Saltwater fish, also called marine fish, are fish that live in seawater. Saltwater fish can swim and live alone or in a large group together, this is called a fish school [saltwater fish are very popular among deep sea fishermen and aquariums all over the country. Saltwater fish are very commonly kept in aquariums for recreation. Many saltwater fish have also been caught for food.   Fish that live in the ocean can be carnivorous, vegetarian, or omnivorous. Many herbaceous diets contain algae. Most saltwater fish eat both macroalgae and microalgae. Algae can never be eaten in any of the salty water of meat eating under any circumstances. Carnivores diets include shrimp, plankton, or tiny crustaceans.  Salty aquariums are a multi-million dollar industry in the United States. About 1 million marine fish are imported into the United States each year for aquarium use.
About 2,000 different species of saltwater fish are imported and used in captivity.  In many cases, fish used for maritime trade are collected using harmful techniques such as cyanide. The way people are trying to protect the coral reefs is to capture and breed marine fish. Captive breed fish are known to be healthy and have the potential to live longer. Captive-bred fish are less susceptible to disease, as they did not come into contact with the wild and were not harmed during the shipment process. Captive fish are already accustomed to aquarium habitat and food.
There are many different elements that m
ake up the habitat of a marine life. Some of these are water temperature, quality and quantity of water (flow and depth). Other factors that may also contribute to saltwater fish habitat are pH levels, salt levels, and alkalinity levels. There are other spiritual features that contribute to the habitat that include physical materials such as rocks, rock flesh and sand or plants like algae, water plants and the amount of salt. Certain fish live in a particular habitat based on what they eat or what cycle they currently live in, another thing is the amount of salt in the water in that particular place. Another issue is that some marine habitats are not technically in the ocean and are called estuaries, areas that form a mixture of sea and river salt water and create a separate habitat for different species of fish and animals to live in freshwater.  [6 ] The ocean is as large as a whale and is home to microscopic marine organisms such as phytoplankton. However, the vast majority of marine life that humans come in contact with is simple non-aquatic fish. Saltwater fish can live in the deepest depths of the ocean where no sunlight can penetrate, but they can also survive on the surface of the water.  Marine fish face many ethnographic threats.
Common human-induced threats include overfishing, pollution, habitat loss and destruction, climate change and endangered species. The above threats directly and indirectly affect all marine ecosystems. As negative human populations grow at a significant rate, the threat trend will continue in marine ecosystems. The power has stopped moving fish is one of the most popular foods in the world and the growing human population continues to grow and it will continue to grow. The global seafood market value has increased by 15% from 2001 to 2020 and is expected to increase further by 2023. ] Although it provides food for many people, the global marine market poses a major threat to fish biodiversity. Bycatch is defined as the direct effect of overfishing and the unwanted capture of various marine organisms while fishing in the industry. As a result, the fish die after catching and discarding different species of fish. Bycatch data is often vague and not well recorded, but it is estimated that the United States alone spends 1-2-22% of their year. 
The mesopredator release hypothesis is one of the indirect effects of overfishing, often also known as “fishing on the food web”. This phenomenon means that fishermen reduce the large top predatory species as well as the medium-sized predatory species increase in size and act as top predators in the food net.  It affects the food web in marine environments and disrupts ecological balance and can cause trophic cascades.
Bluefin tuna: It is generally known that the number of profitable fish stocks like bluefin tuna is declining due to high demand. According to the IUCN Red List, the Pacific, Atlantic, and Southern bluefin tuna are classified as vulnerable, endangered, and critically endangered due to over-exploitation . Ocean Whitetip Shark: According to the IUCN Red List, this species of shark is considered critically endangered due to its market value in marine food. Their rapidly declining population is due to people fishing too much for their wings. Due to the size of the wings these sharks are used in a popular species of shark fin soup. All sharks are used for shark fin soup but some species of sharks are preferred over others because of their larger wing size. Great White Shark: This popular species of shark is listed as weak on the IUCN Red List because its wings are commonly used in shark fin soup and encourage people to harvest their wings.Many examples of shark species threatened by human service due to shark fin soup are the Great White. Since the early 2000s, the huge population of this class has declined due to their high demand for wing, gill raker and liver oil.  Atlantic Code: This fish is historically abundant in the waters off the coast of New England. This fish is a popular choice among people due to its low fat content and dense white flesh. Now considered weak,  their populations have both shrunk dramatically and their distribution has shifted from north to south due to overfishing.  Cage aquaculture Pictures of cage nets located in Australia Aquaculture is defined as the cultivation of aquatic animals in a controlled environment for the purpose of providing food and resources for human beings. Aquaculture can occur in both marine and freshwater environments, but this saltwater fish leaf will only cover the effects of marine fish aquatic life in this entry. The growing global demand for fish has contributed to the growth of aquaculture. Due to the depletion of many wild fish labor, aquaculture is the fastest growing food production system that contributes about 50% of the world’s fisheries.  It is said that aquaculture, especially caged aquaculture, has a significant negative impact on the surrounding environment. Cage aquaculture involves the rearing of aquatic animals in natural water sources enclosed in mesh / net cages that allow the water of the surrounding environment to flow freely and out. Cage aquaculture in the marine environment has been particularly controversial because it has affected the surrounding ecosystem, affecting the wild marine fish population. The main effects of cage aquaculture are the reduction of water quality from fish drainage, the high risk of genetic contamination of wild labor due to protection from aquaculture cages  and the possibility of introducing aggressive species if the fish are reared. Fish sewage is a combination of fish feed, fecal material and antibiotics that accumulate from the fish that are being farmed on the sea floor and in the water column. Not only is it harmful to wild fish stocks, it also threatens the life of marine plants that are often the food source of wild fish stock. Fish waste is harmful because it pollutes the surrounding ecosystem and can cause problems such as eutrophication, parasitic and disease infections in wild populations, and developmental abnormalities in nearby wild fish.  Genetic contamination of wild fish populations is a common risk facing aquatic versions of cages. For example, there are many scientific papers that have examined the effects of Atlantic salmon escaping from their enclosures and interacting with wild populations. Due to the difference between artificial and natural selection, black salmon have lower fitness (lower survival rate and reproductive success) than wild salmon.  But will change the genetics of wild stock. This will reduce the fitness features of the wild stock, which is a serious threat to them.