Changing Eggs

January 13, 2019
By Damond Benningfield

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Red drum eggs, which only grow to the size of a pinhead, actually play a large role in the ecology of the bays and estuaries around them. Photo Credit: Zhenxin Hou

The egg of a red drum, a popular sport fish, is only about the size of a pinhead. Yet those tiny eggs can play a big role in the ecology of bays and estuaries.

Some eggs will hatch into new red drum. But most of the eggs -- about 90 percent -- will be eaten by other organisms. The eggs supply key nutrients, including essential fatty acids, which are needed for proper growth and development. In fact, the eggs appear to be an important source of these compounds for much of the marine food chain.

If red drum eggs had nutrition labels, though, they’d need to be changed every year. That’s because climate conditions can have a big effect on the amount of fatty acids.

Researchers at the University of Texas Marine Science Institute studied red drum eggs at Port Aransas, Texas, over eight years. The researchers also studied red-drum prey in adjoining waters -- shrimp, crabs, and fish. They also studied records of climate conditions, looking for droughts and rainy seasons.

And they found a correlation. The amount of rainfall changed the water salinity, which had a big impact on the fish and shellfish that red drum eat. As the red drum diet varied, so did the levels of essential fatty acids in their eggs. The levels went up during drought years, but down during wet years.

The eggs are eaten by creatures of various sizes, which in turn are eaten by other creatures. So any change in the quality of the eggs can have a big impact throughout the food chain -- all caused by climate events.