Feature
March 5, 2014
‘Dramatic’ decline in crayfish A reduction in crayfish numbers due to overfishing is significantly affecting the health of the Hauraki Gulf, academics say. Jan Hesse is in the final year of his PhD at Leigh Marine Laboratory and is investigating the causes of a dramatic decline in crayfish numbers in the area. His research is indicating that overfishing is a major factor, and he fears that unless action is taken, the species could be threatened. One of the key problems is that large crayfish have been effectively removed from the environment and this has led to an increase in kina, or sea urchin, numbers. They, in turn, have destroyed kelp forests, removing a key marine environment, Jan says. Jan’s PhD supervisor, Professor Andrew Jeffs, says the good news is that crayfish numbers can be revived. “What we saw when Leigh Marine Reserve was established, and what we’ve found at other marine reserves, is an immediate increase in crayfish numbers. And we’ve seen some pretty marked changes in habitat,” Andrew says. “The contrast is like that of a healthy forest, compared to that of a desert,” he says. Having large tracts of deserted sea floor has a broader impact. “The evidence suggests that we have reduced the population of crayfish to levels that are having an impact on the habitat and we are reducing the productivity
BOAT
maintenance??? It’s that time of the year!
Best price o all y n access our ories
Mesh pole sanding sheets Great for antifoul
2.50ea or pkt 25
$
45.80
$
Tungsten blades 50mm
5.99 each or pkt 10 $45.95
$
All prices exclude GST
THE PAINTERS GEARHOUSE
Tradextra Extra for the trade
3 Glenmore Drive, Warkworth (Opposite Warkworth Wreckers)
Phone 0800 425 800
Mahurangi Matters
39
Matakana Re-vegetation & Landscape Services Specialists in Natives: Replanting and Wetland Planting
Erosion Control
Site Preparation Planting • Tracks • Property Maintenance
Phone Greg Courtney 09 422 6106 or 021 886 732
Revision Jan Hesse
of the Hauraki Gulf by taking that population.” Jan and Andrew believe that an upper size limit needs to be introduced to the quota management system to allow large, mature crayfish to develop. Crayfish have to live around five or six years before they are strong enough to break into a kina, and mature crayfish also reproduce more successfully, with a lot more offspring. Australia has successfully implemented a similar programme, they say. A small reduction on the daily maximum limit for recreational fishing, and reduced quota on commercial fishing, may also work to boost numbers, but only in combination with other factors such us an upper size limit.
Professional Sewing Services
For the professional sewing service you desire and deserve Where quality alterations and finishing to all your sewing requirements are guaranteed SAME DAY SERVICE AVAILABLE Jo and Lucy
Shop 6 River View Plaza Tues-Fri 9am-5pm • Sat 9am-12pm Phone 09 425 9673