Genetic improvement and utilisation of indigenous tilapia in southern Africa: final technical report, December 1st 1998 to June 31st, 2002

Mozambique tilapia (Oreochromis mossambicus) is an indigenous tilapia species in southern Africa, until now the majority of genetic research has been carried out on Asian species of tilapia but this project aims to look at this African species. Those most suited to further development in aquaculture in southern Africa have now been identified. The genetic characterisation of strains has been completed. This information has aided the choice of strains for use in small scale aquaculture and for genetically male tilapia (GMT) production. They will form the basis of future strategies for further genetic improvement, and management of genetic diversity of Mozambique tilapia. The information will also contribute towards responsible management and development of genetic resources, particularly with regard to indigenous species of tilapia. Good progress has been made with the adaptation and implementation of producing the supermale fish required to produce all male offspring, resulting in faster growing populations of tilapia. The presence of the project and its associated activity has been a catalyst for a surge in interest in tilapia culture throughout southern Africa. [PDF contains 183 pages]

Traditions of fish utilisation for recipes in Nigeria

Some recipes for fish utilization in particular zones of Nigeria are assessed, giving details of their modes of preparation. The traditions of use of fish in the recipes shown appear to be based on the successful agricultural practices in particular zones and areas of Nigeria. This has helped to promote taste and values, since easily procured food items are cheaper for use in particular areas than others. The use of such fish items in the recipes are useful for promoting protein intake and stemming of malnutrition, especially in the rural areas, as well as helping to improve the incomes of women-in-agriculture

Digestibility and nutrient utilisation of soybean bran-based diets in Nile tilapia Oreochromis niloticus

The digestibility and utilisation of two soybean bran-based diets and two fishmeal-based diets serving as control, at optimal (30%) and suboptimal (20%) protein levels were evaluated in Oreochromis niloticus. These were Diet I (Control)-fishmeal based diet at 30% crude protein, Diet II (Control) - fishmeal based diet at 20% crude protein, Diet III - hydrolysed Soybean Bran based diet at 30% crude protein, Diet IV - hydrolysed Soybean Bran based diet at 20%. Dry matter digestibility differed insignificantly with variation in diets (P<0.05). There was significant variation in the protein (p 20.05), lipid and ash digestibility. Protein was more digestible at optimum level than sub-optimum level, while lipid and ash digestibility did not vary with their inclusion levels. Variation in the utilisation of the diets was significant (P<0.05) except for survival. It was observed that the best diet was Diet 1, closely followed by Diet II with highest values of mean final weight, specific growth rate, protein efficiency ratio and the apparent net protein utilisation. The high digestibility values of Diets III and IV suggests their inclusion in fish diet to spare protein for growth

WEFTA interlaboratory comparison on nitrogen determination by Kjeldahl digestion in fishery products and standard substances

14 Laboratorien aus 12 europäischen Ländern nahmen an einer Laborvergleichsuntersuchung zur Stickstoffbestimmung in Fischerzeugnissen und Standardsubstanzen nach Kjeldahl teil. 13 Laboratorien erzielten dabei Ergebnisse, die alle in engen Grenzen um die gefundenen Mittelwerte streuten. Der von den einzelnen Teilnehmern erzielte Variationskoeffizient war mit etwa 0,5 % gering. Auch die Standardsubstanzen mit bekanntem Stickstoffgehalt konnten überwiegend mit hinreichender Genauigkeit (98 % der vom Hertsteller angegebenen Gehalte) analysiert werden. Der ideale Kjeldahlaufschluß ist durch kurze Aufschlußzeiten (ca. 120 min), eine Aufschlußtemperatur bei 430° C und durch die Wahl des für die jeweilige Matrix geeigneten Katalysators gekennzeichnet.

Tests of some specific effect substances in duck nutrition. Translation from: Biologisace a chemisaze vyzivy svirat 5, 43-48, 1969.]

There is a constantly increasing collection of manufactured substances, whose effectiveness in the sustenance of ducks is under investigation. The author examines the effects of some substances already previously tested and also there were examined substances which had not hitherto been studied. The use of different supplements for late autumn fattening is studied through various experiments.

Studies on the complex formation of iron with humic substances [Translation from: Vom Wasser 53, 243-247, 1979]

Most of the humic substances which occur in natural waters have an iron content of a few percent, indicated by the mg/1 content of organically-bonded carbon. This iron is apparently bound in a complex with the humic substances, for it quite plainly differs in its chemical and physico-chemical properties from what one would expect from the purely inorganic iron-water system. The deviations range from the solubility to the redox behaviour, and thus are frequently the basis of analytical and technical difficulties. The key to the solution of most of this problem lies in a better understanding of the aforementioned bonds between the iron and the humic substances. This paper studies the iron content of the humic substance concentration from a bog lake sample and the complexing of iron by humic substances from the surface of the bog lake.

Optical properties of the organic substances from aqueous humus surface waters. [Translation from: Gidrochim. Mat. 23, 31-35, 1955]

Dissolved organic matter, especially turf and peat, is repsonsible for the colouration of water. The reported study tried to determine the nature of the colouring agent or organic matter by the establishment of a relationship between the intensity of colouration and the total organic matter content. 44 waters from different sources were examined.

Essais d'utilisation de "nourrisseur à la demande" pour l'alimentation de Chrysichthys nigrodigitatus en cage-enclos

An experiment using demand feeder was carried out on the catfish Chrysichthys nigrodigitatus reared in cage-enclosure in the lagoon Ebrié (Côte d'Ivoire). The study lasted 5 months, from October to March, and showed that the demand feeder improves the growth rate of the fish and the feed conversion. It was able, as well as the conventional hand feeding, to show monthly variations of performances.

Copépodes pélagiques du plateau ivoirien. 2 - Utilisation de l'arbre de longueur minimum dans le classement des récoltes

The minimum spanning tree algorithm is used to classify two sets of planktonic copepod samples. This algorithm links the samples the distance of which is minimum, without doing a loop, so that the sum of the segment lengths is minimum. The authors estimated the distance between samples by 2 different ways: by a coefficient of association the Jaccard's index - and by the x2 distance. Jaccard's index is not retained but the use of the x2 distance allows comparison with the 'analyse factorielle des correspondances'. The results are discussed from an ecological point of view.

Copépodes pélagiques du plateau ivoirien. Utilisation de I'analyse des correspondances dans l'étude des variations saisonnières

Several 'analyses factorielles des correspondences' were used with the numerical data of planktonic copepods issued from a 1 year sampling programme at different stations of the Ivorian shelf. The main results were the following: (1) 'Ecological seasons' approximately corresponding to hydrological seasons may be defined for planktonic populations. (2) Each 'season' is characterized by one group of species, whose maximum abundance occurs in this period. (3) The same definition of ecological season is obtained whether all species present are used or whether only the most important ones are used. (4) The first principal axes may be interpreted as temperature and salinity or as the station's distance from shore.

Utilisation of trash fish. Pt. 1. Preparation of fish flake

The paper deals with the investigations carried out on the preparation of odorless fish-starch flakes using partially deodorized trash fish meat and different sources of starch like corn, tapioca, maida and black gram. It has been found that the products using corn and tapioca are better compared to those prepared using other two starches, the product from corn being the best. The product has a protein content of about 20% and has been found to have a storage life of 4 months at 37°c.

Utilisation of trash fish. Pt. 2. Studies on preparation of fish soup mix

The paper deals with the investigations carried out on the preparation of fish soup mix using partially deodorized trash fish meat. The product contained about 25% protein and had a storage life of 4 months at ambient temperature (28-31°C).

Effect of mixed feeding schedule on growth and nutrient utilisation in Rohu, Labeo rohita (Ham.) fingerlings

Studies on nutrient utilisation and growth of rohu (Labeo rohita) fingerlings (3.13-4.09 g) raised on seven feeding schedules under laboratory conditions (26.3-33.5°C) showed that two days regular feeding on Diet B (high protein, 38.90%) resulted in maximum growth and protein retention efficiency. While regular feeding on low protein diet (Diet A) resulted in poor nutrient utilisation and growth of fish, high protein diet (Diet B) did not show any significant difference in growth from the mixed 2A-3B schedules but exhibited comparatively low protein retention efficiency. The other feeding schedules were 1A-2B, 1A-3B, 2A-2B and 2A-4B, where the numerical value refers to the number of days for continuous feeding of a particular diet. The diets A and B served as the controls which contained 3.40 and 3.67 kcal/g gross energy respectively. The 2A-3B feeding schedule was also found to be highly economic as an expenditure of Rs.11/- only was required for raising the body weight by one kilo as against Rs.17/- with high protein diet (Diet B) as calculated

Utilisation of vegetable leaves for carp production

The results of two sets of experiments on mono-culture of grass carp (Ctenopharyngodon idella) and mixed culture of carps (grass carp 50 : catla 20 : rohu 15 : mrigal 15) fed exclusively with vegetable leaves are reported. The experiments were conducted with two replicates each in 0.02 ha ponds of Wastewater Aquaculture Division of the Central Institute of Freshwater Aquaculture, Rahara during 1991-93. Monoculture of grass carp stocked at 1000/ha demonstrated an average net production of 21.0 kg/ 0.02 ha/8 months (1501 kg/ha/yr). Mixed culture of carps stocked at 5000 /ha recorded an average net production of 22.5 kg/0.02 ha/8 months (1903.7 kg/ha/yr). Field studies revealed that water bind weed (Ipomoea aquatica) is the most preferred feed of grass carp amongst vegetable leaves followed by amaranths (Amaranthus gangeticus and Amaranthus viridis), cauliflower (Brassica oleracia var. votrytis) and cabbage (Brassica oleracia var. capitata) leaves. Through selection of highly productive leaf vegetables and suitable crop planning on fallow fish pond dykes, round the year feeding programme of grass carp has been explored. Recycling of sewage effluent for vegetable production and utilisation of vegetable leaves for fish production is considered an ideal way of integrated resource management for low cost production.