Hawksbury Lagoon update Sept 2020

Spring is definitely in the air and I am sure we are all pleased to see an end to winter (although it hasn’t been too severe fortunately). The lagoon outlet was opened a couple of weeks ago, resulting in the main lagoon draining quickly, I am a bit concerned that we may end up with a dry lagoon for the summer, but of course with no culvert cover we are unable to stop the outflow and are reliant on the outlet closing at some point before this happens. Which as I write this a week later it appears the outlet has closed again, although probably only briefly.

It is very timely that the outlet is open though as it helps support the migration of whitebait (Inanga) into the lagoon environs. We saw a few small shoals last year making their way up P O Creek which was very exciting. The earliest history of the lagoon says it was a very important food collecting area (Mahinga kai) for local Maori and that at times the lagoon was white with whitebait spawn. I doubt that we will ever see that again, but just to see a few small shoals demonstrates some progress.  Inanga are relatively tolerant of low levels of pollution fortunately, and they prefer slow running water with overhanging grasses in which to lay their eggs. They spawn where freshwater meets salt water especially during high spring tides.

Whitebait (Inanga)

Generations of adult inanga return to the same areas time after time. Many fish die after spawning or are left in poor condition, vulnerable to disease and predators. Each female can release up to 13,000 eggs which develop for 2-4 weeks and have to wait for another high tide which will stimulate them to hatch. They then spend about six months in freshwater before migrating downstream waiting for a high tide to take them out to sea. DOC has been doing a lot of work to identify and protect specific spawning sites, but as we know whitebait numbers are gradually declining and the Ministry of Conservation is considering strategies to improve whitebait management across New Zealand in an effort to stop this decline. Here at the HL we can continue to work to improve  water quality and keep planting around the lagoon in the hope that we may see increased numbers coming into our lagoon. 

Finally, can I ask that the locals who helped themselves to the woodchips on the Inverary Reserve, which were left by DOC for us to use on the reserve, make a donation to our account as reparation. Our account is Westpac 03 7370020799 00. The $$ will be well used towards our work at the lagoon and much appreciated. Thank you.

Shirley McKewen

Chair