one to two months, depending on the river characteristics. The highest values of the dry seston mass (580.9 mg/dm³) was recorded in river Krapiel in November 2006. It seems that in spite of remarkable influence on values of individual physical and chemical indices of the river water quality, the effluent discharge from the fish ponds is not a factor hampering the self-purification processes of the rivers.     

The effect of seasonal variation in abiotic factors on fish community structure in temporary and permanent pools in a tropical wetland

1. Fish community structure depends on biotic interactions and abiotic variables. Abiotic variables appear to gain importance in highly variable freshwater systems, such as tropical wetlands where a marked seasonal hydroperiod (dry and wet seasons) modifies water quality and quantity, differentially affecting fish survival and, consequently, modifying species richness and abundance. 2. We evaluated the relationship between abiotic variables and fish community structure in variable (temporary) and stable (permanent) pools that were interconnected in a tropical wetland with marked annual dry and wet seasons. 3. All fish species were able to occupy any of the studied pools, but our results showed distinctive fish community structures in permanent and temporary pools. Community structure was related to temperature, depth, pH and macrophyte coverage. Total fish abundance in the wetland was negatively related to water depth and positively related to macrophyte coverage. 4. Null models of co‐occurrence indicated a non‐random pattern at the wetland scale and a random pattern within groups of pools with similar characteristics, suggesting that fish communities are structured according to habitat features. We conclude that seasonal abiotic variation and habitat characteristics in this highly variable pristine wetland play major roles in structuring fish communities.     

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.     

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.     

Response of epiphytic algae to nutrient loading and fish density in a shallow lake: a mesocosm experiment

Studies on the effect of eutrophication on the ecology of shallow lakes, usually pay scant attention to changes within the epiphytic algal community, though the contribution of this to the ecosystem dynamics is transcendental. In order to test the influence of nutrient loadings and fish densities in the structure of algal epiphyton in a shallow lake, an experiment was performed using in situ mesocosms. Nutrient additions were related to significant decreases in the total epiphyton biovolume and that of bacillariophyceans and zygnematophyceans, but with increases in the abundance of cyanobacteria. The different response of algal groups at the higher nutrient concentrations (increases or decreases in their abundance and/or biovolume) can be related to their ecophysiological constraints such as different resistance to toxicant ammonium accumulation. Plant-associated macroinvertebrates numbers were positively correlated with total numbers of epiphyton. The presence of planktivorous fish enhanced the abundance and biovolume of all algal groups, except cyanobacteria. Fishes enhanced the abundance of plant-associated animals and of total epiphyton. Fish indirect effects (e.g., nutrients release) and their dietary particularities were among the factors that together with nutrients influenced epiphyton growth. The role of indirect effects of fishes and the importance of their dietary particularities are stressed as key factors to understand the processes controlling epiphyton ecology and the food web structure of shallow lakes. Handling editor: D. Ryder.     

Strong top-down effects of omnivorous fish and macroinvertebrates on periphytic algae and macrophytes in a tropical reservoir

Aquatic Ecology - Top-chain predators play a fundamental role in the functioning of shallow reservoirs. Studies to elucidate the cascade effects produced by fish on macroinvertebrates and...     

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.     

The relationship between fish species richness, abundance and habitat complexity in a range of shallow tropical marine habitats

A simple habitat assessment score (HAS) was designed to assess habitat complexity across several different shallow tropical marine habitats including sandy patches, algal beds, seagrass beds and reefs. It measured rugosity, variety of growth forms, height, refuge size categories, percentage live cover and percentage hard substratum. Multiple regression models using HAS variables as predictors accounted for 71 and 22% of the variation in observed species richness and total fish abundance respectively. The two most important predictors of observed species richness were rugosity and variety of growth forms, while height was the most important predictor of total fish abundance. The HAS method worked consistently across a variety of habitat types and the complexity map closely mirrored the map of observed species richness, reflecting the patchy habitat mosaic of shallow tropical marine areas. Stations at the mouth of an enclosed lagoon, however, had a higher number of species than might have been expected judging from the habitat complexity scores. It is possible that this was linked to the preferential settling of pelagic fish larvae in this area as tidal water exchanges between the bay and the reef were funnelled through one small gap. This study highlights the need for fish biodiversity studies to take habitat complexity into account.     

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.     

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.     

Secondary productivity and energy flow in a tropical pond

Monthly changes in density and biomass of a Pila globosa population were estimated in the littoral area of the pond Idumban. Mean density of active snail was 10.4, equivalent to 76 g dry weight/m² during 1973 and 6.5, equivalent to 45 g/m² during 1974. Total population size of the snail decreased from 9.2 × 10⁶ individuals, equivalent to 6.5 ton during 1973 to 6.3 × 10⁶ snails, equivalent to 4.4 ton during 1974. The period from December to May represented the time of abundance and active growth. Mortality assessed from marking and recapture as well as from monthly changes in population density, averaged to 2.7 snails/m²/month or 20% of the density. Growth estimated by marking and recapture suggested that the snail required a period of over 4 years to attain a body (wet) weight of 35 g. Laboratory experiments revealed that young (<4 g), intermediate (4 g><24 g) and old (>24 g) P. globosa grew at the rate of 4.0, 1.5 and 0.3 mg dry weight/g live weight/day. Using these values and the size-wise population density data, net productivity of the snail was estimated as 74 and 40 g/m²/year in 1973 and 74, respectively. The snail exhibited an efficiency of 70% for absorption and 10% for conversion. Using these values, it was further possible to estimate rates of feeding and absorption for the population. Consumption amounted to 1039 g/m² in 1973 and 560 g/m² in 1974. The efficiencies of exploitation, gross and net productions were 21, 7 and 10%, respectively; ecological efficiency amounted to 1.4% only.     

Interactions of biotic and abiotic environmental factors in an ectomycorrhizal symbiosis,and the potential for selection mosaics

Background  

Geographic selection mosaics, in which species exert different evolutionary impacts on each other in different environments, may drive diversification in coevolving species. We studied the potential for geographic selection mosaics in plant-mycorrhizal interactions by testing whether the interaction between bishop pine (Pinus muricata D. Don) and one of its common ectomycorrhizal fungi (Rhizopogon occidentalis Zeller and Dodge) varies in outcome, when different combinations of plant and fungal genotypes are tested under a range of different abiotic and biotic conditions.     

Production of a fish taxocene in a Texas pond

Synopsis Production rates of seven species of fishes were determined for one year in a 0.95 ha pond. Total annual production of all fishes in the pond was 209 g m^–2y^–1 (after the subtraction of 16.2 g m^–2y^–1 of negative production). Over 90% of the production occurred in the months of June through September, with young-of-the-year fishes contributing 84% of the total. When Y of Y fishes shifted to benthic diets in the spring, the small biomass of benthos available could not sustain the large biomas of fish. Severe competition for the available food then resulted in decreased production rates for the entire fish taxocene.     

Life cycle and growth ofPotamogeton crispus L. in a shallow pond,ojaga-ike

The life cycle and growth ofPotamogeton crispus L. were studied in a shallow pond, Ojaga-ike. With respect to the shoot elongation and seed and turion formations, the life cycle of this plant in the pond could be divided into following five stages: germination, inactive growth, active growth, reproductive and dormant stages. It was suggested that the plant showed these successive stages depending mainly upon water temperature. The turions germinated on the bottom in autumn when the water temperature fell below ca. 20 C. The plant showed hardly any growth during winter (December—early March) when the temperature was below 10 C. In the spring when the bottom water temperature rose to above 10 C (mid-March), the plant started to grow again and the shoot elongated rapidly at the rate of 4.2 cm day⁻¹ until the shoot apex reached the pond surface in late April. Both the increment of node number and the internodal elongation were associated with this rapid shoot growth. On 10 May (last sampling date), the mean values of shoot length, internodal length and the number of nodes estimated for 10 predominant plants were 238.2±5.6 cm, 7.1±0.8 cm and 34.9±4.0 cm, respectively. The turion formation and flowering occurred during the period from mid-April to mid-May when the surface water temperature ranged 19 and 22 C. The dry weight of a plant reached the maximum mean value of 1180 mg on 10 May. At its peak biomass, an individual plant produced 1–10 turions (5.5 on average) of which the mean individual turion dry weight was 53.2 mg. The turion dry weight accounted for ca. 42% of the total plant biomass m⁻² at that time.