Tempest treats Teewah
  |  First Published: March 2013

The wild weather from former-cyclone Oswald had minimal effect on Teewah Beach with erosion mainly confined to the rocky areas in front and south of Teewah.

Excellent holes and gutters have formed up in these rocky areas and provide improved opportunities for species such as bream, tarwhine, tailor and trevally to be taken. Worm, eugarie or mullet baits are most effective for bream and tarwhine and will also occasionally tempt golden or giant trevally. However, be prepared to snag on the coffee rock that is present in these gutters when fishing with baits. Metal lures, which would be most effective for tailor and trevally, allow snag-free and potentially productive fishing.

Weather events such as Oswald are historically a trigger for inshore feeding frenzies as the surf clears of sediment washed from the estuaries. March is when such frenzies have occurred in the past with all of the main predatory species generally present. The potential for Spanish, school and spotted mackerel is dramatically increased as the water clears and mac and longtail tuna are often taken from Teewah Beach in these circumstances.

Tailor are returning south following their spawning migration and still in our waters and March is in the middle of the traditional trevally season.

Bream often exit the estuaries during a flood and at this time of year can be taken in numbers from the surf. Post-flood captures of species like bonefish, cobia, yellow-tailed kingfish, mulloway and shark are not uncommon.

Dart, surprisingly can be taken at the height of the flood and from dirty water, although catches generally improve as the water clears.

Of course, this is all dependent on what weather systems present over the remainder of the cyclone season. Another large system like Oswald would have us waiting until early winter before clean conditions prevail. By this stage, many of the pelagic species will have moved on, leaving frustrated anglers in their wake. Consolation for anglers is in the knowledge that these high rainfall weather events are good for fish stocks generally in both the estuary and marine environments.

Author’s opinion

Regular readers of this column would be quite familiar by now with theories associated with fish behaviour in relation to commercial netting that I have written about on a regular basis. For those that aren't, here is a quick summary:

Netted fish release audible and chemical alarm signals which alerts nearby fish of the 'predator' and is further transmitted to fish further afield. The reactions by fish to these alarm signals is, in a surf environment, generally to flee the area with long term observations revealing that the fish tend to stay away from the netted region for a week or so. Over time and with continual netting in that area, fish increasingly avoid these dangerous areas altogether.

Avoidance of these areas that have sustained species for perhaps millions of years, leads to insufficient nutrient ingestion which slows growth rates. Spawning away from the ideal locations that historically have allowed maximum egg fertilisation and larval survival can have serious impacts to recruitment.

The threat of predation and the avoidance of such a voracious predator as a commercial net, causes the release of stress-related hormones associated with 'flight or fright' responses which is common to all vertebrates. Glucocorticoids and other stress hormones that are released from internal glands, are known to reduce reproductive output by up to 25-30%, cause infertility, increased vulnerability to disease and loss of mass. Larval survival to 10 days of age is known to be reduced by up to 61%.

Scientific research over the past 2 decades into slower growth rates of commercially harvested species and smaller size at maturity than in the past, has revealed that these changes occur as a result of the fishery selecting fast growing individuals. This leaves slow growing individuals as the predominant spawning stock which evolve into slow growing offspring with each generation being slower growing than previous generations.

Evolutionary changes to a smaller size in commercially harvested species is not a new phenomenon. Many species from around the world are documented to be smaller now than they were in the recorded past. Scientists well understand that reduced size has impacts on recruitment that can impact as seriously on population levels as the harvest itself.

The consequences of evolutionary change to a smaller size are therefore a very significant factor in modern fishery management. But new research by the CSIRO into human-induced evolutionary change to a smaller size of five Australian fish species, adds a further dimension to the complexities involved. The study, conducted in Tasmania, found that the fish of species which have evolved through the generations to be smaller, are more likely to be taken by natural predators and that reduced growth rates and size are leading to declines in fish populations.

This new research is significant for four reasons:

1. The increased predation levels associated with smaller size is concerning in itself when this aspect is not considered by managers in current natural predation estimates and when Australian harvest levels can be high – up to 80% of legally sized fish.

2. The finding by Australian Government scientists that species that undergo evolutionary change to a smaller size are likely to deplete in number, is recognition and confirmation in this country of the long term findings of scientists overseas.

3. The cause of reduced sizes of harvested fish has long been debated by the international scientific community. The CSIRO researchers have stated as fact that evolution is the cause which should be of great concern to managers. The evolutionary changes recorded in species to smaller sizes can occur within five generations, but can take much longer to reverse when fishing pressure is removed. This is of particular concern in relation to tailor.

4. The findings of this study compound the known impacts of harvesting associated with predator avoidance mentioned earlier in the article.

There is no question that the existing knowledge of reduced size of harvested species is a vitally important component of modern fishery management and the sustainability of key commercial and recreational species. However, in trying to establish which Queensland species are assessed for growth rates and size at maturity, I was informed that tailor are not one of the species on the long term monitoring list (LTML). This is despite Fishery Queensland's knowledge of tailor being of a reduced size in 2004 compared to the 1970s, but not why?

We now know that any harvested species which is smaller now than in the past is likely to have serious recruitment problems and be vulnerable to higher levels of predation than is being currently estimated. The ramifications to Queensland's fishery managers of this knowledge are very substantial indeed. Precautionary measures that cater to this knowledge are now essential and long term monitoring of commercial species a must.

In recent times there has been, and will continue to be a strong push from the recreational sector for net free areas to be established in appropriate locations along the Queensland coast. There is substantial evidence that such recreational only areas allow fish populations to recover in number and also in size of individual fish. Scientific assessments and commercial catch data from several net free areas have universally found improved catches by both the commercial and recreational sector within such areas and outside with 'spill over' clearly occurring.

The need for net free regions along the Queensland coast is now of extreme importance if we are to have sustainable fisheries.

Reads: 1609

Matched Content ... powered by Google