Mackerel and Horse Mackerel Are Shrinking, Silver Pomfret as Small as 6 cm! Fearing Ecological Imbalance, Environmental Groups Urge Passage of Marine Conservation Law

How big were the mackerel and horse mackerel you remember seeing at the market? Depending on your age, the answer may be very different. Environmental group Greenpeace set up a fish stall in front of the Executive Yuan, and the difference was striking: fish purchased from today's markets on the right looked noticeably smaller compared to fish from the 1990s on the left.

The environmental group partnered with the National Museum of Marine Biology and Aquarium to conduct a survey, visiting fish markets in Keelung, Yilan, Kaohsiung, and Pingtung. Collecting 1,716 valid data points, researchers found that over 97% of chub mackerel, horse mackerel, and blackthroat seaperch were caught and sold before reaching their "maturity length*." The smallest silver pomfret sampled at Qianzhen, Kaohsiung measured just 6.85 cm — only half of its maturity length.

*Maturity length, also known as the 50% maturity length (Lm50): the body length at which 50% of individuals in a population have reached sexual maturity. It serves as a reference baseline for assessing population health and formulating fisheries management policy.

Survey: 100% of Chub Mackerel Did Not Reach Maturity Length

"We have not given these fish the chance to reproduce."

When juvenile fish are caught before reaching sexual maturity and the ability to reproduce, fish populations will decline over the long term. In the case of the chub mackerel surveyed, all 84 market samples — 100% — fell short of the maturity length of 32.3 cm, with the smallest measuring just 17.97 cm.

"We have not given these fish the chance to reproduce," said researcher Ho Hsuan-Ching of the National Museum of Marine Biology and Aquarium, who participated in the survey. He cited the example of the U.S. National Marine Fisheries Service conducting surveys in Alaskan waters: "They survey species populations every year, calculate reproduction rates, and use that data to determine how much can be harvested from the market the following year."

Taiwan, by contrast, currently has no legal basis to impose equivalent restrictions, nor does it have systematic research data to draw on — which highlights the importance of strengthening ocean scientific monitoring, as called for in the proposed Marine Conservation Act.

Which Fish Can Be Caught? Fishers Hope the Marine Conservation Act Will Provide Guidance

Wang Ming-Hsiang, a dive instructor known as Coach Piston, grew up in Keelung and also holds a recreational vessel captain's license. With over 20 years in the fishing industry, he has experienced the depletion of fishery resources firsthand. He transitioned to working as a dive instructor partly out of concern for both his livelihood and the sustainable future of the ocean. Speaking from the perspective of fishers, he said: "Which fish can be caught and which cannot — for fishers, it comes down to following the rules. There needs to be a legal foundation to tell fishers what's allowed. I hope the Marine Conservation Act passes quickly, so that future generations will have more fish — and bigger fish — to catch."

Chung Meng-Hsun, Oceans Project Lead at Greenpeace, added that the importance of the Marine Conservation Act lies in its ability to facilitate the expansion and effective management of marine protected areas (MPAs). "When an MPA's ecosystem is healthy, fish naturally congregate there — and once they do, they spill over into surrounding waters," he said, noting that this dynamic can create a positive relationship with fishers as well.

Progress on the Marine Conservation Act: "To Be Submitted to the Legislature This Session"

Even as the Ocean Affairs Council has been in operation with various conservation actions and policies underway, marine protected areas (MPAs) designated and managed under different competent authorities illustrate the problem: the Ocean Conservation Administration is the overseeing agency, yet it lacks the legal basis to formally designate MPAs — making it a tiger without teeth.

In fact, at the "Our Ocean Conference (OOC)" hosted by Palau last year, Taiwan explicitly pledged to pass the Marine Conservation Act. Yet the relevant legislation remains stalled at the Executive Yuan. In response to widespread concern over the bill's progress, Chen Ying-Jung, Director of the Department of Transportation, Environment and Resources at the Executive Yuan, stepped forward to represent the government's position, stating that the various ministries have largely reached consensus and that efforts will be made to submit the Marine Conservation Act to the Legislative Yuan during the current legislative session.

Full Data: Survey of Common Fish Sizes at Taiwan's Fish Markets

Species	Sample Size	Percentage Below Maturity Length
Chub Mackerel	84	100% below maturity length
Blackthroat Seaperch	685	99% below maturity length
Horse Mackerel	144	97.9% below maturity length
Japanese Tilefish	61	85.3% below maturity length
Pampus argenteus (Pomfret)	568	82.2% below maturity length
Silver Pomfret	174	77% below maturity length

Further reading:

• Six Common Fish Species at Taiwan's Fish Markets Are All Shrinking! Fish-Eating Culture at Risk — Greenpeace Demands Marine Conservation Act Be Submitted for Review in March
• At the 7th "Our Ocean Conference" (OOC) hosted by Taiwan's government in Palau last year, Taiwan explicitly pledged to pass the Marine Conservation Act — yet that commitment has still not been fulfilled. The government's pledge can be found in this document, p.23, fourth point from the bottom.
• While the Marine Conservation Act Remains Stalled, Marine Life Is Disappearing — When Will the Government Make Good on Its Legislative Promise?
• Is a Marine Protected Area the Best Answer for Ocean Sustainability? Ocean Encyclopaedia Takes You Through MPAs — Part 1
• Taiwan People's Party Legislative Caucus Draft of the Marine Conservation Act