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25_EEL_09
Filename
25_EEL_09.pdf
Link to file
25_EEL_09.pdf (498.7 kb)
Abstract
Longfin eel
The Working Group recognises that there are no stock assessments on which to base specific recommendations on longfin catch levels. Nevertheless, recruitment data, CPUE indices, and information on spawner escapement allow for a cautioned assessment to be made of longfin and shortfin stock status.
From the age composition of juvenile eels there is evidence that glass eel recruitment has declined in two North Island and three South Island waters, and there is anecdotal evidence that glass eel runs are now substantially smaller in the Waikato River that in the 1970’s.
Nevertheless, results from 2007–08 show that, with the exception of 1997-98, the number of longfin elvers at two of the main monitoring stations (Karapiro and Matahina dams) was the highest that has been recorded in the past 16 years.
The only reliable estimates of relative abundance are based on CPUE data. For the North Island, the ESAs with the largest longfin commercial catches (ESAs AA, AD, and AH) all showed declines of 25-75% in CPUE indices from 1990-91 to 2003-04, with the largest reduction occurring in Rangitikei-Wanganui (ESA AH). By contrast, although the main commercial longfin fisheries in the South Island (ESAs AX, AV, and AW) had either relatively stable or decreasing CPUE indices from 1990-91 to 2000-01 (the year eels were introduced into the QMS on the South Island), these generally increased from 2001-02 to 2005-06.
A key component to ensuring the sustainability of eels is to maintain spawner escapement, and to that end approximately 30% of available longfin habitat in the North Island and 34% in the South Island is either in reserves or in rarely/non-fished areas. If hydro development and habitat loss are included, and based on biomass estimates from several South Island rivers, it is estimated that the biomass of longfin eels above the minimum weight at migration is less than 20% of historical values. Following concerns that exploitation rates of longfin eels were unsustainable, in 2007 management actions to reduce this risk included reductions in TACCs and the introduction of an upper size limit for longfin eels in the North Island, as well as three areas being closed to commercial fishing (the Mohaka, Motu and much of the Whanganui River catchments).
Shortfin eel
Based on available information, the Working Group does not consider that the same level of risk applies to shortfin eels. For example, shortfins have a wider geographic distribution than longfins, and their recruitment into New Zealand waters could be supplemented by juveniles which originate from other sources (e.g., South Australia, Tasmania, and New Caledonia stocks). Furthermore, the CPUE indices for the main commercial shortfin fisheries in the South Island (ESAs AX, AR, AV, AW, and AS) generally increased from 2001-02 to 2005-06, especially in ESAs AX (Westland) and AS (Te Waihora/Lake Ellesmere). By contrast, the North Island ESAs with the largest commercial catches (ESAs AA, AD, and AG) showed less consistent trends in CPUE indices, with ESA AA (Auckland) showing a general increase from 1990-91 to 2003-04 whereas those for ESA AD (Waikato) and AG (Hawke’s Bay) generally decreased. Caution is therefore required in managing shortfin stocks given the nature of their biology and the fact that they are harvested before they can spawn.
Document date
Sunday, 31 May 2009
Document type
V 1.3
File format
Adobe PDF
File size
498.7 kb
Reference number
2009
Sort order
Uploaded from
M:\SCIPOL\Working Groups 2009\Plenary 2009\FINAL\MFish 2009 May Plenary\May 2009 - PDF\25_EEL_09.pdf
Uploaded date
Wednesday, 10 June 2009
Search tags
Species:
ANG;
EEL;
LFE;
SFE;
Stock:
ANG11;
ANG12;
ANG13;
ANG14;
ANG15;
ANG16;
LFE17;
LFE20;
LFE21;
LFE22;
LFE23;
SFE17;
SFE20;
SFE21;
SFE22;
SFE23;
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