OIL PRESENCE IN FISHERIES

When one thinks of an oil spill in the ocean they rarely consider that it could affect fisheries, as they are controlled environments. Despite this fact, efforts still have to be made to protect it. In fact these areas may need more protection as there is valuable equipment housed there. Unlike the open ocean where fishes can swim away from oil this is not so for fishes in fisheries. They are usually in a restricted space so escape is not really an option. Fish there are also subject to taint as well as polycyclic aromatic hydrocarbons as fish in the ocean. This means they also buildup build up toxic substances in their tissue, experience reproductive problems, mutations and heart defects. However the fish are easy to monitor as they are at a particular location. Therefore the contaminated fish can be given time for the contaminants to naturally be removed from their tissues (ITOPF, 2004). This process is called depuration. Fish are constantly monitored for contaminant concentrations and when an acceptable level is reached they can then be used commercially. The limitation of this depuration time period is that the fish may grow larger than the required size for sale. Apart from commercial use there are fisheries for recreation that also support the economy for example there is the presence of bait and tackle shops there as well as other businesses (Upton, 2011).

                                   

fig 1 taken from http://spacecollective.org/matthewspencer

fig 2 taken from http://www.constantinealexander.net/science/page/69/

The pictures show how fish is reared in a controlled environment. The fish here depend on their fish farmers to supply food as opposed to hunting for themselves. Also they are safe from predators so overall this environment provides very few stressors. However it is easy to see how floating oil can enter these areas as they appear very unguarded. Fig 1 shows an Aquapod which has an innovative design and is suited for rough conditions as it is dynamic due to suspension cables and not being attached to other pods. Fig 2 show fish rearing cages arranged close to each but with enough space for small boats to pass through. This access allows for feeding to be done more efficiently.   

It is difficult to know how much an oil spill has affected a fishery as other external factors come in to play. Some include climate, natural population decline and increased fishing. Also conditions at the fishery before an oil spill may be unknown so its impact is not certain. Therefore changes in fish populations can result from a single or a variety of reasons. One of the greatest impacts known to be caused by oil was experienced by fisheries in Louisiana. Fisheries there supply 40% of the U.S. seafood supply. The effects of the Gulf of Mexico oil damaged fisheries to the extent that reporters (Matthew Biggin Venice et. al, 2010) of Reuters described it as a “Fishery Disaster”.

There is various equipment utilized at fisheries, these include lift nets, buoys, cast nets and fixed traps. All this surface equipment is susceptible to floating oil and as a result can become contaminated. Subsurface equipment can become contaminated if it is lifted through the surface coming in contact with oil there. Contaminated equipment can contaminate fish; therefore it must be cleaned, in some cases it must be dismantled before cleaning. The cleaning process involves the use of a pressure washer to remove oil. If the cost to clean exceeds the cost of new equipment the latter option is chosen. Booms and barriers are used to protect fish gear by containing floating oil preventing its spreading. It works well in calm waters but is not effective in more harsh conditions as waves may carry oil over the boom (Tech- Faq). On the other hand a protection method for the fish is the placing of heavy plastic sheets around their cages and securing it at the base. This is so that currents cannot cause the plastic to be removed exposing fish in the cage to oil. Fish tanks on shore as the name implies supports fish. The tank is linked to the sea via a pipeline and in cases where dispersed oil is in the water column the line is closed. This dispersed oil can be carried into the fish tank contaminating the pipeline on the way. This could result in the loss of the entire fish stock housed. 

Overall fisheries are very important to economies throughout the world so it is important to protect it. We as citizens can do our part by limiting the amount of oil derived substance carried to the ocean as run off. It is important to remember that the ocean is where all waterways ultimately lead to.



References

Harold F. Upton. The Deepwater Horizon Oil Spill and The Gulf of mexico Fishing Industry Retrieved from https://www.fas.org/sgp/crs/misc/R41640.pdf

Matthew Biggin Venice, SteveGorman and Pascal Fletcher. Factbox: Gulf Oil Spill impacts, fisheries, wildlife, tourism, Reuters Retrieved from http://www.reuters.com/article/us-oil-rig-impact-factbox-idUSTRE64T23R20100530

Tech-Faq. How Do Booms Work? Retrieved from  http://www.tech-faq.com/how-do-oil-booms-work.html

ITOPF 2004. Effects of Oil Pollution on Fisheries and Mariculture, Retrieved from  https://www.scribd.com/document/191508407/Itopf-Oil-Spill-Effects-on-Fisheries