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Measure or weigh your fish??

Why Measuring Fish is More Accurate than Weighing Them.

While both length and weight are common metrics, measuring length is widely considered more accurate and informative. Here’s why.

Indeterminate Growth: A Key Factor

Fish exhibit a biological phenomenon known as indeterminate growth, meaning they grow continuously throughout their life. This characteristic makes length a crucial indicator of a fish's actual size. Unlike mammals, whose growth is determinate (they stop growing after reaching adulthood), fish keep growing, albeit at slower rates as they age. Therefore, a longer fish not only represents a larger specimen but also an older, more experienced one.

Weight: A Fluctuating Measure

Weight, on the other hand, is not a reliable size indicator due to its variability. It fluctuates significantly based on several factors:

1. Feeding Patterns: Fish can gain or lose weight rapidly depending on their access to food sources.

2. Spawning Cycles: Many species experience weight changes during spawning seasons.

3. Seasonal Variations: Time of the year affects a fish’s feeding habits and metabolism, influencing its weight.

This variability means a fish's weight at any given time is more an indicator of its recent conditions and health, rather than its true size or age. This can obviously be an interesting metric for example for fishery owners, scientists and others.

The Challenge of Catching Larger, Older Fish

Larger, older fish are often more challenging to catch. They have experienced more, including previous encounters with anglers, making them warier and more elusive. Hence, a longer fish should be a more prized and respected catch in the angling community, symbolising both the fish's survival skills and the angler’s skill.

Handling and Conservation Concerns

From a conservation perspective, measuring length is less invasive and harmful than weighing. Weighing a fish, especially larger specimens, often requires more handling and time out of the water. This can be particularly stressful for predatory fish like Perch, Zander or Pike, which are more susceptible to longer periods without oxygen when removed from their aquatic environment. Cyprinids, like carp, though more resilient, still benefit from minimal handling. Quick measurement ensures the fish is returned to the water promptly, promoting better survival rates post-catch.

For anglers, time is of the essence when handling a catch. Measuring a fish is generally quicker than setting up a scale, especially in field conditions. This time efficiency is crucial for the fish's health and increases the angler's ability to continue fishing with minimal interruption.


In summary, measuring fish length is not only a more consistent and reliable indicator of size but also better for the fish's health and conservation. It reflects the true nature of a fish's growth and life, providing a more accurate story of its journey.

Tight lines,

Momo SFL


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