A review of diseases associated with cage culture systems: diagnosis and control in smale scale fish farming

Fish cage culture is a rapid aquacultural practice of producing fish with more yield compared to traditional pond culture. Several species cultured by this method include Cyprinus carpio, Orechromis niloticus, Sarotherodon galilaeus, Tilapia zilli, Clarias lazera, C. gariepinus, Heterobranchus bidorsalis, Citharinus citharus, Distochodus rostratus and Alestes dentes. However, the culture of fish in cages has some problems that are due to mechanical defects of the cage or diseases due to infection. The mechanical problems which may lead to clogged net, toxicity and easy access by predators depend on defects associated with various types of nets which include fold sieve cloth net, wire net, polypropylene net, nylon, galvanized and welded net. The diseases problems are of two types namely introduced diseases due to parasites. The introduced parasites include Crustaseans, Ergasilus sp. Argulus africana, and Lamprolegna sp, Helminth, Diplostomulum tregnna: Protozoan, Trichodina sp, Myxosoma sp, Myxobolus sp. the second disease problems are inherent diseases aggravated by the very rich nutrient environment in cages for rapid bacterial, saprophytic fungi, and phytoplanktonic bloom resulting in clogging of net, stagnation of water and low biological oxygen demand (BOD). The consequence is fish kill, prevalence of gill rot and dropsy conditions. Recommendations on routine cage hygiene, diagnosis and control procedures to reduce fish mortality are highlighted

Surveying bacterial human pathogens in shrimp culture in Thailand

Any presence of bacterial human pathogen in shrimp products may be of public health concern. This note concludes that Salmonella do not appear to constitute a part of the microbial flora where shrimp culture is practiced in Thailand. Vibrio cholerae 01, the cause of cholera are rarely recovered from the environment with no isolates containing genes encoding cholera toxin. Further studies are needed to describe the prevalence of bacterial human pathogens in shrimp culture, especially determination of possible postharvest cross-contamnation with these pathogens

Mangrove forests and shrimp culture in Ngoc Hien District, Minh Hai Province, Vietnam

As a result of increased population growth, the attraction of high profits from shrimp culture and ineffective mangrove forest management, a number of serious environmental problems exist in Ngoc Hien District, Minh Hai Province, Vietnam. These environmental problems are highlighted in this article.

The potential for crop rotation in controlling diseases in shrimp culture

The use of antibiotics and other chemicals in controlling shrimp pathogens become ineffective as the strains grow more resistant to these chemicals. Moreover, the bacterial pathogen (Vibrio harveyi) produced biofilm coating that protects it from dying and disinfection procedures that are followed during pond preparation. Biological control is being considered as an alternative means of preventing shrimp disease outbreak. The main principle behind biological control is to enhance the growth of beneficial microorganisms which serve as antagonists or target pathogens. The paper discusses shrimp and tilapia crop rotation as a form of effective biological control, a technique which is already being practiced in Indonesia and the Philippines.

Length-weight relationships of Penaeus monodon reared in semi-intensive culture systems of Kerala, India

The results of a study on length-weight relationships of Penaeus monodon, reared in fertilized ponds in Kerala, India, and fed three different supplementary feeds are presented.

Improvement of traditional shrimp culture in the Mekong Delta

Improvements to traditional brackishwater shrimp culture in the Mekong Delta, Vietnam are discussed. A technical support program has been implemented based on a so-called improved extensive shrimp culture method, as previously developed and tested by the Artermia and Shrimp Research and Development Center (ASRDC). The program focuses on: 1) the use of hatchery-produced postlarvae (of Penaeus monodon and P. merguinensis) nursed for three to four weeks, and 2) the application of low-cost pond management practices including predator control, supplementary feeding and frequent water renewal. A credit program, managed as a revolving fund was made available. A dialogue among participating farmers was encouraged through the organization of group meetings before and after each production cycle.

Expansion of improved-extensive shrimp culture in the Mekong Delta

This paper describes the expansion of improved-extensive shrimp (Penaeus monodon) farming in the Mekong Delta, southern Vietnam, emphasizing management decisions, technological constraints and economics.

Growth performance, recovery rate and fish yield of GIFT strain at various water depths under rice-fish culture systems

Effect of water depth on recovery rate, growth performance and fish yield of GIFT in the rice-fish production systems was studies in experimental plots of 123 m2 with a pond refuge of I meter deep which covered 10% of the total land area. Mortality rate of fish was very low ranging from 0.81-1.63%. However, at harvest, recovery rate ranged from 76.69-82.93% with the highest recovery at 11-15 em of water depth. Significantly the highest absolute growth (99.97) and specific growth rate (2.42%) were found at 21-25 cm water depth. The same treatment also produced significantly higher fish yield (909.76 kg/ha) although statistically similar to the fish yield (862.60 kg/ha) obtained at ll-15 em of water depth. Results also suggested that higher water depth can produce bigger fish but no significant effects of water depth was found on fish yield in the treatments 11-15 cm and 21-25 cm water depths of this experiment.

Integrated cage-cum-pond culture systems with high valued climbing perch (Anabas testudineus) in cages and low-valued carps in open ponds

An on-farm trial was conducted over 150 days to determine appropriate stocking ratio, growth and production of climbing perch (Anabas testudineus) in cages and carps in open water of ponds in eighteen farmers' ponds from Haluaghat Upazila at Mymensingh district of Bangladesh. One or two 1 m super(3) cage was suspended in each of 12 earthen ponds and other 6 ponds served as control without cages. Climbing perch of 2-3 g in size were stocked in cages while fingerlings of silver carp (Hypophthalmicthys molitrix), catla (Catla catla), rohu (Labeo rohita), mirgal (Cirhinus cirrhosus), rajputi (Puntius sarana) and common carp (Cyprinus carpio) were stocked at 1 fish/m super(2) with a species ratio of 5:4:4:4:2:1 in open water of all ponds to give cage to open-pond fish ratios of 1:1 (T sub(1:1)) and 2:1 (T sub(2:1)) and 0:1 (T sub(0:1)) as three treatments with six replicates each. Survival of climbing perch was higher in T sub(1:1) (61.67%) than that of T sub(2:1) (29.5%) and was significantly different (p>0.05) between the treatments. Stocking of small size climbing perch fry increased the mortality rate in cages. The net yields of Thai koi were 0.13±0.01 (t/ha) and 0.10±0.01 (t/ha) in treatments T sub(1:1) and T sub(2:1), respectively and both were significantly different (p>0.05). Survival of-open-pond carps was high, ranging from 50 to 91.67% with significantly lower in T sub(0:1) than that of T sub(1:1) and T sub(2:1) treatment. Net and gross yield of each carp species were significantly higher in the T sub(1:1) and T sub(2:1) treatment than that in T sub(0:1) treatment. Net revenues were positive but low in all treatments. Therefore, bigger size climbing perch with lower stocking ratio (T sub(1:1)) is suitable for integrated cage-pond culture of climbing perch and carps. However, more on-farm trials in different ecosystem with scientific interventions are necessary to develop the technology for further dissemination among the rural farmers.