A fish’s lifespan is directly proportional to the size of its body. Larger fish can live for a lot longer than smaller ones. For example, the Blue Marlin can reach a size of 12 feet and weigh over 600 pounds, while the average fish is only 3 feet and weighs less than 10 pounds. This being said, fish normally live for about three to five years, though they can live as long as ten years in some cases.
There are several factors that determine how long a fish can live. Genetics, environment, and diet are the main factors. However, the main factor that limits a fish‘s lifespan is its girth. When a fish‘s girth reaches a certain threshold, it becomes mechanically difficult for the fish to move around, resulting in decreased activity, which in turn causes the fish to age quicker.
Anatomy Of A Fish
A fish‘s anatomy is composed of a mouth, teeth, head, and body. The head, which is the part of the body directly above the mouth, contains two powerful and complicated brains – one on the left and one on the right. These brains control numerous organ systems in the body, such as the heart, muscles, and liver. The liver is the central processor of toxins and performs various functions, such as creating blood, filtering it, and producing bile.
The heart is a muscular organ that pumps blood throughout the body. Digestion, growth, and reproduction are controlled by the endocrine system, a complex system of glands that secrete hormones. Some of these hormones play a critical role in the development of muscles, while others regulate the functioning of the digestive system.
Why Is Girth Important?
The girth of a fish is a dimensionless measurement that refers to the overall width of the body, not the length. In general, the thicker the body, the longer the lifespan. This is because the body’s proportionately thickened and becomes less agile with age. In turn, this causes the fish to have decreased mobility, which in turn causes it to age quicker.
The thickness of the body is also important because it affects how a fish travels through water. Specifically, the thicker the body, the more buoyant or less dense it will be. Fish with low body density will float to the top of the water, and vice versa. This being said, a fish with a body density of 0.7 will float at approximately the same level as fresh water.
Fishes with higher body densities will be more difficult to catch because they are harder to see in the water. Low body densities are also associated with faster growth rates, larger adult sizes, and longer lifespans. For example, the Basking Shark’s body density is 0.9, compared to the Average Fish’s body density of 0.63.
How Does Fish Size Affect Its Lifespan?
When a fish’s girth increases, it undergoes physiological adaptations that increase its lifespan. These adaptations include a massive increase in growth rate, as the girth of a fully grown fish doubles its lifespan. Another important adaptation is the development of an efficient breathing system. The larger the fish, the more air it must take in, which again extends its lifespan. While fish breathe through their mouth, increasing their girth also causes them to develop more efficient nasal passages.
When Does Fish Size Matter?
Obviously, fish size matters when it comes to catching the fish. Smaller fish are easier to catch and consume than larger ones. However, even those of us who like to fish for fun have to admit that bigger is better when it comes to keeping fish. For example, when fishing for Bonefish, which can grow to be over 30 inches long and weigh over a pound, the chances of catching the fish are much greater if you use massive amounts of artificial lures or bait. This is because bigger fish require more food to sustain themselves, and the bigger the fish, the more food it requires. Artificial lures do the trick because they look like small fish and allow the fish to grab the bait, which in turn entices a larger fish to strike at the lure.
When Does Fish Size Matter Most?
When a fish’s girth reaches 10–12 inches, it becomes optimal for the fish to be released back into the water. Specifically, this is because the bigger the fish, the more buoyant it becomes. This reduces the efficiency of anglers who fish for fun because the more difficult it is to keep up with the rapid lateral movements of larger fish.
As a general rule of thumb, the bigger the fish, the shorter its lifespan. This is because bigger fish are more efficient predators and cause other wildlife to decrease their activity levels, which in turn causes the fish to age quicker. As previously mentioned, a fish’s girth is directly proportional to its size, which makes precise calculations very easy. The equation is simple: bigger = longer life.
Knowing how long fish live for and when it is best to let them go allows anglers to make better decisions about what kind of fish they should be targeting, where they should be fishing, and for how long they should be fishing. It also allows them to time their trips effectively, maximizing their enjoyment while also increasing their catch rates.