The Role of Marine Reserves in Ecosystems and Fisheries Management in New Zealand (2011)
Marine Reserves are spatially defined areas of ocean or estuaries where natural populations of marine species are protected from exploitation or other detrimental anthropogenic pressures. Reserves are often referred to as ‘underwater national parks’ and act as the government's most comprehensive means of area-based biodiversity protection within any marine environment <ref> Department of Conservation, Marine & Coastal, viewed 1 October 2011,< http://www.doc.govt.nz/conservation/marine-and-coastal/></ref>. They have been created from both conservation and fishery management perspectives as a technique to restore over-fished populations <ref> Eddy, T.D. (2011) ‘Marine Reserves as Conservation and Management Tools: Implications for Coastal Resource Use’, Doctoral Thesis, Victoria University of Wellington, Wellington. </ref>. Around the world, marine reserves help conserve habitats and biodiversity, maintain marine communities, and can foster the recovery of certain species. Within New Zealand, marine reserves provide the greatest level of protection for the marine environment.
Between both the South and North Islands of New Zealand there is a total of 33 Marine Reserves. Of New Zealand’s total marine area, which covers more than 4 million square kilometers, only about 7% is protected within these marine reserves <ref> Department of Conservation, “Marine Reserves A-Z”, viewed 1 October 2011. <http://www.doc.govt.nz/conservation/marine-and-coastal/marine-protected-areas/marine-reserves-a-z/></ref>. Inside the reserves, all marine life is entirely protected because all New Zealand marine reserves act as ‘no-take’ zones, also referred to as Marine Fisheries Sanctuary (MFS). ‘No-take’ zones strictly prohibit fishing, the removal or dumping of any materials, dredging, construction, and/or any other human disturbance of any living or non-living marine resources within the marine reserve <ref> Ministry for the Environment, 2008, Marine Areas with Legal Protection Environmental Report Card, Ministry for the Environment, Wellington, New Zealand, viewed 5 October 2001, < http://www.mfe.govt.nz/environmental-reporting/report-cards/marine-reserves/2008/>. </ref>.
The Marine Reserve Act was established in 1971 as the statutory framework for marine reserves and was initially administered by the Marine Department but this changed to the Ministry for Agriculture and Fisheries. In 1987 the responsibility of the Marine Reserves Act fell to the newly created Department of Conservation where it has stayed ever since.<ref>Taylor, N. Buckenham, B.(2003) Social Impacts of Marine Reserves in New Zealand. Ministry of Conservation.</ref> In the course of the first 15 years only two marine reserves were created, these were Cape Rodney-Okari Point in 1975 that was one of the worlds first “no-take” reserve and Poor Knights Islands in 1981. External groups, such as tangata whenua, Conservation Groups, fishers, divers and marine interest groups, lodged for over half of the Marine Reserves now found in New Zealand.
The purpose of the Marine Reserve Act is to provide for the setting up and management of areas of the marine environment as reserves to preserve them in their “natural” state, Over a 25 year period from 1965 there was a very slow and irregular, but continuous development of:
- The concept of a Marine Reserve
- Public acceptance of Marine Reserves
- Establishment of actual Reserves
- Learning about the benefits, uses and values of Marine Reserves<ref> Ballantine,B.(1999).Marine Reserves in New Zealand: The Development of the Concept and the Principles. Proceedings of an International Workshop on Marine Conservation for the New Millenium</ref>
There were early problems with the establishment of Marine Reserves as when Poor Knight Island was proposed there were strong arguments over the “no-take” rule. Initially they authorities decided to allow fishing on certain species as they thought it would not cause significant harm. For the first few years the plan seemed to be working but it was short lived as problems started to occur. Two opposing groups started to appear, visitors that were coming to the reserve to see the undisturbed natural biodiversity and those coming to the reserve because the fishing was better due to the restrictions. After 16years of allowing fishing in Poor Knights Island reserves, it was finally decided to make it a “mo-take” zone and that all subsequent reserve are strictly “no-take” zones.<ref> Ballantine,B.(1999)Marine Reserves in New Zealand: The Development of the Concept and the Principles. Proceedings of an International Workshop on Marine Conservation for the New Millenium</ref>
Classifications and Criteria
Under the Marine Reserves Act, a marine reserve is an area protected for the purpose of conserving marine life for scientific study<ref></ref>. A wide range of activities are managed, controlled, or prohibited in a marine reserve including fishing, marine farming, research, anchoring, bio-prospecting, discharges, and tourism. A variety of classifications and guidelines are used to identify potential marine reserve areas in New Zealand which help to determine which sites should be developed as proposals that can be progressed through the relative statutory processes. These classifications and guidelines are outlined by the Department of Conservation (DoC) in ‘Marine Protected Areas’<ref>[Ministry of Fisheries and Department of Conservation. 2008. Marine Protected Areas: Classification, Protection Standard and Implementation Guidelines. Ministry of Fisheries and Department of Conservation, Wellington, New Zealand. 54 p.]</ref> and are discussed below.
- Protect whole habitats and ecosystems: When selecting a site it is desirable that the whole habitat or ecosystem can be encompassed in the protected area due to the dispersal range of many marine species. e.g. It would be much more effective and efficient to incorporate a whole reef in a protected area rather than establishing a boundary that cuts across the reef habitat as species would continue to move in and out of the protected area.
- Size of protected areas: A marine reserve needs to be a sufficient shape and size to provide for the maintenance of populations of marine plants and animals. It is more beneficial for the success of the marine reserves to protect fewer, larger areas rather than many smaller areas, as larger reserves help to maintain healthy, resilient, self-sustaining ecosystems, and allows more efficient and cost effective management and enforcement.
- Maximise connectivity: The design and location of marine reserves should aim to maximise and increase the linkages among individual and groups of reserves within similar biogeographic regions, and across biogeographic regions.
- Represent latitudinal and longitudinal variation: The latitudinal and longitudinal differences in habitats and ecosystems are important criteria to consider when planning a marine reserve. A reserve should seek to maximise the biogeographic representation and habitat heterogeneity that is encompassed within a reserve in efforts to include all vulnerable habitats, critical life stages, and areas with rare and endemic species. e.g. A marine reserve may span from the intertidal zone to deep waters offshore.
- Consider sea and adjacent land uses in planning protected areas: Due to the interaction between marine, terrestrial, and freshwater systems, the placement of a marine reserve should take into account the neighbouring environments and their associated human activities. Past and present uses of the neighbouring environments can influence the integrity of biological communities in the marine reserve. e.g. A marine reserve placed on an existing no-take area or adjacent to a terrestrial national park would have greater biological integrity than one placed next to a shipping lane.
- Keep boundaries simple and aim for low boundary to area ratio: For a marine reserve to have a low boundary to area ratio the reserve should aim to be a simple shape and reduce the fragmentation of areas. Straight line reserves following major latitude and longitude line such as square shaped reserves allow users and surveillance staff to find and protect the reserve more easily and enforcement of boundaries more realistic.
Marine Reserves have become such an effective tool in the maintenance of ecosystems and fisheries management as a result of the strict legislative backing enforced by the New Zealand Government. Numerous Acts and governing bodies surround the operation of Marine Reserves which ensure that they are able to operate without any threats of abuse from the general public.
The Department of Conservation is the main governing body of all the Marine Reserves in New Zealand while these following Acts deal with the technical and legal aspects to assure the longevity and security of these natural wonderlands:
- The Fisheries Act 1996,
- Resource Management Act 1991 - (note; this is only enforcable within 12nm off the shore),
- Maritime Transport Act 1994,
- Biosecurity Act 1993,
- Marine Reserves Act 1971,
- Resource Management (Marine Pollution) Regulation Act 1998,
- Marine Mammals Protection Act 1978,
- Submarine Cables and Pipelines Protection Act 1996 - (e.g. the protection of Cable Bay Wellington which holds the telecommunications cables, connecting the North and South Islands).
- Special legislation e.g. what seen at the Sugarloaf Islands Marine Protected Area and Fiordland (Te Moana o Atawhenua) Marine Area.
For the legal enforcement of a Marine Reserve reference is to be made to Section 4 of the Marine Reserves Act 1971. Here the Governor General has the ability to declare an area a Marine Reserve, subject to predetermined requirements and resulting legal safeguards will stem from this declaration.
The Role of Marine Reserves in Ecosystems
Biodiversity and Conservation
Benefits of Marine Reserves in New Zealand
Marine ecosystems are highly valuable resources of biodiversity; the Exclusive Economic Zone alone contains two-thirds of New Zealand’s total biodiversity<ref>Hewitt, C., Willing, J., Bauckham, A.,Cassidy, A., Cox, C., Jones, L., Wotton, D. 2004. New Zealand marine biosecurity: delivering outcomes in a fluid environment. New Zealand Journal of Marine and Freshwater Research, 38, pp 429–438.</ref>. Marine reserves provide significant protection of these ecosystems and international studies have found that the biodiversity of the community and the mean size of organisms found within a marine reserve are approximately 20% to 30% higher than outside a reserve. Also the population density of organisms almost doubles, while the biomass of organisms almost triples. These significant increases have been observed throughout marine reserves in New Zealand with considerable increases in the size and abundance of protected species recorded in reserves such as Cape Rodney-Okakari Point, Te Whanganui-a-Hei, Long Island-Kokomohua, Leigh and the Poor Knights Islands.
Marine reserves have two common goals involving both the maintenance of high yields in fisheries and conserving biodiversity values<ref> Hastings, A., Botsford, L. 2003. Comparing designs of marine reserves for fisheries and for biodiversity. Ecological Applications, 13(1) pp. 65–70.</ref>. As a conservation effort marine reserves can provide unique protection for critical areas, provide spatial escape for intensely exploited species and act as buffers against management miscalculations<ref> Allison, G., Lubchenco, J., Carr, M. 1998. Marine reserves are necessary but not sufficient for marine conservation. Ecological Applications, 8(1), pp. 79-92.</ref>. Achieving these conservation goals may be measured by comparisons of density, abundance, diversity and size of species. Therefore, there are complexities associated with achieving conservation goals such as the varying life histories, size and length of protection, migration of species, and fishing intensity around the reserve. Providing an area without fishing activities is particularly important for the protection of critical areas, such as spawning grounds and the areas of high species diversity. Species with life history characteristics of sedentary or nearly sedentary adults are more likely to benefit from reserves. Furthermore, the maintenance of biodiversity depends upon dispersal distances and the minimum level of recruits required of the species targeted for protection.
The impact of reserve size on achieving conservation goals has been found to increase effects directly, not proportionally, to the reserve size<ref> Halpern, B. 2003. The impact of marine reserves: Do reserves work and does reserve size matter?. Ecological Applications, 13(1) pp 117-137.</ref>. Size has the potential to affect a reserves ability to serve as a larval source as it must be large enough to sustain themselves as well as supply target areas. In addition to this, larger reserves are more likely to contain rare species and a greater variety of habitat heterogeneity because they cover a greater area and can therefore provide some biological functions not possible in smaller reserves. However overall, regardless of size, reserves have shown to produce higher densities, sizes and diversity of organisms. The age of a marine reserve affects overall fish densities, causing increases by 5% per year relative to nearby unprotected areas<ref>Molloy, P., McLean, I., Cote, I. 2009. Effects of marine reserve age on fish populations: a global meta-analysis. Journal of Applied Ecology, 46, pp743-751.</ref>. This suggests that longer durations of protection may be required for reserves to experience one or more recruitment episodes that drive recovery of populations. The impact of reserves over time also affects other biological components which show variability in their responses due to diverse life histories, trophic position or the degree of harvest of a species. For example slow growing, late maturing species respond more slowly to reserve protection than short lived, faster growing species<ref>Halpern, B., Warner, R. 2002. Marine reserves have rapid and lasting effects. Ecology Letters, 5, pp361-366.</ref>.
Case Study: The Leigh Marine Reserve
The Leigh Marine Reserve established in 1975, located on the north-east of New Zealand, provides evidence of the role reserves play in enhancing marine ecosystems including increases in species abundance, and thus affecting the entire community structure. Pagrus auratus is the most common demersal predatory fish, which feeds upon sea urchins, and were found to be 5.75-8.70 times more abundant inside the marine reserve compared to adjacent unprotected areas. Furthermore, P. auratus was larger in size inside the reserve with a total mean length of 316mm compared to 186mm outside the reserve. Other species such as the crayfish species Jasus edwardsii were also found to be approximately 1.6-3.7 times more abundant inside the reserve. Both P. auratus and J. edwardsii feed upon the dominant grazer, Evechinus chloroticus, a sea urchin species which has shown density decline in a number of sites in the reserve since 1978. Due to the decrease in abundance of E. chloroticus , this lead to an increase in the macro algae Ecklonia radiata which has dramatically expanded over a twenty year period into areas previously dominated by sea urchins. Major primary producers such as kelp and macro algae play a central role in the functioning and diversity of marine ecosystems<ref> Babcock, R., Kelly, S., Shears, N., Walker, J., Willis, T. 1999. Changes in community structure in temperate marine reserves. Marine Ecology Press Series, 189, pp. 125-134.</ref>.
The response of species within the Leigh marine reserve subsequent to protection are a valuable indicator of the ecological impacts that fishing activities have had on New Zealand’s north-east coast, which go beyond target species and impact entire marine ecosystems. The conservation of abundance and biodiversity is the key to creating sustainable, healthy marine ecosystems as high species abundance and biodiversity promotes high ecosystem resilience; the ability to recover from disturbances such as over-exploitation, and continue to function and provide ecological services. This is true as usually only a small number of species have major function in ecosystem processes, however when the ecosystem is disturbed, a larger number of species act as a buffer, contributing to the resilience of the system.
With the creation of marine reserves an initial negative impact was seen to affect the commercial and recreational fishing in those particular areas. This is due to marine reserves in New Zealand having strict “no-take” rules unlike other countries where some reserves allow fishing. Marine reserves have become very popular locations for people to visit as activities such as swimming, snorkeling and diving. The increase in visitor numbers means there is a greater demand for infrastructure around the reserves such as parking, waste facilities and tourist operations.<ref>Taylor,N. Buckenham, B. (2003). Social impacts of marine reserves in New Zealand. Ministry for Conservation����������</ref> The Department of Conservation is faced with the issue of managing Marine reserves in a way so they protect the natural environment but still allow visitor access to the reserve
The increasing numbers of visitors to Marine Reserves for recreational purposes can have negative effects on the conservation of the reserve. In New Zealand, very few studies have been done to monitor the long-term damage visitors have to the Marine reserve environment. Overseas studies have shown that visitors do have a negative impact especially activities such as harvesting, trampling, diving and boating. These activities have direct impacts such as reducing densities and altering the size structure of populations. Indirect effects on other species and the ecosystem such as habitat loss and species competition and predation also occur<ref>McCron, A. (2001). Visitor impacts on marine protected areas. Ministry for Conservation����������</ref>. In New Zealand the main negative impacts seen in Marine reserves is damage to the intertidal and sub tidal reef systems, and a noticeable change in fish species behavior due to being feed by visitors. Visitors don’t just have negative impacts on the reserve, positive effects also occur; there is an increased public awareness of the importance of Marine reserves and conservation.
The Role of Marine Reserves on Fisheries Management
Reduced Fish Mortality
No-take reserves have the potential to eliminate, or at least substantially reduce, the rates of direct fishing mortality, of specific targeted species and/or specific size/age classes, within the reserve area. In areas outside of no-take reserves, the rates of direct fishing mortality can reach several times the natural mortality rates. By simply reducing this rate to zero in a portion of the fishing grounds, no-take marine reserves serve as a fisheries management method for regulating the overall rate of mortality on a type of stock. No-take fisheries reserves were not created to replace traditional fisheries management control efforts; instead, they were created to work as an additional control tool to be used in collaboration with the other management methods. The capturing of targeted size/age class of species is not the only type of mortality caused by fishing activities. Other sources of species mortality from fishing methods are due to the bycatch (fish caught unintentionally) of illegal-sized individuals by the fisheries targeting that species and/or the bycatch of the main species by fisheries not targeting that species. Some destruction is incidental as well, such as the mortality from fishing gear and practices and the incidental mortality indirectly caused from damage to habitats or from the removal of crucial prey species from the area. By not allowing these fishing practices to take place inside the reserves, no-take marine reserves provide refugia for species from these harmful actions. The benefits of no-take marine reserves on fishing mortality rates can be realized immediately, and often produces direct short-term benefits <ref> Ward T. J., D. Heinemann and N. Evans, 2001, ‘The Role of Marine Reserves as Fisheries Management Tools: a review of concepts, evidence and international experience’, Department of Agriculture Fisheries & Forestry Australia, Bureau of Rural Sciences, Canberra, Australia. pp 22-23, viewed 14 September 2011, < iwlearn.net/publications/misc/reviewofmarinetools.pdf></ref>.
Population Size and Abundance
As a direct result from the decreasing fishing mortality rates, no-take marine reserves can also cause an increase to the number of individuals within the different populations of the reserves. This boost in population then increases the overall density and biomass of the reserve area as well. In addition, the abundance, density, and biomass of spawning size/age classes of species increases. The change and benefits of species’ population size inside no-take marine reserves can occur within a short-to medium-term. <ref> Ward T. J., D. Heinemann and N. Evans, 2001, ‘The Role of Marine Reserves as Fisheries Management Tools: a review of concepts, evidence and international experience’, Department of Agriculture Fisheries & Forestry Australia, Bureau of Rural Sciences, Canberra, Australia. pp 23-24, viewed 14 September 2011, < iwlearn.net/publications/misc/reviewofmarinetools.pdf></ref>.
Case Study: In one particular study of the Goal Island Marine Reserve in New Zealand, where there was little to no seaweed left due to over-grazing by sea urchins. The over-exploitation of snapper and rock lobster, the true predators of sea urchins in this area, caused this to occur. After over 20 years of protection within the marine reserve, thus protecting the species from fishing practices, the snapper and rock lobster populations have increased, causing a decrease in sea urchin densities, and allowing the seaweed beds to recover and the marine habitat to return to a more natural state <ref> Shears & Babcock 2002, Oecologia, viewed 1 October 2011 < http://www.piscoweb.org/files/images/SMR/UrchinDecline.JPG_></ref> <ref>Allsopp, M. et al, 2009, ‘Marine Reserves’, in State of the World’s Oceans, Springer Science + Business Media B.V., pp 199-213, DOI: 10.1007/978-1-4020-9116-2_7 </ref>. Snapper abundance levels with the Goat Island Marine Reserve have continued to increase according to surveys taken between 2002 and 2008. In 2011, a higher frequency of legal sized snappers were also recorded inside marine reserves than outside, when compared to the number of which was found in 2008. Also, consistent with previous surveys, an autumn 2011 survey conducted by the Department of Conservation indicated species diversity to be higher within the Goat Island Marine Reserve than in non-reserve areas. Overall species of snapper, butterfish, john dory, banded wrasse, parore, blue cod and silver drummer are all more abundant inside the reserve than outside. <ref> Department of Conservation, 2011, ‘Cape Rodney-Okakari Point Marine Reserve (Goat Island)-Monitorin’, viewed 1 October 2011, <http://www.doc.govt.nz/conservation/marine-and-coastal/marine-protected-areas/marine-reserves-a-z/cape-rodney-okakari-point-goat-island/monitoring/></ref>.
As a direct result of the elimination of high fishing mortality rates within no-take marine reserves, individual species are then able and expected to live longer and grow larger as well. This allows species to increase both in number and density, therefore producing mass amounts of larger, more mature https://geog397.wiki.otago.ac.nz/Special:Preferencesfish within the protected area. This increase in number, density, and biomass of reproductively active individuals can then lead to an even larger reproductive potential within the reserves. As a result, restoration and eventually preservation of the “natural” or “normal” size and age structure of a population within the reserves can occur, which without a reserve present can often be offset by over-exploitation. These changes to the overall population structure of a specific species in a no-take marine reserve can occur within a relatively short-to mid-term time period. <ref> Ward T. J., D. Heinemann and N. Evans, 2001, ‘The Role of Marine Reserves as Fisheries Management Tools: a review of concepts, evidence and international experience’, Department of Agriculture Fisheries & Forestry Australia, Bureau of Rural Sciences, Canberra, Australia. pp 23-24, viewed 14 September 2011, < iwlearn.net/publications/misc/reviewofmarinetools.pdf></ref>.
Case Study: According to an ongoing monitoring system within the Tonga Island Marine Reserve of New Zealand, blue cod numbers and individual size of species within the reserve have shown to be steadily increasing since it was established in 1993. The mean size of blue cod within the Tonga Island Marine Reserve has increased from 271mm in 2000 to 311 mm in 2007, while the mean size of blue cod in sites outside of the reserve remained relatively the same, 227 mm to 228 mm, from 2000 to 2007. <ref> Department of Conservation, 2007, ‘Tonga Island Marine Reserve Monitoring, viewed 2 October 2011, <http://www.doc.govt.nz/conservation/marine-and-coastal/marine-protected-areas/marine-reserves-a-z/tonga-island/monitoring/> </ref>.
Marine reserves have the potential to increase prospective and actual reproductive output. Reserves were established in hope of moderating selection for early reproduction/small size caused by over-fishing <ref> Rowley, R.J. 1992. “Impacts of Marine Reserves on Fisheries, A report and review of the literature”, Department of Conservation, Wellington, New Zealand. </ref>. By resulting in an increase in population size, which then contains more mature, larger and more densely packed individuals, no-take marine reserves can generate more spawning activity, overall increased fertilisation success for species with external fertilisation techniques, and a greater production of eggs and larvae. This is hypothesized to then enhance the settlement/recruitment within the reserve area. The direct benefits to reproduction within no-take marine reserves are expected to occur within a short-to medium-term <ref> Ward T. J., D. Heinemann and N. Evans, 2001, ‘The Role of Marine Reserves as Fisheries Management Tools: a review of concepts, evidence and international experience’, Department of Agriculture Fisheries & Forestry Australia, Bureau of Rural Sciences, Canberra, Australia. pp 23-24, viewed 14 September 2011, < iwlearn.net/publications/misc/reviewofmarinetools.pdf></ref>.
Case Study: A study done by the University of Auckland recorded the abundance, size, biomass and reproductive output of spiny lobsters within New Zealand’s northeastern seas, comparing locations both outside and inside established marine reserves. The four marine reserves studied included the Tuhua Marine Reserve, Leigh Marine Reserve, Cathedral Cove Marine Reserve, and the Tawharanui Marine Reserve. The results indicated that the mean density of the total population of lobsters increased 3.9% to 9.5% each year in which the reserves were established. The mean size of lobsters was estimated to increase by 1.14 mm per year of protection as well. As a result of increased population and size, the overall lobster biomass was estimated to increase by 5.4% per year of protection in shallow sites and 10.9% per year in deep water sides. As a consequence, egg production within the area increased as well, by 4.8% per year in shallow waters and 9.1% per year in deep areas. <ref> Kelly, S., Scott, D., MacDiarmid, A.B., & Babcock, R.C. 2000. ‘Spiny lobster, Jasus edwardsii, recovery in New Zealand marine reserves’, Biological Conservation 92, pp. 359-369. </ref>.
Overall Habitat Quality
Certain fishing practices and gear types, such as trawling, drive netting, poisons, and explosives, can be particularly destructive within the marine environment. This devastation can lead to the reduction of population structure and overall biodiversity of an area. Establishing a no-take marine reserve area, thus preventing these practices from taking place, can provide protection against the loss of keystones species, as well as allows the recovery of ‘normal’ habitat characteristics to take place. Ultimately the biodiversity of the area will increase as a direct result. No-take marine reserves allow for the original and natural community composition, trophic structure, food web, and ecosystem processes to be re-established. Thus, the overall habitat quality within a reserve improves. Habitat quality improvements can enhance fish biomass and catch levels. The restoration of a ‘natural state or balance’ of a reserve habitat is expected to be largely apparent in areas where keystone species have been heavily exploited. High quality habitats are expected to sustain the highest rates of recovery and eventually attain higher biomass and/or biodiversity than lower quality habitats Overall, the improvement of habitat biodiversity and total communal composition within a no-take marine reserve is can produce secondary medium-to long-term benefits for the area. <ref> Ward T. J., D. Heinemann and N. Evans, 2001, ‘The Role of Marine Reserves as Fisheries Management Tools: a review of concepts, evidence and international experience’, Department of Agriculture Fisheries & Forestry Australia, Bureau of Rural Sciences, Canberra, Australia. pp 23-24, viewed 14 September 2011, < iwlearn.net/publications/misc/reviewofmarinetools.pdf></ref> <ref>Rodwell, L.D., Barbier, E.B., Roberts, C.M. & McClanahan, T.R. 2003, ‘The importance of habitat quality for marine reserve-fishery linkages’, Canadian Journal of Fisheries and Aquatic Sciences, vol. 60, no. 2, pp. 171-181. </ref>.
The process ‘spill over’ refers to the net movement of juvenile and adult marine species from inside the marine reserve to outside the marine reserve’s boundaries. However, the marine species’ origin is irrelevant, as spill over applies equally to both a species produced in the sanctuary, and a species which was produced outside the reserve and settled inside <ref> Ward T. J., D. Heinemann and N. Evans (2001) The Role of Marine Reserves as Fisheries Management Tools: a review of concepts, evidence and international experience. Bureau of Rural Sciences, Canberra, Australia. 192pp. </ref>. In a simplistic sense, spill over is meant to improve fisheries and ecosystems close to the reserve through the spill over of aquatic life from within a rich marine reserve. Some academics have criticised how effective spill over is in improving fish stocks. Critics state that spill over will only benefit fisheries close to the boundaries, and even then still be under extreme pressure from people fishing close to reserve boundaries <ref> Parrish R. (1999). Marine Reserves for Fisheries Management: Why Not. Pacific Fisheries Environmental Laboratory. 40 (1), p1-10. </ref>. A study in the Long Island – Kokomohua Marine reserve showed that blue cod numbers within the reserve increased four fold after seven years of protection, yet remained the same in sites 1-5km outside the reserve <ref> Rowley R. (1992). Impacts of Marine Reserves on Fisheries. Department of Conservation. 1 (51), p1-55. </ref>. The two most significant medium-term benefits seen from spill over include; net immigration of juvenile and adult species from reserves and increased catches of larger, more valuable species near the boundaries of reserves. Spill over generally occurs between a few hundred to a few kilometres from marine reserve boundaries. There are many factors which influence the rate of spill over, such as; organism size and mobility, habitat requirements, population characteristics, predation rates, suitability inside/outside reserves, fishing pressure outside the reserve, and boundary length.
Larval export is a process which involves the net movement of eggs and larvae by currents out of marine reserves. Larval export in a sense is the spill over of eggs and larvae. Larval export is a process which can enable the use of marine reserves to enhance fisheries. Marine reserves typically have a larger amount of reproduction, density and biomass than unprotected marine ecosystems. This creates a greater potential for larval export to enhance fish stocks, as marine reserves enable species to grow larger, which evidently produce more eggs and larvae than smaller species outside of marine reserves. Larger species exporting increased amounts of larvae than species outside reserves creates the potential for an increase in fish stocks outside of marine reserves <ref> Ward T. J., D. Heinemann and N. Evans (2001) The Role of Marine Reserves as Fisheries Management Tools: a review of concepts, evidence and international experience. Bureau of Rural Sciences, Canberra, Australia. 192pp. </ref>. In a simplistic sense, bigger species in marine reserves produce a greater amount of eggs and larvae than unprotected fish, the transported eggs and larvae then can create larger fish stocks outside reserves. At the Goat Island marine reserve, crayfish produce 12 times as many eggs as crayfish located in a similar sized area outside of the reserve <ref> Rowley R. (1992). Impacts of Marine Reserves on Fisheries. Department of Conservation. 1 (51), p1-55. </ref>. This exemplifies the capacity marine reserves have in producing a greater amount of larvae and eggs than unprotected areas. The destination of larval export is very inconsistent, as it is dependent on the local currents. Larval export does not generally have a local effect. Instead, due to large travel distances, it creates regional benefits.
How effective are they?
Marine reserves have proven to be quite successful in increasing species diversity and fish stocks as early as two years after becoming a ‘no take’ marine reserve.
Results from a survey conducted of marine reserves around the world shows that fishes, invertebrates, and seaweeds drastically increased inside marine reserves. <ref></ref>
- The biomass, or the mass of animals and plants, increased an average of 446%
- The density, or the number of plants and animals in a given area, increased on average 166%
- The body size of animals increased an average of 28%
- The species density, or the number of species, increased an average of 21% in the areas sampled.
Heavily fished species often showed the most dramatic increases where some species have showed more than a 1000% higher biomass or density inside marine reserves.
It has also been found that larger, older fish produce disproportionately more young than smaller individuals, so they contribute much more to the next generation. This increased reproduction inside marine reserves can also help to replenish nearby fished areas For example, a 50% increase in length of snapper from 40 to 60 centimeters (16 to 24 inches) results in a 1000% increase in the number of young produced.
Therefore the major benefit of marine reserves is that they increase productivity to allow stocks to recover from overfishing.
Although minimal literature exists surrounding the effectiveness of marine reserves in New Zealand, evidence does suggest that they are an effective management tool in both fisheries and ecosystem management. Marine reserves have shown to improve the value of the ecosystem due to increases in species size and abundance, as well as increases in biodiversity and therefore ecosystem resilience. However, certain aspects of the reserve such as its age and fishing intensity outside the reserve may have an influence on its effectiveness. Due to the limited number of long term studies on the effects humans have on reserves, it is hard to know whether they are damaging the reserves environment. Initial studies do show some damage due to human recreational activities, but the long-term outlook is still unknown.
Marine reserves have also shown to have positive affects on fisheries management inside the boundaries of the established reserves in New Zealand. Although marine reserves were initially established as an additional method for fisheries management,and are to be used in combination with other management tools, they have been shown to successfully reduce the fishing mortality rates, while also increasing species' population size, reproduction rates, and overall habitat quality within the country's reserves. In addition, Marine reserves have shown to have positive affects on fisheries and ecosystems outside of their boundaries, through processes such as spill-over and larval export. However, due to complexities such as marine reserve size and outside fishing pressure, the effects marine reserves have on areas outside their boundaries are unique to their location. For example, a small marine reserve with intense fishing pressure outside the reserve’s boundaries will receive significantly less benefit from spill-over and larval export than a large marine reserve which has less fishing pressure outside its boundaries. Overall, we conclude that marine reserves provide an efficient and collaborative way to maintain and manage fisheries throughout New Zealand, while simultaneously preserving biodiversity and meeting conservation objectives and human needs.