Collection of fish lengths for stock assessment in developing countries

A review of the data (handling) requirements for length-based stock assessment is presented, with emphasis on the relationship between the expected outputs and the key features of the samples required, and on biases and other sources of inaccuracy.

Pen fish culture in reservoirs: an alternative to land based nurseries

An experiment to rear carp seed was conducted in Tamil Nadu, India during October 2001 to April 2002 as a part of an ambitious programme aimed at standardization of pen fish rearing technology for production of stocking material of desired size at a lower cost. The experiment used six pens erected using locally available materials in the exposed marginal area of an existing reservoir. The high survival rate of carps (67.2-94.7%) and reasonable returns on investment (26.2%) obtained in the experiment indicated that fish seed rearing in pens erected in suitable areas of existing reservoirs could serve as a cheaper alternative to the expensive land-based nursery ponds.

Length-weight relationship of marine fish species off Sao Sebastiao system, Sao Paulo, Southeastern Brazil

The parameters a and b of the length-weight relationship of the form W = a . L super(b) were estimated for 57 fish species sampled in Sao Sebastiao Channel and shelf system in 1997, Sao Paulo, Brazil. The b values ranged from 2.746 to 3.617. The Student's t-test revealed that mot (44) species had b values significantly different from 3. A normal distribution of the calculated LWR exponents (b) was obtained.

Nearshore fish resources and fisheries around Kigoma, eastern coast of Lake Tanganyika

The fish habitats along an inshore water stretch along the eastern/central coast of Lake Tanganyika are discussed and a quantitative analysis of the species composition, distribution and abundance of the littoral fishes within the area of study is presented. Seventy-one species of fish belonging to 48 genera and to 15 fish families were collected and identified during the study. The majority of species belonged to the Cichlidae family. Intensive beach seining for clupeids is suggested as one of the causes of low fish biomass in the area surveyed. The areas south of Kigoma appeared to contain more fish, with average catch rates of 11.7 kg/haul than those north of Kigoma where average catch rates of 7.6 kg/haul were recorded. Some suggestions for improved management of these resources are given.

Food consumption/biomass ratios of the pelagic fish community of Lake Malawi/Niassa

An empirical model relating food requirements to morphometric indices of metabolic rate was used to calculate consumption/biomass ratios (Q/B) for 16 species of fish that make the pelagic fish community in Lake Malawi/Niassa. The Q/B/year varied from 3.31 to 9.82, with the large catfish (Dinotopterus nyasensis) having the lowest and a small cyprinid (Engraulicypris sardella) having the highest Q/B ratio. Direct estimates of Q/B for four of the most abundant species, based on analysis of diel feeding patterns, ranged from 4.20 to 24.70; the extreme values in this range representing replicate studies on the same species, the predatory cichlid Rhamphochromis longiceps. Previous studies that indicated exceptionally low Q/B ratios (1.0) in pelagic cichlids from Lake Malawi are not supported by this more recent work.

Rice-freshwater prawn (Macrobrachium rosenbergii) farms in the Mekong Delta, Vietnam

Aquaculture in riceland has been practiced in Mekong Delta, Vietnam for a long time and integrated rice-freshwater prawn (Macrobrachium rosenbergii) farming has become more and more popular. The integrated farming systems developed and practiced by farmers in the area to produce more food and more cash crops are presented and discussed.

A simple and inexpensive fish tagging method

In many developing countries, availability of suitable tags for use in genetics and aquaculture research has been a problem as they are often expensive and have to be imported from other countries. A simple and inexpensive method used by scientists in Ghana that can be tried and improved by others is described in this article.

Updating names, distribution and ecology of riverine fish of Kenya in the Athi-Galana-Sabaki river drainage system

Few studies of the riverine fish of the Athi-Galana-Sabaki river drainage area in Kenya have been carried out since the last comprehensive surveys of the 1950s and early 1960s. This paper presents updated information on scientific and recommended common names, distribution and ecology of selected fish species of this catchment. At least 28 riverine fish families consisting of 46 genera and 62 species occur in the drainage system, of which, 39 species are strictly freshwater (4 introduced) while 23 species are of marine origin. Five unique behavioural categories of the riverine fish of the drainage system are discussed. The four most speciated riverine fish in the system belong to the families Cyprinidae (14 species), Cichlidae (6 species), and Mormyridae and Gobiidae (4 species each). Thirty fish species occur in areas below the River Tsavo-Athi confluence, 18 fish species above the confluence, while 12 fish species occupy the entire drainage system. One cichlid fish, Oreochromis spilurus spilurus (Gunther, 1894), only occurs in the Tsavo river, while the occurrence in the entire system of one snoutfish species, Mormyprops anguilloides (Linnaeus, 1758) is uncertain. The use of information from this study is recommended when carrying out further studies of fish from the Athi-Galana-Sabaki river drainage.

Estimating the girth of fish by applying an elliptic model

A new method for estimating the maximum girth of roundfish is proposed as illustrated; this is based on an elliptic approximation of the cross sections of the fish body. Results derived from a small sample horse mackerel, Trachurus trachurus, suggest that maximum girth estimates based on the elliptic model are more precise than the values estimated by applying a conventional method.

On-farm trials with rice fish cultivation in the west Kano rice irrigation scheme, Kenya

The viability of integrating rice farming with fish culture was studied in ten (10) rice plots. The on-farm research was done during one rice-growing season starting May 2003. The rice variety used was IR 2793-80-1 while the fish species was the Nile tilapia, Oreochromis niloticus. The fish culture period lasted 77 days. An average fish production of 132.4 kg/ha was obtained. The mean recovery rate of tilapia was 43 per cent. Total rice yield from the fields stocked with fish was lower than from unstocked fields. The net returns were not significantly different.

Rice-fish-vegetable integrated farming: towards a sustainable ecosystem

An outline is given of procedures to take in order to adopt an integrated rice-fish-vegetable farming system in India. Vegetables, which are cultivated in the dikes of the system, may include Luffa acutangula, Vigna unguiculata and Phaseolus vulgaris . When the water depth of the field rises to 30-40 cm, fish fingerlings (Puntius javanicus, Cyprinus carpio and Labeo rohita ) and prawn juveniles (Macrobranchium rosenbergii ) may be stocked. The advantages of such a system are listed and include year round employment opportunities for the farm family and improved farm family income and nutrition.

Life cycle and biological parameters of several Brazilian Amazon fish species

This contribution summarizes knowledge on the biology (population dynamics, reproduction, ecology) of 25 fish species from the Lower Amazon, Brazil, based on data from a Brazilian-German field project (IARA) and a review of the literature.