Ignoring changes due to human influence, the seasonally oscillating environment in which long-lived fish hatch and grow remains nearly the same throughout life. This means that the general explanation that fish become sexually active or spawn for the first time after experiencing certain environmental stimuli cannot adequately explain this phenomenon.
In a new article published in Fish Biology Journal, Daniel Pauly, Senior Researcher The sea around us The UBC Institute for the Oceans and Fisheries initiative challenges the previous hypothesis that sought to explain why fish first mature and offers another explanation.
“Textbooks are usually the reason why fish spawn by explaining the processes that are likely to be caused by the environmental” stimuli “experienced at the beginning of the spawning season, passed to the hypothalamus, and from there to the hormonal cascade. I’ll try to answer the question, “said Pauly. “This explanation is about the process of perception. Environmental stimulation It is a self-starting type. However, it is not because the same environment always exists and was not previously generated. “
Some long-lived fish, such as the white sturgeon and the orange roughy, can live for nearly 30 years without reaching their first maturity. That is, suddenly after decades of unaware clues about the surrounding environment.
“The first time I really think it spawns is the increased oxygen stress experienced by growing fish,” Pauly said. “This hypothesis is Gill oxygen restriction theory (GOLT) explains that the tension between the growth of the fish’s gill surface area, which limits the supply of oxygen to the body of the fish, and the growth of the body, which produces oxygen demand, is responsible for causing the hormonal cascade. increase. For gonad maturation and spawning. “
The gills are the surfaces on which water needs to flow. It’s like the wind passing through the blinds. The surface area of the gills grows in two dimensions, length and width, but cannot keep up with the body, which grows in three dimensions, length, width, and depth.Therefore, as the fish grows, the surface area and gills of the gills decrease. Providing less oxygen Per unit volume or weight.
“Weight gain leads to a relative decrease in gill surface area, and there are times when the critical level of oxygen supply is reached, which tells the fish that it has reached the stage of maturity and spawning. Environmental condition It is appropriate to act on specific environmental stimuli for spawning. “
When a fish lays eggs, it loses the gonadal tissue that it had to supply before. air Therefore, its relative gill area increases, promoting new growth until the next spawning season when respiratory stress reappears.
Knowing how and when fish sexually mature, when and where they lay eggs, and the duration of the cycle from the onset of ovarian development to the final release of eggs helps fishery managers estimate the size of the stock. This is useful and important information. And its reproductive potential. Such knowledge is also useful for farmed fish, who generally want to avoid creating stressful conditions that promote fish breeding in ponds.
Thesis “Why fish Do they reach their first maturity when they do so? ” Fish Biology Journal..
Daniel Pauly, why do fish mature first? Fish Biology Journal (2021). DOI: 10.1111 / jfb.14902
The sea around us
Quote: What makes fish sexually active (October 26, 2021) October 26, 2021 Obtained from https://phys.org/news/2021-10-fish-sexually.html
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