Not to be cited without prior reference to the author ICES CM 2006/J:05

Status of freshwater stocks and management initiatives

D. J. Jellyman

Abstract

New Zealand has two main species of freshwater eel, the shortfin Anguilla australis shared with south-east Australia, and the endemic longfin eel, Anguilla dieffenbachii. Both species are subject to extensive commercial and customary fishing. The shortfin is the shorter- lived species with typical generation times for females ranging from 15-30 years, whereas generation times for longfins females are double this. The distribution and abundance of both species have been compromised by habitat modifications, with shortfins, the more lowland species, being affected by wetland loss, and longfins by weirs and dams. While there are few concerns about the status of shortfins, there is increasing evidence of over-exploitation of longfins, including reduced recruitment, reduction in CPUE, reduction in abundance and average size, and a regional reduction in the proportion of females. are managed under the Quota Management System, although individual and regional quotas are set from catch histories as biological parameters are inadequate. Maori, New Zealand’s indigenous people were allocated 20% of commercial quota, with additional quota set for customary take. The annual commercial catch has halved over the past decade, and is now about 700 - 800 t, with shortfins comprising 66% of catches. Recent management developments have included enhancement of upstream waters with juvenile eels, the consolidation of processing into fewer but larger units, setting aside of additional reserve areas to increase escapement of silver eels, increased management involvement of Maori, and development of regional management strategies.

Keywords: Anguilla, freshwater eels, status, abundance, recruitment, exploitation, Maori, management, quota

Contact author:

Don Jellyman: National Institute of Water and Atmosphere,, P.O. Box 8602, Riccarton, Christchurch 8440, New Zealand [tel: +64 3 348 8987, fax + 64 3 348 5548, e-mail: [email protected]].

1 Eel species

New Zealand has 2 main species of freshwater eel - the shortfin eel, Anguilla australis, also found in south-east Australia and some Pacific islands, and the endemic longfin eel A. dieffenbachii (McDowall 1990). Within the last decade, a third species the Australian longfin eel, A. reinhardtii, has been found in the northern parts of the North Island of New Zealand (Jellyman et al., 1996); although it appears to be a reasonably frequent immigrant, this species is not a significant component of New Zealand eel biomass.

Both main species frequently coexist, but the shortfin is principally a lowland species, and dominates populations in lowland lakes, estuaries and the lower reaches of rivers. The species reaches a maximum size of about 1.1 m and 3 kg, compared with 2.0 m and 25+ kg for the native longfin (Jellyman 2003). Longfins prefer flowing water and hence are found extensively in mainstem rivers; they penetrate long distances inland and inhabit high country lakes and rivers. Both species have different habitat preferences (Jellyman et al., 2003) – although juveniles of both species prefer shallow water (< 0.5 m deep), shortfins prefer slow velocities (< 0.5 m/s) and fine substrates, whereas juvenile longfins prefer faster water (> 0.5 m/s) and coarse substrates; adults of both species prefer deep and slow-moving water, but shortfins again preferring finer substrates (mud) to longfins (coarse gravel and boulders). There is experimental evidence that shortfin glass eels make specific olfactory choices about the types of waterways they will invade, although longfins appear indifferent to water types, a response in keeping with their broader habitat preferences (McCleave and Jellyman 2002).

Customary fisheries

New Zealand's indigenous Maori people had a highly developed fishery for freshwater eels. In the absence of native mammals, eels were enormously important as a basic foodstuff to Maori, as they were widespread, abundant, easily caught, and able to be preserved. As a result, Maori had an extensive knowledge of the ecology of eels, and had developed effective fisheries for both species, harvesting feeding and silver eels through combinations of traps, spearing, bait fishing, and large weirs (Downes 1918, Best 1929, Schmidt 1925, McDowall 1990).

Eels feature extensively in Maori mythology, with large eels often being credited as being spiritual guardians of waterways (Best 1929). Wars were sometimes fought over the rights to fish for eels in particular rivers. Maori practised various forms of management including imposing fishing bans on a particular waterway for ceremonial or conservation reasons, and seeding areas with small eels.

Although most present-day harvest by Maori utilises European fishing techniques, some customary fisheries practices still operate. For example, in a small coastal lake (Lake Forsyth, 560 ha) in the , migrating shortfin eels accumulate at a gravel bar separating the lake from the sea - eels are gaffed on dark nights when they enter drains dug into the gravel bar, with several hundred taken on a good night's fishing (Todd 1978).

Maori have frequently expressed concern that commercial fishing has compromised their own ability to harvest sufficient large eels for ceremonial purposes, but also that such land- use practices as wetland drainage and stream clearance have led to a significant degradation of eel habitat. There is also a general desire for eel stocks to be built back to pre-commercial

2 fishing levels, although unfortunately this is impossible because of irreversible landuse changes.

Development of the commercial fishery

The commercial eel fishery in New Zealand commenced in the early 1960s, and rapidly grew until catches of 2000 tonnes per annum were recorded in the early 1970s. Development of the fishery can be classified into three phases:

• An exploitation phase (1965-1980) • A consolidation phase (1980-2000) • A rationalisation phase (2000 onwards)

The exploitation phase was characterised by rapid expansion of the industry, a proliferation of processing factories, and generally large export volumes of a relatively low-value product. There were few management constraints, and early concerns were more to do with the possible impact of fishing on the important recreational trout fishery than on eel stocks themselves. In the early 1990’s, 23 processing factories operated (Jellyman 1993), and there was no limit on catches or the number of commercial fishing licences issued. An initial minimum size of 150 g introduced in 1981 was increased to 220 g in 1992, in an endeavour to improve marketability, and yield- per- recruit. To “cap” the escalating catches in the Lake Ellesmere, then New Zealand's single largest fishery eel fishery, the lake was declared a “controlled fishery” in 1978, and a maximum Total Allowable Catch (TAC) set.

During the consolidation phase, Government moved to reduce the pressure on eel stocks, as there were some concerns about over-exploitation. Two important constraints were the exclusion of part-time commercial fishers from the industry (1982), and a “freeze” (moratorium) on the issuing of new licences in 1988. Associated with the licence “freeze” was a voluntary agreement by the eel industry not to increase fishing effort beyond that of the late 1980’s. To assist with this, a “legal loophole” that enabled multiple fishers to operate from a single fishing permit was closed in 1997. Towards the end of this phase, fishery managers encouraged cooperative management planning by industry and Maori, which resulted in a series of regional management plans for the South Island (Te Waka a Maui me ona Toka Mahi Tuna. 1996). These plans formed the “information base” required for the next phase, the entry of eels into the Quota Management System (QMS).

In the rationalisation phase, the South Island was introduced into the QMS in 2000, whereby a (maximum) total allowable catch was set, with the commercial portion of this allocated to fishers largely on the basis of previous fishing history. The allocation of individual transferable quotas (ITQs) to fishers is considered to provide an incentive for conservation through allocation of transferable rights to harvest in perpetuity (Batstone and Sharp 1999). Similar to marine species, Maori received 20 % of the commercial quota, and in recognition of the historic importance of eels to Maori, catch allocations were also made for customary purposes (also 20% of the TAC). Unfortunately, South Island quota was set for both species combined, meaning there is no segregation of quota by species; quota was allocated to 6 regions, with fishers often permitted to fish in more than one region.

The North Island entered the QMS in October 2004, with catches again allocated by fishing history. In recognition that longfins were being harvested at a rate the fishery managers did

3 not consider sustainable, quota for this species was set at 18% less than recent commercial catches. Again, a substantial allowance was made for customary purposes (14 % of TAC), and 11% for recreational eel fisheries. A recent development has been a marked reduction in the number of processing companies to two main ones, who also hold much of the quota for both islands. One of these companies is owned by Maori. In recognition that eel stocks in some regions are showing signs of significant depletion, eel fishers have sometimes voluntarily forgone opportunities to catch their annual entitlements to assist stocks to rebuild. A consequence of the entry of both island commercial eel fisheries onto the QMS, has been the loss of a considerable number of experienced commercial fishers who have opted to sell their ITQ’s. For instance, whereas there were 70-80 commercial eel fishers in the South Island prior to the QMS introduction, there are now about 20. There has also been an overall reduction in commercial fishing activity, as security of quota holdings has meant commercial fishers can fish more conservatively, often on a rotational basis provided access agreements can be made with landowners.

Because of a lack of stakeholder involvement in the management of key fisheries, current Government management initiatives are in the development of Fishery Plans whereby collaborative plans for particular species, stocks and areas can be drawn up cooperatively by fishery managers and industry stakeholder groups. Whether freshwater eels will constitute a single national plan, or a series of regional plans, is uncertain at this stage.

Current status of eel stocks and fisheries

Commercial fishery catches (Fig. 1) show the rapid increase in catches in the late 1960’s to a peak of 2077 t in 1972; catches fluctuated markedly for the next 25 years, but since 1994/95 there has been a gradual decline in catch to just over 700 t at present. Declines in the commercial catch since 2000 will be attributable to the QMS introduction (and attendant loss of experienced fishers), varying overseas markets, some reductions in areas available to commercial fishers, droughts, and also availability of eels. Shortfins have always been the dominant species, averaging 64% of the total catch over the past 30 years; while longfins have sometimes contributed as much as 45% of annual catches, their proportion over recent years has consistently been a third of total catch. North Island catches have always exceeded South Island catches, with the relative contributions over the past 14 years being 64% and 36% respectively.

The present South Island TAC is 539 t, of which the Total Allowable Commercial Catch (TACC) comprises 78%, with 20% available for customary fishing and 2 % for recreational fishing (Fig. 2). The customary and recreational catches are not monitored, but on average, only 2/3 of the TACC has been caught in any of the 5 years since being established. For the North Island, the TAC is currently 885 t, of which 73% is the TACC, 14 % is for customary fishing, 11 % for recreational fishing, and the remaining 2 % is in recognition of other sources of fishing-related mortality. For the North Island, the TACC is separated by species, and in 2004/05 fishing year (the only year of data since North Island eels were introduced into the quota system), the TACC for shortfins of 457 t was only 65% taken, while the TACC of 193 t for longfins was only 67% taken. Much of this reduction is considered to be associated with the industry rationalisation associated with entry of eels into the QMS. Today, apart from National Parks, various reserves, and a few designated non-commercial areas, virtually all accessible waters are commercially fished.

4 There are no commercial fisheries for glass eels in New Zealand, and it is not legal to catch or export glass eels. Small quantities can be caught for research purposes only. High overseas prices for glass eels in the 1970’s stimulated experimental glass eel capture in the , the river with New Zealand's largest recruitment. Six tonnes was caught in one year (Jellyman 1979), although anecdotal reports indicate that such large recruitment is now infrequent. Apart from an experimental eel farm in the north of the North Island (Whangarei), there is currently no intensive farming in New Zealand; trials of eel fattening (short-term, low density) showed some promise although the economics were uncertain (Chisnall and Martin 2002a, b).

With the exception of Lake Ellesmere, there are no targeted fisheries for silver eels in New Zealand. This is not a legislative requirement, but largely because New Zealand rivers are subject to considerable flow variability, making capture of silver eels very difficult during the periods of increased flow when most migrate (Todd 1981b; Boubée et al., 2001; Boubée and Williams 2006). However, a voluntary ban by commercial fishers is in recognition that adequate adult eel escapement is critical to the sustainability of stocks. Shortfin silver male eels usually comprise two-thirds of the commercial catch for the Lake Ellesmere fishery, as there is evidence that managing this fishery in favour of larger shortfin females is beneficial (Jellyman and Todd 1998; Jellyman 2001).

Estimates of mean age at migration, were made using averaged growth rates estimated from catch-sampling of commercial landings (Beentjes 1999; Beentjes and Chisnall 1998), relative to lengths of 740 mm for silver female shortfins, and 1150 for female longfins (Jellyman and Todd 1978). Growth rates for both species are higher in the North Island than in the South Island and result in shorter generation times (Table 1), and longfins are twice as old as shortfins at migration. These ranges in age at migration substantially exceed those of the other temperate eels important in world commerce (Anguilla anguilla, e.g. Svedang et al., 1996, A. rostrata, Oliveira and McCleave 2000; A. japonica Tzeng et al., 2000). Despite heavy expoitation, there is little evidence that shortfins are declining nationally (Beentjes and Bull 2002; Jellyman in press). As shortfin males seldom exceed the minimum commercial size of 220 g, the commercial fishery is effectively one for females only (with the exception of the fishery for male silver eels in Lake Ellesmere where this size restriction is relaxed).

Fishing techniques are very efficient, and research has indicated baited fyke nets can consistently remove over 50% of longfins in a single nights fishing (Jellyman and Graynoth 2005); also, being ecologically dominant, large longfins are more vulnerable to capture then smaller longfins. A number of reviews and research programmes have highlighted the vulnerability of longfins, and the need to implement more conservative management practices to avoid substantial reductions in this fishery (Chisnall and Hicks 2003, Jellyman et al., 2000; Hoyle and Jellyman 2002; McCleave and Jellyman 2004; Jellyman in press).

Because they migrate extensively inland, longfin eels have also been negatively impacted by the installation of weirs and dams. Historically, no provision was made for upstream or downstream passage of eels, as reduced abundance or exclusion upstream was deemed to be favourable to recreational fisheries based on imported brown and rainbow trout. The resulting exclusion from upstream habitats has been extensive-for example, a series of 8 hydro dams on the Waikato River (the largest river in the North Island) effectively excluded eels from 30 % of this catchment. Likewise, installations of major hydro schemes on large South Island rivers (Waiau, Clutha, and Waitaki Rivers), collectively impacted upstream recruitment to over 20% of all of the South Island. Fortunately, facilities are now in place at most major

5 hydro dams to enable upstream recruitment of juvenile eels, while several dams have facilities in place, or are investigating options, to enable downstream migration of silver eels.

Research and management initiatives

Initial research on eels in New Zealand was prompted by concerns that they were significant predators on trout (Cairns 1942; Burnet 1968). An outcome of this research was that the predatory pressure by eels was beneficial to production of of a size of interest to anglers. Subsequent research then focused on understanding recruitment (Jellyman 1977a, b), the ecology of yellow eels (e.g. Jellyman 1989; Chisnall 1989; Chisnall and Hayes 1991; Broad et al., 2001), and factors associated with the onset of immaturity and downstream migration (Todd 1981 a, b). With the rapid development of the commercial fishery, emphasis changed to understanding the age composition and growth rates of eels in a range of waterways (e.g. Beentjes and Chisnall 1998), and monitoring and modelling impacts of commercial fishing (e.g. Beentjes and Bull 2002). Recent advances now enable researchers to estimate biomass of eels in waterways (Graynoth and Niven 2004), by linking eel biomass to a GIS rivers database.

Considerable effort is underway investigating the behaviour of eels approaching dams, in order to design appropriate means of downstream passage. To date, the use of submerged bypasses has met with some success, although during floods eels preferred to migrate over a spillway in preference to the much smaller flow provided by a bypass (Boubée and Williams 2006). Likewise, selective opening of spillway gates can be an effective means of enabling downstream passage (Watene et al., 2003), and predicting migration periods from rainfall events significantly reduces loss of stored water (Boubée et al., 2001). The use of radio and acoustic telemetry continues to be very important to understanding migratory behaviour. In Lake , where a large hydro station diverts up to 97% of the outflow, studies have indicated that approximately 50 % of silver eels entering the lake are attracted to the power station forebay and will be killed by passage through the turbines.

In the absence of glass eel fisheries, some recruitment monitoring has been implemented. Representative locations in both North and South Islands are electric fished for glass eels, to obtain an index of annual recruitment (Chisnall et al., 2002, Jellyman et al., 2002). From the 10 years of data, there are no clear indications of changes in abundance of either species. In addition, the annual congregation of juvenile eels (elvers), below hydro stations is now monitored through joint initiatives between the eel industry and fishery managers. Currently, up to 3 million juvenile eels are transferred upstream annually (Martin et al., 2005). Such ventures were initiated by industry to “seed” hydro lakes where resident eel stocks had become depleted through lack of recruitment. Growth rates resulting from such transplants have been impressive, with eels achieving minimum commercial size of 220 g within 4 –6 years, compared with 13 – 17 years in reaches downstream of dams (Boubée et al., 2003). In the North Island especially, there is considerable potential for additional stocking such waterways, especially in the many small dams and ponds that proliferate throughout much of the farming country - for example, there are over 28 000 lakes and ponds < 0.5 ha in the North Island (Table 2), many of which will not contain eels. Industry sees seeding many of these lakes with juvenile eels as a means of maintaining high productivity while reducing pressure on riverine stocks of eels.

6 Smaller-scale transplants have also been trialled as a means of enhancing both shortfin and longfin customary eel fisheries in both islands. Transplants have generally proved successful, although the use of small eels captured in areas of high density, has probably resulted in a disproportionate ratios of males in receiving waters, with subsequent emigration of these at maturity (Beentjes and Jellyman 2003). A recent review of factors associated with the onset of sexual differentiation confirmed the significance of density as a major factor (Davey and Jellyman 2005).

Present government management strategy emphasises elver transfers as an effective means of stock enhancement. Additional emphases have been on establishing the extent and adequacy of silver eel escapement, a reduction in catch of longfin eels, and setting aside of additional reserves for this species. There has also been increased recognition of customary Maori fisheries through assessing their well-being and opportunities for enhancement.

It is recognised that maintaining and preferably enhancing adult escapement is arguably the most effective measure for maintaining the sustainability of stocks. Fortunately, the importance of maintaining eel passage both up- and downstream is now widely recognised and required by Regional Councils, the statutory authorities that manage freshwater resources. Habitat management and control of exotic invasive plants and animals is critical to maintaining aquatic biodiversity; longfin eels are New Zealand's largest native fish, and historically eels dominated biomass and all waterways, often constituting over 90% of total biomass (Hicks et al., 2004). With the loss of significant numbers of large longfins, there is now concern about the ecological impacts of this on lower trophic levels (Chisnall et al., 2003; Jellyman et al 2000).

Concerns

Fishery management

In response to the concern about well-being of longfin eel stocks, fishery managers are taking active steps to reduce exploitation, including setting the TACC for North Island longfins at a level below recent catches, and the setting aside 3 significant rivers as free from commercial fishing. However, it is debatable whether such measures are extensive enough to forestall the predicted major reduction in recruitment of this species (Jellyman et al., 2000; Jellyman in press). Although the QMS provides upper harvest limits, these have been mainly set from catch histories as the biological data are inadequate. Results from economic modelling (Doole 2005) suggest that this strategy will not permit stock recovery and may indeed lead to stock collapse. There are further concerns that the system does not provide enough fine- scale management (at a catchment level), that quotas have not been adjusted since their inception, and that little recognition has been paid to enhancement of stocks by elver transplants. In response to these issues, fishery managers are investigating finer scale management units. Many Maori are still fundamentally opposed to the commercial exploitation of eels, believing they should be utilised for customary and recreational purposes only. Apart from a general concern about lack of availability of larger eels, Maori have also expressed concern about the need for protection of additional areas of high customary importance.

7 Habitat

Being principally a lowland species, shortfins have been significantly impacted by the loss of up to 90 % of New Zealand's wetlands, and the extensive channelisation and straightening of lowland rivers that has occurred over the past 50+ years. Current practices of waterway management (removal of sediment and aquatic weeds to facilitate drainage, by mechanical and chemical means from 15 500 km of waterway each year - Beentjes et al., 2005) result in widespread loss of habitat and also in direct mortality of eels when they become stranded on banks - several regional councils are taking steps to reduce such impacts, including employing people to return stranded eels to waterways. The impact of these practices on eels is unstudied, but collectively must be substantial.

In addition, there are extensive pumping systems in some regions, and intakes are often unscreened and result in unreported eel deaths. Several decades ago, eels were regarded as nuisance species - fortunately their status has changed and Regional Councils (who manage land and water resources) are required to protect indigenous fish species. Councils now routinely require installation of fish passage facilities at weirs and dams, fish exclusion facilities at irrigation and hydro intakes, and often encourage minimal mechanical stream clearing.

Conservation

Previous investigations of the extent of reserve areas for eels (Jellyman 1993) suggested a nominal target of 20% of species habitat should be set aside, although, as pointed out by Doole (2005), there are insufficient biological data to use in optimal reserve design. A recent survey using GIS techniques to estimate total lengths of waterways and areas of lakes (Graynoth and Niven 2004) estimated that 14% of the total eel biomass in the West Coast and Southland regions of the South Island (representing approximately 1/3 of total area of the South Island) were fully protected, with a further 14% largely protected (except that silver eels could theoretically be exploited when they migrate from reserve areas). However, given that there is evidence of continued growth overfishing and decreased recruitment of longfins (e.g. Jellyman et al., 2000; Hoyle and Jellyman 2002; Doole 2005), escapement from present reserve areas must be considered inadequate, and reservation of additional areas is essential.

For shortfins, it is not known to what extent marine stocks provide a largely unexploited buffer for spawning escapement. Although this species is shared with south-east Australia, management is carried out independently by both countries, rather than by eel stock. Research has indicated that although glass eels are genetically homogenous at recruitment (Smith et al., 2001), some selection takes place during the freshwater phase - an important corollary of this is that escapement should be maintained over a wide geographic area to maintain this genetic heterogeneity.

Conclusions

The commercial harvest of freshwater eels in New Zealand has declined progressively over the past decade, mainly as a result of more restrictive fisheries management. The commercial fishery is a valued one, with an estimated asset value of $NZ 23 m (Statistics New Zealand 2005). Widespread concerns that the endemic longfin eel has been over-exploited have lead

8 to a recent acknowledgement by fishery mangers that the current levels of exploitation are not sustainable (Ministry of Fisheries, Science Group (Comps.) 2006). Despite the additional gazetting of reserve areas, it is considered unlikely that such measures will be sufficient to arrest a predicted substantial decline in recruitment of this species. Although there are not similar indications of concern for the status of shortfin eels, both customary and commercial harvest of this species are almost exclusively of females; this fact alone means that this fishery must be closely monitored and managed to ensure there is no similar decline in stocks.

Acknowledgements

I wish to thank my NIWA colleague, Eric Graynoth, and Peter Todd and Dave Allen of the Ministry of Fisheries for helpful comments on the manuscript.

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11 Smith, P.J., Benson, P., Stanger, C., Chisnall, B.L., and Jellyman, D.J. 2001. Genetic structure of New Zealand eels Anguilla dieffenbachii and A. australis with allozyme markers. Ecology of Freshwater Fish 10: 132- 137.

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12

Figures

2500

t

t 2000

t

1500 Total Tonnes 1000 Shortfin

500 Longfin

0 1965 1970 1975 1980 1985 1989/90 1995/96 2000/01 Year/fishing year

Figure 1. Trends in commercial eel catch, 1965 – 2004. Note that from 1988/89, the catch was recorded by fishing year (1 October – 30 September) rather than calendar year.

13 700

Other

600 Recreational South Island 2000/01 - 2004/05

Customary

500 TACC

Actual

400

North Island 2004/05 Tonnes 300

200

100

0 Shortfin Longfin Both species

Figure 2. Allowable eel catches per catch category for both North and South Islands. TACC = total allowable commercial catch. Actual = actual TACC taken (for South Island = average of fishing years 2000/01 – 2004/05; for North Island fishing year 2004/05)

14 Tables

Table 1. Estimated age of female shortfin silver eels (for a mean length of 740 mm) and longfin silver eels (for a mean length of 1150 mm) for various regions in New Zealand. Estimated ages are derived from growth rates in Beentjes and Chisnall 1998, and Beentjes 1999.

Shortfins Longfins No. aged Mean age No. aged Mean age North Island Western 288 18.1 126 33.5 Eastern 150 15.3 25 27.6 Southern 140 16.4 123 29.0 South Island Western 65 40.2 151 63.9 Northern 7 27.9 9 54.5 Central 116 25.7 263 44.5 Southern 316 23.3 525 51.4

Table 2. The number of lakes of different sizes in both North and South Island of New Zealand

Lake area (ha) North Island South Island < 0.5 28209 19405 0.5 – 0.9 1656 1636 1.0 – 9.9 1212 1898 10 – 99.9 156 400 100 – 999 41 76 1000 – 9999 11 18 > 10 000ha 1 7

15