49
Table 1. Frog farming practices from three major Chinese farming provinces.
Farming practice
Guangdong
Guangxi
Fujian
0.8-1.2
0.3-0.6
0.1-0.2
Water depth (m)
Pond area (m2)
Stocking density (froglet/m2) 300
200
150
Stocking size (gram/pcs)
4-6
4-6
Culture duration (month) 5-9
Harvest size (g/pcs)
250-450 250-450 150-400
Yield (MT/ha)
300-450 225-300 150-225
Net profit (USD/ha)
120 50 50 4-6
85,700-128,500
4-7 3-7
64,200-85,000
107,000-160,000
China has been on a fast track. Nowadays, the bullfrog is widely cultured in 13 provinces with an annual production of 400,000 MT, becoming an important high-value aquatic species in China.
Breeding Since the first artificial bullfrog fry was produced in 1982, the bullfrog seed industry has made a stable development and achieved professional and mass production to meet the increasing demand. Currently, most of the bullfrog fry on the market are supplied by intensive bullfrog hatcheries and produced according to standard operational procedures. A standard bullfrog hatchery facility is divided into broodstock, spawning and hatching, and larval tadpole rearing areas. The optimal sizes of male and female breeders are 300-400 grams and 350-500 grams per pieces respectively, with a male:female ratio 1-1.5:2. In the spawning and hatching tank, a pair of parent bullfrogs will spend 30 minutes mating and spawning. A 500-gram female can produce 30,000 eggs per spawning. The fertilized eggs will be hatched into larval tadpole within 3-4 days and then transferred to a larval tadpole rearing tank. Farming Currently, the bullfrog is mainly cultured in superintensive small earthen ponds with high density, high yield and high profit. There are two different stages during the bullfrog culture cycle. At the nursery stage, farmers grow larval tadpole to froglet size (4-6 grams/pcs) within 60-90 days,
Figure 1. Frog fed on conventional feed (left) and on functional feed (right).
with a stocking density of 1,000-1,500 tadpoles/m2. For grow-out stages, farming practices are different between different provinces (Table 1). Farmers in Guangdong province adopt deep water ponds and floating plates. The advantages of this farming practice are a higher yield and lower frequency of water exchange, but it has disadvantages such as higher requirements for farming management, survival rate and unit profit. In contrast, the farming practice of Fujian province requires a shorter culture cycle and higher selling price, but it is susceptible to climate and water source changes. The practice of Guangxi province is between Guangdong and Fujian. Over the past decade, these intensive bullfrog farming practices has brought tremendous income to farmers, as well as a series of adverse environmental effects. As a result, some coastal provincial authorities have released strict environmental protection policies to restrict or forbid bullfrog farming, which pushed the farmers to relocate their farms to central and western provinces where the policy is mild. Furthermore, the government has taken more measures to promote sustainable farming practices, such as paddy field
Aquafeed: Advances in Processing & Formulation Vol 12 Issue 4 2020
