Photothermal Manipulation Of Reproductive Cycle In Tiger Puffer(Takifugu Rubripes)

The reproduction of fish is seasonal,and the spawning time is consistent with the annual variation rhythm of environmental factors.Under the condition of circulating aquaculture,controlling the temperature and photoperiod change is an effective technical means to realize the year-round spawning of fish.The tiger puffer Takifugu rubripes is temperate fish,which spawns once in late spring and early summer every year,and has very high economic value.Study on the annual gonadal development characteristics,the optimal temperature and photo environment,and photothermal manipulation techniques,is vital to the management of tiger puffer brooder.In order to study the annual gonadal development characteristics of tiger puffer brooder,from2020 to 2022,samples of the gonads of tiger puffer were collected regularly for gonadal index(GSI)measurement,histological observation of the gonads,and ultrasound diagnostic testing.GSI varied with seasons,with a peak value appearing from April to June.The vitellogenesis period appeared in September,and mature oocytes appeared as early as March.There are significant differences in the structure of the testes and ovaries of Fugu rubra.Ultrasound diagnosis can accurately distinguish between male and female.To study the temperature and light parameters that affect the gonad development of tiger puffer,single-factor experiments on spectrum,photoperiod and temperature were carried out in this paper.Each experiment was divided into two groups.The experimental fish were 2-year-old tiger puffer with 12 fish in each group.The results of spectral single factor experiment showed that the full spectrum promoted the development of tiger puffer oocytes,and the green spectrum promoted the development of spermatogenic cells.The single-factor experiment results of photoperiod showed that 12L: 12 D promoted the development of tiger puffer oocytes,and shortened the photoperiod(12L: 12 D to 10L: 14D)inhibited the development of oocytes.The results of temperature single factor experiment showed that the 17 ℃ could promote the oocyte development of tiger puffer compared with the temperature gradually reduced to 13 ℃.In order to explore the effect of temperature and photoperiod regulation on the reproductive cycle of tiger puffer,this experiment carried out the research under the condition of recirculating aquaculture.A total of 90 tiger puffer adults were subjected to accelerated and natural photoperiods for almost a year.The fish exposed to natural photoperiod spawned in March,while those exposed to manipulated photoperiod spawned almost 2 months earlier than the former.These results suggest that the photoperiod plays an important role in accelerating maturation and spawning.The present findings can be implemented in the tiger puffer year-round spawning.The research results in this paper show that the temperature and photoperiod regulation of reproductive cycle is simple and effective,and has potential application value in the year-round spawning and production of tiger puffer.The research results provide a reference basis for the development of industrialized circulating water cultivation technology for tiger puffer adults.