Environmental impacts of deep sea overfishing on marine ecosystems

¶ … Sea Fishing

Environmental Effects Over fishing Deep Sea Fisheries

The environmental impacts of deep sea over fishing are many, including detrimental reductions in fishing species/populations. Over fishing can result in a modified community species composition and reduced genetic diversity through "selective targeting on species and particular size classes" (Shotton, 2003).

Over fishing has the greatest impact on the environment at large. Reductions in genetic diversity and in species or populations alter the composition of habitats and can impact the environment in many ways. Coral reefs are one example, facing extinction because of a lack of herbivorous species to keep algae in check.

The equipment utilized by deep sea fisheries may also impact the environment in a negative way. Not only are habitats and ecosystems destroyed as a result of deep sea fishing, but entire species are on the verge of distinction, while other non-target species have also been impacted in a negative manner. The research below will describe the environmental impacts of deep sea fishing in greater detail.

Consequences of Over fishing on Environment

By far the most obvious impact of over fishing is the devastation of ecosystems and marine life communities (Simpson, 2001; Dayton, Thrush, Agardy, & Hofman, 1995). Over fishing may impact other species directly by simply killing available populations, or indirectly, via increased "incidental mortality" that occurs as a result of lost or abandoned gear, and destruction of the existing sea bed due to the equipment used by fisheries including trawls, dredges, dynamite and abandoned gear (Shotton, 2003). At any time that a species is drastically reduced the ecosystem and subsequent environment as a whole is affected in a negative manner.

Over fishing also has many indirect effects on marine ecosystems including pollution, noise and air travel pollution and habitat destruction (Shotton, 2003). All of these effects can also affect an economy, which must work to restore the ecosystems most affected by over fishing, and work to find new ways to supplement the populations that have been dying off.

Destructive fishing practices are common in environments that have been over fished. Bottom trawls are an example of how over fishing can destroy environmental habitats. Bottom trawls are equipment used to catch "groundfish" and other crustacean species including crab and crawlers; they are considered one of the most destructive forms of equipment because they "directly threaten species richness and biodiversity" and also catch many non-target species in addition to the species for which they are intended (CSI, 2004).

Deep sea corals and sponges are among the habitats that are often destroyed by bottom trawls (CSI, 2003). Any bottom dweller will be indirectly affected by the use of heavy equipment that invades the natural habitat (CSI, 2003).

Another common way that over fishing impacts environmental destruction is via use of long line fishing, where a line up to eight miles long is set out, consisting of baited hooks. These lines catch many unintended species as well including birds and turtles. Researchers estimate that as many as 180,000 birds die as a result of these hooks each year, and that many of the birds caught on these hooks are rare or endangered species (CSI, 2003). Still other deep sea fisheries practices that have been identified as hazardous include the use of flash fishing and the use of sodium cyanide, which taints the fish it captures (CSI, 2003).

As a result of over fishing, the size of fish in the deep sea has also decreased over time (Clarke, 2003). Studies show that fish in the North Sea have gotten smaller with time and over fishing has been cited as a cause (Clarke, 2003). According to ecologists from the Netherlands Institute for Fisheries Research, fish that are smaller than 30 centimeters in length are increasing in numbers (Clarke, 2003). The idea is that over fishing of larger fish including cod and hake allows more small fish to survive. Thus the entire composition of many marine ecosystems is changing. Researchers and citizens alike have good reason to be concerned, as the long-term consequences of habitat destruction and the change of ecosystems is unpredictable and uncertain at best.

Houlder (2003) notes that coral reefs are in danger of extinction if immediate action is not taken to preserve and protect them, due primarily to over fishing and pollution. The Great Barrier Reef for example, considered the best protected reef, "is nearly a third of the way toward extinction" and in other places including Jamaica corals are all but extinct (Houlder, 2003).

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).

Conclusions/Analysis

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.