Research Items (19)
The edible bivalves Perna viridis (green mussel), (n = 100) were analysed for their total Hg, Pb, Cu, Ni, Zn, Co, Fe, Cr, Cd, and Mn concentrations to indicate heavy metal contamination in Paradise Point of Karachi coast using atomic absorption spectrophotometer. There are large seasonal variations in the metal concentrations of Mn (0.025-0.67 µg/g), Fe (0.055-7.740 µg/g), Ni (0.004-0.52 µg/g), Hg (0.0001- 0.004 µg/g), Zn (0.04-3.32 µg/g), Cu (0.008-1.66 µg/g), Pb (0.022-2.43 µg/g), Co (0.01-0.044 µg/g), Cd (0.04-0.88 µg/g) and Cr (0.13-1.20 µg/g) recorded in bodies/soft tissues of P. viridis obtained in the samples of the year 1993 and 2012 at the Paradise Point of Karachi coast. The results of heavy metals are in the following descending order of concentration in the samples collected in the year 1993: Fe>Cr>Zn>Mn> Pb>Cd>Cu>Ni>Co>Hg, while Fe>Zn>Pb>Cu>Cr>Cd>Mn>Ni>Co>Hg order was recorded in samples collected in the year 2012. The high accumulation of metals was found mostly in the samples collected in the year 2012 when compared with the samples of the year 1993. This is an indication that the area under study showed signs of being exposed to significant levels of heavy metal pollution due to direct discharge of industrial and domestic wastes along the coast. The concentrations of these heavy metals were lower than the permissible limits for human consumption. However, if this pollution persists, it can prove to be very detrimental in future.
Attempts to raise Tilapia zillii both on an experimental and production basis by researchers and fish farmers have indicated some problems exist which are not found with the culture of other tilapia species. Thus, the relevance of this study was necessitated using garlic (Allium sativum) to enhance the growth potential of T. zillii which is the bottleneck in the mass production of this species. Monosex Tilapia zillii fry with 0.09 g initial average weight were reared under laboratory condition with a dried garlic-containing diet at inclusion levels 0, 1, 2 and 3% / kg diet for a period of 60 days to evaluate the effects of inclusion levels of dried garlic (A. sativum) on growth performance, nutrient utilization, survival and body chemical composition of monosex red belly tilapia, T. zillii. The obtained results of the present study showed that the treatments supplemented with garlic at 3% / kg diet had a significantly higher (P<0.05) final weight (12.38g), total weight gain (12.29g), survival rate (100%) and better feed conversion ratio (1.02) when compared to other treatments. Body chemical composition of T. zillii revealed lower content of lipid (7.24%), dry matter (74.37%), ash (16.92%) and higher protein (66.55%) in treatments supplemented with garlic at 3% / kg diet. Above all, the highest growth performance, nutrient utilization and flesh quality (crude protein and lipids) were recorded in T. zillii at 3% inclusion rate. The study therefore recommends that T. zillii should be fed on a garlic-supplemented diet at 3% / kg diet to enhance their growth performance. However, since the present study was conducted in laboratory condition, further studies are necessary to test their efficacy in pond condition.
Seasonal sampling of the edible green mussel Perna viridis of two different sizes 6-8cm (n=100) and 4-6cm (n=100) from Manora channel of Karachi, were analyzed for their total Hg, Pb, Cu, Ni, Zn, Co, Fe, Cr, Cd and Mn concentration. There are large seasonal variations in the metal concentrations found in green mussel Perna viridis. The high accumulations of metals were found mostly in small size 4-6 cm mussels as compare to largeones. The present study has confirmed thatgreen mussels have greater capacity for accumulation ofmetals.All the studied metal levels found in green mussels collected in 2012 were higher than those detected in mussels collected in 1993, irrespective of mussel body size. The concentrations of Fe was highest compared to other heavy metals. The results of heavy metals are in the following descending order of concentration: Fe>Pb> Zn>Cu>Mn> Ni> Cr> Cd> Co> Hg. It is supposed that in Manora channel water, high input of metals and other inorganic and organic substances are coming in the form of industrial and domestic wastes and need to be monitored on a regular basis.
A study was conducted to compare the growth potential of Tilapia rendalli at three different stocking densities, using different rearing facilities. T. rendalli fry of 0.9±0.1g average weight were stocked in tanks and hapa-in-ponds at the stocking density of 30, 60 and 90 fry/m 3. Locally made feed (CP-18%) was administered at 5% body weight three times a day for three months. Monthly sampling was conducted to assess growth by measuring weight and length for specific growth rate (SGR), average daily gain (ADG), weight gain (WG), and biomass (BM). The results of the study showed a significantly higher (P < 0.05) growth rate in low stocking density (30 fry/m 3) as compared to 60 and 90 fry/m 3. There was a highly significant (P < 0.05) growth rate from hapas mounted in pond rearing facility as compared to tanks. There was no significant difference in profitability between the two rearing facilities (P > 0.05) as well as within the stocking densities (P > 0.05). The results of this study have a significant contribution towards stocking densities as well as rearing facilities used by hatchery operators. It is recommended that hapas mounted in pond fry rearing for T. rendalli fingerling production is most ideal. The results of the present study suggested that production of good quality fingerlings at stocking densities of 30 fry/m 3 must be adopted in the culture of T. rendalli as fish grows faster than the other stocking densities of 60 and 90 fry/m 3 as demonstrated in this study.
The use of feed additives as natural growth promoters has received considerable attention in the aquaculture industry. Besides, the utilization of antibiotics, antioxidants, feed stimulants, feed colourants as well as the use of hormones has been well established by several authors. However, the absorption or ingestion rate of the widely used feed additives by cultured fish species has not been thoroughly quantified and researched in fish nutrition while on the other hand; further investigation needs to be focused on the nutritional effects of the commonly used feed additives in the aquaculture industry. In spite of the growing interest and success obtained using feed additives as supplements in farmed fish diets, several physical anomalies or alterations in the normal development of farmed fish species have been reported by several authors. The present review therefore emphasizes on new areas of further research to improve growth, feed utilization, absorption or ingestion rates and disease resistance in cultured fish species fed feed additives. Special emphasis is focused on the elucidation of the biochemical contents and dietary supplementation levels of feed additives by cultured fish species which has received relatively little attention in the aquaculture industry. The development of a cost-effective new natural source of antioxidant; the development of algal meal-based diets as feed additives; adoption of a reliable and cost-effective method to quantify the absorption or ingestion rate in cultured fish species as well as the utilization and adoption of acidifiers consisting of organic acids and their salts as a potential replacement for antibiotic growth promoters are recommended as real and achievable research goals for future.
Polycyclic aromatic hydrocarbons (PAHs) and heavy metals contribute to pollutants in aquaculture facilities and thus need to be further investigated. Besides, there is little information regarding PAHs and heavymetals in the tissues of cultured fish, and the risks associated to consumption. In this review, emphasis has been made on the detection of PAHs and heavy metals in cultured fish species which has relatively received little attention in the aquaculture industry compared to researches on the levels of PAHs and heavy metals from the wild catch. The reviewalso focuses on the detection of PAHs and heavy metals in most of the feed ingredients commonly used in the formulation of feed for farmed fish species. The use of chemicals like antibiotics, feed additives, soil and watertreatment and other products used in the aquaculture facility or site is also well emphasized and need to be well documented. Future research goals are well stressed and need to be given more attention in aquaculture. @JASEM
In spite of the growing interest and success obtained using cultured-copepods, their use in marine aquaculture remains sporadic. Besides, mass culture of several marine copepods has been well established by several authors. However, the upscale of copepod cultures to commercial levels is still a challenge. The practice of using wild copepods from natural ponds which thus increases the risk of parasitic infections of most species has limited their application in aquaculture. The present paper thus emphasizes on recent research efforts focused on the use of chemical treatments and freeze-thawing methods to eradicate procercoids from copepods. Research efforts focused on copepod culture systems which subsequently improved and refined their culture in marine fish larviculture are also well discussed. Advances in the use of copepod eggs as potential source of nauplii for marine fish larvae with special emphasis on the viability, storage conditions and biochemical compositions of the copepod eggs are underscored. Additionally, recent advances in the biochemical compositions (protein, amino acids, pigments, and vitamins) of copepods, which has received relatively little attention compared to researches on the lipid and fatty acid compositions are well emphasized. Specific recommended areas for further research are also proffered. KeywordsLarviculture–Culture systems–Nutritional value–Copepod eggs
The paper emphasizes on the several attempts made to raise the brackish water tilapia species, Tilapia guineensis both on an experimental and production basis by researchers and fish farmers in Nigeria. Besides, the aquaculture potentials of Tilapia guineensis have been reported by several authors. However, problems exist which are not found with the culture of other tilapia species. Even under most favourable conditions (e.g. the monosex culture of Tilapia guineensis), a poor growth rate and a mediocre feed conversion do not presage profitable aquaculture exploitation. The present review therefore throws light on areas of further research to enhance the growth performance of Tilapia guineensis with emphasis on fish larvae nutrition and first feeding (development of bio-encapsulated feed for larval fish based on nutritionally enriched nematodes and Calanoid copepods), digestibibilty of the feed ingredients, elucidation of the dietary protein requirements, improved culture technique through the use of the Recirculating Aquaculture Systems and the adoption of the most recent technology (The YY Male technology) that produces Genetically Male Tilapia through genetic manipulation. Specific recommended areas for further research are also proffered. Keywords Tilapia guineensis -Nematodes-Calanoid copepods-Digestibility