MARINE REPORTS (MAREP)

Effect of dietary phosphorus level on defense system parameters and liver HSP70 concentration in juvenile Japanese flounder, Paralichthys olivaceus

2022-07-20T13:52:35+03:00

A feeding trail was performed to investigate the effect of dietary phosphorus (P) level on defense system in juvenile Japanese flounder. Calcium mono phosphate was used as dietary inorganic-P source. Three semi-purified diets with 3 levels of P (6, 10 and 18 g/kg diet, respectively) were prepared and fed to juveniles (average initial body weight, means ± S.E., 7.3 ± 0.3 g) for 30 days. After termination of the feeding trail, growth parameters were calculated, and mucus lysozyme activity, mucus bactericidal activity and the levels of heat shock protein 70 family (HSP70s) in liver were measured. Results indicated that final weight, weight gain and feed efficiency significantly improved with increasing dietary P level, and the highest growth parameters were obtained from the fish fed diet containing 18 g/kg P. Mucus lysozyme activity and mucus bactericidal activity were significantly improved with the increasing dietary P level. The highest level of HSP70s in liver (35.97 ng/mg protein) was observed on fish fed the diet containing 18g/kg P, and it was 2 and 2.6 folds higher (P<0.05) than those fish fed the diet with 10 and 6 g/kg P, respectively. In conclusion, P deficiency has significant effect on growth and measured defense system parameters, therefore, the dietary inclusion of P might affect the defense system and stress tolerance of juvenile Japanese flounder. Highest level of mucus lysozyme activity, HSP70s in liver, and bactericidal activities with reduced survival rate of E. coli was observed in fish fed diets incorporated with 1.8% P, that also maintained best growth performance in Japanese flounder.

Biomass gain, feed efficiency and survival rates in Whiteleg shrimp (Litopenaeus vannamei) cultured in Aquamimicry concept and conventional methods with water exchange and settling chamber

2022-10-21T18:09:57+03:00

In the present study, biomass performance, feed efficiency, and survival rates of shrimp produced in Aquamimicry concept were comparatively evaluated along with conventional water-exchange-systems with -and without the use of settling chamber. Survival rates of shrimps cultured in the Aquamimicry concept were higher (91-92%) than those farmed with water exchange method with (68.6%) or without settling chamber (81%). In the water-exchange method (0.39) and Aquamimicry treated groups (0.32-0.39), apparent FCRs were almost 3-fold lower than the shrimps exposed to water-exchange system equipped with a settling chamber (0.97). Final biomass at harvest were higher in the Aquamimicry groups compared to traditional methods of water exchange with -or without settling chamber. The Aquamimicry group supplied with twice higher pellet-feed, but same amount of rice bran, demonstrated 1.4-fold higher final biomass compared to the less pellet-feed, but same level rice bran supplement group at DOC30. Water temperature (27.28 ± 1.12°C), dissolved oxygen (6.96 ± 0.46 mg/L), and pH (7.65 ± 0.18) were similar in all treatment groups. Minimum total ammonia nitrogen (TAN) of 0.67 and 1.17 mg/L were found in the water-exchange and Aquamimicry treatment with less pellet supply, whereas higher rates of 2.23 and 5.85 mg/L were found for the Aquamimicry group fed twice more pellet-diets and the water-exchange with settling chamber treatment, respectively. The lowest NO₂ level (1.84 mg/L) was obtained in the Aquamimicry group with less pellet supply, and the highest NO₂ (4.02 mg/L) was found in the Aquamimicry group fed with high pellet supply. Alkalinity were similar in both water-exchange treatment groups either with or without settling chamber. The findings of this study provide useful support for farm managers for improving shrimp production towards more environment-friendly level by less -or even zero water exchange, with cost-effective method supporting population stability and economic improvements for the sustainability of shrimp aquaculture in future.

Preliminary sagitta otolith sections of some small-scale fishery species in the Colombian Pacific Ocean

2022-11-01T17:23:18+03:00

Preliminary sagitta otolith transversal sections of six small-scale fishery species were performed (Lutjanus guttatus, Lutjanus inermis, Haemulon flaviguttatum, Haemulon steindachneri, Rhencus panamensis, Diapterus brevirostris). Sections showed clear growth rings in all species and the best section part to count them. Together with other few studies, these sections confirmed otoliths as a good tool to improve knowledge of fish life history aspects for fisheries management.

Comparison of production trends in Japan with long history in aquaculture and challenging success of Türkiye as a fairly new country in fish farming

2022-10-11T13:49:24+03:00

The struggle efforts and success of the Turkish aquaculture industry from past to present have been investigated with comparative evaluation of aquaculture trends in Japan, a country with significant infrastructure in fish farming. Despite its long history of fish farming, Japanese aquaculture production has stabilized over the last two decades, while Turkish aquaculture is in a rapid growth period, ranking among top producers in the world. The lower correlation between production and annual increase of population growth recorded for Japan (R= 0.795207) compared to the higher correlation for Türkiye (R= 0.930835), based on statistical data over the past 40 years, showed that population growth has influence on fish farming yields. The increasing number of younger adults in Türkiye provide advantageous conditions for the selection of qualified personnel from a wider range with higher opportunities in the employment of staff for the Turkish aquaculture sector. In Japan however, along with a variety of reasons, the industrialization has potentially shifted the interests towards technology-based businesses rather than marine works. Introducing high-tech aquaculture systems might reattract young generations, that may help restructuring Japanese aquaculture business. Hence, this study provides useful indications for decision makers in the management of securing the future of the aquaculture industry by reducing the so-called generation gap in aquaculture recruitments.

Effects of feeding frequency on growth performances and nutrient digestibility of juvenile Japanese flounder, Paralichthys olivaceus (Temminck & Schlegel), under varied dietary protein levels

2022-11-10T14:04:24+03:00

The effects of feeding frequency on growth, body composition and nutrient digestibility were studied for the juveniles of Japanese flounders (Paralichthys olivaceus) under four different dietary protein levels. Four isocaloric fishmeal-casein based diets containing different dietary protein levels from 46 to 65% were formulated and fed to juvenile flounder (initial mean weight 0.4 g) daily near satiation corresponding to three different feeding frequencies (1, 2 and 3 times/day) for 40 days. Results of feeding trial indicated that both dietary protein level and feeding frequency significantly affected the growth parameters. Regardless of the dietary protein level, the optimum growth performance was obtained from the fish fed 2 times/day. Under two times feeding a day, no significant difference was found between the fish fed diet containing 54 and 59% protein, and no further significant improvement on growth was observed when the dietary protein level increased from 59 to 65%. Protein digestibility was not affected by the feeding frequency or dietary protein level. Findings of this study suggest that feeding frequency twice per day was found to be the optimal, and the optimum dietary protein level could be 54-59% for the superior growth performances of juvenile Japanese flounder from 0.4 to 18 g.