Ecological Services of Grey Mullet Lost Through Fishing

The humble grey mullet may have been an important vector in transporting sediment through our estuaries.  They were in huge abundance 100 years or so ago, but now are present in just a shadow of their former numbers.

When grey mullet were in huge numbers they would have been an important vector in transporting sediment through our estuaries, by swallowing mud in the upper estuary and releasing it near the estuary mouth.  Unfortunately there are so few left that this service is no longer effective

When grey mullet were in huge numbers they would have been an important vector in transporting sediment through our estuaries, by swallowing mud in the upper estuary and releasing it near the estuary mouth. Unfortunately there are so few left that this service is no longer effective

There are historic photos of clinker dinghies in the Kaipara Harbour, loaded to overflowing with mullet, many huge by todays standards and upwards of 70 cm long.

In my youth I saw a few schools of grey mullet while snorkeling, but then they “disappeared from the face of the earth”. Only in the last eight or so years have they been starting to come back, and I now frequently see adult grey mullet in the mangroves of Whangateau, and juveniles are seen in the lower reaches of the Brick Bay stream. A couple of years ago I saw a school of around 200 grey mullet, swirling around like a school of kahawai, in the Whangateau 100 metres or so below the Ti Point wharf.

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Kahawai school at Horseshoe Island channel

A school of several hundred young kahawai was seen in the channel behind Horseshoe Island on Saturday.  This was the largest number of kahawai I have seen in this area, and is a very encouraging sign.  There were also large numbers of adult parore, and the usual school of around 200 trevally which have grown since last summer.  There were no juvenile snapper, however, which were common in the summer but have departed for winter.

With 8 to 10 metres visibility, this is the clearest I have seen the harbour waters since the big cockle die-off in 2009.  There had been no rain or wind for several days, however, and the water on the coast is very clear at the moment too, which all helps the harbour’s water clarity.

Part of a school of hundreds of young kahawai in the channel behind Horseshoe Island on Saturday.