Journal of The World Aquaculture Society最新文献

Male postsmolt maturation (“jacking”) is undesired in Atlantic salmon aquaculture due to economic and welfare impacts. Unfortunately, incidence of jacking has increased linked to intensive rearing conditions. This study subjected 1000 salmon (52.1 ± 5.2 g) to one of two temperatures (15, 12.5°C) and one of two photoperiods (constant light-LL, a 5-week LD12:12 winter signal regime-WS) to assess their effects on spermatogenesis regulation. Indicators included testis histology images, mRNA transcription of gonadotropin receptors for follicle-stimulating hormone (fshr) and luteinizing hormone (lhr), and of factors regulating spermatogenesis like anti-Müllerian hormone (amh), gonadal-soma-derived factors 1 and 2 (gsdf1 and gsdf2), and insulin-like growth factor-3 (igf3). High temperature (15°C) induced early testis development processes irrespective of photoperiod, evidenced by presence of type B spermatogonia before clear increases in testis size or any transcriptional changes. The winter signal at 15°C caused a synchronized onset of spermatogenesis not present under constant light. This was evidenced by a pronounced downregulation of the spermatogenesis-inhibiting factor amh and a clear upregulation in the stimulating factor igf3. Consequently, combining high temperatures with winter signal regimes pose risk; high temperature can stimulate early cellular/endocrine processes of spermatogenesis, which can later be synchronized in the population by an increase in daylength.

The Florida pompano, Trachinotus carolinus, is an ideal species for commercial aquaculture because of its rapid growth, tolerance to a range of environmental parameters, and high demand in the seafood market. This study detailed embryonic and early larval development of this species. Florida pompano followed similar developmental sequences to those observed in other marine teleosts, and embryos hatched between 22 and 28 h post-fertilization. Significant brain lobe differentiation occurred prior to hatching. Pectoral fins were functional within 1-day post-hatch (dph). Substantial eye development occurred within 3 dph, indicating visual acuity prior to the onset of exogenous live feeding. Intestinal segments were differentiated by 3 dph, and rotifers were seen in the digestive tract by 4 dph. Digestive functions were limited through the first 7 dph because of the absence of functional gastric glands and gastric mucous cells in the rudimentary stomach, lipid vacuoles in the anterior intestines, and the persistence of acidophilic supranuclear vesicles in the posterior intestines. Within 7 dph, the pharyngeal arches differentiated, and hematopoietic tissue and mesonephric tubules were visible in the larval kidney. Their rapid larval development and organogenesis are additional factors that make Florida pompano an ideal species for aquaculture production and should encourage continued efforts toward commercialization.

This study examines the use of dragon fruit peel (DFP) powder as a dietary supplement on growth performance, immune responses, and gene expression of Nile tilapia, Oreochromis niloticus, cultured within biofloc systems. A total of 300 Nile tilapia fingerlings (14.64 ± 0.09 g) were subjected to five dietary treatments, with DFP added to a basal diet at doses of 0, 20, 40, 80, and 160 g kg⁻¹ DFP. Growth and immunological responses were assessed after 4 and 8 weeks of feeding, and the transcriptional level of immune and antioxidant-related genes was measured after 8 weeks. Fish fed diets containing DFP exhibited significantly greater weight gain, faster growth, and enhanced levels of key indicators of immunity than control fish (p < 0.05). A diet containing 40 g DFP kg⁻¹ produced the best result in terms of growth, enhanced immune response indicators in skin mucus and blood serum, and the upregulation of IL-1, IL-8, LBP, GPx, GST-α, and GSR expression (p < 0.05). Based on the quadratic regression analysis, the optimum concentration of DFP was 80 g kg⁻¹. These findings collectively suggest that powdered DFP may serve as a promising feed supplement for Nile tilapia raised in biofloc systems.

The Delta Select channel catfish strain (DS) was developed by selection for increased growth and carcass yield. Progeny from DS and the Delta Control (DC) strain (a randomly bred strain from the same base population as DS) were compared in three trials. Trial 1: unvaccinated ~1-year-old fingerlings from each strain reared communally in 0.4-ha ponds. Trial 2: vaccinated ~ 1-year-old fingerlings from each strain grown in separate replicated 0.4-ha ponds and fish in about half the ponds were given an ESC vaccine-booster at 13 months post-hatch. Trial 3: same procedures as Trial 2, except fish were raised in replicate 0.04-ha ponds with no vaccine-booster. In Trial 1 DS were larger at stocking, larger at harvest, and had higher carcass yield than DC; in Trial 2 DS were larger at harvest, had better survival and higher production/ha than DC. Vaccine-booster had no effect on fish growth or survival. DS and DC were not different for any traits in Trial 3. Although outcome varied among trials, the overall results indicated a vaccine booster did not affect growth or survival, DS strain fingerlings grew faster than DC fingerling, and DS had higher carcass yield than DC strain fish when reared communally.

Weight loss during feed deprivation is correlated with feed conversion efficiency (FCR) in several fish species, suggesting weight loss could be used to indirectly select for improved feed conversion. Trials were conducted to determine relationships among weight loss and FCR with Delta Select and Delta Control line channel catfish fingerlings. Weight loss was measured for 79 Delta Select line families and 20 Delta Control line families in replicate feed deprivation trials. Weight loss was higher for Delta Controls than Delta Selects. The 10 Delta Select families with the highest weight loss, 10 Delta Select families with the lowest weight loss, and 10 random Delta Control families were used in a feeding trial. Initial weight, final weight, percent weight gain, and percent feed consumption were similar among Delta Select groups but higher than the Delta Control's. Feed conversion and survival were similar for all groups. Fish from the feeding trial were used in a third feed deprivation trial. Family means for weight loss were positively correlated across three feed deprivation trials but not correlated with feed conversion indicating selection for weight-loss would not improve feed conversion. The faster growth of Delta Select catfish is as a result of increased feed consumption.

Intensified production of stocker-size tilapia can be accomplished using the biofloc technology production system. Stocker-size tilapia (ca. 10–200 g/fish) are raised for subsequent stocking for grow-out to market size. The relationship between stocking rate and the production of stocker-size hybrid tilapia (Oreochromis aureus × O. niloticus) was evaluated in two studies in outdoor mixotrophic biofloc tanks. Hybrid tilapia were stocked in 18.6-m² (15.7-m³) tanks at 50–150 fish/m² (59–178 fish/m³) in 25 fish/m² (30 fish/m³) increments in Study 1 and grown for 141–143 days. Stocking rates evaluated in 4.7-m² (3.6-m³) tanks during Study 2 over 78–79 days ranged from 100 to 300 fish/m² (132–396 fish/m³) in 25 fish/m² (33 fish/m³) increments. Linear regression models best described growth to stocker size in both studies. Fish yield increased linearly with stocking rate and ranged from 20.1 to 38.3 kg/m³. Individual weight at harvest was inversely related to stocking rate and ranged from 389.8 to 163.4 g/fish and 155.2 to 81.4 g/fish in Studies 1 and 2, respectively. Partial budget analyses suggested positive net changes in profit with incremental increases in stocking rate for producing a 75-g stocker. Water quality concentrations were impacted directly by daily feed ration and total feed fed, which increased linearly with stocking rate. In Study 2, whole-body dry matter, protein, protein retention, and lipid were unaffected by stocking rate, whereas whole-body ash increased with stocking rate. Whole-body energy retention significantly decreased with stocking rate. The outdoor mixotrophic biofloc production system is well suited for intensive production of hybrid tilapia stockers. However, additional replicated research and economic analysis are needed to evaluate stocking rate and culture duration to produce specific-sized stocker hybrid tilapia.

Dynamic models of sugar kelp (Saccharina latissima) growth are used to estimate the production potential of seaweed aquaculture in many regions around the world. These models do not currently account for the existence of S. latissima ecotypes that are adapted to regional environmental conditions, particularly temperature. We tested the hypothesis that recalibrating the temperature parameters of a dynamic energy budget model using literature data for S. latissima from regions with a similar climate to the region of interest would result in more accurate predictions than using a general species-wide temperature response curve. Calibrating the model using data from warm regions significantly improved model accuracy for kelp cultivation at the southern end of the species range (Rhode Island, USA) in cases where the original parameters underestimated growth but resulted in drastic overestimates when heavy frond erosion occurred. In Trømso, Norway, a cold parameterization produced extremely accurate predictions: the model predicted a final frond length of 88.2 cm, compared with the observed length of 87.5 (±4.70) cm. Our results demonstrate that recalibrating temperature response curves allows one model to be applied to kelp aquaculture in different regions, an important step toward the prediction of S. latissima productivity over large areas.

The effects of dietary mannan oligosaccharide (MOS) supplementation in a biofloc system on growth performance, whole-body proximate composition, whole-body fatty acids, nonspecific immune parameters, antioxidant enzyme activities, digestive enzyme activity, and gut microbiota of brown shrimp, Farfantepenaeus aztecus, were investigated. Shrimp were fed five diets containing different levels of MOS doses (MOS0: basal diet, MOS1: 0.1%, MOS2: 0.2%, MOS3: 0.3%, and MOS4: 0.4%) during the 90-day trial. The results indicated that all MOS-supplemented shrimp showed significantly higher growth rates and better feed utilization than shrimp fed the control diet. Experimental diets had varying effects on the nonspecific immune parameters and antioxidant enzyme activities, indicating that MOS supplementation resulted in significant differences in the parameters except for respiratory burst activity. Significantly higher protease activity was observed in shrimp fed MOS1 and MOS2 diets compared with MOS0, MOS3, and MOS4 diets. Shrimps fed MOS2 and MOS3 diets had the highest lipase and amylase activities among all groups. Proteobacteria were the most abundant phylum in all groups and were higher at increasing MOS doses. In conclusion, these results suggest that supplementing the diet of brown shrimp in the biofloc system with 3 g kg⁻¹ of MOS may improve production parameters.

The culture of seahorses Hippocampus erectus in captivity represents a window of opportunity for the diversification of the aquaculture activity in the ornamental industry. In this study, we have constructed a bioeconomic model to evaluate the optimal harvest time (OHT) over a culture period of 562 days. The bioeconomic model was integrated with three submodels: biological, technological, and economic. Three different mortality rates were used for different periods in culture, registering a higher survival in the period from 0 to 60 days with a rate of 53.4%. The sensitivity analysis showed that the mortality rate in this period was the parameter with the greatest influence on the benefits. The Von Bertalanffy growth model was indicated to describe the growth of H. erectus given its statistical significance using Theil's inequality coefficient, registering parameters of (L∞ = 141.62 mm) and (k = 0.0049 month-1). The bioeconomic model determined the OHT in the 4th month of culture, the time when the maximum profit is recorded. It is concluded that the culture presents challenges to be addressed although the bioeconomic model allows for demonstrating the OHT.