Comparative drift studies on streams in lower Austria (Flysch, gneiss and chalk formations) [Translation from: Schweizerische Zeitschrift fur Hydrobiologie 30 138-185, 1968.]

Seasonal changes and flooding have an extraordinarily great influence on the drift of organisms. The free water space plays the main part in the provision of food for some fish (Salmo trutta - trout): drift and content of the stomach are balanced here (Simuliidae): whereas others (Thymallus vulgaris) only selectively chose certain animals living at the bottom (molluscs). The total drift, drift of organisms and drift of organic material and minerals, plays a main role in the rate of production in streams. Besides the biology of the organisms living on the river bed, also the geological and hydrographical situation of the area plays a very important role for the composition of the drift. During the years 1964-1966 three streams in the characteristical geological formations flysch, gneiss and chalk of lower Austria were studied in regard to their drift. The Tulln (above St. Christopen), the Krems (above Senftenberg) and the Schwarza (above Hirschwang) seemed to be ideal for this comparative study because they are easy to reach. After summarising the hydrography and chemistry of examined rivers, the author examines the relationship between water level and total drift and the stratification of the total drift before analysing the drift of living organisms. Also considered are seasonal changes of drift of organisms and drift of exuviae.

Effects of flow regime on the young stages of salmonid fishes. Summary and conclusions based on results for 1981-1985

The main British salmonid species spawn in clean gravel in streams and rivers, many of them in the upland areas of Britain. The earliest stages of the life cycle (eggs and alevins) spend some months within the gravel of the river bed. During this period their survival rate can be strongly influenced by flow regime and by related phenomena such as movement of coarse river bed material, changes in water level and the deposition of silt. In recent years human influence upon the flow regimes of upland water courses and upon the sediment inputs to them has increased. In order to conserve and, if possible, enhance the populations of salmonid fishes a deeper understanding of the interrelationships between survival of young salmonids and flow-related phenomena is needed. The acquisition of appropriate information is the main aim of the present project, which included: Studies on silt movement and the infilling of gravel voids by fine sediments, together with initial studies on the relationship between intragravel oxygen supply rate and the survival of intragravel stages of salmonids; studies in the general field of egg washout. The latter investigated the physical background to gravel bed disruption, the examination of the physical characteristics of sites chosen for redds, dimensions of redds and burial depth of eggs relative to the size of the fish constructing the redd and a series of smaller studies on other aspects of egg washout.

Natural habitat and population control mechanism of Crassula helmsii (Australian Swamp Stonecrop) in Australia

The plant Crassula helmsii (Kirk) Cochayne, was likely to become widely distributed and to dominate many damp and wet areas of nature reserves, recreational waters and agricultural drainage of Britain. The aim of this report was to study Australian Swamp Stonecrop in its natural habitat where it is in balance with its environment. This contrasts with its rapid and widespread distribution in the U.K. where its growth interferes with the use of fisheries and amenity lakes but also reduces the value of nature reserves and sites of special scientific interest by suppressing native flora. It was proposed to observe its growth at a variety of sites over its natural distribution and to include some environmental factors, e.g. water-level, water-chemistry (nutrients, acidity and alkalinity), frost-tolerance, salinity, with the help of portable sensors, locally-available services or data. 8 weeks of travel in Australia allowed time to study the plant in its natural habitat including the coastal areas of the southern half of the continent i.e . Western Australia, South Australia, New South Wales, Victoria, Tasmania and southern Queensland. The overall objective was to determine the environmental range by visits to selected sites of Crassula helmsii over its geographic range.

Trapping success and population analysis of Siren lacertina and Amphiuma means

Siren and Amphiuma are two poorly known genera of aquatic salamanders that occur in the Southeastern United States. A primarily bottom-dwelling existence makes these salamanders difficult to detect with conventional sampling methodologies. Therefore, the current status of their populations is unknown. I compared the capture success of modified crayfish traps and plastic minnow traps in capturing these salamanders. In addition, a mark-recapture study of S. lacertina (Greater siren) and A. means (Two-toed amphiuma) was conducted at Okefenokee National Wildlife Refuge (southern Georgia) and at Katharine Ordway Preserve (north-central Florida) from August 2001 until September 2002. Crayfish traps were much more successful than minnow traps in catching siren and amphiuma. Crayfish traps yielded 270 captures for an overall capture success of 16%, whereas minnow traps yielded only 13 captures for an overall success rate of 0.05%. In addition, several marking techniques were evaluated, and of these, only passive integrated transponder (PIT) tags were retained for the duration of the study. Therefore, I recommend this marking technique for long-term monitoring of S. lacertina and A. means. Several variables were found to have significant effects on capture rates of salamanders. A. means were most often captured in summer and the number of captures was positively correlated with water temperature, water level, and rainfall. S. lacertina were most often captured during winter and spring. Number of captures was negatively correlated with water temperature, while no relationship was found with water level or rainfall. Trap day and baiting had no significant effect on number of A. means or S. lacertina captured. Recapture probabilities of both species were low, 0.025-0.03 for S. lacertina and 0.08-0.11 for A. means. Monthly survival rates were high, 0.77-0.97 for A. means and 0.88-1.00 for S. lacertina. Density estimates of 1.3 salamanders/m2 (S. lacertina) and 0.28 salamanders/m2 (A. means) were obtained for Lake Suggs using Jolly-Seber models. Siren and amphiuma make up a substantial part of wetland biomass and can impact many other wetland species. Thus, more attention must be focused on evaluating and monitoring their populations.

Simple method for backyard production of snakehead (Channa striata Bloch) fry

The snakehead (Channa striata ) is a common freshwater fish species in Malaysia. Details are given of a simple technique for breeding this species, suitable for small-scale farmers practising backyard aquaculture. Two techniques were used to induce spawning - the first used water level manipulation to simulate rain and the second used injected with human chorionic gonadotropic hormone. The former, more natural, spawning technique was found to provide a viable alternative for the small-scale farmer, being much simpler than hormone injection.

Stillwaters monitoring programme summary results 2000

This is the Stillwaters monitoring programme summary results 2000 from the Environment Agency. 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. During 2000, stillwaters monitored for the fourth year of the Stillwaters Monitoring Programme were Hatch Mere, Marbury Big Mere, Comber Mere, Tabley Mere, Tatton Mere and Melchett Mere. Algal, zooplankton and water chemical samples were taken on all meres. Surveys of Tabley Mere and Comber Mere continued on from last year when water quality concerns were highlighted. Continuous monitoring in Oak Mere, including water level data continued in 2000. Fish surveys were carried out in Tatton Mere and Comber Mere. Tabley Mere survey was abandoned due to the awkward bathymetry of the mere. No invertebrate samples were taken in 2000 due to lack of resources.

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.

Wetland resource evaluation and the NRA's role in its conservation. 1. Resource assessment

This is the Wetland resource evaluation and the NRA's role in its conservation: Resource assessment report produced by the National Rivers Authority in 1995. This R&D document provides a strategy for the assessment of the wetland resource of England and Wales. As a first step the report defines wetlands in their UK context. The following working definition is suggested: Wetland is land that has (or had until modified) a water level predominantly at, near, or up to 1.5 m above the ground surface for sufficient time during the year to allow hydrological processes to be a major influence on the soils and biota. These processes may be expressed in certain features, such as characteristic soils and vegetation. The report also summarises a hydrotopographical classification of wetlands. The report then develops a strategy for the establishment of a wetland resource Inventory based on a geographical information system (GIS) as a means of storing and manipulating site data from across England and Wales.

Limnological studies of a freshwater tropical impoundment : Powai Lake. 1: Morphometry and physical features

Powai Lake, an impoundment, came into existence in 1891 when the riverlet Dhanisar was dammed to conserve rainwater for drinking purpose. However, the water was found to be unpotable and the lake was leased out to the Angling Association, Bombay, exclusively for angling and sports. The lake is located about 27 km in the northeast of Bombay city at a height of 55m above MSL. It is rainfed with an average rainfall of 2,400 mm. The maximum waterspread area is 220 ha with a maximum capacity of 8.11 million m super(3) in the peak monsoon period when the water overflows the dam. There is no drawdown from the lake. Fluctuation in the water level is mainly due to evaporation and percolation. Transparency is low mainly due to suspended organic particles. There is hardly any difference in the water temperatures of surface and bottom, hence the annual heat budget is low at 2,818 cal m super(-2).

Studies on some physico-chemical factors of Kaptai lake

The present investigation dealt with the climatic and some physico-chemical conditions of the Kaptai lake with respect to their monthly variation. Air temperature was found always higher than water temperature. Vertical variation in temperature (0.8-4.7°C) was observed in all months. The water level fluctuates appreciably throughout the year. Wide seasonal fluctuations were also noted in water transparency. The lake was found to be slightly hard and alkaline pH. Dissolved oxygen (DO) (6.4-9.1 mg/l) and free carbondioxide (4.7- 6.0 mg/l) contents showed favourable condition for aquatic lives. DO at different depth has shown no wide variation (1.0-2.4 mg/1). Conductivity ranged between 91.9±7.1 and 106.4 ±5.2 mS/cm.

The fisheries resources of Lake Nakivali

Lake Nakivali is one of the four small lakes that form what is known as the koki lake sysyem. It is 14km long,6km wide.26km sqaured in area and has maximum depth of 3.5m at high water level. The lake is located in lake-swamp complex with river Rwizi as the principle inflow, and a number of peripheral lakes among which are four major ones,i.e Lake Nakivali, Mburo, Kachira and Kijanebalola. Lake Nakivali is a controlled lake with four official landing sites, namely: Kikusi, Kahirimbi, Kashojwa and Rukinga. The latter three are located within a Refugee settlement whereas Kikusi is outside. The Nakivali Refugee settlement initially established for Rwandese of Tutsi origin in 1963, now has at least seven nationalities which include people from Rwanda, Democratic Republic of Congo, Somalia, Sudan, Ethiopia, Kenya and Eritrea. By the end of 2006, the lake’s hinterland of about 378 km squared contained 43,448 people of whom 22,448 were refugees. This large population has had stressful impacts on both land and lake resources to the extent that now there is an apparent overfishing on the lake.

Cultivation of Gracilaria lichenoides in Puttalam Lagoon

A brief description is given of experimental rearing of the red alga G. lichenoides using a coir net frame method. Frames of 1x1 m were made and tied to bamboo poles which were planted in water; the frame was fixed at a level about 1 ft below the water level. 2 cm fragments were used as propagating material. Plants were found to grow more luxuriantly and were more greenish than using other methods, and in addition were free from extraneous matter such as sand. The regeneration time of the plant is low, and it reaches marketable size in 3-4 months.

Suitable sites for sustainable aquaculture development in Mymensingh, Bangladesh: A GIS methodological perspective

A GIS study was carried out to find out the sites suitable for aquaculture in Mymensingh region. A number of criteria were selected for GIS modeling followed by the approach of Kapetsky (1994). The criteria were developed from a range of existing data sources such as, surface and underground water level, availability of feed ingredients and animal wastes, sources of fish fry, market facilities, extension support and communication facilities for aquaculture development. The data were located, collected and compiled from different GOs and NGOs located in the region along with primary data from the field survey wherever necessary and then prepared for computer analyses. Using the database, a series of GIS models were developed in order to ascertain and prioritize the most suitable areas for aquaculture development in the region. Out of total 407,528 ha available lands in the region, the study identified 99,415 ha very suitable and 302,754 ha moderately suitable for aquaculture promotion. Result of the study is indicative to the modeling power of GIS for aquaculture application and could be used to refine the models in future, particularly if it is supported with further detail field data. To get a more concrete and complete model, detailed study should be made available on the availability of mustard oil cake, rice bran, wheat bran, and usable animal and urban wastes that could be used as low-cost feed for sustainable aquaculture.

Hydrobiological studies of an irrigation tank with reference to the culture of large murrel, Channa marulius (Hamilton) and striped murrel Channa striatus (Bloch)

The importance of selection of species for culture according to the ecological niches and fish food organisms is highlighted with respect to the Fox Sagar, an irrigation take. The tank was infested with submerged vegetation as well as minnows and weed fishes, which rendered the tank unsuitable for the culture of Indian major carps. The tank was stocked with 8000 fingerlings of Channa marulius and C. striatus during 1981 by the local fisherman co-operative society. Only partial harvest was possible during 1982 because of high water level. The final harvest was in April-May, 1983. The yield obtained was 3640 kg during the culture period of about 20 months.

Survival rates of different postlarval stages of Penaeus monodon Fabricius

The objective of this study is to determine survival rates of different postlarval stages upon stocking in the Leganes ponds. Twelve 3m x 2m x 2m suspension nets made of nylon cloth (mesh size = 0 . 1 mm) were set up in a Leganes Station pond (ave. water depth = 1 m) by means of 3-m long poles stacked at distances approximating the area of each net. The net bottom was filled with topsoil at least 15 cm thick to stimulate the pond bottom. At least 60 cm of the upper edge of each net was above the water level to prevent mixing of water inside and outside the net. P.monodon of stages P SUB-11 , P SUB-15 , P SUB-21 (from the hatchery) and P SUB-25 (from the wet lab) were stocked in the nets at 200/sq m or 1,200 fry/net. Due to lack of fry, only one P SUB-25 net was stocked. Each net had two large dried miapi branches as shelter from predation and cannibalism for the young sugpo fry. Fresh lablab was fed at the rate of one pail (approximately 5 kg) every four days per net. Harvest data show relatively higher survival rates for P SUB-15 and P SUB-18 compared to P SUB-11 and P SUB-25 with no significant difference between these two stages. The results for P SUB-25 may not be valid because the stock came from the wet lab in comparison to the other postlarval stages which were reared in the hatchery. Moreover, the P SUB-25 stock had no replicates and the net itself (no. 10) was discovered to have many holes. These preliminary results point to P SUB-15 as the best stage for harvest from the hatchery in terms of high pond recovery and lesser expense in rearing compared to older postlarvae.