Smaller coastal fish feeling the heat

Dozens washing up on shores, an ugly effect caused by El Nino’s intensity

GEORGE TOWN: It might be a little depressing for some Penangites taking evening walks by the beach of late.

Dozens of small dead fish are regularly washing up, testament to the fact that the sweltering heat caused by the El Nino weather phenomenon is killing weaker fish.

Many Penangites have shared the ugly sight of rotten spotted scat (kitang), small croakers (gelama) and juvenile catfish (duri) appearing along the beach.

The spotted scat is a macro feeder, dwelling in submerged rocks just off the seashore, while young croakers and catfish hug close to the coastline and dare not venture into deeper waters for fear of predators.

“Because they live so close to the seashore, they are more at risk of heatwaves,” said Universiti Sains Malaysia’s (USM) ichthyologist (fish expert) Dr Khaironizam Md Zain.

He said in the sweltering heat, the sea warms up too, particularly in the shallows by the seashore.

“When seawater is too warm, it does not hold on to dissolved oxygen.

“This causes fish to suffer from hypoxia (a state of low, insufficient oxygen),” he said.

To add to the problem, USM marine biologist Prof Datuk Dr Aileen Tan said the intense blooming of algae would rob more dissolved oxygen from the sea.

“Whenever there are weeks of hot, rain-less weather, followed by a period of sudden heavy showers, algae at sea will grow tremendously.

“During the day, they do photosynthesis and release oxygen, but at night, they absorb oxygen and release carbon dioxide.

“Sea algae have short lifespans too and when they die, their decomposition robs more dissolved oxygen.

“Weak fish and fish that do not flee to deeper, cooler waters can die,” said Prof Tan.

She said this was part and parcel of the theory of natural selection expounded by 19th century naturalist Charles Darwin.

“It may look depressing, but it is part of the cycle of life,” she added.

USM atmospheric physicist Assoc Prof Dr Yusri Yusup agreed that the heatwave alone may not be causing fish deaths along the coastline.

For several years, he has had several gauges monitoring conditions between the atmosphere and the sea at a station about 800m off the unpopulated coast of Teluk Bahang here. The readings of the gauges are uploaded onto the Internet every 90 minutes and the public can access the data at atmosfera.usm.my.

“At present, the sea temperature has begun rising by half a degree Celsius on average since the start of this month.

“The coastline sea temperature averages around 28°C. Last November, it recorded a peak of 31°C,” he said.

Yusri said since last December, the coastal sea temperature – using Teluk Bahang coast as the benchmark – had settled into stable fluctuations without extreme temperature spikes that merit alarm.

“The El Nino weather phenomenon has a role to play in the heat we are experiencing.

“Though the data shows it is not as severe as prior years, it does seem to be long-lived. We are now in the inter-monsoon transitional phase, but up north here, we are not getting much rain, so the weather is causing rarely-seen effects such as small fish dying close to shore,” he added.