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Mysterious deep-sea creatures: Why do bottom fish avoid the deepest waters?
The diversity of deep-sea creatures is breathtaking, especially some bottom fish, and their survival methods and habitat choices are even more eye-catching. However, many bottom fish choose to live on the safe edge of the deep sea, refusing to enter the deepest waters. Why is this? Let’s delve deeper into the secrets of bottom fish and their survival strategies in the deep sea.
What are groundfish?
Demersal fish refer to fish that live and feed at the bottom of oceans or lakes. They usually live on the seafloor in areas made of mud, gravel or rocks. Bottom fish are different from pelagic fish that live in the water column. They mainly feed on organic matter or other organisms on the seabed. Bottom fish can be divided into two categories: strictly benthic fish and bottom pelagic fish. The former can rest directly on the seabed, while the latter feeds in the water layer above the bottom.
Habitat selection
The habitats of bottom fish vary, but they are mainly found in shelf waters and deep water slopes. Coastal bottom fish are common in shallow water areas within 200 meters, while in deeper areas, such as deep water slopes and sea ridges, deep water bottom fish are mainly found. These creatures are not commonly found in the deepest parts of the ocean, such as the abyssal plains or the abyss.
Why not enter the deepest sea?
Many scientists say the reason why bottom fish avoid the deepest waters is mainly related to energy acquisition and survival pressure. Biomass and food sources in deep-sea areas decrease rapidly with depth. In these areas, light cannot enter and photosynthetic organisms cannot survive, resulting in a significant reduction in the energy supply of the ecosystem.
Research shows that as depth increases, the biomass of plankton can drop to about 1% of the surface area.
Rather than struggling to survive in areas where energy is scarce, bottom fish choose to live in shallower areas where food sources are more abundant. This is their smart survival strategy, which not only helps provide a steady source of nutrients but also reduces the risk of facing the extreme pressures of the deep sea.
Biological characteristics of bottom fish
According to different survival needs, bottom fish also show significant characteristics in their physiological structure. For example, many bottom fish have flat bodies that help them rest more easily on the seafloor, while some fish have mouths that extend downward, allowing them to easily swallow organisms and organic matter on the seafloor.
Demersal fish in deep water usually have flabby body structures and low metabolic rates to reduce energy consumption.
The special adaptations of these fish not only help them survive in a competitive environment, but also allow them to focus on finding food on the bottom, using the resources of their habitat more efficiently.
The relationship between prey and prey
Bottom fish that inhabit shallow water often face strong predatory pressure, and their choice to inhabit deep water for safety is also related to this. These fish engage in minimal movement to conserve energy and use their superior camouflage abilities to blend in with their surroundings and avoid detection by other predators.
Some bottom fish, such as flounder, bury themselves in the sandy bottom and become part of their natural environment, allowing them to remain invisible when predators approach.
However, bottom fish also play an important role in the food chain. They are not only a food source for many predators, but also an important link in the flow of energy in the ecosystem. The food web in the deep sea is more complex, which makes bottom fish face more challenges in survival.
Protection and the future
With the increase in human activities, deep-sea fishing, pollution, climate change and other factors have threatened the survival of bottom fish. Recent research shows that many important commercially caught fish species in the North Sea have fallen "beyond safe biological boundaries". This makes the future of many marine species very challenging.
Marine scientists stress that to protect these fish we need to take steps to reduce overfishing and improve their habitats.
Against this background, we can’t help but wonder: How will the marine ecosystem evolve in the future? Can a balance be struck between protection and utilization to preserve our precious marine resources?
