Well I’ve been hard at work on my first ever eBook and it is beginning to take some shape and should be ready after our Fishing & Reef Tour Specialist’s trip to Weipa in mid June.
For those that haven’t noticed yet, I have included a link on the www.skippermeggs.com site to a You Tube video with some huge fish in it. You can take a look at;
This week though I’ll discuss another member of the Trevally family – the Golden Trevally or Gnathanodon Speciosus.
Unfortunately little is known on how the Golden Trevally’s life cycle begins but on the basis that most large members of the species are found around reef areas it is likely that this is where spawning takes place.
The other clue to the theory that the fish spawn on coral reefs is that the larval and juvenile stage of the Golden Trevally’s development is spent living on the edge amongst the tentacles of either a blue bottle or portuguese man-of-war. This would point to the fact that the Golden Trevally spawn offshore so that the currents and winds would send their larval stages to the same areas where the jellyfish are likely to be.
Right, so living in amongst the stingers doesn’t sound like much fun does it? Well in fact this is quite a good defence mechanism and it actually ensures that the juvenile fish survive their early life as predators steer clear of the impending danger of stinging tentacles.
The young Golden Trevally on the other hand marinates itself with a mixture of its own mucus and that of the jellyfish so that it becomes immune to any danger of being stung.
As if this gutsy start to life is not enough once they grow to about 50mm they leave the shelter of the stingers and take up residence alongside large sharks!
You’d think they had a death wish from an early age but swimming in the wake of sharks helps conserve their energy and they just love the scraps of food that the shark leaves behind when they feed.
Not only that, what silly predator would even bother to have a go at them and risk running into a shark for their trouble?
Fish up to 3kg take up residence in rivers and are often caught when casting for mangrove jack and barramundi.
They are a schooling fish and will migrate up and down the coast. They will also feed on the sandy bottoms in shallow water and can often be found “tailing” ie feeding off the bottom of the shallows with their tails sticking out of the water.
Like my mother, Golden Trevally don’t have any teeth and those soft mouths and Mick Jagger lips are good for sucking food off the muddy bottom of a river or sandy reaches of an ocean floor.
Larger more mature fish will almost always live on reef areas and can grow to a size of 1 metre in length and are said to weigh in up to 35kg although interestingly the Australian record is only 15kg.
Next week I will start to review the life cycle of some of the Northern Australian pelagics.
Last week I travelled from Queensland’s Gold Coast through to the Harvey Bay region.
Wow, it’s been a long time since I’ve been up to the Sunshine Coast and I couldn’t help but remember a brace of good size bream I caught as a 5 year old in Maroochydore by casting under the Commonwealth Bank flat’s wharf whilst everyone else turned up empty handed as they tried to hit New Zealand with their lines.
The Harvey Bay area has also come on with a fantastic marina and rumours of another to be built sometime down the track. Compared to other major towns that I have travelled to in the past few weeks (eg Cairns, Townsville and Mackay) Hervey Bay still seems cheap with some houses valued in the high $200 to early $300K’s.
The F&RTS team also got together last weekend to pool all our fishing gear for the upcoming Weipa trip. It’s a great way to determine any gaps in what we’re taking away with us and also saves taking seven lots of individual gear.
Anyway, to this week’s life cycle story on the amazing Fingermark or Lutjanis Johnii – what a great name!
Fingermark can be found from East Africa to Fiji and are easily identifiable by the big blotch (fingermark or thumbprint) just below the dorsal fin.
The Fingermark lives to a ripe old age of 25 years and can reach a length of just over 1 metre and weigh in at 15kg. A one metre Fingermark is roughly 12kg cleaned.
It would appear that Fingermark spawning varies with changes in latitude and is thought to occur during the mid summer months. Fingermark around Townsville are sexually mature at an average size of 70cm (4.5kg) and 8 years of age whilst up in Darwin that stage is reached at 45cm.
These fish spend their early days in the mangroves before venturing out to rocky headlands, islands or deeper turbid water. They can also be found in and around inshore reefs.
Although they can live up to 25 years, the Fingermark is a slow growing fish and by age 2 will be around 40cm and 1 kg in weight. At age 4 they are only 50cm. Queensland fishing regulations (sorry to keep picking on them!!!) have a minimum size limit of 35cm with a bag limit of 10 which puts this fish clearly in the category of potentially endangered.
It is a sad fact that when you combine late spawners with a system that allows the cull of immature fish, future populations are obviously jeopardised and once more responsible fisherman taking fish legally within size and bag limits are unwittingly contributing to the species demise.
In the case of the Fingermark this is exacerbated by the fact that they hold fast in places like headlands, snags or pinnacles sometimes for a period of years thus making them particularly vulnerable to fisherman armed with GPS.
Anyway, until next week after 12 noon EST Friday – don’t forget to come back for a further installment of the life cycle of yet another Northern Australian fish species.
During the week I took the opportunity to head out on a night fishing expedition in the turbid waters of Darwin Harbour. I can report that apart from a plague of small sharks the only decent catch was a 14kg Black Jewfish.
Now I know what you are thinking – yes I did write a post on the plight of the Black Jewfish but this was caught on a charter boat with paying passengers and I was not the one who hooked it.
Interestingly, the charter boat used straight hooks and the fish was hooked in the gut. The depth of the water was around 15 metres and this combination would appear to have stacked the odds against the poor old fish even if it was let go.
I also discussed the aspect of aggregation and territorialism with the crew and they believed this to be a good thing as it meant that they could rely on the black jewfish being around for their customers.
Ok, enough of that – this week I will discuss one of the monsters of the sea; the Giant Trevally (GT’s) or Caranx Ignobilis (sounds like an ex Roman Emporer). They are the largest of the Carangidae family that boasts members such as the Queenfish, Amberjack and other Trevallys.
These fish are spread from Japan to Australia, East Africa to Hawaii in warm tropical waters in both the Pacific and Indian oceans.
GT’s reach sexual maturity between the ages of 3 and 4 at a time when they are around 60cm in length. Interestingly males outnumber females.
Spawning takes place during the summer months on shallow seaward reefs or offshore banks and the resultant larvae is thought to head to open waters.
At age one the GT’s are around 20cm in length and juveniles and young adults spend time schooling in turbid inshore, lagoon or estuary areas feeding during the day time.
Once they reach about 40cm they will head out to reef areas, channels or inhabit inshore sand flats.
Large adults are solitary predators often guarding clear lagoons or seaward reefs to a depth of 80m and feeding on crustaceans and other fish at night.
These huge GT’s can live to 15 years of age, weigh in at 60Kg and reach lengths of 1.7
Next week I’ll discuss the life cycle of a fish that comes complete with its own thumb print!
I managed to make a few minor changes to the www.skippermeggs.com site last week with another sensational Weipa fishing article added to the “Links” section.
I also travelled to Tasmania and believe it or not was caught in a huge dust storm half way between Hobart and Devonport.
When I finally reached my destination it was pouring with rain and the wind was still howling so I gave all thought of trying out a local seafood restaurant on behalf of readers and decided to eat in at the Motel. Great decision! I will update the site’s “Recommended Fish Restaurants” link with the results next week.
Ok, the Northern Australian fish life cycle stories continue and this week we’ll take a look at the coral trout which is actually related to the Cod and Grouper family known as Serranidae.
There is not one Coral Trout but several different species.
The most common is the Leopard Trout or Plectropomus Leopardus.
These fish have a blue ring around their eye and are generally found around the inner to outer shelf reefs in Northern Australia where the visibility in the water is around 5-10m. Interestingly where the visibility in the water is between 15-20 metres on the outer mid shelf you will find the highest density of Leopard Trout. They can grow to 70cm and weigh in at 6kg and live to 16 years of age.
The Bar Cheeked coral trout or Plectropomus Maculatus is mainly caught in the turbid surrounds of the coastal to mid reef areas (visibility less than 5 metres) and these fish are characterised by the fact that their spots turn into “bars” at the side of their heads. Bar Cheeks can grow to 80cm in length and weigh 8kg.
The Blue Spot or Footballer coral trout Plectropomus Laevis are all but exclusively outer reef and Coral Sea dwellers (where the visibility is between 25-30 metres) and these can be identified by the blue spots with dark edges on their head, body and fins. These are relatively large coral trout and can grow to 120cm and weigh upwards of 25kg and live to the ripe old age of 18 years.
Finally, the Passionfruit coral trout or Plectropomus Areolatus has large blue spots everywhere – and it is the only coral trout to have the spots under its belly. These fish are relatively scarce but can grow to 70cm and weigh 6kg.
Being protogynous hermaphrodites coral trout are the opposite to Barramundi.
What the??
This basically means that they begin their lives as females and change sex later in life to become males (as discussed in a previous post, barramundi begin life as a male and change later to become females). It therefore follows that small fish are generally female, whilst large fish tend to be males. It could also be extrapolated that the male of the species is best able to provide the necessary survival traits and genes to pass on to future generations.
Sex change happens between 23-62cm in length and on average at 42cm and most often after spawning.
Spawning itself is more to do with water temperature change than seasons or months of the year and generally occurs when the water reaches 25-26.5 degrees (September – December in the north and October – February in the south Great Barrier Reef regions).
What is interesting is that the coral trout aggregate in huge numbers to spawn. In the past I have fished in various waters where large sizes and numbers of either nannygai, morwong or even leatherjackets have appeared in plague proportions and I now wonder whether this was due to their spawning activity. Future posts will tell.
Anyway, aggregations of coral trout peak during the new moon when the tidal flow is strong (especially the ebb tide) particularly at dusk. It’s thought that this allows the eggs to be transported far and wide away from the reef and the lack of light prevents likely predators from getting in the way.
Ok, so what’s so special about the coral trout spawning? Well by the sounds of things it would be an event well worth the watching.
Aggregations of fish cluster around reef slopes in depths of 10-15 metres and individual males stake out their territory and begin to attract females by flashing the darkened edges of their fins on and off. In turn, the females lay close to the ocean floor and the schmoozing male virtually lies down next to it on its side with its head on a 45 or 90 degree angle.
Although it doesn’t quite have a beer and a smoke in its fin, the male shakes its body and head from side to side and with its underbelly rubs the female’s head or body. It continues this many times until finally a phenomenan known as a “spawning rush” occurs.
If the female agrees (complies?) the pair will swim really fast to the surface and once they turn they release sperm and eggs. Some fish, mainly males (wouldn’t you know it!), spawn a few times throughout the night.
As for the eggs, these are carried away by the currents and float below the surface. They are incubated for probably up to 45 hours and then the larvae lives off the yolk for awhile until it is completely absorbed. The young can then start to catch its own prey.
Juvenile coral trout are around 14cm in 6 months and reach 22cm by year one. At 2 years they are around 30cm, at 3 years 35cm and 40cm at 4 years of age.
Fish over the 60cm mark are at least 15 years old.
Next week I will continue with yet another post on the life cycle of a northern Australian reef fish.
