Data confirms link between respiratory stress


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Constant metabolic report found in 133 species of Chinese marine and freshwater fish provides new evidence to support the idea that fish become sexually active – and reproduce for the first time – in response to induced respiratory stress through growth.

Using the maximum size and the average size at first maturity of more than 200 fish populations of 133 species of fish, Chinese and Canadian researchers indirectly estimated the ratio of oxygen uptake of each species at these two sizes. They found that fish pass from juveniles to adults when that ratio is around 1.40, in a study published today in the Journal of Fish Biology.

“The consistency of this relationship between the species we examined – and other species studied in the past or under study – supports the idea that reproduction is initiated by changes in the balance between supply and oxygen demand, “said Dr Daniel Pauly, lead author and UBC principal investigator. The sea around us initiative.

“Maturation and spawning appear to be induced when the oxygen supply relative to the weight of individual fish decreases. Thus, growing fish gradually become limited in oxygen, and there is a threshold, now identified, that tells them it is time to respond to external stimuli for maturation and spawning, ”he said.

Dr. Pauly’s Gill Oxygen Limiting Theory (GOLT) suggests that the oxygen supply of fish gradually decreases as their weight increases, because their gills – the organs that extract oxygen from the water and bring it to their body – are surfaces that develop in two dimensions and cannot follow their body, which grows in three dimensions.

“There comes a time when the growth in weight of the fish results in a decrease in the relative area of ​​the gills, which leads to a critical level of oxygen supply. This triggers the hormonal cascade that causes fish to respond to environmental stimuli to mature and spawn, ”said Dr Pauly.

The GOLT takes issue with claims that it is only environmental stimuli at the start of the spawning season that trigger the maturation and spawning process.

“Being able to corroborate with empirical evidence that respiratory stress is what causes fish to reach their first maturity when they do is a great achievement,” said Dr. Cui Liang, co-author and researcher at the Chinese Academy of Sciences. science. “This has important implications for aquaculture practitioners, who have long recognized the importance of dissolved oxygen in fish production.”

Drs. Pauly and Liang said the constancy of the critical ratio warranted in this study can also be used to understand why fish stressed by climate change-induced increases in temperature and deoxygenation will tend to breed at smaller sizes. they survive and reproduce.

“The relationship between length at first maturity and maximum length of marine and freshwater fish” has been published in the Journal of Fish Biology https://onlinelibrary.wiley.com/doi/10.1111/jfb.14970


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