If fishermen could plan the mass movement of their favourite fish to suit their own requirements it would be hard to find a more accommodating fish than the snapper which we so love to catch around our coasts. They can be found from inshore shallows, harbours and surf beaches out to depths of 200 metres. It is this ability to thrive in a wide range of sea conditions and habitats and to take advantage of different foods that is the key to their success and abundance.
Snapper are found all around the North Island and in the top part of the South Island, also in New South Wales and South Australian waters, with a closely related species occurring in Japan.
Scientists identify our snapper as separate families – those found on the west coast of the North Island, at the top of the South Island, and the east coast of the North Island. These families display different characteristics tempered by their environment, for example colder water in the south, and they do occasionally intermingle.
Our snapper is not actually a true snapper
Our snapper is not in fact a true snapper in international terms. There is a large family of fish called snappers throughout the world which are totally different, and our fish is actually a member of the bream family.
The oceans and seas cover over 70 per cent of the surface of the planet, and most life in the sea relies on the energy from the sun that filters through the upper layers, and the closer to the surface one looks the richer the life becomes.
Microscopic plants and bacteria live among the plankton, converting the energy from the sun through the process of photosynthesis, just like plants and trees on the land.
This process was started by microbes more than three billion years ago.
The key to the food chain which starts here is the phytoplankton. These are myriad forms of plant plankton, as distinct from the animal plankton which make up the zooplankton – which could be regarded as the next step up the ladder of life and which prey on phytoplankton.
The phytoplankton are so vast they are like a forest in the sea, and the numbers are incomprehensible.
For example one group, called diatoms, are preyed on by other plankton predators. Diatoms are about as small as you can get. They are single-celled organisms less than half a millimetre in size that come in every shape you can imagine, from long cylinders to round and triangular ones.
Their bodies contain carbon which is accumulated during photosynthesis and become intricate skeletons, and when they die their remains fall to the depths. It is believed that over the millennia vast deposits of diatom remains have been transformed by heat and pressure into the oil we seek so avidly.
Diatoms are found in every type of aquatic environment, from the brown growth on the inside of a toilet cistern or an aquarium to alpine tarns to the algae blooms that appear in lakes and at sea.
One of the smallest members if this group may be responsible for the largest contribution to marine photosynthesis – the blue-green bacterial algae called cyanobacteria. They create the slimy filaments found in geothermal pools, and are thought to be responsible for fully half of all photosynthesis at sea.
While diatoms may be regarded as pretty small creatures, they are giants compared to the cyanobacteria. They are among the smallest microbes on earth. Try to imagine a measurement that is 0.5-0.7 microns, when one micron is one-thousandth of a millimetre. One drop of sea water can contain up to 20,000 of these cells.
About half of the different varieties of plant plankton use the sun’s energy to convert water and carbon dioxide into sugars, which provides their food. The other half are hunters, feeding on fellow life forms
Scientists estimate that phytoplankton are critical to the survival of the planet, as they are responsible for half of the carbon dioxide which is removed from the atmosphere by photosynthesising organisms - which includes all plants and trees – and replacing it with oxygen, which they produce.
Like all populations in Nature, plankton follow boom and bust cycles. The blooms occur when conditions combine to create an environment favourable for growth. In other words you get a combination of nutrients, perhaps following upwellings from deep water as a result of wind conditions, warm temperatures and plenty of sunlight (read summer).
The most common is the ‘red tide’ seen at many points around our coast. This is a natural phenomenon, but still can raise concerns; particularly when phytoplankton produce toxins that become concentrated in some species of fish and in filter feeders like scallops, mussels and pipis. The two culprits are our old friend the diatom and another type of plant plankton – dinoflagellates.
Extreme cases can result in shellfish poisoning of people, and mass deaths of fish such as occurred in the Firth of Thames one summer when many thousands of pilchards were washed up on beaches, and at Orewa in October, 2002, when thousands of dead fish were washed up on the beach.
In the sea everything gets eaten by something else and the plant plankton are the basis of the marine food chain.
They also remove half of the carbon from the atmosphere and free up oxygen.
Useful little critters, aren’t they? In fact, we probably wouldn’t be here if it wasn’t for their existence.
Neither would the snapper.
There are nine different types of licences anglers can buy for the new trout fishing season which opens on Sunday next weekend. The best value are the season and family licences, and the family covers a spouse and children or grandchildren. Day licences remain at $20, but there are also three-day and nine-day licences for those wanting a short break to take in some fishing. Older anglers also qualify for a reduced cost for their season licence
The Fish and Game licences cover the whole country, except for Lake Taupo, but a restricted licence for a particular area is also available at a reduced cost.
Bite times are 2.05am and 2.30pm tomorrow and 3.50am and 4.15pm on Sunday.
Tip of the week
When fishing around an island fish on the shady side when the sun is low. You are more likely to hook larger fish in the shadow than in bright sunlight.