Aquacultural Engineering最新文献

Combining protein skimming with ozone (O₃) is a common method for removing microparticles in recirculating aquaculture systems (RAS). Nevertheless, there is a limited number of studies that have validated protein skimming's performance at a commercial scale. Additionally, variations in protein skimmer designs and operational variables may yield different performance outcomes. In the present study, the performance of two types of full-scale protein skimmer (S1 and S2) were compared and evaluated under two levels of hydraulic retention time (HRT) (1.8 and 2.2 min) and three levels of O₃ doses (0, 7, and 14 g O₃/kg feed) in a commercial seawater RAS facility. Samples from the inlet and outlet of the protein skimmers were collected at each combination of operational variables. They were analysed for several relevant water quality parameters to quantify the treatment efficiency. O₃ dose significantly improved water quality and reduced the numbers of microparticles and bacterial activity in a single pass. Besides that, doses as high as 14 g O₃/kg feed significantly increased total residual oxidant (TRO) concentration. Additionally, an increase in HRT exerted a moderate effect on removing microparticles and a strong effect on redox potential (ORP) and TRO. Finally, the type of protein skimmer only affected the ORP, causing no significant changes to other water quality metrics. The correlations between the investigated water quality parameters defined a clear pattern of the ongoing processes and particle characteristics. Overall, the results demonstrated that protein skimming combined with carefully selected O₃ doses can improve general water quality and control critical factors such as bacterial activity and microparticles under commercial operations.

The outbreak of aggregative diseases in the process of sea cucumber cultivation has brought huge economic losses to aquaculture farmers. It is of positive significance to realize intelligent detection of abnormal behavior to avoid the outbreak of aggregative diseases. Therefore, this paper researches the approaches of intelligent recognition and behavior tracking of sea cucumbers. Fusing the Coordinated Attention and Bi-directional Feature Pyramid Network, the DT-YOLOv5 intelligent recognition model is proposed to enhance the representation ability and feature extraction ability. A multi-object behavior tracking approach is presented based on the automatic frame-matching coordinates, which can track multiple objects and calculate the volumes of exercise. The experimental results show that the precision, recall and AP_50:95 are 99.43%, 98.91% and 84.89%, respectively. This research provides a theoretical support for the detection of abnormal behavior of aquatic animals during intensive aquaculture and has potential practical application value for protecting the welfare of sea cucumbers and improving the intelligence level of aquaculture.

ficoEst – Fish Composition Estimator is a public web tool to estimate the whole-body proximate composition of farmed fish (https://webtools.sparos.pt/ficoest/). The tool was designed for researchers in fish nutrition and fish farmers, and is available for six commercially relevant species: gilthead seabream (Sparus aurata), European seabass (Dicentrarchus labrax), meagre (Argyrosomus regius), rainbow trout (Onchorhynchus mykiss), Atlantic salmon (Salmo salar), and Nile tilapia (Oreochromis niloticus). ficoEst uses three different types of mathematical models (BC1, BC2, and BC3) to estimate the body composition of fish in terms of crude protein, crude lipids, water, ash, phosphorus, and energy. The models differ in the input data used to perform the estimates. BC1 models consider only body weight, BC2 models consider both body weight and water, and BC3 models consider body weight, water, and ash as inputs. The model evaluation results demonstrate that considering water and ash as additional inputs to body weight (BC3 models) significantly improves the accuracy in predicting some body composition components, such as crude lipids (e.g., up to 67.9 % and 28.1 % more accurate, compared to BC1 and BC2 models, respectively, depending on the species considered). ficoEst can be used as a complementary tool to analytical methods to obtain additional information about fish body composition. As a public web tool, ficoEst has the potential to be a valuable resource for researchers and fish farmers interested in estimating the body composition of farmed fish.

Almost all the Portuguese oyster Crassostrea angulata in China are grown in nearshore farms using suspended culture. Problems such as overstocking and environmental degradation have occurred in many suspended oyster farms. In this study, two batches of C. angulata, which were pre-grown in suspended culture in Dapeng Cove, South China Sea, were transplanted onto the seabed at the mouth of the bay. The first batch of small-sized C. angulata was deployed on March 16, 2019 (bottom culture A), while the second batch of large-sized oysters was deployed on July 6, 2019 (bottom culture B). Temporal variations in the survival and growth of these oysters were tested against their counterparts that continued growing in suspended culture. Results indicated mortality of oysters in bottom culture A was mainly a result of crab predation, while summer mass mortalities in the suspended culture and bottom culture B were a result of stress from reproduction and high temperatures. Oysters in bottom culture A exhibited smaller but cleaner shells than those in suspended culture. The soft tissue of C. angulata in all treatments continued to increase until August 22. Accelerated increases in tissue weight and condition index (CI) from early July to late August were mainly attributed to gamete formation, while subsequent decreases in tissue weight and CI likely resulted from the spawning activity. Oysters in bottom culture A consistently performed better in terms of tissue growth and CI than those in suspended culture. Individuals in both the suspended culture and bottom culture B exhibited very similar growth patterns after July 6, when overcrowding at the oyster farm was partially resolved. The results of this study indicate that bottom culture is a promising strategy for producing meaty and clean C. angulata within a short duration. This method also provides a feasible solution to the overcrowding problem in suspended oyster farms. Nevertheless, a simple, efficient, and economical method to reduce crab predation in bottom culture is needed.

We present a low-cost monocular 3D position estimation method for perception in aquaculture monitoring. Video surveillance of aquaculture has many advantages but given the size of farms and the complexity of their habitats, it is not feasible for farmers to continuously monitor fish health. We formulate a novel end-to-end deep visual learning pipeline called Aqua3DNet that estimates fish pose using a bottom-up approach to detect and assign key features in one pass. In addition, a depth estimation model using Saliency Object Detection (SOD) masks is implemented to track the 3D position of the fish over time, which is used in this paper to create 3D density heat maps of the fish. The evaluation of the algorithm's performance shows that the detection accuracy reaches 80.63%, the F1 score reaches 87.34%, and the frames per second (fps) reaches 5.12. Aqua3DNet achieves comparable performance to other aquaculture-based computer vision and depth estimation models, with minimal decrease in speed despite the synthesis of the two models.

Sturgeon farming requires special attention. In addition to a relatively long rearing, climate change has resulted in increasingly high temperatures favorable to the emergence of pathogens. The control of water quality is essential especially the first years of life of the fish to prevent a mimivirus (AcIV-E) and a mycobacterium (Mycobacterium liflandii). These crises can lead to significant mortality (up to 70%) and have only been documented in hatchery populations where mortality can reach as high as 100 %. Mycobacterium liflandii, fatally affects young generations of Siberian sturgeon (Acipenser baerii) mainly in year N + 1 with mortalities reaching 30 % when river temperatures rise above 21 °C (summer period). The retention of these pathogenic microorganisms and of total flora by ultrafiltration was evaluated at a semi-industrial scale. The first part focuses on the specific removal of mimivirus, total flora and mycobacteria and the second part aims to evaluate over the long term (5 months) the hydraulic performances of the ultrafiltration process. Although the temperature (maximum 21 °C) was not sufficient for the mycobacteria to be detected, a good retention of mimiviruses (up to 4.7 log removal) and total flora was observed throughout the study. A more stable water quality was obtained after ultrafiltration and this work confirms the potential great interest of ultrafiltration for the biosecurity of fish production.

Dietary phosphorus (P) levels affect the excretion of orthophosphate (PO₄-P) from fish. Since most recirculating aquaculture systems (RAS) do not specifically remove PO₄-P within the recirculating loop, dietary P levels may influence PO₄-P concentrations in RAS water. A feeding trial was performed in freshwater RAS, aiming to determine the relationship between dietary P levels and PO₄-P accumulation in RAS water, and to examine potential effects of dietary P levels on microbial activity and abundance in RAS water given that P is an essential mineral for all microorganisms. Three diets with 1.49% (HiP), 1.20% (MeP), and 0.89% (LoP) total P, respectively, were each fed to triplicate pilot-scale RAS with juvenile rainbow trout (Oncorhynchus mykiss) for five weeks, applying a daily feed loading of 1.67 kg feed/m³ make-up water. Digestible dietary P levels correlated significantly with the PO₄-P concentrations in RAS water at the end of the trial, while no similar correlations with microbial abundance or activity were observed. Nitrate-N concentrations measured by the end of the trial matched predicted equilibrium concentrations. In contrast, measured PO₄-P concentrations were approximately 40 – 50% lower than predicted regardless of diets, suggesting that PO₄-P was likely utilized by RAS microbes. We therefore speculate whether lowering dietary P levels could become an effective tool for microbial management in RAS.

Despite the commercial potential of mussel populations along the Patagonian coast of Argentina, studies on mussel farming and fisheries to the south of parallel 42° S are clearly insufficient thus far. In this study, variations in mussel settlement (between sites and across depths) were monitored for 12 months at two contrasting sites in San Jorge Gulf, Argentina. The effect of depth on spat density was evaluated through monthly samples taken from artificial collectors at three depths (3, 7 and 11 m). The temporal settlement pattern was consistent at both sites, with the maximum spatfall recorded in early March (late summer), coinciding with the peak of sea water temperature. Settlement also correlated with Chl a and particulate organic carbon peak values, typically manifesting 2–3 months later and followed the initial decline in mussel condition during late spring and early summer. Significant differences between localities were detected in settlement abundance. The optimal temporal gap for mussel settlement was observed in mid / late summer, suggesting that this is the optimal time to deploy spat collectors in the field. Settlement was uniform between depths, thereby implying that the specific depth of collector placement did not appear to emerge as a key factor of settlement success.