Growth, Mortality and Exploitation of Sardinella maderensis (Lowe, 1838) in the Liberian coastal waters

Sardinella maderensis also known as flat ‘sardinella’ forms part of the commercially important fish species of Liberia which prefers areas of lower salinities close to the mouth of river. Though S. maderensis appears throughout the year in Ivory Coast coastal waters with a strong reduction from May to July due to the transition from warm season to cold season, adults S. maderensis are more sedentary. S. maderensis fishery is of great importance to fishing households within most coastal communities in Liberia, both economically and food security wise. As a result, S. maderensis fishery like other commercially important fish species in Liberia is currently subjected to intense fishing pressure. Intensive fishing pressure on marine biodiversity by location and depth has led to decline of marine capture fisheries.

In Liberia, factors such as poor fisheries data collection, limited resources, conflicts and illegal, unregulated and unreported (IUU) do not only make it difficult to estimate the status of almost all of the marine biodiversity but also presents a great challenge to fisheries managers. However, Togba reported that Sardinella, Barracudas, Croakers, Sharks and Ilisha africana constituted 83% and 59.06% of local fish supply in 2004 and 2005 respectively; indicating that there has been a declined in fish catches.

Role of Plasmids in Microbiology

The dynamics of bacterial genome has aroused from a long series of evolutionary events. These evolutionary events are responsible for unique set of biological function in large number of bacteria. Bacteria have two separate genetic systems such as chromosomal DNA and extra-chromosomal DNA. Both genetic systems can undergo gene transfer by various means which accelerates process of evolution in bacterial community. Genetic diversity led by evolution is main cause of bacterial adoptability to vast range of conditions. Bacteria are present everywhere even at extreme conditions such as high salinity, extremely high and low temperature where no higher animal will survive. They have different phenotypic characters along with diverse metabolic activity. There are many processes involved in bacterial genomic diversity such as mutation, recombination and Horizontal gene transfer. 

Mutations are natural alteration during DNA replication or it may occur due to a mutagen. Recombination most commonly takes place between closely related bacterial strains and its frequency decreases with decreasing sequence similarity between the donor and recipient. While mutation brings variation in existing genome, recombination serves alteration within a species. But both of them has little contribution for microbial evolution in comparison to the horizontal gene transfer which alters the genes across the species boundaries.

Comparative Ecology of Backwater

Physico-chemical characteristics soil and water basically determines the potentiality of anaquatic habitat in terms of aquaculture production. Proper understanding of these characteristics is the prime requisite to achieve success in aquaculture programmes. 

Considering the biological and economic importance of estuarine habitats and the mangrove dependant or associated fisheries and aquaculture the present investigation depicts a comprehensive account on water quality, soil condition, plankton and benthic faunal components of Kayamkulam Lake and the Ayirumthengu mangrove habitat.

Identification of Growth Hormone Receptor of Rainbow Trout Oncorhynchus mykiss

Hormones, growth factors, and other regulatory proteins associated with the so-called “somatotropic axis” are candidate markers for quantitative trait in farm animals. The biological effect of growth hormone (GH) plays numerous importantand central physiological roles in the growth, metabolism, reproduction, immune function, osmoregulation, and other physiological functions of fish and other vertebrates. Growth hormone receptor (GHR) is the cell surface receptor for GH and is required for GH to carry out its effects on target tissues. As a receptor, GHR mediates the biological actions of GH on target cells by transducing the GH stimulating signal across the cell membrane and subsequently inducing the transcription of many genes, including IGF-I. Although there are few studies on GHR in fish, in Atlantic salmon GHR appears to play a similar role within the somatotropic axis as in humans and its differential expression is what mediates the cellular response to GH plasma levels, and in particular the production of IGF.

The fish GHR gene has been successfully cloned and characterized in several fish species such as gilthead sea bream (Sparus aurata), Atlantic (Salmo salar) and masu salmon (Oncorhynchus masou), and rainbow trout (Onchorhynchus mykiss). Significant associations have been observed between GHR gene polymorphism and growth rates by PCR restriction fragment polymorphism (RFLP) marker (using four restriction enzymes) in 353 individual Cyprinus carpio fish.

Ultrastructural Alterations in Anabas testudineus

Aquatic pollution by pesticides and/or herbicides, either through run-off from agricultural land, or by direct applications such as spray drift, aerial spraying and by discharge as effluents from manufacturing industries, is recognized as strong biological poisons. Now, it becomes a threat to non-target aquatic organisms such as fin-fish and shellfish. Now-a-days, the application of herbicides into the aquatic bodies increases several folds to control the invasive plant species such as water hyacinth and hydrilla etc. Glyphosate is the most effective modern third generation, broad-spectrum herbicide andwidely used both in agriculture and paddy-cum-fish-culture system inrecent times. It is a non-selective, cost- effective and post-emergence herbicide. Glyphosate is a weak organic acid; its chemical name is N-(phosphonomethyl) glycine. Glyphosate is soluble in water (12 g/l at 25o C) but insoluble in most organic solvents. Glyphosate is readily degraded both from water and soil by soil microbes to aminomethylphosphonic acid (AMPA) and carbon dioxide (CO2 ). Due to strong adsorptive characteristics, glyphosate and AMPA are not likely to move to groundwater but have the potency to contaminate surface water. Glyphosate is in the toxicity class of III (on I to IV scale, where IV is least dangerous) for oral and inhalation exposure. 

Cytopathological study provides a fast and efficient process to delineate the health status of organisms exposed to xenobiotic substances. Currently, histopathological biomarkers are used extensively for documenting and quantifying exposure level, as well as expressing the effects of environmental stressors. A number of studies on histopathological biomarkers in the evaluation of fish health exposed to contaminants, both in the laboratory and field studies were reported.