UK fish industry may be damaged by global warming causing smaller fish

Drawing of cod a predator fish near the top of the food chain

The UK fish industry is in the news because of Brexit. It was a central part of the negotiations. Global warming may make those negotiations seem incidental in the long term because a study by Aberdeen University tells us that adult cod, haddock and other fish are getting smaller in UK seas because of climate change. The study is published on the British Ecological Society’s Journal of Applied Ecology.

Drawing of cod a predator fish near the top of the food chain

Drawing of cod a predator fish near the top of the food chain. Image: Pixabay.

They found that young fish grew faster but they topped out at a smaller size as adults because of a rising ocean temperatures. This would seem to affect the overall weight of an individual ship’s catch which in turn would reduce its value on my estimation.

The researchers studied fish stocks in the North Sea and the West of Scotland. Both regions have seen a rise in sea temperatures. Juvenile fish are getting bigger while adult fish are getting smaller. The change coincides with an increase in sea temperature. It is believed that even a small rise in sea temperature can affect the size of fish.

The UK fishing industry is worth around £1.4 billion to the British economy. It employs 24,000 people. If yields are significantly reduced there may be long-term profound implications. Although the larger size of the juveniles may help to compensate. They are investigating this trade-off between more numerous and larger younger fish against smaller older fish.

They say that global climate change should be factored into the management of fisheries. The change will possibly impact marine ecosystems. For example, the cod is a predator near the top of the food chain. They have an important role to play in the ecosystem that they inhabit. If adult cod are smaller in size it may affect their predation of other fish.

The causation apparently is that when the seas are warmer there is less oxygen in the water which dictates the body size of fish. Warmer water also increases the metabolic rate and therefore the demand for oxygen. The phenomenon has been referred to as the “temperature size rule” and it has been observed in other species of animal, plants and bacteria.

The researchers obtained the data from International Bottom Trawl Surveys provided by the International Council for the Exploration of the Sea. They provided 30 years of information from 1970 to 2017 for the North Sea and between 1986 and 2016 for the West of Scotland.

The research will continue to include management implications based on modelling.