Sustainable Seafood | Climate Change and Shellfish

Welcome back to my Sustainable Seafood series. In this final part I’ll be addressing climate change and expanding our seafood diets away from just fish. If you didn’t catch the previous posts, you can find them here. I started the seafood sustainability guide because whilst I know seafood can be immensely good for you, it also has environmental and ethical implications. Despite my degree in marine biology, I still felt confused, so figured that I wasn’t alone. I’ve broken down the concept of seafood sustainability into a set of topics to help shed some light on this issue. Once again, special thanks to Prof. Michel Kaiser and Dr. Claire Szostek for their help in getting providing the facts for this post. 

Sustainable seafood

How will climate change affect what species are available?

One big topic is climate change. We are all very aware that daily decisions make an impact upon our environmental impact, including that of what we eat. However, when eating wild harvested food, such as seafood, climate change can also affect their distribution. Recently, blue fin tuna have been pictured in the Irish sea, where the haven’t been seen since the 1960’s when waters were warmer. We can definitely expect to see colder water species retreating further north, potentially putting pressure on stocks as their habitat decreases in size. 

Are shellfish more sustainable seafood options?

Shellfish are further down the food web than fish, which are often carnivorous, and many are herbivores. As such, less energy is required to produce, say, 10kg of mussels than of cod. in the Menai Straits in North Wales, an artificially-produced mussel bed was found to benefit local seabird populations that feed upon shellfish, without negatively impacting the mussel farm. Due to the nature of bivalve’s reproductive strategy and lifespan, they can support high levels of harvesting without damaging the population. That being said, filter feeding from polluted waters are definitely not something you want to eat, as they are vital to “clean” the sea that they live in. The environmental footprint of mussel and other shellfish farms is low. On top of this, they are fairly easily managed. 

What about prawns? In the UK, retailers and processors of prawns take the issues relating to prawn fisheries very seriously. Marine biologists are hired to inspect farms to ensure that they reach certain standards. Unfortunately, there are many problems in South East Asian regarding human trafficking and slavery and habitat damage. In 2014, the director of Anti-Slavery International stated that “If you buy prawns or shrimp from Thailand, you will be buying the produce of slave labour,”. Some 55% of prawns sold are from farms (source), yet many of the farms are created at the expense of mangroves and other wetlands. These mangroves are unique and highly important habitats, particularly for eggs and juvenile fish. My personal take would be to stick to species harvested around Europe and check for eco labels on any South East Asian-sourced prawns, or avoid entirely. 


Another factor about crustaceans and bivalves (and all seafood for that matter) is microplastics. Fibres from our synthetic clothes, beads from cosmetics and broken down plastic litter all make their way into the sea as microplastics and are very likely to be ingested. The scale of micro plastic coverage still isn’t really known (I’ll update this article as more information comes through) but it is a growing issue. Bivalves used for “cleaning” the sea aren’t used in farming and rightly so -they take in pollutants and micro plastics as they filter feed. Bioaccumulation states that species higher up the food web will have more plastics as they consume many prey that have plastics in their system as well. As a consumer, the best thing you can do is to reduce waste and dispose of plastic responsibly. The less waste we produce, the less of an issue micro plastics in our food will be. 

In summary

  • Expect to see more warm water species in fishmongers, and be open to trying new fish.
  • Also consider consuming a greater variety of seafood, especially British or European farmed mussels.
  • Be mindful of where your prawns have come from in terms of ethics and habitat damage.
  • Keep an eye out for more news on microplastics and try to reduce your own waste.