Bass are a catadromous species that can live in fresh water but must migrate back to
the sea to breed in marine salt water. Bass are winter breeders and start breeding
around May and finish about September each year. Each mature female migrates
downstream to the salt water, breeds and then generally returns back to the fresh
water. It is a bit of a concern that due to climate change and drought we are not
getting the flood events that we used too. Generally starting in May on the east coast
we would get storm events that would give us good flood levels in the freshwater river
systems, this assist the bass to migrate down river.
We capture Bass from the rivers and streams of NSW and take them straight back to
our hatchery for breeding or hold them in ponds or tanks until required. We capture
bass under a broodstock collection permit issued to us by NSW DPI Fisheries. We supply
fish for restocking back into the rivers and streams of NSW and by catching the stock
from the rivers their offspring are going to be restocked back into, this ensures that
the fish genetics are correct for each area. Also by catching wild fish and breeding
with them we ensure that the offspring are good healthy genetic stock.
Bass captured from both freshwater and salt water are taken straight to our state of
the art Hatchery and anesthetised with clove oil. It is a stressful process catching
Bass and we do try and catch our fish that day and breed them in the late
afternoon/evening, this reduces the stress and need for extra handling.
anesthetise the bass with clove oil which is a natural product. We add
approx 30 drops of clove oil to 40 litres of water and drop the fish in. After 5
minutes the fish are knocked out. By having the fish anesthetised we can handle them
easily without damage to the fish or ourselves. Australian Bass are a very spiky,
spiny fish which can injure you if you are not careful. We remove them from the
anesthetising tank then weigh/measure and health check the fish taking blood samples to
ensure they are disease free.
We will inject our bass with a hormone HCG at a dosage rate of 1000 iu/kg. This
will ensure the fish will breed some 36 hours later. We then transfer them to our
hatchery breeding tanks that are filled with salt water and temperature and light
controlled. We try and inject our fish around 6 pm in the evening so that they will
spawn around 6 am 36 hours later.
tanks are 1,400 litres, heated to 18° C and we aerate to keep eggs in suspension.
Bass have no problems going from freshwater directly into the salt water tanks.
Unfortunately Bass are an extremely difficult fish to breed and no end of problems
can occur. Generally we prefer 1 males and 1 females
per tank but it is just catch of the day and we do not like to hold fish over. What we
catch today we want to breed today. Last year at Aquablue we did have difficulty
catching enough males to meet our requirements. We did persevere and managed to just
get enough but we had to work hard to get the desired amount.
36 hours after injection if all goes well the bass will have spawned naturally
themselves in the tanks. We sneak in at 34 - 36 hours with a glass and just scoop out
a glass of water and check the number of eggs in the water. It is essential that the
fish do not see or hear you as it might put them off the critical task of spawning. If
there are a good amount of eggs we will wait 2 hours to ensure they have fully finished
and then remove all the fish from the tank.
When the fish spawn naturally we have 100% fertility of the eggs. However
occasionally we have fish that just have not got with the program and have not
spawned. These fish can be removed and hand stripped. Eggs and sperm are stripped
from the fish and mixed in a bucket. It’s a reasonably successful method but fertility
rates are lower at only 40 to 60% After spawning the eggs take another 48 hours to
hatch dependant on water temperature. We either keep the bass larvae in the breeding
tanks for another 5 – 9 days before transferring them into outside ponds or we will
transfer then to larval rearing tanks inside the fish shed.
The outside ponds are earthen and constructed from impervious clays. They range in
size from 500 square metre surface area up to 1800m². They are filled 2 – 4 weeks
prior to stocking with marine salt water in the range of 24 – 28,000 ppm salt. They
are fertilized to promote algal and zooplankton growth on which the larval bass feed.
Additionally we have plankton ponds that just grow marine plankton and we will add
water from these ponds just prior to larval release.
The outside ponds are
stocked with larvae at a rate of approx 1000/m². This is very
high but our final survival of harvested fingerlings is very low at a rate of 1 – 20%.
It’s just survival of the fittest and ensures you only get the tough survivors. Ponds
initially are only 50% filled with salt water and after 3 – 4 weeks we start adding
fresh water and by time of harvest they are 90% fresh and 10% salt.
Keeping food up to our bass is a big task. In addition to the plankton ponds we
have 4 only 10,000 litre rotifer tanks that give us a constant supply of rotifers that
we harvest daily and feed to our bass. Additionally in the internal larval rearing
tanks we hatch and grow artemia which we also feed to our bass.
Prior to harvest 1000 sample bas are sent out for disease checking to ensure that
they are disease free. Once the all clear is received we harvest.
The bass when
they reach around 25 mm are drain harvested from the ponds. Once
harvested they go into 100% freshwater tanks back in the hatchery building without any
problems. Fingerlings are kept for 7 days in the tanks and are disease tested checked
and treated as part of the NSW DPI Hatchery Assurance program to ensure they are free
of any diseases or parasites prior to sale. This ensures the fish fingerlings you
receive from us are the best you can buy. Bass fingerlings are available from
October/November each year.