Aquac. J., Volume 2, Issue 1 (March 2022) – 3 articles

Water quality plays a substantial role in maximizing fish productivity. Despite the efforts made by government to improve fish production, there are general complaints about the small size of fish produced in aquaculture systems. This study was conducted in order to assess the effect of water quality on aquaculture productivity in Ibanda District, Uganda. The specific objectives were to examine the status of water quality parameters (temperature, turbidity, pH, alkalinity, Ammonia content, hardness, Carbon dioxide content, and Iron content) and assess their effect on fish pond productivity. Using data from fish farmers and water samples taken from 25 restocked fish ponds in ten sub-counties, the study revealed that of the eight water quality parameters examined only four (average turbidity, alkalinity, hardness, and Carbon dioxide content) were within the acceptable ranges, while Ammonia content, temperature, pH, and Iron content were slightly outside the recommended ranges. In addition, the study revealed that water quality parameters such as temperature, pH, and Ammonia Carbon dioxide, and Iron content had a significant effect on the weight and size of both tilapia and catfish. The study concluded that certain water quality parameters have a detrimental effect on fish farming. There is a need to educate fish farmers on how to maintain water quality at suitable levels in order to improve fish farm productivity in Ibanda district. Full article

This study aimed to identify the effect of stocking density on growth, feed efficiency, and survival during the transition from Peruvian grunts (Anisotremus scapularis) fingerlings to juveniles. Fingerlings were reared in triplicate for 63 days until reaching the juvenile stage, at 1000 fingerling·m⁻³ (low-density LSD, 0.79 kg·m⁻³), 2000 fingerlings·m⁻³ (medium-density MSD, 1.58 kg·m⁻³), and 3000 fingerlings·m⁻³ (high-density HSD, 2.37 kg·m⁻³), and production performance parameters were evaluated. At the end of the experiment, results showed a negative correlation between stocking density and growth, individual growth, and the specific growth rate for HSD. The final biomass per treatment was 3.53 ± 0.26, 6.79 ± 0.08, and 7.70 ± 0.46 kg·m⁻³ for LSD, MSD, and HSD, respectively, the biomass harvest and weight gain were significantly lower for HSD. At the end of the experiment, there was no significant difference in survival (99%) among all treatments. Furthermore, the average food for each individual and the protein efficiency ratio were significantly lower for HSD, while the feeding efficiency was higher for HSD. In summary, our results indicated that initial biomass values above 1.42 kg·m⁻³ did not significantly improve growth and feed efficiency in the fingerlings rearing process. Full article

Lordosis of the haemal part of the vertebral column is a frequent abnormality in reared fish. Haemal lordosis develops during the late larval and early juvenile life stages of fish, mainly due to the high swimming activity of the fish in the rearing tanks. In the present study, we have examined whether haemal lordosis recovers during the growth of European seabass. Furthermore, we aimed to develop simple morphometric indices (PrAn₁ and PrAn₂) that might link the severity of lordosis at the juvenile stage with fish morphological quality at harvesting. At 111 days post-hatching (dph, 53 ± 4 mm standard length, SL), 600 seabass juveniles with lordotic (L, 200 fish) or normal (N, 400 fish) external morphology were selected and introduced in a common tank. At 150 dph (75 ± 7 mm SL), 350 fish were randomly selected, pit-tagged and transferred to a sea cage for on-growing up to 502 dph (234 ± 16 mm SL). The morphological examination of the fish at 150 and 502 dph revealed that 60% (46 out of 77) of L juveniles turned into normal phenotype by the end of on-growing period. Interestingly, 56% of the fish with recovered external morphology (N-Rec) presented either a completely normal vertebral column (31%) or minor abnormalities of individual vertebrae (25%). Following the results of geometric morphometric analysis, the differences in the body shape between N-Rec and N fish were not statistically significant (p > 0.05, canonical variate analysis). The examined morphometric indices were effective in discriminating the normal fish from 58% (PrAn₁) to 65% (PrAn₂) of lordotic juveniles. Results are discussed with respect to the mechanism of lordosis recovery, and spotlights on their application for quality control and cull out of the abnormal fish in commercial hatcheries. Full article