Interesting article...
I skippered a ferry between Russell and Paihia for a while back in the late 90s and I saw many penguins on the run. Up at Opua they have been a fixture since myboyhood, but sadly now these Little guys are not seen very often in the inner bay. Dogs have played a part in that. But it should be mentioned that siltation also plays a part.
Studies in the Kaipara have shown that suspended sediment infiltrates the gill plates of fish, and introduce land based bacteria to their bodies.
The incidences of Brown Water events in the Bay of Islands have increased in the last twenty years as weather bombs become more common. Fifteen years ago the Bay got nailed by big weather events for just over three years. This had a devastating effect on small fish populations. Those populations get knocked back by every brown water event that happens. Anchovies in particular, but also mackerel and yellow eyed mullet and
pilchards.
This has resulted in at least three species of bird and one fish declining in the inner
bay. This is the inner bay. Inside Tapeka.
Those species are the little blue penguin, the small black shag,the Caspian tern, and the John Dory.