The present study was carried out to investigate a simple method for recording the occurrence of early maturing females in Nile tilapia at a fixed time after stocking and to estimate the response to bi-directional selection for this trait and a possible correlated response in growth performance.
Selection experiments with the herbivorous blunt snout bream or Wuchang bream (Megalobrama amblycephala) were started in 1985. Mass selection for size and length/depth ratio resulted in a significant increase in growth and better shape, while inbreeding led to a significant decrease in growth. The total selection ratio from fry to mature brooders was about 0.03 per cent per generation.
Although women have proved to be competent in adopting new aquaculture technologies, their role is very much restricted and often ignored. One of the major reasons is the location of aquaculture sites and several sociocultural taboos against women who strive to earn for their family’s subsistence in rural areas. There is a gender bias in many aquaculture activities. To ensure that women utilize their full potential in profitable activities like aquaculture, it is necessary to provide capacity building support to rural women, which will eventually lead to their empowerment.
This issue of Naga features three articles about a project on the Genetic Improvement of Farmed Tilapias (GIFT) and a related article on the trend to genetic deterioration in some carp hatcheries. The first is on the genesis of the project — from relatively modest collaborative research efforts that began in the early 1980s to some of the significant results from the GIFT project.
Details are given of a framework for developing breeding programmes using experience from the Genetic Improvement of Farmed Tilapias project which focussed on Nile tilapias (Oreochromis niloticus ). The following aspects are outlined: Analysis of targeted production and marketing systems; Breeding goals; Systematic documentation and evaluation of available genetic resources and choice and genetic base; Number of strains; Breeding strategy; Selection criteria and evaluation; Production and dissemination of improved strains; and, social, economic and environmental impacts.
This paper documents the emergent snake ‘fishery’ occurring on Tonle Sap Lake where an estimated 6.9 million snakes (mostly homalopsids) are removed annually, representing the world’s largest exploitation of a single snake assemblage. Based on interviews with hunters, we found that snake catches declined by 74–84% between 2000 and 2005, raising strong concerns about the sustainability of this hunting operation.
Investigations on the source, abundance, migration, exploitations and management options of Jatka (juvenile hilsa, Tenualosa ilisha) fisheries were conducted in the Gajner beel, located at the south-east corner of the Pabna Irrigation and Rural Development Project (PIRDP) in Sujanagar Upazila of Pabna district. This article reports exclusively on the important Jatka fishery of the Gajner beel. The Padma and the Jamuna was identified as the sole source of Jatka in the Beel.
This review is a compendium of most of the available biological and engineering knowledge relevant to the breeding and mass propagation of the Mugilidae species, particularly the grey mullet Mugil cephalus Linn.
The valuable sea cucumber Holothuria scabra, known as ‘sandfish’, has potential for restocking. However, there is little information available to determine the size of the no-take zones (NTZs) needed to protect the released animals so that they can form nucleus breeding populations. To do this, we measured short-term movement paths of released juvenile (1–105 g) and wild adult (130–690 g) sandfish in a seagrass bed in New Caledonia.
The demand for fish is expected to rise substantially by 2020. Although aquaculture must provide much of the additional fish, it remains to be seen whether restored or enhanced capture fisheries can also help fill the projected gap in supply. The key challenges for capture fisheries involve reducing fishing effort, removing excess fishing capacity and building the institutional arrangements needed to restore spawning biomass to more productive levels, and to reverse degradation of the supporting habitats.