Maximum size limit for freshwater eels in the north island and chatham islands

Executive Summary

1. The Ministry of Fisheries (MFish) is proposing to extend nationwide the maximum size limit of 4 kilograms (kg) for commercially fished freshwater eels⁴. Currently, the maximum size limit of 4 kg for commercially caught freshwater eels applies in the South Island only. There is no maximum size limit in place for commercial fishing of freshwater eels in the North Island or Chatham Islands.
   
2. The number of elvers or glass eels observed migrating upstream at monitoring sites is relatively low, particularly for the longfin eel⁵. Improving the number of spawning females undertaking migration to breeding grounds could potentially lead to an increased number of elvers or glass eels returning to New Zealand. Ensuring sufficient spawning escapement is a key focus for the management of freshwater eels as they only breed once at the end of their life.
   
3. Fisheries management measures that improve spawning escapement of freshwater eels include:
   1. Setting and then refining catch limits to manage the level of eel harvest;
   2. Prohibiting fishing in particular catchments to allow eels to grow to sexual maturity and undertake their spawning migration without the prospect of being vulnerable to fishing activities; and
   3. Imposing a maximum size limit to allow female eels above a specified size to continue to grow to an age where they undertake their spawning migration, without being susceptible to commercial fishing.
      
4. In 2003 and 2004, new management measures were applied to the eel fishery in the Chatham Islands and North Island respectively (including introduction into the Quota Management System (QMS)). MFish intends to further refine the catch limits and catchment closure measures over the next few years as further information becomes available. Some further research will be available in 2007.
   
5. This paper proposes to address the inconsistent approach of a maximum size limit between the South Island, and the North Island and Chatham Islands. MFish recognises that a maximum size limit is part of a wider management strategy to further improve spawning escapement of eels across the country.
   
6. A maximum size limit is desirable to ensure the protection of large eels (particularly longfin) from being commercially fished. A maximum size limit of 4 kg would mean that large female longfin eels have the potential to undertake their spawning migration without the prospect of being vulnerable to commercial fishing activities once an individual eel reaches 4 kg weight. Large female eels are significantly more fecund⁶ at greater weights. Therefore, larger female eels potentially make a greater contribution to the eel population in subsequent generations.
   
7. At present, a significant amount of the annual eel catch is taken by commercial fishers. The maximum size limit proposed does not apply to non-commercial fishers. Non-commercial fishers currently take fewer eels and are unlikely to affect the overall sustainability goal of improving spawning escapement.
   
8. Extending the maximum size limit for commercial fishing nationwide may potentially lead to a small loss of commercial longfin eel catch in the North Island and Chatham Islands. However, a commercial maximum size limit of 4 kg would help to improve the amount of large eels escaping to spawn and the potential recruitment of eels into New Zealand fisheries waters.

Preliminary Recommendation

9. MFish recommends that the Minister of Fisheries agree to recommend the amendment of regulation 50 of the Fisheries (Commercial Fishing) Regulations 2001, such that a commercial fisher may not take or possess a freshwater eel of more than 4 kg from any New Zealand fisheries waters.

Rationale for Management Proposal

10. The introduction of the eel fishery into the QMS has provided a restriction on the catch of eels. The present limits on catch are likely to maintain the current depleted state of the eel fishery. However, fishery interests have indicated that they have a desire to improve the status of the fishery using a variety of management measures including further refinement of the catch limits initially set. One suggestion to improve the eel fishery is to ensure that a greater number of adult eels in spawning condition are able to undertake migration to spawning grounds before being fished.

Problem definition

Life history characteristics

11. The biological characteristics of eels are unlike other species as eels only breed once at the end of their life. Over-exploitation could lead to poor recruitment of eels into New Zealand fisheries waters. A declining trend in the number of longfin eels being recruited into the fishery could take many years to become apparent.
    
12. The biological characteristics of longfin and shortfin eels are quite different in terms of longevity, growth rates, and size at maturity. Many of these differences are apparent between both males and females, as well as for each species. A maximum size limit of 4 kg is particularly relevant to longfin eels given that they grow larger than shortfin eels. Shortfin female eels rarely reach a 4 kg weight, other than in some places like the Rangitaiki River catchment. In addition, female longfin eels grow much larger than male longfin eels.

Monitoring of upstream elver migrations

13. There is some information indicating that the number of glass eels or elvers observed in recent years is less than the 1970s, and this may indicate a declining trend in the abundance of eels. The relative indices of elver abundance obtained at four key sampling sites around New Zealand over the past eight years show that longfin recruitment in some areas is not sufficient to maintain or rebuild longfin stocks in these catchments. The low numbers of longfin elvers suggests that there is inadequate spawning escapement of longfin eels, and females are particularly more vulnerable to fishing because of their longevity compared to male longfins. Catch per unit effort (CPUE) indices from commercial fishing over the 1990s indicate a declining trend for longfin commercial catch.
    
14. It is concluded that the number of adult eels escaping to spawn is enough to maintain the existing depleted state of the fishery. However, the current level of escapement of eels is insufficient to increase the level of biomass so that the fishery can support better outcomes for all fishery interests. This view is based on the relatively low number of elvers migrating up river (longfin in particular).
    
15. The concerns that New Zealand fishery interests have about the significant reduction in the abundance of elvers or juvenile eels are also expressed by researchers from other countries for European, American and Japanese eels. Eel populations in Europe and North America are in serious decline – more so than that observed in New Zealand.

Fecundity & relationship to number of juveniles produced

16. Research has shown that larger female eels are much more fecund than smaller female eels. Larger female eels potentially make a greater reproductive contribution by producing a higher proportion of eggs for potential recruitment to New Zealand fisheries waters. Fecundity estimates in migrant eels showed that egg counts increased with total length and total weight (see Figure 1 in Appendices). In addition, female longfin eels are long-lived and take several decades to reach reproductive maturity. Until they reach maturity and migrate to sea, eels are susceptible for a long period of time to fishing activities as well as mortality caused by non-fishing activities (e.g. drainage clearance, pollution events).
    
17. The level of egg production to ensure sufficient recruitment of eels is unknown. However, there are concerns about a decline in the number of large longfin female eels in the fishery and what impact this might have on spawning escapement. An assessment of the size and age structure of eel populations in the 1990s emphasises that the number of large (>700 mm) female longfin eels has significantly reduced in comparison to observations made prior to, or during, the 1970s. The length frequency distributions of eels caught by commercial fishers in recent years throughout the country shows that few large eels are caught.
    
18. There is a low level of escapement of longfin eels from fished areas. However, it is likely that eel populations in unfished areas contribute a greater proportion of large migrant females to the spawning population. The exact proportion of eels escaping to spawn from fished and unfished areas is unknown.

Management strategies

19. There is only one biological stock for each eel species found in New Zealand fisheries waters, with spawning occurring in the South Pacific Ocean. A fundamental part of eel fisheries management is to ensure that eels are able to escape and produce a sufficient number of eggs to enable successive generations to replenish the eel stock.
    
20. In 2004, MFish proposed that “the management strategy for the North Island eel fishery should be to improve the stock structure and abundance of eels over the medium term, while bringing to a halt any decline in the eel fishery over the short term”. The aim of this management strategy is to increase the average size and availability of eels by 2014 to ensure sustainability, to improve the availability of eels for non-commercial fishers and to improve the relationship of interdependent stocks. In the case of the South Island, Maori customary interests and the eel industry agreed in the mid to late 1990s, in short, that their common goal was a sustainable fishery that was soundly managed. Various measures, including the maximum size limit, were implemented with this common goal in mind.
    
21. A maximum size limit for commercial fishing is only one part of the management strategy for eels. The effectiveness of a maximum size limit to improve spawning escapement is likely to be dependent on other management measures. Combined with other fisheries measures (such as catch limits, catchment closures and minimum size limits) a maximum size limit is expected to make further progress towards achieving the management strategy for eels. MFish has implemented a combination of these management measures throughout the country and a maximum size limit will assist to achieve the management strategy for eels, as it relates to spawning escapement.
    
22. Fisheries management measures presently in place to aid the escapement of spawning eels include:
    1. Implementation of catch limits: Recently, freshwater eels were introduced into the Quota Management System (QMS) in the North Island (2004), South Island (2000) and Chatham Islands (2003). Introduction of eels into the QMS placed catch limits on the amount of eels that could be fished and consequently reduced the amount of eels that could be taken by commercial fishers. Reducing the exploitation rate will allow the biomass of eels to increase over time subject to continued recruitment.
    2. Closure of catchments to all commercial fishing: Catchment closures were also put in place at the time of the QMS introduction for North Island eel stocks. Closures include the Motu River, Mohaka River and much of the Whanganui River catchments.
    3. Maximum weight for eels: A commercial fishing maximum size limit of 4 kg, in South Island waters only, was set in November 1995.
       
23. As longfin and shortfin eels each form a biological stock throughout New Zealand, it is logical that an appropriate maximum size limit should apply nationally, not just in the South Island. At present, the commercial eel fishery in the South Island accounts for only one quarter of the national commercial eel catch.

Assessment of Management Proposal

Effectiveness of maximum size limit and its relationship to other factors

24. MFish proposes to prohibit the taking of eels larger than 4 kg by commercial fishers in all New Zealand fisheries waters. The purpose of setting a maximum size limit for commercial eel fishing is to help ensure that a proportion of female eels are no longer vulnerable to commercial fishing. These large female eels (mainly longfin) will be allowed to mature to a size where they can undertake their spawning migration.
    
25. Research in New Zealand has revealed that relatively high harvest rates are capable of considerably reducing the breeding population of longfin females. This will lead to low numbers of longfin eels reaching the 4 kg protection zone. Recent modelling suggests that, under recent exploitation rates, putting in place a maximum size limit of 4 kg would increase the relative spawning population to a small degree (Hoyle and Jellyman 2002). However, coupling a maximum size limit with a reduced harvest rate would substantially increase the spawning population over the long term (see Figure 2 in Appendices).
    
26. Conservative maximum weights lower than 4 kg have been suggested as being more suitable to protect female longfin. Using information from Lake Ellesmere, Lake Onoke and the Makara Stream, it was shown that imposing a 4 kg maximum size limit would protect around 50% of longfin female eels in breeding condition. Another research study carried out in the Aparima River estimated that only 22% of longfin eels in breeding condition would be protected by the maximum size limit of 4 kg.
    
27. The results from these previous studies were within the context of relatively high exploitation rates. These exploitation rates may not prevail at present, or in the future, and as such the number of eels protected by the 4 kg limit may be higher in future surveys. Nevertheless, these studies indicate there is a portion of the eel population in breeding condition that can be protected with the application of a maximum legal size of 4 kg to the commercial fishery.
    
28. A further reduction in the maximum size limit showed a considerable increase in the contribution to the relative spawning population, however, such a reduction would lead to a significant decrease in harvest (see Figure 2 in Appendices). MFish considers that obtaining a nationally consistent approach of adopting a maximum size limit is important in the first instance.
    
29. Adopting a nationally consistent maximum size limit of 4 kg for the commercial fishery should provide greater sustainability benefits for the eel fishery (mainly longfin) than continuing with the present position of inconsistent application of the maximum size limit measure. The relative egg contribution that large female eels make to the spawning population is of particular significance in assessing those benefits. Adjustment of catch limits to reduce exploitation rates would also provide additional benefits to a nationally consistent maximum size limit of 4 kg.

Environmental considerations

30. Large eels, particularly longfin, play an important role in determining the population structure of eels, including species composition, sex ratios and size distribution. The environment and the number of individual eels who share that same environment contribute to determining the sex of an eel, with females tending to be more common at lower eel population densities. This may be due to large female eels being cannibalistic feeders. This habit may also influence the distribution of smaller longfin and shortfin eels. Without this ecological relationship, a higher density of smaller eels can induce sexually immature juveniles to become male. This may have implications not only on inter-related species, but also on the number of female eels contributing to the spawning population.
    
31. Large longfin eels are the top predator in freshwaters and may therefore contribute to the maintenance of biodiversity. Freshwater eels have an important role to play in moderating the abundance of other fish species when, at a certain size, their diet focuses more on these species than aquatic insects and snails. A maximum size limit would help to protect large eels that naturally compete or predate on other species, such as koi and bullies. The displacement of undesirable species could reduce the competition that smaller longfin eels encounter.

Compliance considerations

32. The introduction of a 4 kg maximum size limit in the South Island in 1995 was strongly supported by both customary and commercial fisheries interests. There is some difficulty in enforcing an inconsistent maximum size limit. Illegal commercial harvest of freshwater eels greater than 4 kg in the South Island could be landed in the North Island where there is no maximum size limit at present and this activity could go undetected. There have been reports of eels over 4 kg being moved from the South Island to the North Island to circumvent the maximum size limit in the South Island. A nationally consistent maximum size limit of 4 kg would reduce the likelihood of commercial fishers misreporting commercially caught freshwater eels.

Statutory considerations

Appendix 3 contains the ‘Statutory Considerations’ relevant to this paper.

Costs and Benefits of the Proposal

34. The management strategy focuses on three key measures to improve spawning escapement of eels, these are catch limits, catchment closures and size limits. A maximum size limit of 4 kg is a complementary control to help further achieve the management strategy for eels. The exact combination of these measures will be better specified once objectives for the entire fishery are more clearly expressed. Progress has been made on the first two measures in recent years, and it is desirable to make progress on the third measure at this time.
    
35. The consistent application of a 4 kg maximum size limit across all New Zealand waters, aided by other management measures, has the potential to protect large female eels and improve spawning escapement. MFish notes that the total allowable commercial catch (TACC) for the Chatham Islands longfin eel stock is only one tonne, and as such the implications for that fishery are likely to be small as the eel fishery in the Chatham Islands is mainly based on shortfin eels.
    
36. One North Island licensed fish receiver estimated that approximately 8% (representing 12-14 tonnes) of the recent annual catch of longfin eels landed to his factory is over 1 kg in weight.  Of this 8%, the quantity of longfin eels that would be over 4 kg in weight would be only 2-3% of the annual catch landed to this licensed fish receiver.  This is not a significant amount when considering the overall tonnage processed and the relative economic values associated with the different size grades. However, these preliminary assessments may need further evaluation and consideration across a broader scale. In the medium term, as the size structure of the eel fishery improves, the maximum size limit should become increasingly effective in providing a level of escapement for female longfin eels.
    
37. A nationally consistent 4 kg maximum size limit for freshwater eels would remove any uncertainty for compliance when carrying out enforcement activities. Information has been received suggesting that eels have been taken illegally (equal to or more than 4 kg) in the South Island, and subsequently landed in the North Island. A consistent maximum size limit for eels removes any ambiguity for the enforcement of a maximum size limit for commercial fishing.

Administrative Implications

38. There are no significant administrative implications associated with the implementation of this proposed measure. Enforcement of this measure should not impose any complication in this relatively small fishery. There are relatively few licensed fish receivers that receive landed commercial eel catch, and an increasing number of commercial fishers recognise the desirability of increasing spawning escapement.
    
39. An amendment to regulation 50 of the Fisheries (Commercial Fishing) Regulations 2001 will be required. If a commercial fisher then breached the amended regulation 50 (ie, caught eels greater than 4 kg), it would be an offence under regulation 84(3) of the Fisheries (Commercial Fishing) Regulations 2001. In such circumstances the commercial fisher would be liable on summary conviction to a fine not exceeding $100 000 (regulation 85(4) of the Regulations). The cost of a regulatory change can be accommodated within existing processes.