recruitment of freshwater eels

Project: Recruitment of freshwater eels
Project Code: EEL2004/01
Start Date: 1 October 2004
Completion Date: 30 September 2006
Vessel Use: None

Overall Objectives:

1. To monitor the recruitment of juvenile eels.

Specific Objectives:

1. To contribute to a times series of data to monitor the relative recruitment of shortfin and longfin eels by co-ordinating to specific standards the collection of data on abundance, timing of migration and species composition of elver runs at four locations: Karapiro, Matahina, Waitaki and Roxburgh for the elver migrations 2004/2005 and 2005/2006.
2. To collect data from other individuals/organizations undertaking elver transfer activities and collate information from all sites for the elver migrations 2004/2005 and 2005/2006

Note:

1. This project is a continuation of EEL2002/01 - Recruitment of juvenile eels.
2. This project does not require the tenderer to undertake any collection of elvers. The objective is to use selected authorized existing or future elver transplant initiatives as a means of establishing a time series of relative recruitment indices for freshwater eels.
3. This project can be attributed to the requirement for the assessment of recruitment for the sustainable utilisation of both customary and commercial eel fisheries.

Rationale:

General

The eel fishery is an important commercial fishery, with LFR returns in 2000-2001 totaling about 1078.9 tonnes. There is also significant Maori interest in customary eel fisheries. Maori have strong traditional ties to eels and harvest. Monitoring of recruitment is important for the sustainable utilization of both components of the fishery. The fisheries are based on the two temperate species of eels found in New Zealand; Anguilla australis (shortfin) and Anguilla dieffenbachii (longfin). A third species, Anguilla rheindhartii, has recently been recorded from the upper half of the North Island. Landings of this species are not significant. Shortfin eels are found along the south-eastern seaboard of Australia and throughout the south-west Pacific islands. The longfin is endemic to New Zealand and the immediate offshore islands.

Shortfin eels from throughout the extensive geographical range comprise a single genetic population. Longfin eels, confined to a smaller geographical area, also comprise a single spawning stock.

There is very limited stock assessment information available for eels, and it is not known if recent catch levels are sustainable. The stock assessment of eels presents particular problems because of the biology of the species. As adults, eels undertake a long homing migration to their oceanic spawning grounds and die after spawning. The location of the spawning grounds is not known but are likely to be in the south-west Pacific. Juvenile eels migrate back to freshwater and appear to distribute randomly into freshwater. After a period of residence in the lower reaches, juvenile eels known as elvers undertake an upstream migration to disperse throughout the catchment. Because of their biology, all eels are harvested before spawning. The relationship between the escapement of adult eels to spawn and subsequent recruitment has not been determined.

In the Northern Hemisphere the eel fisheries are based on the European eel Anguilla anguilla, the Japanese eel A. japonica and the American eel A. rostrata. Data from glass eel fisheries and elver migration data show a steady decline in recruitment from almost all data sets over the past 20 years. The decline in recruitment for the European eel is now equal to a period equivalent to the average life cycle.

For New Zealand there are no data sets to establish any trends in recruitment. Glass eel studies are presently being funded through the Public Good Science Fund (PGSF). Research has been conducted over the past three years (EEL2000/01 and EEL2002/01) that is establishing a times series of data on the relative abundance of elvers at selected locations.

The monitoring of elver runs and hydro dams and other locations where the upstream migration is blocked provides a cost effective means of establishing a longterm data series on the relative abundance. Provided data are collected in a consistent manner each year, the data can be used to determine overall trends in recruitment. The use of existing elver transfer programmes undertaken under special permits issued by MFish provide the most cost effective means of using existing data sources to provide a time series on recruitment.

The Medium Term Eel Research plan proposes that research on recruitment to establish a time series of relative abundance should be ongoing. While the recruitment index will not be used for any predictive modeling of recruitment into the eel fishery, a relative abundance index will provide critical information on recruitment, which will indicate over time the relative status of each eel stock. A major component of any decline in recruitment would be a decline in spawning escapement. This would indicate that management action would be required to maximize spawner escapement.

Objective 1

This objective is designed to extend the results from EEL2002/01 to establish a long-term data series on the relative abundance of elvers at selected locations. This objective will continue the time series for a further two years, 2004/2005 and 2005/2006. The research provider will not be required to undertake any collection of elvers. The provider will work with organizations/individuals undertaking elver capture and transfer activities to monitor these activities ensure that the required data is collected in a consistent manner (weight and numbers of elvers, effort, timing of samples, species composition).

This will include visiting sites, sampling caught elvers to check on species composition and estimates of the number of elvers. The data collection instructions and forms are provided in Final Research Report EEL2000/01.

Objective 2

In addition to monitoring the collection of data from the specified locations, the provider will also distribute instructions and data collection forms to other organizations/individuals undertaking elver transfer activities to provide additional data. No monitoring role is required.

Strategic Relevance

The objective of this project is consistent with the Fisheries Resources goal and Strategic Objectives in the Ministry of Fisheries Strategic Research Directions document.

Cost Recovery Information:

The percentage allocation for this project will be attributed to the following Fishstocks according to rule 9.2 of the Fisheries (Cost Recovery) Rules 2001:

• All ANG stocks
• All SFE and LFE stocks

The project is estimated to cost between $150,000 - $200,000.