Predictions of fish yields and the status of the Kainji Lake fishery, 1998

Length frequency data was collected for the 6 main species from the Kainji Lake fishery for up to 16 months. Growth parameters were estimated and used for virtual - population and length based cohort analysis. The results from cohort analysis suggest that before the ban on beach seines the maximum economic yield from the fishery was overshot by 70%. Yield per recruit analysis showed that the fish are caught far below their optimum size. Fishing gears and the timing responsible for this early mortality have been identified. After the eradication of seines from the lake a 10% increase in total catch revenue can be expected from the fishery. This is equivalent to an increase in income of Naira 18,300 per annum for each fishing entrepreneur using other methods. A scenario for the regulation of cast net mesh size together with the ban of beach seines has been presented. A further increase of Naira 142 million (N25,500 per entrepreneur) can be anticipated if this is implemented by the Kainji Lake Fisheries Management and Conservation Unit. It is expected that the annual increase in fishing effort presently experienced will cause future yields to decline. The rate of the decline has been reduced by the eradication of the beach seine fishery and will further fall if the minimum mesh size for cast nets is implemented. A recommendation is made to the Kainji Lake Fisheries Management and Conservation Unit to first consolidate the beach seine ban and then to implement a ban of undersized cast nets. (PDF contains 70 pages)

Oceanographic Profiling Observations MOCE-4 Cruise: 26 January to 12 February 1998

This report contains results from the fourth cruise of the MODIS Optical Characterization Experiment (MOCE). Also resented are oceanographic data from two MOBY maintenance cruises L-20 and L-25. The MOCE4 cruise was the first NOAAINESDIS-Ied SeaWiFS Initialization cruise during which a variety ofspectroradiometric observations ofthe upper water column and atmosphere were made by investigators from NOAA, the University of Miami, CHORS and MLML. Data presented in this report were obtained by oceanographic CTD profiler: salinity, temperature, dissolved oxygen, beam attenuation and chlorophyll-a fluorescence~ and by water samplers: total suspended matter and suspended organic carbon and nitrogen, salinity and dissolved oxygen. (PDF contains 142 pages).

Report of the Inter-American Tropical Tuna Commission for the year 1966

ENGLISH: The Inter-American Tropical Tuna Commission operates under the authority and direction of a Convention originally entered into by the Republic of Costa Rica and the United States of America. The Convention, which came into force in 1950, is open to adherence by other governments whose nationals participate in the fisheries covered by the Convention. Under this provision the Republic of Panama adhered in 1953, the Republic of Ecuador in 1961, and the United Mexican States in 1964. SPANISH: La Comisión Interamericana del Atún Tropical funciona bajo la autoridad y dirección de una Convención formada originalmente entre la República de Costa Rica y los Estados Unidos de América. La Convención entró en vigencia en 1950, está abierta a la adhesión de otros gobiernos cuyos ciudadanos participen en las pesquerías objeto de la Convención. Bajo esta cláusula, la República de Panamá se adhirió en 1953, la República del Ecuador en 1961 y los Estados Unidos Mexicanos en 1964. (PDF contains 138 pages.)

Limnology in Sicily: A history of fresh waters surrounded by the sea

The aim of this short article is to trace the history of limnology in Sicily, from the end of the last century up to the present, and pay a little homage to a scientist to whom limnology is deeply indebted: G.E. Hutchinson. Due to its insular and climatic conditions, Sicily is characterised by a drainage network formed by numerous short, torrent-like rivers, and by a few small, natural lakes. The geological characteristics of the island strongly condition the quality of these small waterbodies which generally have surface areas of less than 0.2 km super(2). The earliest observations on Sicilian lentic waters go back more than a century; in particular, at the end of the 19th century, some of the issues regarding the natural lakes had already been brought into focus. Subsequent studies on natural waterbodies concentrated on the geomorphology of landslide lakes or lakes created by the dissolution of the gypsum tableland. However, many of the waterbodies no longer exist because of land reclamation which took place up to the first half of the 1950s. During the last 35 years, there has been a notable increase in limnological publications. In addition, these studies show a more careful and integrated approach to the limnological aspects of waterbodies, compared with the early studies.

A brief history of the scientific study of tropical African inland waters

An account is given of a study of African tropical waters, drawing on the personal experiences of the author. Reviewing developments since 1900, the author examines the way in which research has developed and the influence the changes in the policitcal map of Africa, in particular the change from colonial rule, has had on research.

History, origins and importance of temporary ponds

In Europe, temporary ponds are a naturally common and widespread habitat occurring, often in abundance, in all biogeographical regions from the boreal snow-melt pools of northern Scandinavia to the seasonally inundated coastal dune pools of southern Spain. Ecological studies in Europe and elsewhere also emphasise that temporary ponds are a biologically important habitat type, renowned both for their specialised assemblages and the considerable numbers of rare and endemic species they support. They are, however, a habitat currently under considerable threat. Most temporary ponds are inherently shallow and the majority are destroyed even by limited soil drainage for agriculture or urban development. The paper gives an overview of definitions of temporary ponds and examines their formation and abundance. The authors also summarise a visit to the Bialowieza Forest in Poland to investigate the occurrence of temporary ponds.

Life history tactics of Atlantic salmon in Newfoundland

Popular articles about the Atlantic salmon (Salmo salar) usually state that ‘the Atlantic salmon is an anadromous species’, e.g. publications by the Atlantic Salmon Federation (North America), Atlantic Salmon Trust (UK), and WWF (World Wildlife Fund), and the life history is depicted as migration of juveniles from fresh water to the marine environment, with a return to where the fish were born as spawning adults. This article reviews the life history tactics of Atlantic salmon in Newfoundland.

On the nutrition of Polyphemus pediculus (L.). [Translation from: Trudy Instituta Biologii Vnutrennykh Vodnany 12(15) 170-174, 1966.]

Many sides of the biology of Polyphemus pediculus are adequately studied at the present time. Most complicated is the question of its feeding. Dissection does not give an idea of the composition of the food, since Polyphemus strongly grinds its food with its mandibles. For clarification of the composition of the food of Polyphemus pediculus, the authors carried out in July and August 1962 a series of experiments with the application of radio-carbon methods in order to judge the degree of utilization of one or other foods by the quantity of C14, accumulated in the body of the crustacean after feeding. Particular attention in these experiments was given to the question of the possibility of the utilization by polyphemus of plant food - bacteria, algae and detritus.

On the population dynamics of Eudiaptomus gracilis Sars and Heterocope borealis Fischer in the Bodensee-Obersee. Part B. Eudiaptomus gracilis Sars. [Translation from: Trudy Instituta Biologii Vnutrennykh Vodnany 12(15) 170-174, 1966.]

Experimental research was conducted to study the development of eggs of Eudiaptomus gracilis Sars. The egg production was studied as well as the population dynamics. Factors like losses in the lake and through the effluent Rhine at Konstanz were considered.

Generation time and utilization of energy by aquatic bacteria. [Translation from: Trudy Instituta Biologii Vnutrennykh Vodnany 11(14), 198-202, 1966.]

Recent research has shown that the biomass of bacteria in lakes and other water-bodies can attain significant values. The huge production of bacteria is brought about by their great rate of reproduction. In a series of cases their biomass exceeds the biomass of phytoplankton. Therefore in a study of the biological productivity of water bodies it is necessary to calculate the biomass and production not only of the phyto- and zooplankton, but also of bacteria.The authors uses different methods and formulae to to compare the time of one generation of the bacteria.

On a method of determination of chlorophyll in cells of algae collected on a membrane filter. [Translation from: Trudy Instituta Biologii Vnutrennykh Vodnany 11(14), 198-202, 1966.]

The original method, proposed by Yentsch (1957), of determination of chlorophyll directly in the cells, attracts attention by its simplicity. In order to measure the content of chlorophyll by this method, a determined volume of suspension of algae is filtered through a membrane filter. The latter is dried a little, clarified by immersion oil, clamped between two glasses, and spectrophotometrized. Extinction is read off at , wavelengths equal to 670 millimicrons (around the maximum absorption of chlorophyll a in the cell) and 750 millimicrons (correction for non- specific absorption and dispersion of light by particles of the preparation). The method of Yentsch was employed by the authors for determination of chlorophyll-a in samples of phytoplankton. They conclude that in spite of the simplicity and convenience of determination the method must be applied sufficiently carefully. It is more suitable for analysis of cultures of algae, where, non-specific absorption of light is insignificant.

Application of diatom analysis for the study of the history of the lakes of north-west USSR. [Translation from: Istoriya Ozer; Trudy Vses.Simp.Vilnius p1-7. Vilnius, 1970.]

During late - and post-glacial times lakes played a leading role in the development of the landscape of the North-west European part of USSR. A variety of geographic circumstances created great variegation of natural conditions in lakes and determined the composition of their diatoms. The basic stages of the development of the diatom flora of lakes are linked with general climatic changes. The deepwater regions of large periglacial lakes of the North-west USSR are inhabited by plankton diatoms of the genera Melosira and Cyclotella. Diatom analysis is further applied for the study of the history of the lakes of north-west USSR.

Investigations of certain eco-physiological characteristics of the broad and long-pincered crayfish in connection with their interspecific relationships. [Translation from: Lietuvas TSR Mokslu Akademijos Darbai, C Serija 2(40), 279-286, 1966.]

The results are described of eco-physiological investigations of the broad-pincered (Astacus astacus L.J.) crayfish and the long-pincered (Astacus astacus Esch.) crayfish, conducted in 1963—64 in the Institute of Zoology and Parasitology of the Academy of Science of the Lithuanian SSR, for the purpose of studying the interspecific relationship of these two species. In the course of the investigation were determined: the influence of the temperature of the environment on the consumption of oxygen by full grown individuals of both species and on the respiratory movements of the scaphognathites, the threshold temperatures and the saturation of the water by oxygen, the diel activity in the winter period.

Experiments with the hatching of salmon spawn 1966-1971. [Translation from: Vann 1972(1) 86-938, 1972]

Experiments were undertaken with the purpose to find out the tolerance of different species of salmon fish in acid hatching water and if different strains of the same species differ in their response. The study was made in the Fins-river hatchery, Marnardal and the assumption tested that the salmon and trout stock from Sorland are adapted to the more acid milieu, and thus more robust in acid water than are comparable fish stocks from areas where the water is only a bit acid or neutral.