Overfishing of the Bluefin Tuna: New Zealand's Impact on Declining Fishstocks

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Contents

Introduction

Figure 1: Southern Bluefin Tuna, Thunnus maccoyii

The Southern Bluefin Tuna, Thunnus maccoyii, is a highly migratory species of Tuna which is found in southern hemisphere open waters (figure 1). Southern Bluefin Tuna (SBT) are found between 10 and 50° latitude and are caught off the West Coast of the South Island, in Northland and in the Bay of Plenty. Bluefin are a migratory species which travel thousands of kilometers a year, breeding in the Indian Ocean off western Australia before arriving in New Zealand in prime condition at around the age of 5 years old (figure 2) <ref name=SIC> Seafood Industry Council. (2007). The Guide Book To New Zealand Commercial Fish Species, 2007 Revised Edition. May. </ref>.

In New Zealand, since 1991, surface longlines have been the predominant gear used to target southern bluefin tuna in domestic fisheries with 96% of all days fished using this method. Other methods include using hand line (4%) and trolling (< 1%) (MfPI, 2012). New Zealand is a founding member of the Commission for the Conservation of Bluefin Tuna (CCSBT) along with Australia, Taiwan, Indonesia, Japan and Korea. The CCSBT aims to manage SBT stocks in multinational waters and provides a number of stock SBT stock assessment and management initiatives <ref name=Mf> Ministry for Primary Industries. (2012). Fisheries Assessment Plenary, November 2012: Stock Assessment and Yield Estimates Compiled by the Fisheries Science Group. pp 410-440. </ref>.

Figure 2: Spawning Region of Southern Bluefin Tuna. Source: Bakun, 2012 <ref name=Bakun>Bakun, A. 2012. Ocean eddies, predator pits and bluefin tuna: implications of an inferred ‘low risk-limited payoff’ reproductive scheme of a (former) archetypical top predator. Fish and Fisheries 14(3). 424-438</ref>

Overfishing of the Southern Bluefin Tuna and Current State of Fish Stocks

Available stocks of Southern Bluefin Tuna have decreased rapidly in the past half century and today current populations face continued threat of over exploitation. SBT is considered one of the world’s most valuable fish species, overfishing has lead to decreases in available breeding stocks <ref name=Bakun>Bakun, A. 2012. Ocean eddies, predator pits and bluefin tuna: implications of an inferred ‘low risk-limited payoff’ reproductive scheme of a (former) archetypical top predator. Fish and Fisheries 14(3). 424-438</ref>. For stocks to remain positive, egg to adult mortality of the species must be >0.999. Although if this rate was to increase by one ten-thousandth of 1% the overall result would see reproductive failure of Southern Bluefin Tuna stocks <ref name=Bakun>Bakun, A. 2012. Ocean eddies, predator pits and bluefin tuna: implications of an inferred ‘low risk-limited payoff’ reproductive scheme of a (former) archetypical top predator. Fish and Fisheries 14(3). 424-438</ref>. Currently, quotas set by the CCSBT over the recent decade have seen much change and fluctuation, based on claimed population uncertainty. The organisation has struggled to reach agreements on set global total allowable catches, with both economic and environmental factors to be considered <ref name=Kurota>Kurota, H., Hiramatsu, K., Takahashi, N., Shono, H., Itoh, T., Tsuji, S. 2010. Developing a management procedure robust to uncertainty for southern bluefin tuna: A somewhat frustrating struggle to bridge the gap between ideals and reality. Population Ecology 52(3). 359-372</ref>.

History of Fishing in New Zealand and Australia

Initial exploitation of southern bluefin tuna stocks arose during the late 1950’s within Australia and New Zealand as quota management schemes for annual species catch had not yet been enforced. Within the New Zealand context Japanese longliners were granted stay up until 1995, while domestic fisheries developed during the 1980’s under much government encouragement <ref name=STNPlanery2010>Ministry for Primary Industries. 2010. Southern bluefin tuna (Thunnus maccoyii). Fisheries Assessment Plenary 2010. 142-154</ref>. The establishment of the New Zealand Japan Tuna Company Ltd in 1988 saw large volumes of bluefin tuna being caught via Japanese longliner vessels in southern waters, aided by the instalment of ultra-low freezers within the fleet. This gave the ability to travel farther afield to source bluefin tuna stocks, and for longer periods of time <ref name=Tada>Tada, M. 2012. Resource constraints in the development of the Australian Southern Bluefin Tuna industry. Faculty of Agriculture. Kinki University. 45-55</ref>. The 1960’s saw the vast volumes caught in previous years reduced greatly as a result of large quantities being sourced, particularly within Australian waters. It was not until later that international quota systems were developed to allow for preserved stocks, where Australia, New Zealand and Japan agreed to set limits on annual catches. The result was in 1985, where this first quota scheme came into practice between the three nations, with a total annual allowable catch of 38,650 ton, although this was reduced to 31,750 later in the decade, in 1989 <ref name=Tada>Tada, M. 2012. Resource constraints in the development of the Australian Southern Bluefin Tuna industry. Faculty of Agriculture. Kinki University. 45-55</ref>.

In follow up to this agreement the establishment of the CCSBT developed in 1994 between Australia, New Zealand and Japan <ref name=PWard>Ward, P., Sahlquist, P. 2013. A methodology for obtaining regular, statistically robust estimates of recreational and charter fishing catch of southern bluefin tuna in Australian waters. Australian Bureau of Agricultural and Resource Economics and Sciences. Department of Agriculture, Fisheries and Forestry. 1-52</ref>. This organisation aimed to manage quota schemes of southern bluefin tuna, controlling catch limits of the three nations <ref name=Kurota>Kurota, H., Hiramatsu, K., Takahashi, N., Shono, H., Itoh, T., Tsuji, S. 2010. Developing a management procedure robust to uncertainty for southern bluefin tuna: A somewhat frustrating struggle to bridge the gap between ideals and reality. Population Ecology 52(3). 359-372</ref>. Although not all nations agreed to join besides the three establishing nations, of which saw those non member nations, such as the Republic of Korea, Taiwan and Indonesia, not adhering to quota limits set. Subsequently this resulted in a further decline of southern bluefins during the 1990’s as over exploitation of stocks occurred. <ref name=Kurota>Kurota, H., Hiramatsu, K., Takahashi, N., Shono, H., Itoh, T., Tsuji, S. 2010. Developing a management procedure robust to uncertainty for southern bluefin tuna: A somewhat frustrating struggle to bridge the gap between ideals and reality. Population Ecology 52(3). 359-372</ref>.

Further issues arose during the 1990’s and saw Japan disagreeing to set quota limits, and pushing toward southern bluefin catch increases based upon the perception of greater bluefin stocks available than that described by the CCSBT <ref name=Kurota>Kurota, H., Hiramatsu, K., Takahashi, N., Shono, H., Itoh, T., Tsuji, S. 2010. Developing a management procedure robust to uncertainty for southern bluefin tuna: A somewhat frustrating struggle to bridge the gap between ideals and reality. Population Ecology 52(3). 359-372</ref>. This involved Australia and New Zealand opposing such changes to quotas, taking a stricter and more conservative approach to available stocks and disregarding the plea to have this raised. In follow up to this disallowance, Japan established the unilateral Experimental Fishing Program (EFP) in 1998-1999 <ref name=Kwaitowska>Kwaitowska, B. 2001. Southern bluefin tuna, international decisions. The American Journal of International Law 95(1). 162-171</ref>. This of which was challenged by Australia and New Zealand in 2000, after suspecting the Japanese EFP was being used as method of obtaining a higher quota of southern bluefin tuna and was taken to the International Tribunal of the Law of the Sea (ITLOS). The final outcome eventually deemed the practice to be an internal issue referring back to the CCSBT <ref name=Kwaitowska>Kwaitowska, B. 2001. Southern bluefin tuna, international decisions. The American Journal of International Law 95(1). 162-171</ref>.

Japanese Market for Bluefin Tuna and New Zealand Exports

Southern Bluefin Tuna Japanese Market Prices 1975-2009 Source: Tada, 2012 <ref name=Tada>Tada, M. 2012. Resource constraints in the development of the Australian Southern Bluefin Tuna industry. Faculty of Agriculture. Kinki University. 45-55</ref>

Southern Bluefin tuna that are caught in New Zealand are dominantly exported to Japan where they are sold at a high price due to extremely high demand where it is used for sashimi and sushi <ref name=Mf> Ministry for Primary Industries. (2012). Fisheries Assessment Plenary, November 2012: Stock Assessment and Yield Estimates Compiled by the Fisheries Science Group. pp 410-440. </ref>. . Southern Bluefin tuna are also exported to the USA and Canada where it is also highly prized for sashimi and sushi.This high sale price is a driver for fisheries to catch and sell more rather than protect the species. This is added to due to the fact that the meat is highly consumed in food products though out Japan, USA, Canada and though out most of the world <ref name=MoF2011>Ministry of Fisheries. 2011. Southern bluefin tuna. Fisheries Assessment Plenary 2011. 117-118</ref> . The export value of southern Bluefin tuna in 2008 was $7 million in New Zealand with the quota value of southern Bluefin tuna in 2009 was reported as being $15.4m <ref name=Mf> Ministry for Primary Industries. (2012). Fisheries Assessment Plenary, November 2012: Stock Assessment and Yield Estimates Compiled by the Fisheries Science Group. pp 410-440. </ref>.

The largest whole sale market of SBT in the world is the Tsukiji market located in Tokyo Japan.the Tsukiji market handles more than 2,400 tons of fish a day worth around US$20 million every day <ref name=fishprice> newsfeed.time.com/2013/01/07/japan-worlds-most-expensive-fish-sold-for-1-8-million </ref> . The main event at these markets are the pre-dawn auctions for tuna. Blue fin tuna have sold for over $150,000 at Tsukiji. In 2001, a 202-kilogram wild tuna caught in Tsugaru Straight near Omanachi I Aomori Prefecture sold for $173,600, or about $800 a kilogram. In 2013, a 222-kilogram tuna was sold at Tsukiji for $1.8 million, or about $8,000 per kilogram.

Charter vessels operate out of Milford sound target SBT. These charters head west from Milford to the continental shelf where tuna are likely found. There are also charter vessels that operate out of Greymouth and Westport that take Southern Bluefin as by catch <ref name=Mf> Ministry for Primary Industries. (2012). Fisheries Assessment Plenary, November 2012: Stock Assessment and Yield Estimates Compiled by the Fisheries Science Group. pp 410-440. </ref>. All of theses charter vessels add to the pressure that is put on the tuna as it means there is more hooks in the water taking more of the spawning bio mass which will then in future lead to less fish.

Indicators of Southern Bluefin Tuna Stock Health

Determination of the status of the southern bluefin tuna stock is undertaken by the CCSBT Scientific Committee (CCSBT-SC). The stock assessment is based on the results from the CCSBT Operating Model which was finalised in 2011 to a final grid used for assessment. The Model is statistically based and an agreed range of values for key input parameters is run and the results averaged over the whole grid. In 2011 a set of four alternative models considered to be highly probable were run to test the robustness of the results from the base grid. A stock assessment report was produced in 2011 with a second report due in 2013<ref name=Mf> Ministry for Primary Industries. (2012). Fisheries Assessment Plenary, November 2012: Stock Assessment and Yield Estimates Compiled by the Fisheries Science Group. pp 410-440. </ref>.

Fishery Indicators

A range of fishery indicators that are independent of any stock assessment model are considered to provide support and additional information important to current stock status assessment. The two major indicators are:

• Recent recruitment: the age at which SBT can be caught and counted in nets.

• Spawning biomass and vulnerable biomass: the stock population capable of reproducing.

Indicators are derived using a number of different methods of data collection and interpretation. Data is provided by each of the members of the CCSBT as part of either scientific studies or the catch documentation scheme<ref name=Mf> Ministry for Primary Industries. (2012). Fisheries Assessment Plenary, November 2012: Stock Assessment and Yield Estimates Compiled by the Fisheries Science Group. pp 410-440. </ref>.

Catch Documentation Scheme

CCSBT has operated a catch documentation scheme since 1st January 2010. The scheme introduced documentation and tagging requirements for all SBT catches for CCSBT member nations. Additionally a market-based controls and reporting obligations. Recent actions by individual CCSBT members to improve monitoring, control, and surveillance measures for southern bluefin tuna fisheries are also intended to halt the occurrence of unreported catch<ref name=McGregor>McGregor, G. (2008). Ministry of Fisheries, Reporting game fish catches of Pacific Bluefin Tuna and Southern bluefin tuna aboard charter vessels during 2007 and 2008.</ref>.

Data generation

Data is used to generate:

• Catch at age data: calculated using methods such as standard age-length-key (ALK) in combination with the Morton and Bravington (M&B) method.

• Catch per unit effort (CPUE): an indirect measure of abundance where changes in CPUE are inferred to reflect changes in abundance of SBT.

• Information from surveys: these include aerial sightings, tag and release programs and troll surveys.

Catch at age data

Catch at age data is calculated through a number of methods. The standard age-length-key(ALK) was developed in Australia and is based on the the use of otoliths to estimate the age of SBT. An otolith is the ear bone of a tuna and can be easily extracted, otolith ageing is currently considered the most reliable method of direct dating. Direct ages estimated from otoliths are combined with length frequency data from the catch using parametric methods developed by Morton and Bravington (2003). The resulting AlK is a reliable tool for dating BFT. age data were used with the length frequency data from the catch to estimate the proportions<ref name=Farley>Farley, J. (2006).Developing an age-length key for the Australian SBT surface fishery for the 2004/05 fishing season based on direct age estimations using otoliths. CSIRO Division of Marine and Atmospheric Research. December</ref> <ref name=Morton>Morton, R. and Bravington, M. 2003. Estimation of age profiles of southern bluefin tuna.CCSBT Scientific Meeting; 1-4 September 2003, Christchurch, New Zealand. CCSBTESC/0309/32.</ref> .

Aerial Surveying

Aerial surveys use the commercial spotting index to calculate surface abundance per unit of effort (SAPUE) of tuna between 2 and 4 years old. Data for 11 fishing seasons can be used to calculate SAPUE. These surveys occur primarily off the coast of Australia and employ experienced tuna spotters who serve a dual purpose with commercial operations. Younger fish are found predominantly near the surface allowing for aerial survey methods to give an estimation of stock health<ref name=CCSBT2012>Commission for the Conservation of Southern Bluefin Tuna (2012). Report of the Seventeenth Meeting of the Scientific Committee. 27-31 August. Tokyo, Japan.</ref>.

Local Monitoring of Bluefin Tuna Stocks in the West Coast Fishery

Between 2007 and 2010, charter boat operators fishing for bluefin during the West Coast fishing season recorded the number and weight of fish their anglers caught and landed. Initially MFish, the NZ Marine Research Foundation along with Stanford University carried out a programme which used satellite tagging to track Pacific bluefin tuna caught by charter vessels fishing off of the West Coast. Successful tagging and data retrieval was carried out in the 2007 and 2008 seasons. From 1 November 2010 mandatory catch reporting was put in place in recreational fisheries. Data collected from anglers was integrated into the New Zealand Cooperative Tagging Programme; a cooperative project between the Ministry of Fisheries, the New Zealand Sport Fishing Council and anglers who tag and release gamefish such as bluefin tuna. The data produced provides an estimate of the number of fish that are released alive by game fishers. Recaptures provide information on movement, time at liberty, displacement rates, and growth rates of fish <ref name=letter>Ministry of Fisheries (2008) Initial Position Paper – Tagging Scheme For Southern Bluefin Tuna</ref>.

Trends

Spawning stock biomass for the base case, showing the medians, quartiles and 90th percentiles. Also includes reference points of 20% of pre-exploitation spawning stock biomass and the spawning stock biomass in 2004. Source: Report of the Scientific Committee 2011.
Catch per unit effort (CPUE)(number of SBF per thousand hooks) by calendar year for the New Zealand Charter (solid line) and domestic (dashed line) longline fleets operating in New Zealand. Source: CCSBTESC/ 1208/SBT Fisheries New Zealand (2012)

Historical Trends

The declination in SBT had been steadily occurring since industrialisation of fisheries targeting the species from the 1940’s onward (seen in the spawning stock figure). Quota systems had been introduced much later in this period, and enforcement still remains an issue. Over past years, record lows occurred during the 1980’s after a rapid decline during the late 1950’s to 1960’s <ref name=MoF2011>Ministry of Fisheries. 2011. Southern bluefin tuna. Fisheries Assessment Plenary 2011. 117-118</ref>. A regenerative trend was established following the all time low biomass figures during the 1980’s, of which occurred after quota figures were introduced by the New Zealand, Australia and Japanese fishing industries <ref name=MoF2011>Ministry of Fisheries. 2011. Southern bluefin tuna. Fisheries Assessment Plenary 2011. 117-118</ref>. This period of stock gaining was relatively small, where declining biomass statistics resumed from 1995 to present.

Trends in juvenile abundance (recruitment)

Pushes toward recruitment monitoring programs began in 1993 as collaborative work involving the Japanese National Research Institute for Far Seas Fisheries (NRIFSF) and the Australian Commonwealth Scientific and Industrial Research Organisation (CSIRO) <ref name=Davies>Davies, T. 2002. Southern bluefin tuna, recruitment and monitoring program 2001/2002. Australian Fisheries Management Authority. 1-10</ref>. This was established in order to:

• Monitor the abundance of juvenile southern bluefin tuna in order to gauge available stocks for future projections and spawning stocks

• Develop regular monitoring research

• Review proposals for any future research involving southern bluefin tuna

The monitoring of juveniles may be accomplished a number of ways, including the use of spot surveying/aerial surveying of relevant areas of accumulated juveniles, acoustic monitoring, archival tagging, and integrated analysis <ref name=Davies>Davies, T. 2002. Southern bluefin tuna, recruitment and monitoring program 2001/2002. Australian Fisheries Management Authority. 1-10</ref>. These methods may be inconclusive as it is reliant on SBT accumulating in expected research areas, as areas where groupings of juveniles amass vary from year to year.

Recent research has showed less than positive results for future southern bluefin tuna stocks, where in 2009 it was calculated that there remained 5% of the total spawning stock population that was seen prior to the mid 20th century <ref name=MoF2011>Ministry of Fisheries. 2011. Southern bluefin tuna. Fisheries Assessment Plenary 2011. 117-118</ref>. Stated in the 2012 Southern Bluefin Tuna plenary, recent recruitment levels based on recruitment indicators are well below past figures. These statistics represent massive challenges in the species survival, where the decrease in available number to spawn leaves reproduction numbers extremely low <ref name=MoF2011>Ministry of Fisheries. 2011. Southern bluefin tuna. Fisheries Assessment Plenary 2011. 117-118</ref>. At this figure, the spawning stock required to maintain a maximum sustainable yield (MSY) is only at 15% of that required <ref name=MoF2011>Ministry of Fisheries. 2011. Southern bluefin tuna. Fisheries Assessment Plenary 2011. 117-118</ref>. This spawning stock recruitment of SBT is believed to be averaged at 12 years of age. The follow on effects of poor recruitment stock for spawning will decrease at an exponential rate. This has resulted in the need for reduced catch limits, following poor years of recruitment, to help maintain biomass figures. This was exemplified after the poor reproductive years of 2000 to 2002, where in follow up, the CCSBT were forced to reduce global catch limits in 2006 and furthermore in 2009 <ref name=MoF2011>Ministry of Fisheries. 2011. Southern bluefin tuna. Fisheries Assessment Plenary 2011. 117-118</ref>.


Associated Environmental Problems

The southern Bluefin tuna are an apex predator and feed on a mixture of fish, crustaceans, squid. In addition to larger prey juveniles also feed on a variety of zooplankton and micronecton species <ref name=Mf> Ministry for Primary Industries. (2012). Fisheries Assessment Plenary, November 2012: Stock Assessment and Yield Estimates Compiled by the Fisheries Science Group. pp 410-440. </ref>. SBT are a large pelagic predator, this means that they are near the top of the food chain. The removal of such a predator from the food chain will have a top down effect on the fish, crustaceans and squid they feed on <ref name=MoF2011>Ministry of Fisheries. 2011. Southern bluefin tuna. Fisheries Assessment Plenary 2011. 117-118</ref> . SBT exert substantial control over the population size of species further down the food chain. The full effect of the removal of SBT on the food web is not fully understood.

Ecological Effects of Fishing for Tuna (bycatch):

Figure showing fishing effort in blue and observed sea bird captures as red dots.

The over fishing of southern bluefin tuna is directly responsible for driving both the target tuna species and some species of seabirds towards extinction. The longlining method used to catch the tuna also catches several other types of animals that are then harmed or killed. Between 2002-03 and 2010-11 there were 511 observed captures of sea birds in the southern Bluefin longline fisheries <ref name=Mf> Ministry for Primary Industries. (2012). Fisheries Assessment Plenary, November 2012: Stock Assessment and Yield Estimates Compiled by the Fisheries Science Group. pp 410-440. </ref>. The worst places for sea bird bycatch around New Zealand are off the west coast of the south island and also around the East Cape. This was mitigated by implanting a notice that longlines may only be set during hours of darkness and the need to use a tori line when setting. During the same time period (2002-03 and 2010-11) there was also three observed catches of sea turtles in the same area. These have only been caught in the area fished off the east coast of the north island. All documented cases have seen the turtles caught and released alive. This is a great result so far for sea turtle release rates but still leaves room for mortality due to them still being caught.


There is also a threat to marine mammals when longlining for southern Bluefin tuna. Within the same time zone as above there were five observed catches of whales and dolphins <ref name=Mf> Ministry for Primary Industries. (2012). Fisheries Assessment Plenary, November 2012: Stock Assessment and Yield Estimates Compiled by the Fisheries Science Group. pp 410-440. </ref>. This was made up of two long-finned pilot whales and three unidentified cetaceans. All of these captures of cetaceans were documented as being caught and released alive. These catches occurred in the east coast of the North Island, west coast of the South Island, Fiordland and the Bay of Plenty. The capture of cetacean do not correlate to fishing effort as they are more generalised to the east coast of the North Island.

Another animal that is a bycatch of southern Bluefin longlining is the New Zealand fur seal. These seals are predominantly found in waters south of around 40˚S to Macquarie Island. This means that there is an overlap of the area that these seals as mostly found and the commercial fishing grounds of New Zealand. There were 202 fur seals caught between (2002-03 and 2010-11)<ref name=Mf> Ministry for Primary Industries. (2012). Fisheries Assessment Plenary, November 2012: Stock Assessment and Yield Estimates Compiled by the Fisheries Science Group. pp 410-440. </ref>. Most of these captures occur around the continental shelf of New Zealand. This is in areas such as south and west of Fiordland and also in the Bay of Plenty-East cape area. These captures normally result in catching and releasing the seals alive. Although the seals are released alive they are often released with hook and trace still attached. This is likely due to the fact that the fur seals attempt to feed on the fish that have already been caught off on the uneaten bait while retrieving the lines from the water.

In addition to these specific marine animals being caught there is also a large amount of untargeted fish bycatch including many types of shark and other significant fish species <ref name=MoF2011>Ministry of Fisheries. 2011. Southern bluefin tuna. Fisheries Assessment Plenary 2011. 117-118</ref> .

Management method

National Fishstock Allocation by the CCSBT

Allocated TAC for CCSBT memebers and cooperating non-members
Catches by New Zealand vessels since the establishment of the QMS

As a member of the CCSBT New Zealand has been subject to an international fish stock allocation scheme since the inception of CCSBT in 1994. In 2011, the Commission adopted a management procedure to set quotas for 3 year periods based on the most recent fisheries indicators from SBT stock. The management procedure is designed to rebuild the spawning stock to 20% of the unfished level by 2035. In 2011 the Commission decided not to fully implement the first increase TAC including in the the management plan due to concern that the TAC may have to be reduced again at the end of the 3 years. The Commission instead opted for a limited increase in the first 3 year period. Quotas set for the next 3 years allowed a 1000 t increase in 2012 from 2011 to 10 449 tonnes, a further increase in 2013 to 10 949 tonnes and subject to the management plan output in response to fisheries indicators an increase to 12 449 in 2014<ref name=Mf> Ministry for Primary Industries. (2012). Fisheries Assessment Plenary, November 2012: Stock Assessment and Yield Estimates Compiled by the Fisheries Science Group. pp 410-440. </ref>.


A national catch limit of 420 tonnes per year was initially allocated to New Zealand. An increased catch allocation too was approved by the CCSBT for the 2009-10 fishing year. This increase was widely criticised by environmental organisations such as Greenpeace and WWF as whilst New Zealand's quota increased by 27% to 570 tonnes, the CCSBT reduced global catch allocations by approximately 20%. WWF spokesman Rebecca Bird criticised the decision:

"What the Government is saying is completely different to its actions. We have the Ministry of Fisheries Chief Executive stating that 'New Zealand has been a leading voice on putting in place effective measures to manage Southern bluefin and encouraging all nations to take action' whilst at the same time announcing that we plan to harvest 27% more of this species on the very brink of commercial extinction." <ref name=WWF>McGregor, G. (2008). WWF. (2010). NZ Southern bluefin tuna quota increase hypocritical. March 26th. http://www.wwf.org.nz/?3980/NZ-Southern-bluefin-tuna-quota-increase-hypocritical.</ref>.

A further national stock allocation increase to 800 tonnes was provided by the CCSBT in the 2011-12 fishing season followed by an increase to 830 tonnes for the 2012-13 season. These increases were approved by the CCSBT as part of an increase in global allocations due to signs of improvement in SBT spawning stocks<ref name=Mf> Ministry for Primary Industries. (2012). Fisheries Assessment Plenary, November 2012: Stock Assessment and Yield Estimates Compiled by the Fisheries Science Group. pp 410-440. </ref>. .

National Quota Management System

A national quota management system (QMS) was introduced in 2004, with SBT provided for under Section 14 of the Third Schedule of the 1996 Fisheries Act. The QMS was a direct management response to a national allocation of southern bluefin tuna determined for New Zealand as part of an international agreement under the CCSBT. The QMS established a total allowable catch (TAC), a total allowable commercial catch (TACC), a recreational allowance, a customary non commercial allowance and a fishing related mortality allowance. The TAC applies to all New Zealand fisheries waters, and all waters beyond the outer boundary of the exclusive economic zone<ref name=Mf> Ministry for Primary Industries. (2012). Fisheries Assessment Plenary, November 2012: Stock Assessment and Yield Estimates Compiled by the Fisheries Science Group. pp 410-440. </ref>. .

If the domestic catch limit is exceeded next seasons catch limit will be adjusted by an equivalent amount.

Evaluation of Management Methods

There appears to be a high amount of contradiction regarding the management and allocation of SBT fishing stocks and those figures representing the future decline of populations globally. On the one hand the management of tuna stocks looks at allocation from an economic perspective, clearly displayed by the growth in quota limits, particularly in New Zealand. This of which was described prior within the management section and has seen growth of allocated stocks since 2010 in New Zealand and 2011 globally. This growth trend in allocated stocks for New Zealand’s quota, of which provides economic advantage and growth for the SBT fishing industry, especially due to growing demand in Japan<ref name=Mf> Ministry for Primary Industries. (2012). Fisheries Assessment Plenary, November 2012: Stock Assessment and Yield Estimates Compiled by the Fisheries Science Group. pp 410-440. </ref>.

The contradicting perspective of SBT management regards the enabling of future growth and replenishment of already severely depleted SBT stocks globally. The trends described earlier state the recruitment figures are at 15% of the total needed to maintain adequate stocks, where only 5% of the original stock figures remain from that seen earlier in the 20th century. This therefore describes the pressures this species are under in order to maintain populations and prevent total reproductive failure<ref name=MoF2011>Ministry of Fisheries. 2011. Southern bluefin tuna. Fisheries Assessment Plenary 2011. 117-118</ref>.

Based on statistics, and the drivers behind the management schemes in place, it is clear that they need to be reviewed and lowered. The population statistics will not allow continued growth in allocated catch limits, to increase stocks or at least maintain current populations of SBT. It would appear that the increases in stock allocation are in the best interest for those gaining an economic advantage from the exploiting of SBT resources. This would seem that this is simply a short term management solution that grants access to stocks for fishing benefit and completely disregards environmental stability and replenishment of the SBT biomass.

Conclusions & Recommendations

With the current regulations on the fishing and catch limits for southern Bluefin tuna, it is unlikely that the stock numbers will experience a rapid increase. With current restrictions it is predicted that by 2035 the spawning bio stock should rise from the 5% it is at now, to approximately 20%SB0 with a 70% probability <ref name=Mf> Ministry for Primary Industries. (2012). Fisheries Assessment Plenary, November 2012: Stock Assessment and Yield Estimates Compiled by the Fisheries Science Group. pp 410-440. </ref> . This estimate is optimistic with the current rates of recorded catch and also illegal catching, which would make it hard for the existing stock to reach an age to return to spawn. To ensure that the spawning stock has a chance to grow in size, the catch limits would all have to be cut to a more sustainable limit over a period of time that would allow for juvenile tuna to reach an age of sexual maturity, and allow time to breed. After this amount of time there could be a reassessment of the stock numbers and alterations may be made to the catch limit to suit. Strict laws would also have to be endorsed for the catch document scheme and the way that Australia records the amount of catch taken per year. There would have to be more control over illegal fishing and importing into the Japanese market. This would increase the accuracy of the overall amount taken per year and allow for better allocation of catch limits. Only with changes in catch limits and more control over illegal fishing will the southern Bluefin tuna have a chance of repopulating to a safer bio mass stock.

References

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