Impact of mangrove conversion

The article presents the impact of mangrove conversion on fisheries and on coastal areas. The mangrove areas which serve as nursery grounds for important species of fish and crustaceans are also rich feeding ground for many species from various trophic levels. Thus, the destruction of mangroves could affect the availability of fry and broodstock and, consequently, aquaculture production and fisheries. While in coastal areas, the destruction of mangroves increased the risk of coastal erosion from storm surges and winds, accelerates the erosion of riverbanks, exposes acid sulfate soils, leading to poor production and mass mortality of stocks, and affects the freshwater supply through salt intrusion upstream among others.

The milkfish fry shortage

The article presents the Philippines, Department of Agriculture Project Sabalo which aims to address the milkfish fry shortage of the country. The project also aims to evaluate existing hatcheries, assess broodstock conditions, and increase the number of broodstock. Fry requirement for milkfish ponds is also presented.

Interactions of dietary levels of protein and energy on rainbow trout (Oncorhynchus mykiss) in desert brackish water

A 3x3 factorial experiment was conducted to determine the optimum protein to energy (P/E) ratio for rainbow trout in brackish water. Three crud protein levels and three energy levels at each protein level were utilized. Diets were made in semi-purified that in all of them fish meal, casein and gelatin as the sources of protein and dextrin, starch and oil as the sources of energy were used. Each of experimental diets was fed to triplicate groups of 20 fish with an average individual weight of 81.5 g in 9 2000-1 flow trough fiberglass tanks. During this experiment water temperature, dissolved oxygen, PH and EC were 15±2°C, 6.5-8.1 mg/1, 7.7-8.6 and 25400 grills respectively. The diets were fed at a rate between 1.6-2 wet body weight% per day depended to water temperature in three equal rations and adjusted two weekly for 84 days. At each of protein levels, weight gain percent (%WG), average daily growth percent (%ADG), protein efficiency ratio (PER), apparent net protein utilization percent (%ANPU), or percent of protein deposited, specific growth rate (SGR) and condition factor (CF) were found to increase and food conversion ratio (FCR) was found to decrease with an increasing energy levels from 370 to 430 Kcal/100g. Fish fed a 35% protein, 430 Kcal/100g energy diet with a P/E ratio of 81.4 mg protein/ Kcal PFV energy, attained the best growth performance. Fat and moisture of carcass were affected by protein and energy levels of test diets while protein and ash of carcass were relatively constant in different treatments.

Lead exposure through gestation-only caused long-term learning/memory deficits in young adult offspring

Numerous observations in clinical and preclinical studies indicate that the developing brain is particular sensitive to lead (Pb)'s pernicious effects. However, the effect of gestation-only Pb exposure on cognitive functions at maturation has not been studied. We investigated the potential effects of three levels of Pb exposure (low, middle, and high Pb: 0.03%, 0.09%, and 0.27% of lead acetate-containing diets) at the gestational period on the spatial memory of young adult offspring by Morris water maze spatial learning and fixed location/visible platform tasks. Our results revealed that three levels of Pb exposure significantly impaired memory retrieval in male offspring, but only female offspring at low levels of Pb exposure showed impairment of memory retrieval. These impairments were not due to the gross disturbances in motor performance and in vision because these animals performed the fixed location/visible platform task as well as controls, indicating that the specific aspects of spatial learning/memory were impaired. These results suggest that exposure to Pb during the gestational period is sufficient to cause long-term learning/memory deficits in young adult offspring. (C) 2003 Elsevier Inc. All rights reserved.

The technology of milkfish hatchery in Indonesia

The culture of milkfish (Chanos chanos), which is the oldest fish cultured in Indonesia, has spread to almost all the provinces in the country. In order to answer the demand of milkfish fry, without decreasing production and wild fry supply, artificial fry production in big and small-scale hatcheries is being practiced. Details are given of the milkfish hatchery system, listing also the major criteria to be taken into account for site selection. Operation of the hatchery is described, outlining the following activities: broodstock rearing; hormone implantation; broodstock maintenance; egg production and harvest; and, larval rearing.

Catfish aquaculture

This article deals with the biology, broodstock management, seed production techniques and grow-out culture practices in C. macrocephalus.

Aquaculture potential of ornamental fishes of Uganda

Preliminary studies undertaken to investigate the availability of ornamental fish species in Uganda’s natural water systems, revealed significant abundance of coloured fishes in Uganda’s water systems including the Kyoga and Victoria Lake system. These species are able to breed in captivity and to feed on artificial diets in ponds and glass tanks. The species are attractive and are highly marketable. These observations indicate the potential to culture ornamental fishes as away of diversifying the range of aquaculture species, a means to generate income and to improve livelihoods in Uganda.

Status and variation of invertebrates in Lakes Albert and Kyoga

Invertebrates are some of the key food items for fish diets. They thus form an important fish food environment upon which the fisheries thrives in terms of production through dietary support. Invertebrates communities of Lakes Albert and Kyoga have been evaluated and considered the implications for diets and production of commercial fishes.

The feeding of three commercially important fish species in Lake Chilwa, Malawi

The diets of the three species of fish that predominate in the Lake Chilwa fishery are described in relation to various parameters using a semi-quantitative method of analysis of the digestive tract contents. Barbus paludinosus Peters fed during the day on zooplankton, non-filamentous green algae and some higher plant material; small fish fcd predominately on zooplankton but with increasiug size the diet was more varied. Clarias mossambicus Peters fed throughout the day and night and had a highly varied diet with fish becoming the major food item in large fish, Tilapia shirana chilwae Trewawas fed mainly during the day on higher plant material, filamentous green algae and zooplankton; smaller fish fed predominately on zooplankton. The importance of flexibility in the diet of the three fish species is stressed.

Parasitic fish diseases and their impact on potential fish production in East Africa

Protein deficient diets are a standard way of life in many parts of East Africa;this of course tends to result in shorter life expectancy and chronic ill-health. Population increase is sufficiently high to outdistance the economic gains that may be made in various fields. With recurrent shortages of basic commodities not only in East Africa, but in many parts of the world, it is becoming increasingly clear that agricultural production practices must be maximised rapidly in order to meet the world's constantly expanding need for food. Here in East Africa, while our food requirements can be met most of the time, our protein requirements are far from being met. Yields from traditional fishery resources, must therefore be increased. The farming of fish (aquaculture)adds a new dimension to food production in general and high quality protein production in particular, in that it can be incorporated into other agricultural production activities.

MANDIBULAR MORPHOMETRICS AMONG MACAQUES - THE CASE OF MACACCA-THIBETANA

Recent field studies suggest that Macaca thibetana, a large endemic Chinese macaque, may be quite folivorous, distinguishing it from most other macaque species, which tend to be primarily frugivorous. To understand how this diet affects its masticatory system, we conducted a comparative morphometric study of mandibular dimensions. We took linear measurements from male and female mandibles of this species as well as four other macaques-M. fascicularis, M. nemestrina, M. arctoides, and M. assamensis-and four species of Presbytis-P. obscura, P. rubicunda, P. cristata, and P. phayrei-and subjected to them to a variety of analyses. Based on analyses of variances and discriminant analyses on each sex individually, the mandible of M. thibetana corresponds to expected patterns for folivorous primates with respect to its wide condyles and thick corpora: However, the height of the corpus and symphysis are lower, and the anteroposterior length of the condyle is longer than predicted for a folivore. In addition to interpretations specifically relating to M. thibetana, we also discuss the functional morphology of the other species in light of what is published about their diets.

Seasonal variations in stable isotope ratios of two biomanipulation fishes and seston in a large pen culture in hypereutrophic Meiliang Bay, Lake Taihu

This paper reports on seasonal changes in stable carbon and nitrogen isotope ratios of seston and muscle tissue of silver carp and bighead carp during 2004 and 2005, focusing primarily on the carbon sources and trophic relationships among phytoplankton, zooplankton and silver carp and bighead carp in a large fish pen of Meiliang Bay (Lake Taihu, China). delta C-13 showed a minimal value in March 2005 and a maximal value in August 2005 in seston both inside and outside the pen, whereas delta N-15 of seston showed the minimum in winter and the maximum during algal blooms. A positive correlation between delta C-13 of silver carp and that of seston suggested that temporal variation Of delta C-13 in seston was preserved in fish via the food chain. The differences of delta C-13 among seston, zooplankton and muscle tissue of silver carp and bighead carp ranged only 0.2-1.7%, indicating that plankton production was the primary food source of filter-feeding fishes. According to a mass balance model, we estimated that the contributions of zooplankton to the diets of silver carp and bighead carp were 45.7% and 54.3%, respectively, based on the delta N-15 values of zooplankton and planktivorous fishes. (C) 2007 Elsevier B.V. All rights reserved

Effect of dietary linolenic acid/linoleic acid ratio on growth performance, hepatic fatty acid profiles and intermediary metabolism of juvenile yellow catfish Pelteobagrus fulvidraco

The present study aimed to evaluate the effect of dietary linolenic acid (LNA)linoleic acid (LA) ratio on growth performance, hepatic fatty acid profile and intermediary metabolism of juvenile yellow catfish Pelteobagrus fulvidraco. Six isonitrogenous and isolipidic diets were formulated to contain incremental levels of LNA from 0 to 5% at the expense of corn oil (rich in LA), resulting in six dietary treatments with LNA to LA ratios ranging from 0.35 to 14.64. The experiment continued for 7 weeks. Best growth and feed intake were obtained in the fish fed the diets containing the LNA/LA ratios of 1.17 and 2.12 (P<0.05). In contrast, feed conversion ratio was the lowest for fish fed the diets containing the LNA/LA ratios of 1.17 and 2.12 (P<0.05). Dietary LNA to LA ratios significantly influenced viscerosomatic index and hepatosomatic index (P<0.05), but not condition factor (P>0.05). Body composition was also significantly influenced by dietary LNA to LA ratios (P<0.05). Generally, liver FA compositions reflected dietary FA profiles. Declining LA and increasing LNA contents in liver were observed with the increasing dietary LNA/LA ratios (P<0.05). Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) increased with the increasing LNA to LA ratios, suggesting that yellow catfish could elongate and desaturate C18 polyunsaturated fatty acids into highly unsaturated fatty acids. As a consequence, the n-6 fatty acids (FA) declined, and total n-3 FA and n-3/n-6 ratios increased with the dietary ratios of LNA/LA (P<0.05). Dietary LNA to LA ratios significantly influenced several enzymatic activities involved in liver intermediary metabolism (P<0.05), such as lipoprotein lipase, hepatic lipase, pyruvate kinase, succinate dehydrogenase, malic dehydrogenase and lactate dehydrogenase, suggesting that dietary LNA/LA ratios had significant effects on nutrient metabolism in the liver. To our knowledge this is the first demonstration of the effects of dietary LNA to LA ratios on the enzymatic activities of liver in fish, which provides information on diet quality and utilization, and can also be used as an indicator of the nutritional status of this fish. (C) 2009 Elsevier B.V. All rights reserved.

Effects of dietary cyanobacteria of two different sources on growth and recovery of hybrid tilapia (Oreochromis niloticus x O. aureus)

A 115 days feeding trial was conducted to evaluate the effect of dietary cyanobacteria on growth, microcystins (MCs) accumulation in hybrid tilapia (Oreochromis niloticus x O. aureus) and the recovery when the fish were free of cyanobacteria. Three experimental diets were formulated: the control (cyanobacteria free diet); one test diet with cyanobacteria from Lake Taihu (AMt 80.0 mu g MCs g(-1) diet) and one with cyanobacteria from Lake Dianchi (AMd, 410.0 rho g MCs g(-1) diet). Each diet was fed to fish for 60 days and then all fish were free of cyanobacteria for another 55 days. A significant increase in feeding rate (FR) was observed in fish fed AMd diet after a first 30-day exposure (1(st) EP), and in fish fed both AMt diet and AMd diet after a second 30-day exposure (2(nd) EP). Specific growth rates (SGR) of fish fed AMt diet and AMd diet were both obviously affected after the first 30-day exposure, but SGR was only significantly affected in fish fed AMt diet after the second 30-day exposure. After a 55-day recovery, there were no significant differences among diets in the indices mentioned above. Much higher concentrations of MCs were accumulated in tissues of all fish exposed to cyanobacteria. After the 55-day recovery, MC concentrations in fish tissues were significantly lower than those on day 60. (C) 2009 Elsevier Ltd. All rights reserved.

The effect of different dietary iron levels on growth and hepatic iron concentration in juvenile gibel carp (Carassius auratus gibelio)

P>An 83-day growth trial was conducted using a flow-through system to examine the effects of different dietary iron levels on growth and hepatic iron concentration in juvenile gibel carp (Carassius auratus gibelio). Six purified diets supplemented with different levels of iron (0, 10, 30, 60, 100 and 200 mg kg(-1)) (as ferrous sulfate) were fed to triplicate groups of fish (initial weight 2.12 +/- 0.00 g per fish). The results showed that the addition of iron to the basal diet did not significantly affect the specific growth rate (SGR), feed efficiency (FE), survival, red blood cell amount (RBC), hemoglobin content (Hb), mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH) or mean corpuscular hemoglobin concentration (MCHC). Hepatic iron concentration and hematocrit (Hct) were significantly influenced by dietary iron level (P < 0.05). On the basis of the iron concentration for the maintenance of optimum hepatic iron concentration and Hct, it was concluded that the dietary iron concentration of juvenile gibel carp should be not less than 202 mg Fe kg(-1) diet.