Key points and precautions of live fish transport technology explained

This article mainly studies and summarizes the open live fish transport methods commonly used on the market today for freshwater adult fish and fingerlings, and develops a live fish transport method that is simple, convenient, has a large loading capacity, a high transport survival rate, and low transport cost.

1. Transport method

1. Add water to the tank. Before loading fish, first fill the transport truck tank with water. The water used is best underground hard water, and generally the tank is filled to a depth of 40-50 cm. When transporting in summer, when adding underground well water, it is best to also add about 1/5 of the original pond water, so as to avoid too great a difference between the water body in the tank and the water body of the original pond. After loading the fish, the water surface in the tank should be basically close to the top of the tank. This can reduce the back-and-forth sloshing of the water body during truck transport, thereby reducing damage to the fish body.

2. Loading fish. When loading fish, do not make too large movements, so as to avoid injuring the fish body. For long-distance transport, generally the fish to be transported should be stopped from being fed 1-2 days before transport, so that the digestive tract is emptied and the water quality is not polluted during transport.

3. Turn on the aeration facility. During the fish loading process, if the fish loaded in the tank are gulping at the surface, then the oxygen supply switch should be turned on. The amount of oxygen supplied should be such that all the air holes of the plastic hose at the bottom of the tank can evenly release bubbles outward. If a large number of fish are loaded, the oxygen supply can be appropriately increased according to the situation. After loading the fish, fix the top cover firmly.

4. Management during transport. During transport, mainly check whether the oxygen supply facility is intact. Most transport trucks now install the pressure gauge of the oxygen cylinder in the cab, so that if one oxygen cylinder has no oxygen, it can be discovered in time and immediately switched to another oxygen cylinder. Those who often carry out long-distance transport generally connect multiple oxygen cylinders together, which can avoid repeatedly switching the oxygen hose among each oxygen cylinder. During long-distance transport, it is best to go up to the roof of the truck to check about every 3 hours, so as to avoid other unexpected situations.

2. Transport test results

1. Loading capacity

(1) Adult fish loading capacity. Since adult fish are sold directly when transported to the market, the loading capacity can be maximized according to need, as long as it does not affect market sales. Based on one year of transport tests, we summarized the different full-load capacities of common freshwater food fish in different seasons and for different transport durations, with the transport tank specification being 4.2 m x 1.8 m x 0.9 m.

(2) Fingerling loading capacity. Fingerling transport is mainly for re-culturing, so fingerling transport cannot be like adult fish transport. It must not only ensure the survival rate during transport, but also ensure the survival rate of re-culturing after being put into a new culture water body. This requires that transport is best carried out in winter and early spring, when temperatures are relatively low. Through more than one year of fingerling transport tests, we summarized the suitable loading capacities of common freshwater fish fingerlings for different transport durations, with the transport tank specification being 4.2 m x 1.8 m x 0.9 m.

2. Service time of oxygen in compressed oxygen cylinders

Through many tests and studies, we summarized the economical oxygen supply time of one compressed oxygen cylinder: according to the full-load capacity of adult fish, using the 4.2 m x 1.8 m x 0.9 m transport tank specification used in our tests, one cylinder of oxygen can supply about 3 hours. Based on this, the economical oxygen supply time of one cylinder of oxygen in different fish transport containers and how many cylinders of oxygen should be equipped for different transport durations can be calculated.

3. Transport benefit analysis. Taking Luoyang as an example, a 5-ton transport truck, with a fish transport container specification of 4.9 m x 1.8 m x 0.8 m, has a transport cost of about 180 yuan per 100 km. Calculated at a conservative transport volume of 2000 kg, the transport cost per kg of fish per 100 km is about 0.09 yuan. Most adult fish on the Luoyang market are transported from fish ponds about 50 km away (100 km round trip). The difference between the fish price at the pond and the wholesale price on the market is 0.40 yuan/kg, so the gross profit per truck is generally about 600 yuan. During festivals, especially during the Spring Festival, the transport volume per truck is about 5000 kg, so the profit per truck will be even greater.

3. Analysis and discussion

1. During live fish transport, it is best not to load different species and different sizes of fish together, as this can improve the transport survival rate. Generally, crucian carp and common carp of the same size can be appropriately mixed, with little effect on each other. We once tried mixing common carp and grass carp of the same size together for transport, and as a result a large number of grass carp were injured or killed. Attention should be paid to this in future transport.

2. We divide the iron fish transport tank into 2-3 compartments with steel plates about every 1.5 m. This mainly has two functions: one is that different species of fish can be loaded separately during each transport, and the other is that it avoids excessive sloshing of the water body during transport, thereby reducing damage to the transported fish.

3. In previous live fish transport, compressed oxygen cylinders were also used to pass oxygen through plastic hoses into the bottom of the container, with air stones installed at the ends to release many small oxygen bubbles for aeration, but this can only be used for transport with small containers and small quantities. We lay plastic hoses evenly in an "S" shape at the bottom of the iron fish transport tank, with the distance between each two adjacent hoses being about 15 cm. On the hoses, every 10 cm, a thin silver needle used for acupuncture is used to prick a small oxygen delivery hole. This can make the water body oxygenated evenly, and the air holes pricked with the silver needle can release small bubbles like those from an air stone, enabling oxygen to achieve a very high dissolution rate.

4. For fingerling transport, before arriving at the destination, according to the disinfection time of the different fish body disinfection drugs used, put the disinfection drug into the water body, which can achieve a very good disinfection effect, thus reducing unloading time and unloading labor. After arriving at the destination, when transferring the fish from the container into the culture water body, because the fish have been exhausted by the journey and their physical strength is weak, suddenly moving them into an environment with great differences often causes large numbers of deaths because they cannot endure it for a time. To avoid this situation, new water can be gradually added to mix with the old water in the container, so that the fish adapt to the new environment, and then they are transferred into the pond.