Edited by: Isabel C.
Skillman, NJ
Fish migration, similar to the migration of birds or nomadic travelers, is one of the animal kingdom’s most remarkable behaviors. Their patterns, often spanning thousands of miles, are essential for the survival of many different species, as well as contributing to the overall fish life cycle. Understanding these complex journeys provide much insight into the balance of aquatic ecosystems.
The migration process
The mass transportation of fish from one location can extend up to thousands of kilometers! When it is time to migrate, fish will release hormones, typically to signify breeding season.
Why do fish migrate?
There are several reasons:
water temperature - When temperatures become too extreme, sometimes due to weather, fish look for more suitable waters.
water parameters - When the water parameters (alkalinity, chlorine, pH, etc.) do not fit a fish’s ideal conditions, they search for new waters with adequate water quality.
breeding season - When it is breeding season, fish navigate to breeding grounds to meet partners and reproduce.
newly-hatched fish - When fish fry, or baby fish, hatch, they tend to migrate in search of more suitable living grounds, typically to meet the other adults.
food - When there is a lack of food, fish will migrate to areas with more food.
salt-level needs - During the year, fish will have an osmotic process occur to them, which results in higher or lower saltwater requirements.
Fish migration patterns
The patterns fish take when they migrate vary between breeds. There are different types of migration as well, such as:
oceanodromous - Fish that travel from a sea to another sea.
potamodromous - Fish that travel from freshwater to another freshwater habitat.
anadromous - Fish that travel up from freshwater to the sea.
catadromous - Fish that travel down from freshwater to a sea.
Since bodies of water are large, fish rely on odors from their destination to find their way.
Fish, such as salmon, are anadromous migrators. This is possible because they can control their fluids even when moving from freshwater to saltwater, a process known as osmoregulation. Salmon are born in freshwater and move into seas and various coastal waters to spend their seasons.
Hence, such a process is a vital aspect of a fish’s life.
Naturally, fish migration can be affected due to:
geographic location - The patterns of fish journeys mainly depend on the locations of barriers and water quality. Different locations will also have their own individual currents, which will affect the direction of transportation of fish and their eggs.
spawning requirements - Some fish breeds require different levels of salinity for their eggs to hatch.
seasonal changes - Following the irregular changing of climate, some breeds of fish may need to find different waters for higher oxygen concentration or more suitable water temperature. Fish can detect periods of daylight to deem the most adequate time to begin migration.
However, the process of fish migration can be easily disturbed by the effects of external forces, including but not limited to:
man-made barriers - The process involves dewatering or siphoning water from a specified area and then assembling the built structure underwater, which is typically made of either soil, sand, or a stronger material such as concrete or steel. These barriers serve several purposes, such as preventing flooding, conserving delicate marine life, and observing weather hazards in advance.
greenhouse gasses - Due to an influx of greenhouse gasses, bodies of water absorb much more energy from the sun, resulting in warmer water. Ocean heat waves are known to cause habitat loss for underwater creatures. Melting glaciers also lead to slower ocean currents in some areas.
imbalanced water ratio - Water in a fish’s environment typically consists of a healthy mix of marine saltwater and freshwater. However, the ratios of these two different types of water may be imbalanced due to melting glaciers in colder regions.
pollution - Global warming and increased littering have led to a rapid growth rate of bacterial blooms in water, disbalancing water parameters and, as a result, may make it more difficult for fish to intake oxygen.
What can we do?
Although our actions can be harmfully impactful in many ways, they take place because they are advantageous in some way or another. Luckily, there are less harmful ways we are able to address concerning problems such as destructive flooding, overfishing, and obstructing chemical spills.
Protection against flooding
Flooding and dangerous weather lead to often cataclysmic results, and we tackle related issues by building sturdy barriers. While these barriers protect our delicate coastal areas, we need to consider the importance of letting some intricate fish processes be, especially if the results of our actions are permanent. Another issue with flood barriers is that they are extremely vast and tall in order to prevent floods. Hence, we can build temporary flood barriers instead. That is, we can use portable barriers, such as gates, inflatable floodwalls, and sandbags, that can be removed after deluge. While not as protective, they are a more eco-friendly choice and also do am efficient job of impending ruination.
Conserving aquatic life
For years, overfishing has been a severe problem throughout the entire world. Delicate aquatic creatures are taken from their natural habitat and sold for human consumption. Other ways the populations of organisms may dwindle are if they are exposed to environmental hazards, such as pollution. It is difficult for some organisms to recover from their population dent. Therefore, aquatic-life advocates build walls to defend the population. To ensure that the lives contained within the barriers thrive, the barriers often span several miles. Some substitute strategies to protect the environments of these organisms are:
replanting mangroves and seagrass - These aquatic plants protect areas of water against filter pollutants.
wastewater treatment - Upgrading wastewater treatment plants to prevent untreated sewage and other industrial waste from entering water bodies can help maintain cleaner water for everyone!
sustainable fishing - Enforcing catch limits, banning harmful fishing methods, and using more selective fishing weapons and gear can reduce the more destructive aspect of fishing.
ecosystem-friendly infrastructure - Wildlife corridors, such as fish ladders and water tunnels, allow species to move freely between habitats while adding some protection to areas.
Littering
Preventing littering is not as simple as just not tossing non-reducible synthetic materials in natural landscapes. Throwing our trash in dumpsters will inevitably end up in landfills. Therefore, recycling is an excellent alternative; as plastics hold worth, the vast majority end up being recycled. However, it is crucial to ensure that the materials you are recycling are clean before placing them in your bin(s), because contaminated items are less likely to be selected for recycling.
Another alternative would be to invest in reusable items instead. In other words, rather than purchasing plastic bottles, it would be better for the environment to buy a sturdy water bottle that will last for years.
Fish migration is complicated
Like all other phenomena, the complex journeys that these classically “simple” organisms take on are extremely fascinating. The entire process requires excellent natural instinct. More research will be done on this topic for years to come!
To ensure that fish can migrate, we need to make sure that bodies of water are clean and mostly undisturbed. This involves maintaining healthy ecosystems through replanting aquatic plants and preventing the construction of barriers that block migration routes.
Anyone can help by participating in local clean-up efforts, supporting conservation initiatives, and more!
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