Structure for Winter success by Craig McGill

While the associated habitat destruction and pollution from a harbour city have their downsides for many species, there are some 'man-made' benefits.

Weirs increase the available habitat for freshwater species. Moorings can act as surrogate seagrass for many juvenile species as well as harbouring baitfish, shellfish and crustaceans, which in turn provide an increased food supply for bigger predators.

Marinas can provide shade and refuge from commercial nets for many species and even some pollution can benefit some species. Sydney's old North Head sewer outlet had an abundance of species capable of utilising the extra nutrients.

And of course let's not forget all the species that have benefited from the removal of their predators by commercial fishing. I'm sure all the squid along the east coast were very happy with the decline in kingfish numbers 20 years ago.

Moreton Bay in Queensland has seen a dramatic increase in blue swimmer crabs as a result of the increased food supply in the form of discarded 'trawler trash' from the commercial trawl fleet. Who would have ever thought that there would be an upside to discarded by-catch?

There are some species, kingfish for example, that although they use artificial made habitat, have probably not benefited all that much from it.

Lets have a look at some of the species that have done well directly as a result of human habitation.

WEED EATERS

Those algae and weed grazers, luderick and surgeon fish, are classic examples. Incidentally, most of what we refer to as 'seaweed' is not actually weed (an unwanted plant) at all, but simply aquatic vegetation. True sea weeds, likes Caulerpa and Salvinia, are invasive non-natives.

Luderick and surgeons also like the security and shade of structure. The first growth on newly-built structure is algae and weed.

Blackfish are opportunistic and quick. I had my boat parked at a marina the other day while I picked up some lunch. When I pulled the boat out of the water later that day, blackfish had grazed it clean of algae! You could clearly see the tooth structure and mouth shape in each little scrape.

Blackfish are possibly one of the most reliable angling species in the cooler months. They are found from the Heads right through the brackish reaches and I've even seen them in pure fresh water.

Blackfish rods have always been long but these days are of lighter construction.

There are a couple of reasons for the long rods. They are required to lift the belly of line that often forms between the rod tip and the float, and the extra length also cushions against the fish's powerful lunges and helps avoid pulling the tiny hooks from their small mouths.

I prefer an egg-beater reel to the traditional centrepin and load it up with 2kg or 3kg line.

Quill floats are far more subtly efficient than the heavy, long-stemmed floats used for the ocean fish. A No 10 or 8 sneck pattern hook completes the rig.