Warming Oceans and Declining Fish Populations
Ocean temperatures are steadily increasing worldwide due to rising greenhouse gas levels in the atmosphere. A significant impact has been a sharp decline in fish populations, which affects more than just our eating habits. The warming oceans threaten global ecosystems, economies, and our way of life.
Poor water quality from an overwhelming human presence has caused many disruptions in ocean food sources. Let’s explore the effects and determine what actions we can take to address the problem.
How Declining Fish Populations Impact Human Health
According to a study from the University of British Columbia, 82% of analyzed fish species are below population levels that can “produce maximum sustainable yields.” These species are being caught at rates exceeding their growth rate, causing their numbers to slowly dwindle. Of that 82%, 87 different species were categorized as “very bad,” with biomass levels 20% under the level needed to sustain maximum fishery catches. Warmer water temperatures caused by human greenhouse gas emissions are largely to blame.
However, some studies have also shown collective improvements in fish population numbers. One such analysis from the University of Washington in 2020 found that global fish populations have increased compared to two decades ago, showing that most stocks are above target levels. The study also found that many species are still at high risk and human activity continues to threaten marine ecosystems.
In addition, warming water and human pollution, including from sunscreen, have destroyed coral reefs and aquatic breeding grounds, which are essential for the survival of many marine species that we consume. Here are the most devastating consequences humans now face.
1. Declining Food Supplies
Seafood is a primary food source for many coastal communities around the world. A lack of fish means those people have a smaller food supply and nutrient-deficient diets.
For example, shellfish no longer can grow in their shells due to ionized and acidic water from excessive CO2 levels and pollution from coastal development. Popular saltwater fish species like tuna and grouper can’t grow and reproduce properly because warm water impairs crucial enzyme activity. Fish are less healthy overall because of the water conditions that humans have created, and some species are starving because species lower on the food chain are in decline.
As fish and other marine life populations dwindle from the impacts of overfishing and coastal development, we lose access to the biodiversity that made seafood such a nutrient-rich food source in the past. Today, those coastal communities get fewer fish and lower nutritional value from what they manage to catch, while large commercial vessels get the bulk of the nutrient-rich fish that still remain.
Millions of people now face heightened health risks due to a lack of the fish species that previous generations relied upon. These communities could experience deficiencies in iron, zinc, magnesium, and other essential nutrients as fish populations decline.
2. Rise in Marine Diseases
Ocean warming also promotes the spread of more diseases among marine wildlife. Viruses that were previously isolated in warm, tropical areas now have access to warming waters with no previous exposure. Tropical diseases are spreading outside equatorial regions on land and in the seas. Species native to the waters invaded by tropical diseases have developed no immunity and can suffer catastrophic loss of population.
For example, parasites have traveled up along the warming Gulf Stream and infiltrated the waters of New England, causing a shell disease in lobster populations.
Oysters, clams, and other edible species have developed bacteria that make them unsafe for consumption. One of these bacteria – Vibrio vulnificus – can give humans a Vibrio infection from eating undercooked shellfish. The infection kills about 100 Americans annually. Other waterborne illnesses like cholera have also increased in recent years as a result of warmer oceans and disease-ridden fish.
3. Persistent Organic Pollutants
Humans have turned to greater reliance on farmed fish in response to declining wild fish populations. Farmed fish often contain higher levels of persistent organic pollutants (POPs) due to the tight quarters where they grow and commercial feed containing contaminated fish oil and nutrient-deficient fish meal. The chemicals in those products don’t agree with the human body. When we eat fish raised on contaminated food, it can harm our endocrine systems, cause reproductive problems, and increase the risk of developing certain cancers.
POPs are increasingly common in wild fish as well, as rising water temperatures and overfishing have forced them to eat prey with higher mercury levels. Mercury is linked with impaired brain development and cognitive abilities, so those species could become inedible if they continue to ingest harmful pollutants.
4. Economic Factors
The productivity of fisheries has declined by nearly 35% in the last 80 years. Smaller fishing businesses and communities have gone under, losing their livelihoods to big commercial operations that often engage in destructive practices. For example, bottom trawling vessels drag a net or cage along the ocean’s floor, destroying habitats and causing major collateral damage to ecosystems and fish populations they don’t even intend to catch.
A decimated fishing industry leads to higher prices, potentially making food, housing, and medical care unaffordable for low-income populations that rely on local fisheries. Rising ocean temperatures, caused by climate change, exacerbate all of these problems.
How Can You Prevent Ocean Warming With Local Actions?
The changes that have already happened will take centuries to reverse, so it’s crucial that we take action to limit further damage. We can start by reducing greenhouse gas emissions, switching to renewable energy sources, and making our vessels more energy-efficient, no matter their size.
Consumers can also help reduce ocean temperatures by purchasing locally sourced foods and products. Less storage time and transportation translates to fewer emissions per purchase. We must also make sure these local products are sustainably grown and harvested. That means we need to hold businesses accountable, uphold higher ethical standards, and look for organizations with relevant environmental certifications.
You can ask your elected officials to implement effective regulation and conservation efforts. Encourage them to establish marine protected areas, fishing limits, and other adaptive measures to combat climate change.
And lastly, if you eat seafood, ensure you purchase only sustainable options. Monterey Bay Aquarium’s Seafood Watch is a handy resource to help you quickly check which species are environmentally responsible choices.
Go on the Offensive
We can’t ignore the issue of climate change anymore. It’s critical to go on the offensive and seek proactive solutions to the problem before it gets any worse.
Ocean temperatures will not return to normal levels in our lifetimes, but we can create a better world for our children and grandchildren by sparking a change today.