Biological control of incrusting organisms and sediments in Chilean oyster cultures

The oyster culture has the incrusting organism as problem for production, in this context, it evaluated as biological control against incrusting organism and sediments the introduction of gastropod Tegula atra (Lesson, 1830) in Chilean oysters (Triostrea chilensis Phillippi, 1844) cultures in conditions of starvation presence and absence located in floating cages and bottom cultures. The predation and mechanic effect on T. atra grazing generated a decreasing in seven days of 19.8% and 13.7% of incrusting organisms in cage culture and bottom sediments by effects of gastropods without starvation respectively. Whereas it had a decrease of 12.6% and 11.4% of incrusting organisms in cage culture and bottom sediments by effects of gastropods with starvation respectively. The incrusting organism removed were mainly algae, colonial ascidia, polychaeta, bryozoan and small crustaceans.

Isolation and determination of Vibrio spp. pathogen from hemorrhagic disease in Sciaenops ocellatus in cage culture

In this study, 18 strains of Vibrio bacteria were identified from 27 samples of Red drum fish (Sciaenops ocellatus) suffering from the haemorrhagic disease from cage culture in Vietnam. The bacterial strains were identified with the 16S rRNA sequencing method and checked for morphological, physiological, and biochemical characteristics by using the API 20E KIT. Twelve strains of V. alginolyticus, three strains of V. fluvialis, and three strains of V. orientalis were recorded. All Vibrio strains have gene similarities with those on the gene bank ranging from 98 to 100%. The biochemical characteristics of these 18 isolates were similar. These bacteria are susceptible to tetracycline and doxycycline and entirely resistant to ampicillin, amoxicillin, and erythromycin.

Dactylogyrus Infestation in Farmed Common Carp Cyprinus carpio from Aquaculture Facilities in Macedonia

A total of 958 specimens of farmed common carp Cyprinus carpio from eight of the most significant and largest cyprinid aquaculture facilities in Macedonia (pond and cage culture systems) were examined for parasitological investigation for three years. The following parasite species of the genus Dactylogyrus were identified: Dactylogyrus extensus, Dactylogyrus minutus and Dactylogyrus anchoratus. The highest prevalence was determined for D. extensus (38.8%), followed by D. minutus (7.9%) and D. anchoratus (2.8%). The highest mean intensity was determined for D. extensus (6.2), followed by D. minutus (4.7) and D. anchoratus (3.8). By seasons, the highest prevalence (16.5%) was recorded for D. extensus in winter, while the lowest (0.6%) for D. minutus in autumn. The highest mean intensity (8.0) was also determined for D. extensus in winter, and the lowest (1.9) for D. minutus in spring.

Effects of Parasitism on the Production and Productivity of caged Oreochromis niloticus in Winam Gulf of L. Victoria

The general objective of this study was to assess the effects of parasitism on the production and productivity of caged Oreochromis niloticus in Winam Gulf of L. Victoria. With the need to increase food production through fish products amid overfishing and pollution stress in the lake, cage farming is seen to have the potential to bridge the fish supply and demand gap continues to widen. Cage culture is a new technology in the offing that needs to be explored to justify its potential. Fish parasites are always a threat in an enclosed culture system and because of this, it is necessary to assess their effects on fish condition factors before recommendation. It is because of this reason that a total of 480 caged Oreochromis niloticus were purchased and examined for parasites using the recommended procedures for parasitological analysis. The class Trematoda which included seven taxa were found to be the most common and prevalent parasites in cages of the Winam Gulf. This was attributed to the presence of piscivorous birds which are definitive hosts seen more often around the culture systems and also overstocking observed and reported during the study period which increases the spread and transmission of parasites from one fish to another. Despite the prevalence, infestation did not affect the fish condition factor in all the study areas as the majority of infected fish recorded between good and excellent body condition factors. This was due to low mean intensities recorded and a shorter period of exposure to parasitic infestation as most farmers were barely 3 years into the system. In conclusion, for the government to explore the blue economy and achieve the Vision 2030 and SDGs on food security and poverty reduction by 2030, efforts to promote commercial cage culture enterprises in the Winam Gulf must be bolstered, provided that cages are located in deep waters with low concentrations in specific areas and low stocking densities to avoid compromising the environment.

Performance Of Nile Tilapia Oreochromisniloticus (L) In Cages of Varied Stocking Densities

Cage culture is a new venture in Tanzania, and the knowledge of stocking density in cages is still needed. Growth performance of Nile tilapia, Oreochromis niloticus (L) stocked in cages of varied stocking densities and their impacts on waters were evaluated for 212 days in Shirati Bay of Lake Victoria. We started with fingerlings of 18.0±2.1 g, 19.9±14.7 g, and 18.5 ± 8.0 g mean weights. They were raised in cages at stocking densities of 70 (Treatment I), 100 (Treatment II), and 130 fish/ m3 (Treatment III) each in triplicates. We recorded monthly fish weights and lengths, total nitrogen, total phosphorus, ammonia, and micro-benthos. Parameter such as dissolved oxygen, pH, temperature, and transparency were all monitored weekly. The final average fish weights were 374.1±59.8g in treatment I, (194.8 ± 63.7g) in II, and (273.2±20.6g) in III. Percentage fish survival was the highest in treatment I (76.7%), followed by II (65.4%) and III (54.3%). Specific growth rate, production and yield was the highest in treatment I, and significantly different from treatments II and III (p <0.05). This indicates that Nile tilapia flourished well in the lowest stocking density. Water quality parameters were within the range of fish culture throughout the study and observation of water depth, distance from the shoreline, and the prevailing water currents showed lack of adverse environmental effect caused by fish cage culturing