A new study has discovered that larger fish in the ocean are becoming fewer while smaller species are growing in number. Global warming could be a primary driver of the phenomenon.

fish in the ocean
(Photo: Pexels / Hung Tran )

Fewer Larger Fish, More Smaller Fish

According to the study, a prime example for the case was observed among a certain North Atlantic fish, the thorny skate fish, which has significantly shrunk on average since 1960.

Inês Martins, the study's lead author and a macroecology researcher from the University of York, explains that in certain areas, smaller as well as smaller individuals of thorny skatefish are being seen, while fish species with smaller bodies, such as mackerel, are growing in number.

The pattern was seen among several species out of the 4,292 ones observed in the study. More specifically, it was observed among fish, invertebrates, and plants.

Martins adds that their data is lesser when it comes to other organisms, and they did not see any significant changes in the average. Nevertheless, it cannot be questioned that they are seeing significant biodiversity changes and in the kinds of biodiversity that can be observed in certain places.

Other smaller fish species had an increase in population. It generally follows the notion regarding an ecosystem's self-regulation of constant biomass amount, with bigger creatures getting replaced by heightened quantities of smaller ones.

Co-author Maria Dornelas, who is a biodiversity professor from the University of St. Andrews, explains that this could mean that in cases of the disappearance of larger organisms, others may try to take their place and make use of resources that end up available. Dornelas adds that it is imperative to explore and recognize this complexity to understand the mechanisms underlying body size changes as time passes.

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Global Warming as a Possible Primary Driver

While the exact mechanisms and reasons behind the patterns are not apparent, scientists think that global warming in the ocean and overfishing could be probable drivers.

These findings are crucial to understanding how climate change worldwide will affect various species and how these will ripple across various ecosystems. Not to mention, the loss of large fish in the ocean could also affect the fishing industry.

Associate biodiversity and geodiversity professor Franziska Schrodt, a co-author of the study from the University of Nottingham, explains that the study stresses the significance of taking into account the alterations in the characteristics of species at an individual scale and beyond. Understanding how human influences and environmental changes globally affect biodiversity is necessary.

However, there is a lack of data to draw firm conclusions. Further studies could reap the benefits if more resources were invested in these measurements, especially those that look into the interactions of species and delve into various food webs.

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