How Fish Body Size Influences Ecosystem Functioning and Diversity

A study has questioned the idea that fish and other aquatic species will become smaller owing to global warming.

Research revealed that warm water pollution enhanced growth rates while simultaneously increasing mortality rates, leading to a population of younger but larger fish.

Unexpected effects of water warming on fish size

(Photo : Jeff J Mitchell/Getty Images)

The study shows that these require to be verified in large-scale trials and is at conflict in part with general projections of the impact of warming upon natural ecosystems, as per Phys.org.

Animals like fish are expected to develop more quickly as children but mature into smaller bodies as adults as aquatic ecosystems warm.

This pattern has mostly been shown in small-scale tests, and while a few studies have tested this hypothesis in natural settings, they have primarily been done on fish species that have been fished, where the act of fishing might affect growth rates and body size.

Max Lindmark is a researcher at the department of aquatic resources at the Swedish University of Agricultural Sciences in Lysekil, Sweden.

They looked into the way warm water pollution has affected the mortality, growth, and size of fish across many generations using a novel experimental design.

Although not all of these changes were as predicted, researchers observed statistically significant variations in projected growth rates, mortality rates, and sizes for the fish populations among the heated and reference locations.

The scientists predicted that female perches would grow more quickly in the warm environment, and this is exactly what happened.

Therefore, as compared to the reference region, these fish were around 7-11% bigger in the heated area that any age.

Furthermore, the authors claimed  that the increase in growth rate of young fish brought on by warm water was so marked that even though the overall population of fish was younger as a result of warming, the average size and proportion of larger fish was still higher in the heated area.

The idea that fish, especially the huge and elderly ones, will eventually get smaller due to global warming is in contrast with this tendency.

In summary, this study found that ecosystem warming resulted in younger, but bigger fish.

Also read: World's Lakes At Risk Of Continued Algal Blooms Triggered By Warm Waters

Warm water decrease oxygen levels

For every component of oxygen in water, there are two parts hydrogen. The fish, however, do not utilize this oxygen, as per Mister Twister.

In comparison to low barometric pressure, high barometric pressure drives more oxygen into the ocean.

Additionally, the current or wave motion exposed additional surface area, increasing the oxygen concentration.

Compared to warm water, cold water may store more oxygen. Summer heat can heat water to the point where it doesn't contain enough oxygen to support fish life.

The extra oxygen within the water is breathed by them. Once the temperature and oxygen levels are just right, a fish's digestive tract will start to work fast.

Warm water does not, however, have a lot of extra oxygen that fish require.

Fish become lethargic and inactive when the temperature rises too high and the oxygen content falls.

Many bodies of water form a thermocline during the hotter months. The ocean's surface layer and the cooler water underneath it are quite different.

It may be 15 feet deep at the water's surface. The temperature of the water may fall by 10 or 15 degrees below that depth.

Just above the convergence of the warm and cold water, there is high oxygen concentration. This may be the secret to achievement.

Related Article: Atlantic Salmon can Adapt to Warm Waters