The Netflix documentary Seaspiracy caused a lot of controversy for the alleged exaggeration and bias in its narrative of the ocean's decline. 

While the thrust of the film — that the ocean as we know it is doomed unless urgent action is taken — was on point, many of the details were off and critics took to the internet in the days and weeks after its launch to set the record straight. 

Lost amid the reaction, however, was an important yet often overlooked fact that the film brings to light: the symbiotic relationship between coral and fish.

Fish waste provides food to coral, the small animals that construct the majestic reefs people scuba dive through and photograph. They also eat the algae that grows on reefs. Without this constant grazing, the algae would grow out of control and eventually overpower and kill the coral. The reef, in return, provides a habitat for the fish to feed, rest, and raise their young.

Coral reefs aren't just important to fish. They provide habitat to thousands of marine animals and plants, sustain coastal economies via tourism and sustainable fishing, and protect coastlines from flooding and extreme storms. 

In a healthy reef, fish teem in nooks and crannies and swim in schools, a busy and dazzling web of life.

In recent years, this ecosystem has been undermined by overfishing, which is when fishing vessels catch more fish than a species is able to regenerate on an annual basis through normal reproduction. 

When overfishing happens year after year, fish never get a chance to recover. As boats constantly scrape marine ecosystems with massive trawler nets and other means, fish species are rapidly declining. 

In fact, more than a third of fish populations are being plundered beyond their biological limit, up from around 10% in 1990, according to the United Nations Food and Agriculture Organization. 

Because coral reefs are known to harbor fish, they’re often heavily exploited. An estimated 55% of the world’s reefs face overfishing, including 95% of reefs in Southeast Asia, according to Reef Resilience. 

Destructive fishing phenomena such as bycatch — when unintended species are caught — and ghost gear — when fishing equipment is improperly discarded, multiply the harm done to reefs. When fishing nets are discarded on top of a reef, for example, it can cause coral to fragment.

As fish populations decline, fishing vessels often respond with more aggressive tactics and can cause broader ecosystem harm as nets and other materials accumulate in the area.

The loss of fish deprives coral of nourishment, making them more vulnerable to disease, extreme ocean temperatures, and more. It also allows algae to grow out of control, which can subsume the reef. 

It’s important to highlight this relationship because narratives about the plight of coral reefs tend to focus on rising ocean temperatures to the exclusion of other factors. While marine heat waves have been cooking reefs alive, they’re made worse by a host of other threats including overfishing. 

Further, coral reefs are better able to rebound from bleaching events when fish are there to provide sustenance and ecosystem support. 

Saving coral reefs, and the ocean for that matter, demands better fishing regulation worldwide. Countries must strictly prohibit overfishing and work together to enforce marine rules. People can pressure leaders to take these actions by, as Seaspiracy recommends, reducing and avoiding seafood. 

While Seaspiracy featured inaccuracies, its conclusion remains sound: Overfishing is a grave threat to the ocean and countries must stop it.