The Life Cycle of Snapper
Posted by Meggs | Fish Life Cycle Posts | Posted on August 7th, 2010
Greetings all,
I was reminded whilst down at sunny Merimbula the other month that although I have written about a lot of northern Australia fish species, I had neglected to cover off those commonly caught in our own backyard in and around Sydney. Acknowledging that fact I’ve decided to investigate the life cycles of some common and highly sort after fish species and this week we’ll take a look at the fascinating life cycle of pagrus auratus or the snapper.
An old man snapper (most large snapper are males) may live to a ripe old age of 35 years reaching up to 20kg in weight and about 1.3m in length! Spare a though for our South Australian cousins where 22 year old fish tend to inhabit Spencer Gulf. Some New Zealand websites claim that snapper can live up to 60 years of age! Larger snapper are sometimes impacted by hyperstosis (what the?). This means that they have a large knob on their head and sometimes even a bulbous nose (sounds like they’d make great politicians). There are many different theories for why this is the case. Some people believe that it’s a reaction against pollution whilst others think it’s caused from butting their heads against one too many rocks. One of the latest theories is that it could be purely genetic with only certain populations of snapper being impacted with this trait.
Snapper are a part if the sparidae family of fish which includes the humble bream. If you’ve ever caught both bream and snapper you may have noticed that they both have teeth that are tailor made for grinding whatever food comes their way.
Snapper are found in Australia from the southern end of the Great Barrier Reef right around to Coral Bay in Western Australia. They are common throughout New Zealand and populations also exist in temperate subtropical waters eg Japan, Taiwan, China and Indonesia.
One of the reasons that they are quite common (but becoming less so) is because they are serial spawners – they just love having kids between late October and early March. In fact they can spawn over 10,000 eggs up to 60 times in one season alone. They also spawn simultaneously in large aggregations of males and females which makes them susceptible to over fishing (remember this if you are catching larger sized snapper in big numbers). Snapper reach sexual maturity at about 28cm in length when they are between 4 and 5 years of age. They are actually a slow growing fish.
Spawining takes place in areas of little or no current in shallow areas less than 60m in depth. It is believed that spawning is more frequent at night time. Eggs float for a day or two close to or on the surface and hatchlings are up to 1mm in length. It is thought that early stages of the snapper are either mid or bottom dwelling living on small crustaceans and that they stay in a fixed area.
After several months they reach 1cm in length and at this stage they are perfect replicas of larger snapper. At twelve months they are female fish of about 10cm in length. When they mature at 4 or 5 years of age half of them become males. For regular readers of my fish life cycle posts you will be aware that sex change in the fish world is not an uncommon occurrence.
The age of a snapper is determined not only by studying the rings in the otoliths (ear bones) as in most species but also by counting growth rings on their scales (one ring is equal to a winter when growth stops).
Anyway, here is a rough guide to snapper ages…
1 year = 10cm
2 years = 16cm
3 years = 21cm
4 years = 30cm
5 years = 33cm (0.5kg)
6 years = 35cm
They then grow 1 cm in length every year after.
Enjoy the video below.
Sea you later,
Skipper Meggs