Ocean warming is one of the most significant consequences of climate change. It affects marine ecosystems and the people who depend on them in many ways.
One of the most noticeable effects is the shift in the distribution of marine fish, which are moving away from the equator and towards the poles in search of cooler waters.
Why are fish moving poleward?
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Fish are cold-blooded animals, which means their body temperature depends on the temperature of their environment, as per Phys.org.
Fish have a preferred temperature range that suits their physiology and metabolism.
If the water temperature becomes too hot or too cold, fish may experience stress, reduced growth, lower reproduction, and increased mortality.
Thus, as the oceans warm, fish move to track their preferred temperatures.
Most fish are moving poleward or into deeper waters.
For some species, warming expands their ranges, allowing them to colonize new habitats.
For others, warming reduces their ranges, forcing them to retreat from unsuitable areas.
The speed and direction of fish movement vary depending on the species and the region.
According to a recent study published in the journal PNAS, marine fish have shifted their distribution by an average of 226 kilometers over the past 40 years.
The study analyzed data on nearly 50,000 species across three 20-year periods up to 2015 and found that the poleward migration is accelerating.
The movement of fish has significant implications for marine biodiversity, food webs, and fisheries, as per Nature.
As fish relocate, they interact with new species, predators, and prey, altering the structure and function of marine communities.
Some species may benefit from the arrival of new competitors or prey, while others may suffer from the loss of familiar partners or predators.
The movement of fish also affects the availability and accessibility of fish resources for human use.
Some regions may experience an increase in fish abundance and diversity, creating new opportunities for fishing and aquaculture.
Other regions may face a decline in fish stocks, threatening food security and livelihoods.
The impacts of fish movement are not evenly distributed across the world.
The tropics are expected to lose more species than they gain, as fish move away from warmer waters and few species replace them.
The poles are expected to gain more species than they lose, as fish move into cooler waters and encounter less competition.
The study in PNAS found that tropical regions have lost about 1,500 species over the past 40 years due to ocean warming.
The authors warned that this trend could reduce the diversity and productivity of tropical fisheries, which support millions of people.
How can we adapt to fish movement?
The movement of fish poses challenges and opportunities for marine management and conservation.
To cope with these changes, we need to improve our understanding and monitoring of fish distribution and abundance, especially in data-poor regions such as the tropics.
We also need to adjust our policies and practices to account for the dynamic nature of marine resources.
For example, we may need to revise fishing quotas and boundaries, establish adaptive marine protected areas, promote sustainable aquaculture, and enhance cooperation among countries and regions.
Finally, we need to address the root cause of ocean warming by reducing greenhouse gas emissions and mitigating climate change.
By doing so, we can limit the extent and impact of fish movement and protect the health and diversity of marine ecosystems.
