Ocean warming depleting fish, reducing size: Malaysian study

The current hot spell is not helping and to make matters worse, floods and droughts have directly or indirectly affected fishermen’s catch, experts said.

Universiti Malaysia Terengganu (UMT) vice-chancellor Prof Mazlan Abd Ghaffar said as sea surface temperatures rose, the strength of tropical cyclones would increase the frequency of storms in the heart of the sea.

“This directly impacts the risk of fishermen going out to sea to catch fish. This is a global phenomenon, as recent studies have shown that climate change influences fish stocks with adverse effects on coral reefs, causing coral bleaching and altering the species' composition and diversity.

“In this context, it is critical to understand the impact of extreme events such as rising temperatures, sea-level rise, floods, droughts and cyclones to predict and understand the dynamics of fish stocks and their implications for future food production systems.

“The effects of these events are already being observed in the ocean and coastal areas, affecting fish stocks,” he told The Star.

The observations were based on UMT’s Institute of Marine Biotechnology climate change laboratories’ study.

Prof Mazlan said the impact of climate change was greater in tropical regions of Asia, where temperatures are higher, contributing to the reduction of fish stocks.

Citing an example, he said wild ikan siakap (barramundi) has become scarce in waterways and that most of it sold in the domestic market presently was farmed fish.

“Our study found that the body size of the fish has become smaller compared to the past 20 years due to over-fishing activities and the effects of climate change.

“Overfishing causes small fish to be caught before they grow, and warming of the sea affects fish eggs and reproduction,” he said, adding that the size of a variety of fishes had shrunk about 10%.

UMT fishing gears technology and fisheries ecology senior lecturer Mohd Fazrul Hisham Abd Aziz said climate change and uncontrolled fishing activities have led to declining fish hauls off Terengganu, pointing to the ongoing hot weather.

“Sudden temperature rises can lead to the loss of marine habitats and species.

“Shifting ocean currents and warming waters are changing the distribution of fish stocks and altering the structure of ecosystems,” he added.

Mohd Fazrul said climate change might also deprive juvenile fish of their most important early food supply – plankton and zooplankton.

He confirmed that the size of fish was shrinking compared to the average size of various types of fish.

“Fish reproduction depends on food, habitat, ecological factors and environmental factors such as water quality and sea temperature changes,” he pointed out.

As such, he said temperature changes caused by climate change might alter the food quality and distribution of fish.

“Like other marine life, fish will look for a suitable place. And based on the current situation, there is a possibility that fish will migrate to a more suitable environment,” he said.

Mohd Fazrul said coastal fishermen in Terengganu had been struggling due to dwindling catches over the past year, adding that climate change had also affected their livelihood.

“Fishermen used to be able to catch 100kg in just one trip, but now they only get 2kg to 4kg,” he added.

He said Terengganu fishermen have been unable to venture out to sea as often due to the severe weather changes.

“The climate is constantly changing. And very often, the waves are tremendous,” he said, lamenting that their boats were not equipped to deal with rough seas.

Citing another example of how changing weather patterns impacted Terengganu fishermen, he said they used to go out to sea as early as 4am.

These days, it was delayed till between 10am and 11am due to undercurrent changes, he added.

“Last year, fishermen could not go fishing for up to a week every month. And only two to three trips were made this January due to bad weather,” he said.

Mohd Fazrul also said that illegal, unreported and unregulated (IUU) fishing in Malaysian waters led to losses of RM2.1bil between 2020 and 2021.

“Despite the Fisheries Department’s efforts to enforce the rules, many are willing to take the risk of carrying out such fishing,” he said.

Based on marine research from his team, he said climate change and uncontrolled fishing activities could cause a drop of about 40% in fish catch in Terengganu.

Mohd Fazrul said another factor that led to the dwindling fish population was trawl net fishing boats crossing into other waterway zones.

Khoo Gek San

The star

Asia News Network