Coral reefs began declining when more and more large fish, turtles and seals were killed, species which in the past had frequented coral reef systems. The "reduced visits" have led to a reduced number of herbivorous fish and "added nutrients from pollution" all of which result in seaweed overgrowth and destruction of the reef (Houlder, 2003).
Methods for Addressing Over fishing
The government has encouraged many fisheries and local agents to develop strategic plans for combating the problem of deep sea over fishing. In particular much attention has been spent on an 'ecosystem' approach to fishery management which is adaptive, geographically specified and works to balance diverse objectives (Shotton, 2003). An ecosystem approach aims at "conserving the structure and function of marine ecosystems and the fishery resource" (Shotton, 2003).
Longlines can be weighted so that bait sinks faster, and hooks can be set at night, thus reducing the impacts on unintended species including birds (CSI, 2003).
Studies suggest that over fishing is impacting deep sea fishing populations and ecosystems in many negative ways. Unless firm and well thought out actions are developed to provide fishing communities with some relief, the entire marine ecosystem as a whole may change dynamically in the next decade, with unforeseen consequences.
Some ecologists have noted that "there is no place in the ocean left where there are undisturbed fish stocks... The whole ocean has been transformed" (Harder, 2003). In order to realize improvement, governments need to work together on a global level to change the way the activities of deep sea fishing are managed. One method of improvement may depend upon the creation of protected marine areas where fishing is banned, and reduced fishing permissions in other areas where the worst impacts of over fishing is evident (Harder, 2003).
Typically the goal of a fishery is to produce a 'sustainable yield' which happens when fishing stock is kept at approximately half of its natural size (Harder, 2003). At this time, fish generally tend to grow and reproduce more rapidly than in an ecosystem that is more crowded (Harder, 2003). However for most species that are impacted by over fishing, the marine biomass is decreased beyond the halfway point, so that a sustainable yield is not possible, because fish do not have the opportunity to replenish themselves adequately (Harder, 2003).
The consequences of over fishing on the environment are devastating. Over fishing impacts marine ecosystems in many ways, both directly and indirectly. Among the obvious consequences of over fishing which include the destruction or potential extinction of certain species, over fishing may also result in increased pollution and habitat destruction. Many species are also changing in composition due to over fishing practices. The long-term environmental effects of composition changes will only be determined with time.
According to research, more than 90% of large predatory fishes have been decreased to severe levels in the deep ocean, including tuna and swordfish; in addition industrialized fisheries have reduced many marine community biomasses by as much as 80% (Harder, 2003). The reduction of predatory fishes also impacts the community in many indirect ways, including the over breeding or population of certain populations as compared with others.
Over fishing has had many detrimental effects on the environment, including destruction of natural habitats, increased pollution and extinction of species, the full effects of which might not be realized for many years to come. Governments are considering establishment of marine protected areas as a first step in combating the devastating consequences of over fishing in the deep seas. Without immediate intervention it is possible that the environment as a whole will suffer severe consequences as a result of continued over fishing in the next decade.
Clarke, T. (September, 2003). "North sea fish have shrunk." Nature Science - European
Cetacean Bycatch Campaign. 1, December 2004: http://www.eurocbc.org/northsea_number_small_fish_increased_due_to_overfishing_25sept2003page1290.html