At 06:00 AM 1/26/99 -1000, you wrote:
>to catch threadfin salmon which I think is a fish you have in Hawaii. You
>call them something else, a name which Bruce mentioned in one of his posts.
>(Bruce, what is threadfin salmon in Hawaii)
In hawaiian it is called moi. It is now being raised commercially her in
Hawaii for food. I think most of the native stocks have been depleated. I
can recall in my childhood when the sub adults would swarm into the beaches
and people would catchthem for bait!!! It may have been related to the
sugar plantations dumping a lot of trash and silt into the sea. It seemed
to create the optimal conditions for the fish to feed.
>
>P. cyanodorsalis live in salt water and that changes to fresh for several
>months in Darwin and hardly at all in Broome WA where Crab Creek runs into
>Roebuck Bay. The annual rainfall at Broome is very low and there is no
>permanent freshwater for about 165 km (Fitzroy River at Wilare) to the east
>and probably 600 km to the west. Crab Creek has tides up to 9 meters and
>very sloppy light grey mud banks with a shell grit bottom. Once you crawl
>and slide into the creek and walk towards the sea the mud banks are above
>eye level. A friend and I walked for about half an hour toward the sea at
>low tide and ended up being swept back to the mangroves by the incoming
>tide. It was not a nice experience. Last time I drove to Broome from
>Darwin it took 22 hours on the road and there are only about 4 small towns
>in between. Mack I think you need to come and have a look where these
>little fishes live. I can draw you a few mud maps and then you can get
Yes I would like to do that one day.
>plenty of mud on you. Probably 99% of the places where these fish spawn
>would be silty mud. Question - what happens to the eggs in this low oxygen
>environment. In your calculations about cyanodorsalis spawnings you need
>to factor in fast rushing water one way for 6 hours and the other way for
>six hours and what happens to any eggs left in the mud which does not dry
In annual fish (killies in Cynolebias, Nothobranchius, etc) the low O2
conditions cause the eggs to go into a deep diapause. In these conditions
I am told that eggs can remain dormant and viable for 2-3 years. Not sure
if it is the same with cyanodorsalis (another experiment to try). The
question I have is if the spawn on the bottom at both sites? Seeing that
the Crab Creek locale does not get very much freshwater, I wonder if the
fish don't spawn more outside the area where the tides would have the most
effects. Also buried deeply in muck they might adhere to the bottom until a
major tide or monsoon dislodges them. I can't imagine a tide difference of
30 feet. I think 3-5 feet is more what we get in Honolulu.
MTF
>between the tides. The spring tides in Darwin are up to 7 meters (about
>25 ft) and the spring tides in Broome are up to 9 meters (about 30 ft)
>which diminish down to a couple of meters during neap tides. I have
>explored many places where there is fresh water creeks running into the sea
>and have not seen any cyanodorsalis inland past the mangroves. You would
>think they would migrate inland if they could, perhaps they need the salt
>dose after a period in fresh water. I don't know what happens to P.
>cyanodorsalis in Queensland mangrove habitat cause I have not seen it.
>When the wet season drops great loads of water there is a decrease in water
>temperatrure. The pearl farmers at Broome and Darwin keep year round sea
>temperature statistics. As far as salinity goes the salinity near the
>opening of Darwin Harbour at the moment is 30 ppt, just a little below
>normal sea water.
>
>I don't think cyanodorsalis would interbreed with inconspicuus because they
>inhabit different parts of the mangrove creek.
>
>Palintest may make an iodine test kit. I will check my catalogue tomorrow.
>
>Dave Wilson
>
>
>
Mach T. Fukada, Editor
Note New E-mail address:
fukada at aloha.net
Honolulu Aquarium Society
http://www.geocities.com/Heartland/Meadows/2948/HASF.html