Overfishing is one serious threat to fish survival in their ecosystems. People have hunted many species of fish and other marine mammals to extinction in the past, so it is not an abstract concern. Overfishing can also have a domino effect on the entire ecosystem. When one species of fish disappears, it also affects its predators and prey. Demand for top predators, like sharks, is also sharply reducing the supply of some of the ocean's largest keystone species. In addition, it can damage the habitat itself, as overfishing harms kelp forests, coral reefs and sea grass beds.
Additionally, commercial fleets have pushed overfishing to a new level. These huge ships equipped with the latest technology catch more fish than ever before, and also ensnare unwanted species. For some fisheries, unintentional catches and discarded species make up as much as 80 percent of their hauls. These unsustainable practices thus threaten all species, not just commercially popular ones, as enormous trawling nets catch everything in their path.
Overfishing is a problem all over the world, from the shores of Alaska to the Caribbean. Fish can only be protected effectively through international agreements. The solution will likely require a multistep process, such as creating designated marine reserves and identifying alternative sources of protein. On a greater scale, countries could implement family-planning strategies in densely populated coastal areas that demand the most seafood.
Climate change, if left unchecked, will have many serious consequences, including depleting the fish population. According to the United Nations, rising amounts of greenhouse gases threaten a full three-quarters of vital fishing waters, which more than 2.5 billion people depend on for their livelihood. Greater amounts of pollution are taxing the ocean's ability to filter out toxins, while rising carbon dioxide levels are making water too acidic for fish to survive.
Climate change is of course an issue that goes beyond the survival of fish in their ecosystems. However, many steps, like capping carbon output and looking for renewable sources of energy, will also benefit fish under threat. Reducing the pollution that enters the ocean will directly benefit fish and make the water cleaner for all species.
There are many miscellaneous things that threaten fish survival in their ecosystems. A new dam can block salmon spawning routes upriver. An invasive species introduced to a lake can destroy the local population. However, fish are a very diverse and adaptable group of animals that have survived for millions of years. With some human help, they should be able to continue to do so well into the future.