Wrong-way Migrations: Ocean Warming is Trapping Shellfish in Habitats They Can’t Escape
Wed, April 21, 2021

Wrong-way Migrations: Ocean Warming is Trapping Shellfish in Habitats They Can’t Escape


The world’s oceans are warming at a rapidly increasing pace and many species of animal and plant will have to find cooler places to live. However, things are a bit difficult for sedimentary marine creatures, like clams, worms, and snails. A new study carried out by a team of scientists from Rutgers University shows that ocean warming is causing seafloor species to go in the wrong direction.

Wrong-way migration

The authors mentioned that as many creatures respond to ocean warming by traveling to cooler places for refuge, other species do the opposite. They call this phenomenon as the “wrong-way migration.” Marine creatures, like clams, sea scallops, quahogs, and blue mussels, are heading towards less secure habitats. The team said that these marine creatures are valuable resources in the shellfish industry but around 80% of these species could no longer be located in their traditional habitats. Instead, they turn up in warmer and shallower waters.

Destructive feedback loop

The colder and deeper waters of the outer shelf could have provided them a refuge from global warming so the scientists are puzzled why the species are contracting into warmer waters. The scientists added that warm waters are causing the species to spawn (lay eggs) earlier in summer and spring. This, however, exposes the larvae to water currents and wind patterns that they normally would not experience so it would carry weak swimmers into places that they would not normally be. Once they are there, they are more likely to be trapped and less likely to survive. What’s more alarming is that the ones that do survive may become a part of the feedback loop that is destructive since warmer regions will just cause them to spawn their larvae earlier. The cycle will repeat.

The team added that although their research focused only on bottom-dwelling invertebrates in a general location, they believe that their findings are the same with what is observed in other animals whose environment is also affected by climate change.

Moving homes and altered lifestyles

According to the World Wildlife Fund, the marine environment is already experiencing the impacts of climate change. One of the most dramatic effects that can be observed is coral bleaching, which is a stress response of corals due to high water temperatures. This can also lead to coral death. As the oceans continue to warm, marine life has likewise moved further into deeper water and north while other species lose their homes for other reasons.

The rising temperature can moreover directly affect the marine species’ life cycle, behavior, and metabolism. For many of these species, it can serve as a cue for their reproduction so it can affect the successful breeding of their species. Therefore, changing climate will not only skew their sex ratios but will also threaten their population's survival.



Seafood industry: statistics

The seafood industry provides one of the highest traded food commodities globally today, published by Brandon Gaille. However, there is a severe concern that the industry is facing. More than 90% of stocks are either over-exploited or fully exploited and this limits the number of static fishery landings. The Food and Agriculture Organization of the United Nations also estimates that global fish production has reached about 179 million tons in 2018. Production mollusks, for instance, reached 18 million tons in 2018, a significant increase from 17 million in 2017.

World employment for fishers and fish farmers, by region

FAO also found that the highest numbers of fishers and aquaculture workers are found in Asia but there is a gender split. It shows that women account only for 14% of the 59.5 million people that are engaged in the primary sector of fisheries and aquaculture in 2018. But why is caring about the gender of those employed in the said industry important? FAO answers this is because women also play an important role throughout the fish value chain. They provide labor in both artisanal and commercial fisheries and are acting as small-scale entrepreneurs in their area.

Meanwhile, Our World in Data shares the statistics for global seafood and fish production from 1961 to 2013: cephalopods (3.89 million t), mollusks (17.82 million), crustaceans (12.61 million t), marine fish (10.79 million t), demersal fish (20.77 million t), pelagic fish (36.64 million t), and freshwater fish (52.34 million t).



Global warming solutions

The threats that are faced by our ocean may be overwhelming in the face of climate change, overfishing, pollution, and other daunting problems. Yet, there are things we can do on our own that can make a huge difference. For instance, we can keep on learning everyday things that can help restore seas and protect the ocean. Do not also forget to share what you have learned with your family and friends.

Second, be water-wise since all water on our planet is connected. Even if you are not living near the coast, the water that runs off from your yard and drains from your kitchen will still eventually make its way into the ocean. This means that you can keep the waterways and the ocean, as a result, healthy by lessening your use of chemicals in the household.

If you purchase for souvenirs, opt for sea-friendly mementos. Steer clear of products or jewelry that are made from marine animals or other animal parts, including coral and shells. Yet, since global warming is caused by the presence of too many greenhouse gases in our atmosphere, the top sector that can do so much change is the transportation industry. The top GHG emissions by economic sector are transportation (29%), electricity (28%), industry (22%), commercial and residential (12%), and agriculture (9%). To generate power in these industries, fossil fuels, like coal, gas, and oil, are burned. Then, it releases carbon dioxide. In other words, it is these same sectors that can take serious effort to reduce their emissions.



As the world’s appetite for seafood and fish products shows no sign of slowing, biologists are challenged to think of transplanting the marine species to a more favorable environment. We can also do little changes in our way to make the ocean more habitable for species to live.