One of the major contributors to fish decline is habitat loss and degradation, relied on for spawning, travelling and feeding. The potential loss of an entire habitat poses a serious environmental and ecological threat, as one habitat supports thousands upon thousands of species. From 1953 to 1977 in the USA, over 327,000 acres of estuarine wetland disappeared. Of this, 55% were lost to coastal erosion and 45% to urban development.
Coastal and estuarine habitats are very important in maintaining healthy fish stocks. Tidal marshes provide nursery and foraging habitats for a variety of marine life. Plants found here provide nutrients to the surrounding ecosystem.
Deep sea sponges and corals are some of the vulnerable habitats in the North Pacific. There are very few management measures in place to protect them. Coral reefs are the most diverse communities in our ocean where many of them have grown up over hundreds, sometimes thousands of years. Their intricate structure provides animals with refuge from predators, breeding sites and endless feeding opportunities. Coral reefs are under threat by fishing practices. Bottom trawling uses fishing gear that tears up vulnerable sea floor habitat that takes centuries to recover.
Dynamiting is another practice used commonly as it is an effective way to kill all nearby fish. However one blast will completely flatten a patch of reef. In South East Asia 80% of the reefs are in danger of dying or are dead.
Approximately one-quarter of all fish caught and brought on board fishing vessels each year are thrown back into the sea, usually dying or dead. FAO estimated that commercial fishing vessels annually throw back on average about 27 million tonnes of unwanted fish.
Along with these unwanted catch, many other marine animals are being captured or killed in fishing operations. Ten of thousands of albatross are killed each year in the southern hemisphere ocean by long line fishing boats. Driftnets that are used for targeting one or two commercially valuable species indiscriminately kill millions of marine creatures. Marine mammals are frequently killed in large numbers in trawls, set nets and purse seine nets.
The fisheries industry is made up of two major groups, fishers and large scale mechanised fishing vessels. Directly and indirectly these employ about 200 million people worldwide. A continual decline in major commercially valuable fish stock would lead to the collapse of the fishery industry and the subsequent loss of employment and livelihood.
The current annual world fish harvest trend is over 80 million tonnes per year. The demand is expected to increase to 110 to 120 million tonnes in 2010. This marine demand is at great cost not only to the environment and marine biological diversity but perhaps for world food security.
Aquaculture was thought of as a solution to overfishing. The concept of controlled fish farms at first glance seems a positive one, however it may actually be contributing to some of the problems it was intended to resolve. Some of the main species that are farmed through aquaculture are salmon and shrimp. As these species are carnivores, in order to provide food for the unnaturally high volumes in farms, the ocean’s resources are being tested further. This type of fish farming can also cause unnatural pesticides, antibiotics and chemicals to be released into the ocean as well as a higher concentration of natural fish waste than is normal. Non-native species are introduced into farms to meet consumer demands and can escape into surrounding waterways upsetting the food chain.