Effects of Fishing on Hectors Dolphins

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Hector's dolphins, Cephalorhynchus hectori, are endemic to New Zealand. Separated into two sub-species, Hector's and Maui's, the populations are fragmented and spread around the coast of the North (Maui's) and South (Hector's) Islands. The Maui's dolphin population is down to less than a hundred members alive, whereas the estimated 7000 Hector's dolphins are located in three main areas to the south, east, and west of the South Island. Their main threat comes from human activity, particularly fishing practices such as the use of gillnets. The management of fishing practices to give way to protection of the critically endangered dolphins receives much contention from various stakeholders such as animal interest groups, the government, the fishing industry and the Maori, the conflicts of which will be addressed in this study.

Contents

State

The Hector's Dolphin

General Information

The Cephalorhynchus group of dolphins are found only in the southern hemisphere and are the smallest and rarest dolphins in the world. The Hector's dolphins are the only cetacean endemic to New Zealand, with two subspecies of Hector's dolphins having been identified, namely the South Island Hector's Dolphins and the North Island Maui's Dolphins. The Hector's dolphins are classified as nationally vulnerable under the New Zealand Threat Classification system, while the Maui's dolphins are classified as a nationally critical subspecies <ref name="DoC MMAP">Suisted, R. and Neale, D. 2004. Department of Conservation Marine Mammal Action Plan for 2005–2010. Department of Conservation, Wellington. 89pp. </ref>.

Hector's dolphins have a short lifespan of about 20 years, making them vulnerable to low population growth rates<ref name="DoC Threat Management"/>. Exacerbating this low growth rate is the dolphin's low reproductive rate, with calving occurring only every 2-3 years and with adults reaching sexual maturity at 7-9 years of age <ref name="DoC Threat Management"/>. They are easily identified by their unique rounded dorsal fins and from their small size <ref name="DoC Threat Management"/>.

Usually, the populations of Maui and Hector's dolphins do not mix, however during a recent investigation there was the discovery of two West Coast Hector's females within the Maui community. Whether there is interbreeding is unknown at this point, however if there is, the greater genetic diversity which would eventuate would be beneficial for the populations<ref name="Maui's Dolphins Abundance Estimate"/>.

Hector's Dolphins

The South Island Hector's Dolphins (Cephalorhynchus hectori) are found mainly in the South Island with a population number estimated at 7270 animals<ref name="DoC Hectors Dolphin Factsheet">http://www.doc.govt.nz/conservation/native-animals/marine-mammals/dolphins/hectors-dolphin/facts</ref> The Hector's dolphins population is known to be geographically clustered in certain areas around the coast of New Zealand, which has resulted in considerable genetic distinction of three distinct populations. These three groups are clustered in the West Coast of the South Island, the East Coast of the South Island and the South Coast of the North Island <ref name="DoC Threat Management">Ministry of Fisheries and the Department of Conservation. 2007. Hector’s Dolphin Threat Management Discussion Document. </ref>. Some of the issues resulting from this geographical clustering and genetic distinction include the potential loss of genetic biodiversity<ref name="DoC Threat Management"/>.

Maui's Dolphins

The number of North Island Maui's Dolphins (Cephalorhynchus hectori maui) <ref name="DoC Maui's Dolphin Factsheet">http://www.doc.govt.nz/conservation/native-animals/marine-mammals/dolphins/mauis-dolphin/facts/</ref> is estimated to be 55 animals <ref name="Maui's Dolphins Abundance Estimate">Hamner, R.M, Oremus, M, Stanley, M, Brown, P, Constantine, R and Baker, C.S. 2012. Estimating the abundance and effective population size of Maui's dolphins using microsatellite genotypes in 2010-11, with restrospective matching to 2001-07. Department of Conservation, Auckland. 44pp. </ref>. Over the last ten years there have been two main population surveys on Maui's dolphins, the most recent of which concluding with much tighter margins of error and an population of 55 individuals over the age of 1 year. The most recent Department of Conservation (DoC) study into the number of remaining Maui's dolphins has shown their numbers of be severely reduced. The Maui's dolphins population is clustered only in the West Coast of the North Island <ref name="DoC Maui's Dolphins brochure">Department of Conservation. 2013. Maui's Dolphins. Department of Conservation, Wellington. 2pp. </ref>.

Significance of Dolphins

Because dolphins are positioned at the top of the food chain, they are themselves indicators of the health of their habitat. Biomagnification, the effect which describes the increased concentration of a substance up the food chain, occurs, thus the dolphins are indicative of the contaminants present in their environment<ref name="Stockin">Stockin, K.A., Law, R.J., Roe, W.D., Meynier, L., Martinez, E., Duignan, P.J., Bridgen, P.and Jones, B. (2010)Marine Pollution Bulletin 60834-842</ref>. This process is an issue in dolphins particularly not only because of their location at the top of the food chain, but also due to their fast metabolic rates, long lives, and the large relative amount of fatty lipids present in the organisms<ref name="Reijnders">Reijnders, P.J.H. and Aguilar, A (2002) Pollution and marine mammals, In Perin, W.F., Wuisig, B., Thewissen, J.C.M. (Eds), Encyclopedia of Marine Mammals, Academic Press, San Diego, USA, pp 948-957</ref>.

Their place at the top of the food chain also leads to vulnerabilities to changes. Their main food source is fish, if fish stocks are low, a good sized population of dolphins cannot be supported.

One of New Zealand's most significant industries is tourism. As Hector's and Maui dolphins are endemic to the coastal regions of New Zealand, they are an important part of our tourism industry. Supporting this industry is necessary to decision makers, however there are instances where the boat traffic has been detrimental to the dolphin populations<ref>Conroy, M.J., Barker, R.J., Dillingham, P.W., Fletcher, D., Gormley, A.M. and Westbrooke, I.M (2008) Application of decision theory to conservation management: recovery of Hector's dolphin, Wildlife Research, 35: 93-102</ref>

The Maori, the indigenous people of New Zealand, revered Hector’s dolphins as a taonga (treasured thing). There were many names used for the dolphins, the most common being tutumairekurai, which means ocean dweller. Some Maori believed that the spirits of the dead would become tutumairekurai. Other names included papakanua, tupoupou, hopuhopu and upokohue.<ref name="DoC Threat Management"/>

Cultural importance also includes their place within New Zealand's list of many endemic species. For a country which prides itself in its unique life forms, the protection of species such as the Hector's and Maui dolphins is important.

Main Indicators Available

Summary of the findings of the last two DoC Maui dolphin populations with 95% confidence interval error bars<ref name="Maui's Dolphins Abundance Estimate"/>

This section seeks to establish the main environmental indicators available for assessing the state of Hector's dolphins in New Zealand. The three indicators identified include dolphin population numbers, bycatch rates and dolphin population dynamics. The usability and potential problems associated with each of these indicators will also be assessed.

Dolphin Population Numbers

  • DoC Maui's Dolphin Abundance Estimate Report

The Department of Conservation (DoC) recognizes that understanding the population size of dolphins is crucial in planning further actions to conserve the Maui's dolphins<ref name="Maui's Dolphins Abundance Estimate"/>. This Abundance Estimate Report suggests that there are an estimated 55 individuals aged one year or older, with a 95% Confidence Interval<ref name="Maui's Dolphins Abundance Estimate"/>. This does have some issues as most of the time they are just assumptions of estimates found either by using aerial photographs or a boat search in the dolphin habitat, this could give some under or over estimation to the actual population size.

Bycatch Rates

The bycatch rate of dolphins is extremely useful in understanding the direct effects of gillnetting and trawling on Hector's dolphins. From these bycatch rates, further information such as maximum allowable limits and the population viability of the dolphins can be derived.

  • DoC Hector's and Maui's Dolphin Incident Database

The potential rate of bycatch can be estimated using the Department of Conservation's Hector's and Maui's dolphin incident database, which maintains and organizes data from reports of dolphins washed up on beaches, found dead at sea or caught as bycatch<ref name="Doc dolphin incident database">http://www.doc.govt.nz/conservation/native-animals/marine-mammals/dolphins/hectors-dolphin/docs-work/hectors-and-mauis-dolphin-incident-database/</ref>. This comprehensive database includes data derived from as early as 1921, with records of the size, sex, location and possible cause of death of each dolphin reported<ref name="Doc dolphin incident database"/>, making it useful in estimating bycatch rate at a location-specific level. However, this data source is subject to some issues such as biasness in the collection of data. These incident reports may be biased towards areas that are more frequently visited or that are more accessible.

  • NIWA Independent Observations

Using independent observations from the Canterbury region, the National Institute of Water and Atmospheric Research (NIWA) estimated a death rate of about 30 dolphins per year from the region's gillnet fisheries<ref name="WWF Factsheet">World Wide Fund for Nature. 2009. Factsheet: What we know about about Maui's and Hector's dolphins. Wellington, WWF. 2pp.</ref>. This number is thought to be 28 incidents higher than what was reported voluntarily by the fishing industry<ref name="WWF Factsheet"/>, potentially creating some controversy surrounding the credibility of submissions from the fishing industry.

Dolphin Population Dynamics

Some of the other population parameters, other than population numbers, that are useful in understanding the state of Hector's dolphins include death rates, birth rates and sex ratios.

  • NIWA Risk Analysis 2008

In 2008, the National Institute of Water and Atmospheric Research (NIWA) conducted a risk analysis of the Hector's and Maui's dolphin subpopulations<ref name="NIWA risk analysis">Davies, N., Bian, R., Starr, P., Lallemand, P., Gilbert, D. and McKenzie, J. 2008. Risk Analysis of Hector's dolphin and Maui's dolphin subpopulations to commercial set net fishing using a temporal-spatial age-structured model. Auckland, NIWA, 113pp. </ref>. This report estimated a death rate of about 110-150 dolphins each year in New Zealand<ref name="NIWA risk analysis"/>.

Ideal Indicators

Ideally it would have been best to also be able to get information on the sex ratio of the Hector's and Maui dolphin's as it can explain what some of the future outcomes of the population could be, such as if there is a sex bias which would not help the recovery of the species. If there are not enough males for females to mate with, less calves are born. On the other hand, a higher female to male ratio would be ideal as these dolphins mate at such low levels, only reproducing after the age of 7 at 2-3 year intervals. Birth rates could have also been a useful indicator as it would help to know how many new calves are being put into the populations and also it could give an idea on if there are any interbreeding going on between the populations with further genetic research. It can help to know how to manage a population successfully if information on both the inputs and out puts are available and to what degree of help is needed.

The reason these indicators are not freely available compared to others is due to the fact that they are very time consuming and expensive, such as to go out in a boat and try and find every dolphin available it still is likely to leave only a estimation which can be used to make certain assumptions. Also, with the current fragility and sensitivity of both the Hector's and Maui's dolphins, conducting such invasive research may prove detrimental to the current surviving populations of dolphins and may thus be seen as less ideal to carry out.

There are gaps in the death rate of hectors dolphins due to the issues with ones caught by catch or other causes as it occurs in the ocean and the carcass could drift off to sea or sink to the bottom of the ocean. Other major sources of potential error, as mentioned earlier, include the biasness in reports gathered from the public, where more accessible or more frequently visited areas are likely to see higher counts of dolphin deaths although this may not be true in reality.

The Fishing Industry

Common fishing methods in New Zealand<ref name="MinFish">Ministry of Fisheries. 2008. The State of our Fisheries 2008. Wellington, Ministry of Fisheries. 52pp.</ref>

Characteristics of the Fishing Industry of New Zealand

Fishing is one of the primary industries of New Zealand, with significant economic, cultural and social impacts. In 2010-2011 alone 130 species were commercially fished by 1 540 quota holders employing over 8000 full-time employees to catch 418 306 tonnes of seafood and earning $1.56 billion in exports (90% of fish landed are exported overseas). Additionally fishing in New Zealand has a high social and cultural importance. It is estimated that 20% of the population partakes in in recreational fishing activities catching an estimated 25000 tonnes per year, with a further 4500 tonnes attributed to Maori customary rights . <ref name="New Zealand Fisheries at a glance">http://www.fish.govt.nz/en-nz/Fisheries+at+a+glance/default.htm</ref>

A variety of equipment and techniques are used to harvest seafood resources. One of the most common practices is the use of nets to trap and entangle fish. There are a number of different styles of netting used, with one of the most common being set netting<ref name="Common New Zealand Fishing Methods">http://www.fish.govt.nz/en-nz/Publications/The+State+of+our+Fisheries+2008/Common+NZ+Fishing+Methods/default.htm</ref>. This is the process in which a net is set up in a stationary position, attached to the sea floor to entrap marine life that swim into them. These nets can be up to 10m high and several hundred metres long and can be located as low as the sea bed to as high as the mid water column. <ref name="Common New Zealand Fishing Methods">http://www.fish.govt.nz/en-nz/Publications/The+State+of+our+Fisheries+2008/Common+NZ+Fishing+Methods/default.htm</ref>

Another common fishing method is trawling. Trawling is where one or two fishing boats drag a net behind them, capturing any fish that cannot out swim it. This technique is only allowed to be used by commercial fishing vessels.<ref name="Common New Zealand Fishing Methods">http://www.fish.govt.nz/en-nz/Publications/The+State+of+our+Fisheries+2008/Common+NZ+Fishing+Methods/default.htm</ref>

Other common fishing techniques used in New Zealand are; long lining (setting a single line baited with hooks at depths of 50-200m below the surface), dredging (towing a steel net across the seabed) and seining (setting a net to surround schools of fish, trapping them within the boundaries of the net<ref name="Common New Zealand Fishing Methods">http://www.fish.govt.nz/en-nz/Publications/The+State+of+our+Fisheries+2008/Common+NZ+Fishing+Methods/default.htm</ref>.

Effects of Fishing-Related Activity on Hector's Dolphins

Maps showing the general spatial pattern of commercial inshore trawl fishing activity<ref name="Map of Trawling">http://www.fish.govt.nz/en-nz/Aquaculture/Maps+of+Commercial+Inshore+Fishing+Activity/Trawl+Fishing+Maps.htm</ref>

The fishing industry impacts upon hectors dolphins when fishing occurs within their range. Set netting represents the biggest threat to dolphins as they are made from nylon strands which dolphins are unable to see in the water<ref name="Hector’s and Maui’s Dolphin Threat Management Plan">Department of Conservation and Ministry of Fisheries. 2007. Hector’s and Maui’s Dolphin Threat Management Plan August 2007.</ref>. Due to this dolphins have been known to swim into nets, becoming entangled and drowning as they are unable to surface for air. The DoC incident database reports that 63% of instants of dolphin mortality that were able to be assessed were caused by set netting. Although total reported instances of occurrence are much lower than in set netting, hectors dolphins have also been known to be caught in trawling nets<ref name="Hector’s and Maui’s Dolphin Threat Management Plan">Department of Conservation and Ministry of Fisheries. 2007. Hector’s and Maui’s Dolphin Threat Management Plan August 2007.</ref>. Since 1921, 19 known hectors dolphin mortalities have been attributed to trawling, all of which occurred within 2nm of the shore amongst the South Island trawl fisheries. <ref name="Hector’s and Maui’s Dolphin Threat Management Plan">Department of Conservation and Ministry of Fisheries. 2007. Hector’s and Maui’s Dolphin Threat Management Plan August 2007.</ref>

Hectors dolphins hunt for many of the same fish species targeted by fishing fleets and feed at all levels of the water column making it difficult for fisheries to avoid them. This problem is exasperated by the fact that hectors dolphins see fishing boats as a source of food and specifically try to follow them, thus creating a greater risk of injury amongst dolphins<ref name="Hector’s and Maui’s Dolphin Threat Management Plan">Department of Conservation and Ministry of Fisheries. 2007. Hector’s and Maui’s Dolphin Threat Management Plan August 2007.</ref>.

Sustainability and Compromise within the Fishing industry

Environmental regulations within the fishing industry are not new. To protect fisheries in the 1980s New Zealand became the first country in the world to input a quota management system allocating set amounts of maximum take for fishing industries within regions<ref name="Trawl fisheries, catch shares and the protection of benthic marine ecosystems: Has ownership generated incentives for sea floor stewardship?">Rieser, A., Watling, L., & Guinotte, J. (2013). Trawl fisheries, catch shares and the protection of benthic marine ecosystems: Has ownership generated incentives for seafloor stewardship?. Marine Policy, 40, 75-83.</ref>. This was to ensure that certain populations of fish were not over exploited and depleted, damaging the industry. Additionally certain fishing practices such as Danish seigning and drift netting are were banned to protect marine species, including hectors dolphins. Practises such as bottom trawling are also banned in some areas of New Zealands EEZ to protect ecosystems from further damage. <ref name="Trawl fisheries, catch shares and the protection of benthic marine ecosystems: Has ownership generated incentives for sea floor stewardship?">Rieser, A., Watling, L., & Guinotte, J. (2013). Trawl fisheries, catch shares and the protection of benthic marine ecosystems: Has ownership generated incentives for seafloor stewardship?. Marine Policy, 40, 75-83.</ref>


Many of these management decisions are dictated for the fishing industries own benefit through the preservation of resources<ref name="Trawl fisheries, catch shares and the protection of benthic marine ecosystems: Has ownership generated incentives for sea floor stewardship?">Rieser, A., Watling, L., & Guinotte, J. (2013). Trawl fisheries, catch shares and the protection of benthic marine ecosystems: Has ownership generated incentives for seafloor stewardship?. Marine Policy, 40, 75-83.</ref>. As a result the industry is more inclined to be supportive of these measures than that for the purpose of conservation alone. When it comes to protecting dolphins the industry is more hostile as extended set netting bans and fishing restrictions within important dolphin ranges directly impact on industry business practises<ref name="Fishing industry says Government needs to consider full picture to protect dolphins">http://www.nzfishfed.co.nz/Story?Action=View&Story_id=1316</ref>. For example a government proposal to expand protected areas for Maui’s dolphins around the waters of Taranaki, banning set nets, was met with hostility as fishermen feared the restrictions would cause the death of the fishing industry in this region<ref name="Backlash at dolphin protection">http://www.stuff.co.nz/taranaki-daily-news/news/9137049/Backlash-at-dolphin-protection</ref>.. However the larger fishing industry has been known to be more supportive of the conservation when there is public pressure over the protection of iconic species such as dolphins as not doing so can impact negatively on business<ref name="Trawl fisheries, catch shares and the protection of benthic marine ecosystems: Has ownership generated incentives for sea floor stewardship?">Rieser, A., Watling, L., & Guinotte, J. (2013). Trawl fisheries, catch shares and the protection of benthic marine ecosystems: Has ownership generated incentives for seafloor stewardship?. Marine Policy, 40, 75-83.</ref>.

Recently the commercial fishing industry and governmental interests have been working together to achieve more environmentally friendly fishing practices. Commercial interests and the Ministry of Primary industries have invested more than 3.8 million dollars into a program aimed at gaining further understanding of Maui activities since 2008<ref name="MPI factsheet">Ministry for Primary Industries. 2012. The management of Hector's and Maui dolphins Fact Sheet November 2012.</ref>. This program ultimately aims to observe all commercial set net boats operating out of New Plymouth to capture all interactions between Maui and fishermen. Additionally new technology is being developed by joint government/commercial ventures to increase the conservation value of fishing practices. This includes a new netting system designed to capture fish with minimum stress to animals (and that could be developed to deter dolphins) and an electronic monitoring system designed to be able to observe all fishing boat and netting equipment, including the ability to detect when species such as dolphins are within range of nets<ref name="Fishing industry seeks sustainability">http://www.stuff.co.nz/business/industries/9230786/Fishing-industry-seeks-sustainability</ref><ref name="Government and fishing industry trial technology">http://www.mpi.govt.nz/news-resources/news/government-and-fishing-industry-trial-technology</ref>.

Evaluation of management methods

Map of marine mammal sanctuaries in the North Island <ref name="DoC">http://www.doc.govt.nz</ref>
Map of marine mammal sanctuaries in the South island <ref name="DoC"/>
Map of Banks Peninsula Marine Mammal Sanctuary <ref name="DoC"/>

Current Legislation

A number of national-level documents safeguarding marine mammals against the detrimental effects of fishing have been implemented, including the Fisheries Act 2006, the Marine Mammal Protection Act 1978 and the Marine Mammal Protection Regulations 1992 <ref name="DoC Threat Management"/>. Some of the mitigation measures provided by these acts include area closure, addressed by the Marine Mammal Protection Act 1978 and the Fisheries Act 2006, and the establishment of Marine Mammal Sanctuaries under the Marine Mammal Protection Act 1978 <ref name="DoC Threat Management"/>.

In addition to these acts and regulations, the government-wide approach has been implemented in the form of a Hector's and Maui's Dolphin Threat Management Plan, jointly developed by the Department of Conservation (DoC) and the Ministry for Primary Industries (MPI), targetting non fishing-related and fishing-related impacts respectively<ref name="MPI factsheet"/>. It is hoped that this Threat Management Plan will lower the risks posed to dolphins through research, planning and monitoring efforts<ref name="MPI factsheet"/>.

DoC has also developed an independent Marine Mammal Action Plan (MMAP) suited for internal use that serves to guide the Department in making decisions regarding the conservation management of marine mammals. It makes suggestions of recommended and suitable action plans at a local to national scale, and undergoes reviews on an ongoing basis<ref name="DoC MMAP"/>


Marine Reserves in New Zealand

One of the methods in which the New Zealand government has attempted to conserve Hector's and Maui's dolphins and other marine mammal species is through the creation of marine reserves around the country, providing differing levels of protection of these mammals against the adverse effects of human-related activities such as fishing. Two such marine mammal sanctuaries, the Banks Peninsula Marine Mammal Sanctuary, and the West Coast North Island Marine Mammal Sanctuary, will be addressed in this section.


Banks Peninsula Marine Mammal Sanctuary

In the period of 1984-1988, before the establishment of the Banks Peninsula Marine Mammal Sanctuary (BPMMS), an estimated 26-90 dolphins in the region were the victims of gillnets<ref name="DoC, 1988">Department of Conservation (DOC). 1988. Protection of Hector’s dolphins around Banks Peninsula – a paper for public comments. Department of Conservation, Wellington. 22pp.</ref>. During this time, bycatch due to entanglement in gillnets was reported throughout the Canterbury Coast, including the Banks Peninsula<ref name="Dawson, 1991">Dawson, S.M. 1991. Incidental catch of Hector’s dolphins in inshore gill-nets. Marine Mammal Science 7(3). 283–295.</ref>. As bycatch rates reached unsustainable levels, the BPMMS was set up in 1988<ref name="Dawson and Slooten, 1993">Dawson, S.M. and Slooten, E. 1993. Conservation of Hector’s dolphins: the case and process which led to the establishment of the Banks Peninsula Marine Mammal Sanctuary. Aquatic Conservation: Marine and Freshwater Ecosystems 3. 207–221.</ref>, spreading over a 1170 km2 area and covered the area 4 Nm off the shoreline<ref name="Rayment et al, 2006">Rayment, W., Dawson, S., Slooten, E. and Childerhouse, S. 2006. Offshore distribution of Hector’s dat Banks Peninsula. Department of Conservation, Wellington. 23pp.</ref>.

After the creation of the BPMMS, many differing views of the effectiveness of the sanctuary arose. While certain groups argued that the sanctuary has proven to be ineffective as bycatch in gillnets continued to victimize Hector’s dolphins just outside the BPMMS<ref name="Rayment et al, 2006">Rayment, W., Dawson, S., Slooten, E. and Childerhouse, S. 2006. Offshore distribution of Hector’s dat Banks Peninsula. Department of Conservation, Wellington. 23pp.</ref>, others argued that gillnet fishing has positive effects as well<ref name="Stone et al, 2000">Stone, G.S., Cavagnaro, L., Hutt, A., Kraus, S., Baldwin, K. and Brown, J. 2000. Reactions of Hector’s Dolphins to Acoustic Gillnet Pingers. Department of Conservation, Wellington. 29pp.</ref>. Gillnetting is a common method of recreational fishing in New Zealand, and in Banks Peninsula, the majority of gillnetting occurs during summer<ref name="Dawson and Slooten, 1993">Dawson, S.M. and Slooten, E. 1993. Conservation of Hector’s dolphins: the case and process which led to the establishment of the Banks Peninsula Marine Mammal Sanctuary. Aquatic Conservation: Marine and Freshwater Ecosystems 3. 207–221.</ref>. Amateur gillnet fishermen caught Hector’s dolphins to alarming levels, and a group of activists consisting of Department of Conservation (DOC) workers and authors proposed the development of a sanctuary where the population density of dolphins was high and where there was substantial evidence of past gillnet bycatches<ref name="Dawson and Slooten, 1993">Dawson, S.M. and Slooten, E. 1993. Conservation of Hector’s dolphins: the case and process which led to the establishment of the Banks Peninsula Marine Mammal Sanctuary. Aquatic Conservation: Marine and Freshwater Ecosystems 3. 207–221.</ref>. This led to the formation of the BPMMS in 1988. Following the establishment of the BPMMS, there were still reports of dead dolphins along the Canterbury coast immediately surrounding the BPMMS, with some deaths ruled due to entanglement<ref name="Stone et al, 2000">Stone, G.S., Cavagnaro, L., Hutt, A., Kraus, S., Baldwin, K. and Brown, J. 2000. Reactions of Hector’s Dolphins to Acoustic Gillnet Pingers. Department of Conservation, Wellington. 29pp.</ref>. In addition, reports of illegal gillnet fishing activities in the BPMMS were documented<ref name="Slooten and Dawson, 2009">Slooten, E. and Dawson, S.M. 2009. Assessing the effectiveness of conservation management decisions: likely effects of new protection measures for Hector’s dolphin. Aquatic Conservation Marine and Freshwater Ecosystems, doi 10.1002/aqc.</ref>, and the DOC, in 2001, also raised concern of the continued deaths of Hector’s dolphins due to recreational fishing nets in the Canterbury region<ref name="Doc and Minfish, 2001">Department of Conservation (DOC) and Ministry of Fisheries (Minfish). 2001. Hector’s dolphin and set netting, Canterbury area: a paper for public comment. Ministry of Fisheries, Dunedin. 9 p.</ref>. In fact, the survival rates of adult Hector’s dolphins had not appeared to have improved significantly despite the establishment of the sanctuary<ref name="Cameron et al, 1999">Cameron, C., Barker, R., Fletcher, D., Slooten, E. and Dawson, S.M. 1999. Modeling survival of Hector’s dolphins around Banks Peninsula, New Zealand. Journal of Agricultural, Biological and Environmental Statistics 4(2): 126–135.</ref>. Recreational gillnet fishing and trawling were also not made illegal in the BPMMS<ref name="Slooten and Dawson, 2009">Slooten, E. and Dawson, S.M. 2009. Assessing the effectiveness of conservation management decisions: likely effects of new protection measures for Hector’s dolphin. Aquatic Conservation Marine and Freshwater Ecosystems, doi 10.1002/aqc.</ref>. Due to the formation of the BPMMS, some 80% of fishing was pushed outside the 4 Nm boundary, exposing Hector’s dolphins outside the 4 Nm boundary to danger<ref name="Slooten and Dawson, 2009">Slooten, E. and Dawson, S.M. 2009. Assessing the effectiveness of conservation management decisions: likely effects of new protection measures for Hector’s dolphin. Aquatic Conservation Marine and Freshwater Ecosystems, doi 10.1002/aqc.</ref>. Fishermen, however, argued that though bycatches were inevitable in gillnet fishing, gillnet fishing does comparably less harm to the seabed and juvenile fish are small enough to swim through the holes in the nets<ref name="Stone et al, 2000">Stone, G.S., Cavagnaro, L., Hutt, A., Kraus, S., Baldwin, K. and Brown, J. 2000. Reactions of Hector’s Dolphins to Acoustic Gillnet Pingers. Department of Conservation, Wellington. 29pp.</ref>.

The continued deaths of dolphins along the Canterbury coast led to an appeal to expand the BPMMS in 2008<ref name="Chadwick, 2008">Chadwick, S. 2008. Notice of Intention to Redefine the Banks Peninsula Marine Mammals Sanctuary. New Zealand Gazette 104, 2770.</ref>. In the appeal, it was requested that the BPMMS be extended further up North to the mouth of the Waipara river and be expanded further seaward to a 12 Nm radius<ref name="Chadwick, 2008">Chadwick, S. 2008. Notice of Intention to Redefine the Banks Peninsula Marine Mammals Sanctuary. New Zealand Gazette 104, 2770.</ref>. It is hoped that with these new measures, there will be less displacement of fishing efforts along the shoreline, although displacement of fishing efforts further offshore is expected<ref name="Slooten and Dawson, 2009"/>


Map of West Coast Marine Mammal Sanctuary <ref name="DoC"/>
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Map of Proposed Expansion of West Coast Marine Mammal Sanctuary <ref name="DoC"/>

West Coast North Island Marine Mammal Sanctuary

Gillnetting has been a widely used fishing method in New Zealand at low numbers since the 1930s however in the 1970s the fishing industry was introduced to stronger nylon nets which were thought to increase substantially to fisheries<ref name="Cephalorhynchus Dolphins">Dawson, S. (2002) Cephalorhynchus Dolphins, In Perin, W.F., Wuisig, B., Thewissen, J.C.M. (Eds), Encyclopedia of Marine Mammals, Academic Press, San Diego, USA, pp 191-196</ref>. This has resulted in studies showing that continued practice in this way has meant Maui dolphin have fallen below their carrying capacity, they are well below the maximum capacity there environment can be used sustainable as there just isn't enough of them<ref>Van Dyke, F. 2008. Conservation Biology. Springer Science, Illinois, USA</ref>. Set netting involves laying a fine nylon net up to 3km long and 10m deep along the seabed, typically at night however the dolphins cannot detect the nets and can become entangled and drown<ref name="Cephalorhynchus Dolphins"/>. Also a study showed that 14 of 45 North Island dolphins from 1970-2000 stranding data, 7 individuals displayed clear gill net entanglement marks and another 4 individuals had cut fins or slit abdomens, suggesting there interaction with fisheries<ref name="Cephalorhynchus Dolphins"/><ref name="MPI, DoC">Ministry for Primary Industries and Department of Conservation. 2012. Review of the Maui’s Dolphin Threat Management Plan, MPI and DoC, Wellington, NZ</ref>.

The risk of fishing-related mortality on Maui’s dolphins depends on how much fishing activity overlaps with Maui dolphins activities, this becomes difficult to know as they tend to have a wide distribution and in the past have been known to use the whole of the west coast of the North island<ref name="Distribution and abundance along North island west coast">Ferreira, S.M, Roberts, C.C. 2003. Distribution and abundance of Maui’s dolphins (Cephalorhynchus hectori maui) along the North Island west coast, New Zealand. Department of Conservation, Wellington </ref>. Set netting has been considered the largest threat to Maui’s dolphins, estimates of around 95% of human induced mortality is due to this method, however this is more common as they tend to be present between the shore and around 4 nautical miles off shore and with full extent unknown, resulting in issues with management and is most likely one of the leading reasons iit took so long for something to be done<ref name="Distribution and abundance along North island west coast"/><ref name="Marine Mammal Protection">Department of Conservation. 2008. Marine Mammals Protection (West Coast North Island Sanctuary) Notice 2008, Department of Conservation, Wellington, NZ</ref>.

A number of key observations were seen and discovered that resulted in the plan for a protected area to manage this declining species, such as:

  • It seemed there was a decrease in alongshore range of the Maui dolphin over the last 20 years,
  • Decline in the number of mitochondrial DNA lineages in current samples
  • There was an analysis done on the level of bycatch in fishing operations in the Maui area
  • It was continuously discovered that there were gill net-marked Maui’s dolphin carcases, and bycatch in gillnets and trawl nets reported during interviews with fishers<ref name="A new abundance estimate">Slooten, E, Dawson, Rayment, W, Childerhouse, S. 2006. A new abundance estimate for Maui’s dolphin: What does it mean for managing this critically endangered species?. Biological Conservation.28.576-581pp.</ref><ref name="Distribution and abundance along North island west coast"/>.

From the issues causing a decline in population size a marine protected area was set up to help stop population decline in 2003, this area is between Mauganui Bluff and Pariokariwa Point, about 24 nm(44.5 km) north of New Plymouth, covering around 2100km of coastline<ref name="DoC 2013"> Department of Conservation. 2013. West Coast North Island Marine Mammal Sanctuary. www.doc.govt.nz/conservatopn/marine-and-coastal/marine-protected-areas/marine-mammal-sanctuaries/west-coast-north-island, Assessed 28/09/2013</ref>. It has been a long battle to fully work out where the best areas would be to protect and what measures should be in place for these dolphins as many observations by DoC and the public are few due to their low numbers and also management has been confusing as the boundary changes down the coast where at some points it extends to 4 nautical miles while at others extends further<ref name="Marine Mammal Protection"/><ref name="MPI, DoC"/>. Maui Dolphins are now protected against gillnetting both recreational and commercial which is banded in these areas however it is not band in the harbours, while trawling is permitted on the open coast beyond the 1 nautical mile mark off shore<ref name="Marine Mammal Protection"/><ref name="Distribution and abundance along North island west coast"/>. However Maui dolphins have been known to use around 3 of the 5 major harbours along the west coast but these areas are not included in the protected area, only parts of the Manukau harbour is known to have some degree of protection and within the sanctuary boundary there are restrictions on sea bed mining and acoustic seismic survey work<ref name="A new abundance estimate"/>. This seismic survey work may become an issue due to the increased interest of oil and natural gas off the Taranaki coast<ref name="MPI, DoC"/>.

It has been seen that there are restrictions on not just the fishing practices but also the gear such as what trawling gear can be used and how close the boats can get into shore<ref>Stewart, J, Callagher, P. 2013. Industry response to the 2003 set net restrictions for protection of Maui’s dolphin. Marine Policy 42:210-222</ref>. Also Set net restrictions have been put into place to help stop dolphin deaths, the measures include seasonal and area set-net closures <ref name="Marine Mammal Protection"/><ref>Kuruppu, S, Milne, M.J. 2010. Dolphin deaths, organizational legitimacy and potential employees ‘reactions to assured environmental disclosures. Accounting Forum 34: 1-19</ref>. Unfortunately, there is no observer programme and no quantitative data on continued impacts of fishing but it has been seen that there is some trawling and illegal gillnetting in the protected area; this is due to continued gillnet marks being found on some of the carcasses of Maui dolphin<ref name="Marine Mammal Protection"/>. A large issue is obtaining correct and reliable data not just with scientific studies done but also from the fishing industry and fishermen themselves who have been catching them as it’s a hard thing to make fisheries give the right information and right numbers<ref name="Marine Mammal Protection"/><ref> name”Preventing an extinction event”> Bird, R, Palka, M. 2013. Preventing an extinction event: Is New Zealand’s management response enough to save the world's rarest marine dolphin?. IWC Meeting Portal, Scientific Committee Annual Meeting 2013</ref>. And due to the protected areas large size it sometimes seems to be hard to manage as there are not enough resources to comprehensively cover the protected area<ref name="Distribution of Maui’s Dolphin, Cephalorhyncus hectori maui">Slooten, E, Dawson, S.M, Rayment, W.J, Childerhouse, S.J. 2005. Distribution of Maui’s Dolphin, Cephalorhyncus hectori maui. New Zealand Fisheries Assessment Report 2005/28.21p.</ref>.

Currently there are continued talks to extend parts of the North island west coast sanctuary around Taranaki. Its purpose is to provide better protection to Maui dolphin numbers which have been found in this area, from set netting both recreational and commercial<ref name="MPI, DoC"/>. The minister of conservation has asked the department of conservation to consult on a purpose and these are still being finalized as submissions close early October 2012 for the latest extention plans<ref name="DoC 2013"/>. This argument has been going on for a long time as advocacy groups have already urged the government to do something before the Maui dolphin goes extinct however many Fisheries groups are opposed to the extension and have said that it would actually cost the New Plymouth fisheries hundreds of thousands of dollars and jobs<ref>Jolliff, E. 2012. Fisheries criticize Maui dolphin set net ban. 3 News, http://www.3news.co.nz/Fishers-criticise-Maui-dolphin-set-net ban/tabid/1160/articleID/259467/Default.aspx, Assessed 27/09/2013</ref><ref>Cumming, G. 2012. Maui’s dolphin swimming in sea of trouble. The New Zealand Herald, http://www.nzherald.co.nz/nz/news/article.cfm?c_id=1&objectid=10844715, Assessed 28/09/2013</ref>. It is hoped that these new extensions will help the Maui dolphin populations increase, although it is likely to be a long fight with the fishing industry which could be negatively affected by the changes and have been strongly against such heavy measures

Worldwide Examples

The Baiji <ref name="Baiji in lower Yangtze">Zhou, K, Sun, J, Gao, A. and Wursig, B. (1998) Baiji (Lipotes vexillifer) in the lower Yangtze River: movements, numbers threats and conservation needs, Aquatic Mammals, pp123-132 </ref>

The vaquita (Phocoena sinus) is the world's smallest porpoise, found in the Gulf of California in Mexico.<ref name="vaquita">Rojas-Bracho, L. and Jarmillo-Legoretta, A.M. (2009) Vaquita: Phocoena sinus, Ed. Perrin, W.F., Wursig, B. and Thewissen, J.G.M.Encyclopedia of Marine Mammals, 2E, Academic Press, pp 1196-1200</ref>. Its population is less than 200 at the moment and is similar to Hector's and Maui dolphins in that it is critically endangered due largely to unsustainable fishing net caused deaths. The Mexican Government and WWF have been working together to phase out the endangering gill-nets in favour of more selective fishing techniques which do not cause as much harm to vaquita<ref name="vaquita"/><ref>http://worldwildlife.org/species/vaquita</ref>.

Another example of a dolphin which suffers from high by-catch rates is the Irrawaddy dolphin (Orcaella brevirostris) which are found in the three south-east Asia rivers of Ayeyarwady, Mahakam, and Mekong<ref>www.worldwildlife.org/species/irrawaddy-dolphin</ref>. There are only an estimated 78-91 remaining in the Cambodia and Lao PDR region, which has resulted in local government action from Cambodia in association with WWF to conserve the populations and protect them from gill-nets. A ban of the use of the nets has been set in the main habitat of the Irrawaddy dolphin. This limitation has been difficult on the fishing industry of the region, and the WWF is working to find alternatives<ref>www.wordwildlife.org/stories/rare-dolphin-offered-a-second-chance</ref>. Irrawaddy dolphins are important to the region for cultural and eco-tourism reasons, much like the Maui and Hector's dolphins.

The Baiji, Yangtze river dolphin, (Lipotes vexillifer) is an endemic species to china and only found in the middle and lower reaches of the Yangtze river.<ref name="Baiji in lower Yangtze">Zhou, K, Sun, J, Gao, A. and Wursig, B. (1998) Baiji (Lipotes vexillifer) in the lower Yangtze River: movements, numbers threats and conservation needs, Aquatic Mammals, pp123-132</ref>. It was said to be a relict species with it considered the only living ancestor of its whole family of mammals<ref name="Baiji in lower Yangtze"/>. First estimates in 1979-1981 stated around only 400 animals and when the survey was repeated to find the whole species range count in 1997-1999 it was found that this had dropped to around 13 individuals.<ref name="Baiji">Zhou, K. (2002) Baiji, In Perin, W.F., Wuisig, B., Thewissen, J.C.M. (Eds), Encyclopedia of Marine Mammals, 2E, Academic Press, San Diego, USA, pp 191-196</ref>. It was then accepted that the population was continuing to decline and was thought to be due to the continued human activity in the river such as there historic exploitation and interaction with fisheries<ref name="Baiji in lower Yangtze">. During a survey in 2006 it was found that a minimum of 19830 large fishing vessels and 1175 fishing vessels were seen in the river which is thought to have been a major reason for the Baiji's declining population<ref name="Baiji"/>. It was designated in the Chinese national first category of national key protected wildlife species with full protection in its range however continued threats and conservation efforts were unable to save the species<ref>Xie, P. and Chen, Y. 1999. Threats to Biodiversity in Chinese Inland Waters, Ambio, pp.674-681</ref>.It was seen for cultural significance and some ecotourism as the Baiji is thought to be the first cetacean species known to have gone extinct due to human activity<ref name="Baiji"/>.

Conclusions & recommendations

Proposed future developments in marine mammal sanctuaries <ref name="DoC"/>

Currently, gillnetting is banned within marine mammal sanctuaries in New Zealand such as Banks Peninsula, however this has poised the question if they are enough and how big should they get, many advocacy groups believe in a complete ban on gillnetting within the habitat range of both dolphin species so they have a chance to re build there population, such as in the figure below showing the transformation of Marine reserves in New Zealand and what the next step might be. Also there could be measures in place to in some ways encourage interaction between the different fragmented populations to help boost the numbers. the fishing industry needs to develop more sustainable methods of catching there quota that are in a non invasive way where the boats aren't intruding, a key idea that should be implemented in all is seasonality, to make sure that the boasts are not working heavily in the habitat areas during breeding seasons.

The management of Marine protected areas could also improve to help the survival of the Hectors and Maui dolphin such as having the areas large enough to encompass there full range but also integrate a more widely sustainable plan. It seems that there doesn't need to be so much research into how the marine areas are achieving their goals but more into how the animals interact with their environment giving the best outcomes for managing them. Currently there is some indication that there is potential for the integration of governmental and commercial interests to yield positive results as resources are pooled together to produce a more sustainable outcomes for both dolphins and business interests. New technologies and knowledge are being created through this integration of resources to produce more tools to aid in the conservation and protection of hectors dolphin species

Something drastically needs to change with how Hectors and Maui dolphins are managed as if practices continue at these levels there will not be any dolphins left, and New Zealand would have lost an icon.


Maps of New Zealand showing current and desired future protection of the marine environment <ref>Slooten, E. (2013) Population Viability Analyses for Hectors dolphins, PVA Lecture 3 material, 2nd semester,2013, Otago University Zoology department</ref>

References

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