Throughout the world’s oceans fish catches are declining, vast numbers of marine animal populations have been wiped out, while habitats and communities have been irreversibly damaged or destroyed. It’s becoming more evident that marine reserves and marine protected areas (MPA’s), conserve an area’s population and habitats by limiting or preventing human activities in the area, and via ‘spillover’, can sustain, replenish or even increase biomass of nearby fisheries, nullifying the fisheries initial losses when the MPA or reserve was created. Increased efforts are now being focused on identifying key areas and creating the most successful configurations.

Short term

From the initial proposition of the creation of a marine reserve there is need to please multiple and opposing schools of thought on the subject. The greatest opposition against the creation of a reserve usually come’s from fishermen. Fishermen tend to focus on the short term consequences of creating a reserve, this is the period just after the reserves creation, in which the fishermen but not the fish stocks, have time to respond (1). Their main concern is the reduction of fishing ground and fish stocks accessible to them (3). However the intensity of this opposition varies greatly depending on multiple factors.

The main factor in altering the fishermen’s opposition and their willingness to pay (WTP), is the fish stocks in the area. When the proposed reserve sights have a high fish biomass in comparison to the surrounding area and fishing sites, opposition is high. However highly skilled fishermen tend to oppose the creation of a reserve more so than low skilled fishermen, and this is then reversed when the reserve contains lower fish stocks than the surrounding waters (1). Low and high skill fisherman only have similar views on WTP when fish stocks are equal, though all of these views can be magnified depending on the fish prices at the time (1).

The creation of a reserve always reduces short term income for fisheries, however high wages outside of the fishery reduces the opposition to reserves in both the short and long term (1,3). If wages are high outside the fishery fishermen are more likely to leave, this reduces the pressure on stocks and lessens the fishing effort. This is better for conservation efforts, but also can be good for fishermen due to a reduction in competition. This means that reserves should be easier to set up in areas with high non-fishery job opportunities. Fuel costs also alter opposition in a similar way to job opportunities.

There is also the social sciences side of the fishermen’s opposition. If they value the fishing lifestyle what the site would be worth to them would increase. It’s been found that strong emotional attachment has similar effects to having a low non-fishery wage, family life, the fishing culture and relationships with friends will also have similar effects (1,11).

Long term

The main arguments of scientists and researchers is to look towards the long term factors that can benefit all, though fishermen are usually more reluctant to embrace this view. Scientists want to provide the species the best opportunity to repopulate, however they have to plan for spillover effects, and find a balance between conserving a species by reducing spillover and maximizing spillover to rebuild surrounding populations and replenish the surrounding fisheries (2,5,6,8).

Studies show that creating singular reserves to protect a species, the reserve must be the average larval and adult dispersal distance without input from alternate sources. However this can be upto ten’s or hundreds of kilometers (7,8), few are able to create reserves this large and very few have (5,12). Alternatively, a number of countries have created networks of marine reserves (5). Combining multiple smaller reserves can provide a greater impact (4), these multiple linked reserves maximize larval exports to other reserves increasing the likely hood of being self sustaining. Networks can also be used to protect multiple habitats due to a species movement and different habitats used throughout their life.

When placing a reserve it has to be kept in mind what stage of the species needs to be protected, throughout a species life it may move to differing habitats depending on its stage of life (5,7). Using a network of marine reserves rather than one large one, reserve’s can cover multiple habitats possibly protecting a species throughout its life (5,8), or a network can be used to protect a whole ecosystem from damage and natural disasters by acting as back up reserves to help replenish any damaged by a natural disaster (5).

Protecting spawning grounds will benefit any species (5). However while it may be one of the few ways reserves can protect long range pelagic fish (billfish, tuna and oceanic sharks), low to medium range fish spillover can reduce the number of spawning adults enough so that the reserves larval input isn’t enough for it to sustain itself or help maintain surrounding waters (5). Fish with a lower range benefit more from a network than pelagic fish because of inter-reserve dispersal, this will further protect fish from nearby fisheries and increase larval dispersal between reserves (5,7-9). Maximizing larval dispersal is a key design in reserves, this is because when larvae leave reserves they are too small to be caught and are relatively unaffected by human input (excluding pollution), they can successfully move to another reserve were they can survive to adulthood just as easily as in their natal reserve, however by leaving the reserve as adult fish are they are then at risk of becoming part of nearby fisheries (5,12).

Having a network of reserves also benefit fisheries by maximizing spillover. Spillover is a side effect of a prospering reserve or having a reserve protecting a high traveling species, its where an increase of biomass inside a reserve spills over and increases the biomass of species outside the reserve (2,4-10,12). Though spillover can have damaging effects on the reserve, if too many adults are leaving the reserve and getting caught, this will reduce the number of spawning adults and leave the reserve unsustainable (5). Spillover is not just a damaging effect, a successful reserve can replenish surrounding fisheries and used in a network of reserves can increase diversity and sustainability, via dispersal of larvae (2,4-9,12).

Networks can also be used to benefit fishermen as well, by decreasing the distance between fishing areas, increasing the edges of reserves and the amount of reserve edges, increases a fisheries access to spillover and by reducing the distance between them save’s on fuel from not traveling long distances between fisheries (1,5). When designing boundaries of a reserve, placing them on the edge of a habitat boundary such as a reef edge will protect and help contain the species in the reserve conserve them by reducing spillover, however placing a reserve boundary mid habitat will increase spillover and increase benefits for fisheries (5,9,12). The overall location can benefit fisheries as well, through placing reserves by ports or easy access points, this minimizes the cost of travel to the site. Usually areas near access points are the first to be over exploited and are usually the areas most in need of protection. However when spillover is not expected it’s better to set up reserves further away from ports to reduce fishing around it, maximize conservation and to increase the cost to get there which decreases profitability and interest in fishing the site (5). When designing a marine reserve there is a need to find a balance between conservation and spillover. A rule of thumb for reserves is that they both receive and contribute sufficient larvae to other reserves, without this the fate of a reserve is tied to surrounding fisheries, a way to increase this likely hood is to create networks (5).

If a successful balance has been found in the reserve network between spillover and conservation fisheries WTP will decrease over time and can even reach the point where fisheries are paying for the creation of a reserve, or negative WTP (1). However at a reserves creation it can be predicted, but there is no way to know which one of three scenarios that reserve will take in the amount of spillover created. Scenario One; in the network all the reserves are closed systems, all sites are self sufficient and give no output or input, as if the area was walled off. In this closed system opposition rises steadily with time (1). Scenario Two; the source sink, this is were the reserve is a source or breeding ground for a species (1,4,5). The general trend is for the opposition to initially increase (5 years) but then declines and begins to level out over time (20 years). Over this period the surrounding populations initially decrease due to the shift in fishing effort to other waters, but over time with dispersal from the source sink system the population will recover via spillover (this may also be helped by an abundance of jobs outside of the fishery) (1). Scenario Three; is the relative density dispersal system, this has an outcome in-between the previous scenarios, there are spillovers but not less than in the source sink system. Opposition in this scenario is similar to the source sink system, it increases then steadily decreases, however the decrease is usually longer, and there is less chance of negative WTP (1).

WTP is also affected by the number of boats allowed into the reserve, in certain reserves limited numbers of vessels are allowed for recreational and subsistence fishing and fishing with less destructive gear (6). Within a closed system a greater number of boats reduces the difference between short and long term opposition. A high number of boats in a closed system defeats the object of a reserve because stocks will be heavily fished, some boats will leave to non-reserve sites due to the formation of the reserve furthering the degradation of the surrounding stocks. While allowing too few boats into the reserve, the reserve is underutilized and opposition is reduced (1). In a source sink system varying the number of vessels can create large long term benefits, but with varying costs in the short term. If the number of vessels in the source sink system are too high the reserve becomes overexploited, but the reserves dispersal benefits are greater than the losses in the closed system in the long run (1).

Problems in reserve design

However, despite all of this if marine reserves and MPA’s are to become more widespread there are multiple issues and challenges that need to be addressed. First, with the huge biological diversity in marine ecosystems no reserve can benefit all, although some basic rules are appearing that may maximize benefits for more species. Focus is now being placed upon increasing the range of species that are benefiting and reducing the gap between how much different species benefit (4,5). Although, if species are benefiting more than others how will this affect their interactions?  (5,12)

Furthermore, reserves are being created on todays biological and physical conditions, theses features are often climate linked. Marine reserves are immobile, but as the climate and ecosystem shift so too will the species they are designed to protect (5,12). In addition, larval development time are effected by temperature, are the marine reserves of today focused on profitability going to provide the same in an altered ecosystem? (5). Moreover, network design has been focused on maximizing and reaching profit and yield goals for fisheries. Networks of reserves could also be used to reach other fishery goals such as estimating the effects fishing has on the ecosystem for the ecosystem-based fisheries management, stock assessments and separating the effects of fishing from climate change and other effects (3,5,8,12).

Fourthly, the success of these designs remain largely untested, with existing networks only just reaching long term existence and an increase in the creation of new networks, data on their success is relatively sparse and only now can scientists see whether theoretical models work(2,5). Lastly, more data is needed on the costs of establishing and running a reserve. It’s been predicted that to sufficiently protect the earth’s waters 30% must be either a reserve or an MPA, though 20% has been seen as more of a reachable target, it is unknown if anywhere near this target can be afforded (2).

References

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