Giant sea bass are thriving in Mexican waters – scientific research that found them to be critically endangered stopped at the US-Mexico border

I was looking at the sea floor, and focused on identifying fish species as I usually did when diving off the coast of California, when suddenly I felt something big above me. As I turned my head I saw a giant fish – over 6 feet (2 m) long – quietly buzzing about the air bubbles coming from my SCUBA regulator. This was 2016 and it was my first encounter with a giant bass fish.

Maru Brito – The Conversation

I am a marine ecologist, studying how international boundaries pose challenges to conservation and management efforts in the marine environment. Although there are no walls or fences in the ocean, the boundaries still serve as glaring barriers to a variety of things.

The giant sea bass lives off the western coast of North America in Mexican and American waters. I have found that significant differences in organizational and research efforts between the two countries have led to a significant misunderstanding of the health of the population of giant seabass.

Map showing the high density of giant sea bass along the western coast of the United States and on both sides of the Baja Peninsula.
The giant sea bass lives in coastal waters from Northern California all the way south to the Sea of ​​Cortez.
Arturo Ramirez ValdezCC BY-ND

Different countries, different sciences

The giant sea bass is the largest coastal bony fish in the northeastern Pacific Ocean. It can grow up to 9 feet (2.7 meters) long and weigh up to 700 pounds (315 kilograms). It lives in coastal waters from Northern California to the tip of the Baja California Peninsula in Mexico, including the entire Gulf of California.

In California, commercial hunting of this species began in the late 1880s. Large fish were very abundant across the entire range, but the fisheries collapsed in the early 1970s. In response, in 1981 the United States banned commercial and recreational fishing for giant sea bass, and there are many ongoing research and population recovery efforts today.

The collapse, subsequent protectionism, and wave of research in the United States stand in stark contrast to Mexico. In Mexico there are minimal regulations for hunting this species, and there is an almost complete lack of data and research on it – there are only three studies of giant seabass with any data from Mexico.

The International Union for Conservation of Nature considers the giant sea bass an endangered species because it is “severely fragmented, resulting in a persistent decline of mature individuals”. But that decision was based on a report that contained absolutely no data from Mexico. This lack of data is worrisome, given that 73% of the species’ range is in Mexican waters.

This knowledge gap made me wonder if ecologists had a misconception about the health of giant sea bass populations.

A man standing behind a very large black fish on the scales.
Giant sea bass is a common sight at fish markets all over Baja.
Giant Grouper ProjectCC BY-ND

Healthy fish in Mexico

In 2017, she led an effort to document the numbers of giant seabass in Mexico and to look for evidence of what they were in the past. At the beginning of the project, my colleagues and I feared that records in Mexico would confirm the precarious situation of fish in the United States, but the reality turned out to be the opposite.

A man in orange clothes on a small blue boat sits behind four large black fish on the deck of the ship.
Commercial fishermen often do not target giant sea bass, but rather catch it as a bycatch when fishing for other species.
Giant Grouper ProjectCC BY-ND

To our surprise, we found giant sea bass everywhere in fish markets and fishing grounds from our first reviews. Fishmongers never fish out; Instead, they ask us, “How many kilograms do you need?” It was clear that for fishermen in Mexico this species is still widespread in the sea, and therefore in their nets. A large fish can still be found weighing up to 450 lbs and 200 kg, and the average catch was about 26 lbs (12 kg).

It was great to see an abundance of these fish in the markets, but I also wanted to understand fisheries trends throughout history and how current fishing levels compare to previous years. I looked at historical and contemporary fishing records and found that the Mexican merchant fleet has caught an average of 55 tons per year over the past 60 years, and fisheries have been relatively stable over the past 20 years, peaking in 2015 at 112 tons.

According to US and Mexican records, the largest annual catch ever recorded for a giant seabass in Mexico was 386 tons in 1933. Biologists are of the view that the fisheries collapsed when total catches, under the same effort, were less than 10% of Biggest catch recorded. So the steady trend of 55 tons per year shows that fisheries in Mexico have not collapsed. The giant seabass populations evidently experienced a sharp decline throughout their range; However, the health of the species is not as dire as it was thought.

Another interesting finding from my research is that the apparent collapse of the giant seabass fishery that was documented in the 1970s actually began as early as 1932.

During the first half of the 20th century, when the American merchant fleet overfished in American waters, they began fishing in Mexican waters as well—but they continued to account for all catches as of the United States. This changed in 1968 when the governments of Mexico and the United States signed a fishing agreement, limiting the amount of fish each country’s fleet could take from the other’s waters. The collapse of US fisheries in the 1970s was not caused by a sharp decline in fish numbers in Mexican waters, but was driven by changes in the regulation of fishing between the United States and Mexico. California fish numbers have been low for decades, but this has been hidden by fish from Mexico.

Big dark fish swimming in kelp forest surrounded by smaller fish.
Mexico’s giant sea bass has declined, but it’s still much healthier than researchers thought.
Miro BritoCC BY-ND

Better data and better management

Based on my research, I believe that the giant sea bass may not be considered an endangered species. My analysis of recent catch data suggests that the number of this distinctive fish is probably much greater than previously thought by biologists, especially in Mexico.

I am leading the next assessment of the International Union for Conservation of Nature, and now that we have collected better data, we can make a more informed decision balancing responsible species management with human needs.

I hope our study inspires policy makers in the United States and Baja to start a conversation about how to manage this wonderful fish in a collaborative way. But I feel our work also has bigger implications. It shows how research and data asymmetries can create significant barriers to understanding the past and present status of a species like the giant seabass and make it difficult to implement sustainable practices for the future.

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This article is republished from The Conversation, a non-profit news site dedicated to exchanging ideas from academic experts. Written by: Arturo Ramirez Valdez, University of California San Diego.

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Arturo Ramírez-Valdez receives funding from UC-Mexus CONACYT No.: 160083; PADI Foundation, Grant Application. 29020 and 33095; Mia J. Tegner Memorial Research Fellowship at Scripps Institution of Oceanography, University of California, San Diego; Mohamed Bin Zayed Species, Grant Number: 192521063, and Link Family Foundation.

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