Waikato River Fisheries Bylaw 5
Maximum weight for commercially harvested eels
No commercial fisher may take or possess any eel taken within the Waikato-Tainui Fisheries Area weighing more than 2kg.
- Increase the proportion of shortfin and longfin female eels that reach spawning maturity
- Improve the overall size structure of shortfin and longfin eels
- Increase the number of large eels to predate small pest fish
The Conservation status of New Zealand freshwater fish (2009) describes the threat status of longfin eels as ‘At Risk and Declining’.
The abundance of commercial-sized eels has declined in the past two decades, along with the proportion of longfin eels. Loss of habitat and over fishing are main reasons for this decline. Longfin eels are one of five threatened fish species that exist across parts of the Waikato River catchment.
Recreational and customary use has decreased as their abundance and the proportion of larger eels have declined. Areas intensively fished over a long period are less likely to hold a significant number of longfin female eels. Generally eels are not a productive species and a precautionary approach to their management is warranted.
The Waikato-Tainui Environment Plan seeks a reduction in the maximum size for commercially harvested longfin eels from 4 kilograms to 2 kilograms. Sufficient spawner escapement, together with habitat restoration is critical to maintaining a viable eel fishery into the future.
Tribal and community initiatives are being funded by the Waikato River Settlement Clean Up Trust to restore fisheries habitat throughout the Waikato River catchment.
The purpose of a maximum size limit is to ensure that female eels that reach sufficient breeding size cannot be harvested. A reduced maximum size limit from 4 kilograms to 2 kilograms aims to increase the proportion of eels of breeding size. These larger eels if allowed to breed will eventually improve recruitment to the eel fishery. This is especially important to the endangered endemic longfin eel.
Fecundity estimates in migrant eels show that egg count increases with total length and total weight i.e. a female longfin eel of 4 kilograms in weight is likely to carry approximately 8 million eggs, whereas a female longfin eel of 2 kilograms is likely to carry 3.5 million eggs. The range in age a female eel takes to reach reproductive maturity can vary between 9-41 years for female shortfin and 27-61 years for female longfin.
Depending on growth rates, eels of both sexes and species may migrate at younger ages. This length of time before eels reach maturity and migrate exposes them to capture or being killed by non-fishing activities (e.g. drainage clearance, pollution events).
The commercial eel industry, to their credit, voluntarily returns longfin female migrants to the water even if they weigh less than the existing maximum limit.
Freshwater fisheries monitoring performed by the Waikato Regional Council has shown a paucity of large female eels in wadeable streams and rivers. Large eels are crucial to ensure a viable population and adequate recruitment. A 2 kilogram size limit is close to the maximum size a shortfin female migrant will grow. Longfin females grow much larger and will benefit more under this proposal.
Although shortfin eels are less threatened than longfin, this bylaw will improve recruitment to both eel species. This bylaw also aims to increase the number of large eels able to fulfil their natural roles of top predator. These large eels can assist to aid the return of Waikato River and lake fish communities to more natural conditions by predating on small pest fish.
Consistent with this bylaw, the issuing of whakaaetanga (customary authorisations) by Waikato River Kaitiaki for customary fishing will stipulate a maximum size limit of 2 kilograms for both eel species.
The current maximum size limit for both species of eel is 4 kilograms, but very few eels larger than 2 kilograms are caught at present within the Waikato-Tainui Fisheries Area. It is expected that the impact on commercial fishers of not harvesting the largest and most fecund (egg producing) female eels would not be unduly substantial. Very few shortfin female eels grow larger than 2 kilograms.
Reducing the maximum size would have almost no immediate or significant effect on the commercial catch in fished areas of the Waikato-Tainui Fisheries Area due to the lack of abundance of eels weighing 2 kilograms or more.
However in the long term, large longfin eels are expected to increase to a point where some sustainable harvest may occur. In addition, retaining large eels in the Waikato River catchment, particularly lakes, may suppress juvenile pest fish such as koi carp and rudd.
The argument that the bylaw will simply increase the number of eels killed for just the same catch assumes that there is a significant number of eels currently being taken that are greater than the recommended 2 kilogram maximum size.
However, the Waikato-Tainui Fisheries Area is the most heavily fished area in the country and does not have a large abundance of eels greater than 2 kilograms. Very few eels reach 2 kilograms in weight within the Waikato-Tainui Fisheries Area.