Daily Earth Science Environment Repost

Bluefin Tuna: A case of overeating

Ranging up to 15 feet in length and 2000 pounds, Atlantic bluefin tuna are one of the top predators in the open ocean food chain. They have a specialized blood vessel structure that lets them maintain a higher body temperature than the surrounding water. This adaptation gives them an advantage when hunting in cold waters, thus allowing them to move more quickly than other fish.  Evolutionary adaptations like this have made the tuna one of the fastest swimmers in the ocean.

The bluefin tuna literally can’t stop swimming. It lacks the ability to pass water over its gills when it is motionless. The gills extract vital oxygen, so the tuna must swim or die. Swimming forward with its mouth open allows water to continually pass over the gills providing a critical fresh supply of oxygen. 

A list of some facts about these fish provides insight into the ecological and cultural niches they fill:

They can live for up to 35 years

Females can produce up to 10 million eggs a year

They are characteristically torpedo-shaped

Adults feed on mackerel and herring

Sushi lovers consider the Atlantic bluefin tuna a prized delicacy

Under threat

These facts provide insight into why the bluefin tuna is so successful as a species, but why they are now a threatened species. These fish have a limited number of predators to worry about, but unfortunately for them, humans are one of those predators. The Atlantic tuna population suffered a 60% decline between 1974 and 1990 due to overfishing and poor management of the fisheries. The good news is that the populations have recovered somewhat since about 2009. 

Atlantic bluefin tuna populations

Other species have seen a similar fate at the hands of Homo sapiens. But the graph above is a great example of human impact on the earth’s ecological balance. The results don’t just flow one way. As a species, humans represent a two-edged sword that can cut both ways. The Anthropocene extinction currently underway does not have to end in a massive collapse of earth’s biosphere. Likewise, the rapidly approaching climate change crisis can be mitigated if there is a collective will to do so. 

The species Homo sapiens smart, adaptable, and greedy. If our societies can maximize the first two of these characteristics and control the last one, then many things are possible.


Oceana: Atlantic Bluefin Tuna  – https://oceana.org/marine-life/ocean-fishes/atlantic-bluefin-tuna

The Story of Atlantic Bluefin – Science-based management will ensure a healthy future. https://www.pewtrusts.org/en/research-and-analysis/issue-briefs/2017/10/the-story-of-atlantic-bluefin

William House
William is an earth scientist and writer with an interest in providing the science "backstory" for breaking environmental, earth science, and climate change news.