## 4 Discussion  
### Exploration of Blood Collection Methods for CE  
The technique of drawing blood from the fish's artery using a syringe is widely utilized due to its speed and simplicity [16]. However, practical challenges were encountered during its application in this study. Firstly, difficulties arose in locating blood vessels, leading to repeated lancing and causing excessive injury to the fish. Secondly, the needle often slipped out when the fish struggled, making it difficult to draw blood. Lastly, the use of syringes for blood collection was prone to clotting, hindering subsequent experiments. To mitigate these issues, exploratory pre-experiments were conducted before the main experiment. Initially, experimental goldfish were dissected to examine the position and tissue structure of the tail arterial (static) pulse. The investigation revealed that the arterial (static) pulse of the CE tail was distributed in the muscles under the lateral line and on the tailbone. Consequently, the needle was positioned obliquely below the lateral line scales of the goldfish tail stalk. To minimize movement during blood collection, the fish were restrained using medical gauze moistened with water from the goldfish pond. The gauze was wrapped around the fish, covering its eyes and leaving only the tail and caudal fin exposed. Compared to using tap or distilled water, the goldfish's pool water effectively reduced stress and potential harm to the fish during the blood collection procedure. The osmotic pressure and oxygen content of the goldfish's pool water were found to be more suitable, providing a familiar and secure environment for the fish. Stabilizing the goldfish in this manner resulted in minimal struggle and minimal interference during blood sampling, in accordance with the recommendation by [PERSON] [16], which suggested wrapping the fish with a wet towel during blood sampling. Finally, to tackle the issue of coagulation associated with syringe blood draws, a comparative experiment was conducted. Through the experiment, it was determined that the most effective approach involved moistening a 1 mL syringe with 1% sodium heparin and then drawing blood from the tail vein. Although anesthesia was commonly employed to prevent fish from struggling, there were reports indicating that the use of anesthetics caused rapid changes in certain blood parameters in fish [17]. The goldfish selected for this study were medium-sized individuals, approximately 12 cm in length, and by wrapping them in moist medical gauze, they could be easily controlled without the need for anesthesia. In conclusion, these adjustments successfully addressed the challenges associated with the syringe method, offering a more effective and humane approach to blood sampling from CE. In hematological research, particularly for the treatment of blood samples or the lining of blood storage containers, anticoagulants are crucial for preventing premature coagulation. The selection of anticoagulants is pivotal, as various agents like heparin, EDTA-Na\({}_{2}\), EDTA-K\({}_{2}\), and sodium citrate are traditionally employed in fish hematology due to their unique compositions and coagulation inhibition mechanisms [18]. [PERSON]'s research highlighted that among these, EDTA-K\({}_{2}\) was superior for blood cell analysis [19]. Consequently, for the assessment of celestial goldfish blood hematological parameters in our study, EDTA-K\({}_{2}\) was the chosen anticoagulant, integrated into the blood collection process to ensure the integrity of the samples.