How Does The Declining Fish Population Relate To The Environment?

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

Countries are fighting over fishing rights caused by 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 largely 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 determined as 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. The more juvenile fish die, the less the overall population of fish will be. Even with the parent fish increasing their reproduction, if they can, the loss of juvenile fish due to starvation will likely happen again.

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 little new stocks were introduced to boost the population.

When overfishing is combined with the decline in the phytoplankton population, large fish aren’t able to quickly bounce back from depleted stocks.

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

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

In other parts of the world, fortunately, 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 to be too much.

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

Even today, the present 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. In turn, climate change hinders man’s capability to rebuild the stocks of overfished fish populations.

We, humans, have a responsibility in climate change, too, as our activities contribute to climate change, particularly in terms of carbon dioxide emissions.

Impact On Our Food Supply

The declining fish population has far-reaching effects on humans, perhaps even on 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.

It is again a result of the climate change brought on by human activities.

Does 4.1% sound small in the context of 80 years? It isn’t because it translates to 1.4 million metric tons of fish, according to the study’s lead researcher. 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, the expert on climate change and fisheries agree that the best solution is slowing down, if not stopping, climate change brought on by human activities.

There’s also the need for protecting fish populations against overfishing and implementing more effective fisheries management programs.


In conclusion, climate change is a concern not only for the government to respond. 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 do 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 for proper identification of fish and their applicable regulations.

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), so you can practice catch-and-release of large fish.

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