Declining Fish Population

If you’ve been paying attention to world news, you will agree that plenty of weird things is happening in the environment. Avid anglers are seeing unusual patterns in fish.

Countries are fighting over fishing rights caused of a combination of changing migration patterns and declining fish stocks. Oyster farmers are worrying about the adverse effects of ocean acidification.

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We can go on about these weird things happening. But the bottom line here is that fish populations worldwide, on average, are declining! The changing environment has plenty of things to do with it, and, in turn, humans should be held primarily responsible for these changes.

The Decrease In The Amount Of Phytoplankton

Scientists have identified a decline in the number of juvenile fish, the young fish that aren’t of reproductive age yet. Such decline was also closely tied to the decrease in the phytoplankton population in the water.

Phytoplankton, or microalgae, along with other microscopic animals, are the primary food source of juvenile fish.

When juvenile fish don’t find sufficient food within days, they will likely die. Even with the parent fish increasing their reproduction, the loss of juvenile fish due to starvation will likely happen again if they can. The more juvenile fish die, the less the overall fish population will be.

Heavy fishing done by humans may also play a role in the declining population. Commercial fishers favor large fish because these bring in higher profits.

But since large fish also produce the most robust, not to mention the largest eggs, their overfishing meant few new stocks were introduced to boost the population.

When overfishing is combined with the decline in the phytoplankton population, large fish cannot quickly bounce back from depleted stocks.

When they reproduce, their young will have to compete for an increasingly scarce food supply, namely, the phytoplankton.

In North Atlantic, the population of European plaice, American plaice, Atlantic cod, and sole are declining due to these factors. It is also true in South America and Australia, where scientists concluded that the most vital driver in a declining fish population is the lack of phytoplankton.

Fortunately, in other parts of the world, such as in the North Pacific, particularly in the Gulf of Alaska, the fish population wasn’t declining significantly.

Increase In Worldwide Temperature

With the environment closely linked on so many levels, the decrease in the phytoplankton population has been linked directly to climate change. It’s simple, really:

The warming temperature of the oceans has adverse and direct effects on the phytoplankton population that, in turn, are affecting fish stocks.

And with the warming waters, the fish are also changing their habits and finding new habitats where their preferred temperature still exists. Think of fish as the Goldilocks of the earth:

They don’t like too cold or too hot water temperatures, at least where their natural physiology is concerned. The water temperature has to be just right, and it’s a specific preference that they share with their food sources, including phytoplankton and other microscopic animals.

Scientists have also identified trends in the fish population based on the water temperature. Fish populations that stayed in the colder parts of their natural range are more likely to fare better than fish populations in warmer parts.

For the latter, even a slight increase in water temperature proved too much.

Studies have pointed out that fish populations in the tropics may be more challenging to save from increasing ocean temperature.

Even today, the current warm water temperature will continue to rise due to climate change, and we have the responsibility to do our share in decreasing the risk.

The cycle is vicious: Overfishing done by man makes fish populations more vulnerable to the effects of climate change. Climate change hinders man’s capability to rebuild the stocks of overfished fish populations.

Humans have responsibility for climate change, too, as our activities contribute to climate change, particularly carbon dioxide emissions.

Impact On Our Food Supply

The declining fish population has far-reaching effects on humans, perhaps even their survival. In a study led by Chris Free and published in Science, the number of seafood humans can harvest sustainably decreased by 4.1% from 1930 to 2010.

Again, it is a result of the climate change brought on by human activities.

Does 4.1% sound small in the context of 80 years? According to the study’s lead researcher, it isn’t because it translates to 1.4 million metric tons of fish. With increasing ocean temperature, it may well increase.

It is a serious matter, indeed! Take note that fish comprise 17% of the world’s total animal protein intake. In comparison, 70% of people live near the coast, and many depend on the oceans for livelihood.

The fisheries industry supports about 56 million people, and a decreased fishing population means adverse effects on their way of life and livelihood.

Ultimately, an expert on climate change and fisheries agrees that the best solution is slowing down, if not stopping, climate change brought on by human activities.

There’s also the need to protect fish populations against overfishing and implement more effective fisheries management programs.


In conclusion, climate change is a concern not only for the government to respond to. Through your fishing activities, do your share in preventing the decline of the fish population in your favorite hunting spots.

Also, you should know and follow the fishing regulations in your area. You have to be responsible when catching fish and not take more than what you need or what is allowed.

You may use guides like the SW Fish ID 9749091574 Florida Saltwater Fish ID to identify fish and their applicable regulations correctly.

Aside from that, you should adopt sustainable fishing methods. You can use barbless hooks (Gamakatsu Barbless Octopus Hook) or circle hooks (Lazer Sharp Circle Hook) to practice the catch-and-release of large fish.

This way, you’re giving them a chance to reproduce and replenish fish stocks.