Tuesday, June 11, 2013
Keeping Marine Diversity High: A Marine Reserve Need
Keeping Marine Diversity High: A Marine Reserve Need
Globally, marine resources are being depleted, and there is a broad recognition that the oceans and their living resources are under stress (Paddack and Estes, 2000; National Research Council, 2001). An increase of overfishing of marine fish stocks has left countless damaged marine habitats. Traditional forms of fisheries management have historically proven to be unable to prevent crash of the fisheries they are meant to sustain (Halpern, 2003). One controversial method of protecting these fisheries is the establishment of marine protected areas (or MPAs) in which fishing is restricted or prohibited in certain areas. The role of marine protected areas is to both directly conserve marine resources (such as fish) through reduction in mortality of target species through the actions of humans (fishing, mining, shipping) and to indirectly aid conservation through a reduction in incidental impacts caused by these activities (Davies et al., 2012).
Current MPA locations as of 2008
Although marine protected areas are used to restore marine ecosystems as well as enrich neighboring ecosystems through increases in the number of fish larva being produced, some argue that the establishment of too many of these areas will simply forces fisherman into different, perhaps more easily over-exploitable, areas (Tyler et al, 2009; Mireles et al., 2011). Reserves are established in order to protect those species whose home range is centered around the reserves conserving the marine life within the reserves boundaries as well as increasing the areas productivity in regards to adjacent areas through “spillover” (Kendall and Picquelle, 2003; Marine Resource Program 2012).
A newly constructed marine reserve in the local Oregon waters, Redfish Marine Reserve, is under current inspection on its success in restoring species diversity back into local waters after a drastic decline during the establishment of a life fish-fishery. Prior to becoming a marine reserve the area was subject to a high demand live fish- fishery, in which fishes (the majority of which were various species of rockfish) were taken from the area while still alive to be sold on the market. To avoid barotrauma and reduce mortality fishes were only taken from depths of 60 feet or shallower (Summers, 2001). This created an artificial depth refuge, where fishes below the desired depth experienced reduced fishing pressure in comparison to fish inhabiting the shallower areas. The depth refuge stimulated an artificial selection against rockfish and is one of the causes of lowered biodiversity. Specifically, many species of rockfish were removed from the ecosystem due to over fishing. There are over 56 rockfish species found in the Pacific making up for a good part of the marine diversity in the oceans. The rockfish are also one of the longest living fish on earth with ages surpassing 100 years. Rockfish serve as one of the most important and heavily utilized groups of commercial and recreation fishes occurring off the coast of California. Without the rockfish, human fish consumption will decrease as well as biodiversity of the ecosystem since rockfish are a keystone species in the marine benthic environment.
It has been demonstrated that when fishing pressure is applied to a community, it can decrease the maximum length of the fish in the community (Jennings et al., 1999). It has also been shown that when fishing pressure is limited to a certain depth (which in the case of the Redfish Rock Marine Reserve is 60 feet) there is an effect on the richness and relative abundance of commercial species, even after correcting for habitat differences (Tyler et al., 2008). This depth refuge effect has been observed in multiple reefs where fishing depth is restricted, with the fishing having a significant effect on commercial fishes in unprotected areas as compared to protected areas (Tyler et al., 2008; Goetze et al., 2011). It has been shown on multiple occasions that marine protected areas are an effective way to increase the density, organism size, biomass, and age in targeted populations of both fishes and invertebrates (Paddack and Estes, 2000; Halpern, 2003; Mireles, 2011). Some reserves have been shown to improve habitat quality and species diversity. All of these benefits may additionally spill over in adjacent areas through fish movement and the dispersal of eggs and larvae (Halpern 2003, Mireles et al., 2011; Davies et al., 2012).
There has been particular interest in establishing marine protected areas that target populations of rockfish. Rockfish are particularly vulnerable to overexploitation due to their late maturation, stochastic recruitment, slow growth, limited movement and multispecies aggregation (Paddack and Estes, 2000). Due to the relative vulnerability of rockfish, it is hoped that marine protected areas could be an effective way of preserving threatened rockfish populations. While there is an abundance of promising findings on the effectiveness of marine protected areas, some have found that marine protected areas may not be the solution to all of the world’s ocean conservation problems (Allison et al, 1998). Variation among reserves will always exist when examining how marine reserves affect biological measures (Halpern, 2003).
Currently, fish stocks are being exploited and almost depleted to compete with the increasing population of the world. If nothing is done to protect fish stocks, we will lose countless biodiversity in the marine ecosystem and even have a stronger shortage of food in the long run. To protect fish stocks and marine biodiversity, the establishment of marine reserves and marine protected areas is a strong and positive solution. By establishing these reserves, we can secure a safe haven for fish species to repopulate and grow. Not only will this help local stocks, but since the marine ecosystem is so interconnected there is a high chance for leak over. Due to currents, larval stages of marine life are known to spread to other nearby areas and thus populating those areas. Problems with marine reserves are that they are expensive to establish and maintain. Reserves place a economic stress on local fisherman and other buisnesses that depend on fishing as the major source of income. However, marine reservers are designed for improvement in the long run. Initially, the results will not be idea, but over time stocks will flourish and fishermen and other businessman can even profit more off abundant fish stocks. Not only this, but it will also help maintain marine biodiversity because rockfish are an old living species with multiple species in that group. They are also a keystone species marine ecosystem and a major source of food for humans. Establishing more reserves, maintaining the current reserves, and increasing awareness for reserves is a key step to maintaining a healthy and thriving marine ecosystem and biodiversity.
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