Aquac. J., Volume 3, Issue 1 (March 2023) – 7 articles

Mycotoxins have become a serious issue in the animal feed industry and have also affected the aquaculture industry. Mycotoxins can create serious health problems in aquatic and terrestrial animals, and their presence in agricultural products may result in significant economic losses. To reduce the impact of mycotoxins on Nile tilapia fry, two commercially available products—Organically Modified Clinoptilolite (OMC) and multi-component mycotoxin detoxifying agent (MMDA)—were used in this study. Six diets as treatments (T1 = Control (C); T2 = Control + OMC 2 g/kg (OMC); T3 = Control + MMDA 2 g/kg (MMDA); T4 = AFB1 0.5 mg/kg (AF); T5 = AFB1 0.5 mg/kg + 2 g/kg OMC (AFOMC); T6 = AFB1 0.5 mg/kg + MMDA 2 g/kg (AFMMDA)) with similar crude protein levels (35.75 ± 0.35%) were formulated and fed to Nile tilapia fry (1.97 ± 0.1 g) for a period of 84 days. These fish were housed in 18 aquaria (100 L) at a density of 50 fish/aquarium. The results from this study showed that MMDA significantly (p < 0.05) improved the survival of fish by 16% as compared to the control group. Nevertheless, growth parameters were not affected among the treatments. These results also indicated that protein intake was significantly higher in the control and OMC diet (T2) compared to aflatoxin B1-fed tilapia. The protein efficiency ratio (PER) was significantly higher in the AFMMDA as compared to the control and MMDA. A 14-day bacterial challenge test with Aeromonas hydrophila demonstrated that diets containing MMDA or OMC improved survival when AFB1 was present in the diet. Therefore, the supplementation of feed with MMDA or OMC is recommended to ameliorate the negative effects of AFB1 in Nile Tilapia feeds. Full article

The effect of adding inulin to balanced diets for tropical gar (Atractosteus tropicus) larvae on growth, survival, digestive enzyme activity, and antioxidant activity was evaluated. The diets were supplemented with 0.5, 1.0, 1.5, 2.0, and 2.5% inulin in addition to a control diet (0% inulin). A total of 1800 larvae of A. tropicus distributed in 18 tanks were used; the larvae were fed five times a day (8:00, 11:00, 13:00, 15:00, and 18:00) with Artemia nauplii from the absorption of the yolk (from 3–7 days after hatching, DAH) up to 10 DAH, which was mixed with the experimental feeds from 8–11 DAH (co-feeding) and exclusively with the balanced diets from 12 DAH to 21 DAH. Larvae fed the control diet (0% inulin) had the highest growth in weight and length, followed by fish fed the 2.5 and 2.0% inulin inclusions. However, survival showed that the fish fed with the inclusion of 2.5% inulin had the highest percentage (34.7%) compared to the rest of the treatments. On the other hand, the highest digestive enzymatic activities (acid and alkaline proteases, amylase, and lipase) were recorded in the larvae fed with 2 and 2.5% inulin. Likewise, catalase (CAT) and superoxide dismutase (SOD) activities were higher in larvae fed the control diet with 0% inulin. Supplementation of 2.0% to 2.5% inulin in the diet is recommended for A. tropicus larvae as it improves survival and digestive enzyme activity during this early stage of life. Full article

This is the first study to examine the effect of three different cultivation methods (bottom-tray culture, suspended-tray culture, and beach/bottom culture) on the growth and survival rates of the snout otter clam, Lutraria philippinarum, after 12 months of grow-out cultivation from seed to commercial size. Analyses included weight, survival, shell size, and total fat. Although the results showed limited differences in growth among cultivation methods, survival rates were significantly different among three different culture methods. The bottom-tray cultivation method had the highest survival rate (76.5%), compared with suspended-tray cultivation (31.6%) and beach/bottom cultivation (52.5%). This demonstrates that the most suitable method for commercial snout otter clam farming is cultivation trays placed on the bottom of the substrate. Improving commercial farming of the species will support the development and expansion of aquaculture in Vietnam and elsewhere, while reducing the harvest pressure on wild populations. Full article

Cultivation of the common ragworm—Hediste diversicolor—has attracted a great deal of interest in recent years. Growth optimization is a key aspect for its intensive production. We have assessed the effect of body weight (Bw) and temperature (T) on growth-related parameters in common ragworm using correlation and multiple regression analyses. We used ragworms of 13 different weight classes in 15-day growing assays at 12 different temperature values. These polychaetes were stocked at a density of 1000 individuals m⁻², and fed with commercial fish feed. Our results show that growth increases with T; when expressed as an absolute growth rate (AGR), growth increases as Bw increases; and when expressed as a specific growth rate (SGR), growth decreases as Bw increases. A change in the growth pattern was observed from an individual Bw of about 400 mg. Simulations performed with the equations that provided the best fit revealed that optimum T for growth changes with Bw, so that in individuals below 400 mg, optimum T is 24.9 °C, and above this temperature growth decreases. In individuals above 400 mg, growth increases slightly with temperature, but as weight increases, the effect of temperature on growth is less and less, and from a weight of 1050 mg, growth decreases as temperature increases. Mortality increases significantly at temperatures above 22 °C, especially in individuals with a Bw above 400 mg. Simulations of individual growth showed that up to 400 mg growth is quite fast at warmer temperatures, but from 400 mg to 1000 mg, the influence of T on growth rate is not significantly relevant in operational terms. This study demonstrated the huge usefulness of growth modelling for production planning. Full article

Stress and disease are critical factors hindering the industrial development of red swamp crayfish (Procambarus clarkii). Breeding crayfish with stress- and disease-resistant characteristics can overcome these limitations and promote their industrial development. In this study, the crayfish breed F3, which exhibits rapid growth and a favoured haplotype combination of the immune genes R, ALF, and crustin2, encoding the Toll-like receptor, anti-lipopolysaccharide factor, and antimicrobial peptide, respectively, were selected as parents to breed offspring (the selected group (SG)). The genotype, stress resistance, and disease resistance of crayfish in the SG and unselected group (USG) were compared. The results showed that the ratio of the favoured haplotype was higher in the SG crayfish than in the USG crayfish, leading to stronger stress and disease resistance. Compared to that of the USG crayfish, the mortality of the SG crayfish subjected to stress during eight days of transport and challenged with bacteria (Aeromonas hydrophila or Vibrio parahaemolyticus) or white spot syndrome virus were significantly reduced by 60% and 20%, respectively (p < 0.05). Based on these results, the stress- and disease-resistant SG crayfish were named the “Huachizhen-1” breed. Additionally, the ratio of the unfavoured homozygous genotypes of R, ALF, and crustin2 sharply decreased, whereas those of the heterozygous genotypes increased together with stress and disease resistance during crayfish maturation under natural conditions, indicating that the heterozygotes of these genes also exhibit strong stress and disease resistance. All of this taken together, the crayfish breed “Huachizhen-1” may be applicable for improving stress and disease resistance and the production of crayfish. Full article

An increasing body of evidence shows that seaweeds, including kelp, can be used as a tool to neutralize or remove excess nutrients and metals from the water column. Here we report on a preliminary field assessment showing potential nutrient and carbon removal differences in sugar kelp and ribbon kelp grown in common gardens. Seawater and tissue samples were collected systematically from two farms in Alaska. Results show differences between the %N and %C content between Alaria marginata and Saccharina latissima. Results also show that tissue nitrogen in ribbon kelp varies sharply due to nitrogen availability in the water column. In contrast, the percentage of tissue N in sugar kelp remains comparatively stable. Our outcomes provide insight into potential differences in nutrient removal and harvest timing for different kelp species. Full article