When To Wage a War Against An Alien (Fish)

Recently we looked at fire ants. Now it’s fish.

Invading Thailand’s Fisheries

When we combine more than 500 thousand fish farmers and 236 thousand fishery workers with 2,600 km of coastline and 316 thousand km2 of EEZ (Exclusive Economic Zone) fishing water, we wind up with a country that cares about its fish.

During 2023, fisheries added 2.2% to the growth of the Thai GDP. Below, you can see what composes the industry:

As a result, no one was pleased when the blackchin tilapia arrived in Thai waters (we don’t know how or why). Representing the recipe for a disaster, blackchin tilapia females produce as many as 700 eggs (or more). At that point the male does the fertilizing and then sticks around to care for his babies. Then, as adults, they all nibble on small fish and shellfish. As of mid-July 2024, the blackchin tilapia had spread to Thailand’s fisheries in more than 13 Thai provinces.

These horrifying numbers display their potential as an invasive species:

Our Bottom Line: Supply and Demand

As economists, we can say that the battle against an invasive species is all about supply and demand. Faced with an increasingly overwhelming supply, scientists are experimenting with infertile blackchin tilapia that they hope will prevail. They also released the Asian seabass and long-whiskered catfish that eat them. Meanwhile, to increase demand, for each kilogram caught in Thai waters, the government offered 15 baht ($0.42; £0.33). Sufficiently high, the bounty inspired crowds to wade in shallow water with plastic basins. From there, the dead fish could become fertilizer or pla ra–a fermented fish product.

My sources and more: Thanks to the BBC World Business Report podcast for alerting me to the dangers of the blackchin tilapia. Then, for the academic perspective, this paper came in handy as did this species summary from the University of Michigan and this article. I also thank my student Maya for suggesting the analytic relevance of invasive species’ supply and demand.

Our featured image of the blackchin tilapia is from the BBC.