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On 30 Nov 2005 09:29:26 -0800, wrote:

Hi:
Finally a topic that I can legitimately declare that I am an expert.

As an ex NMFS Fisheries Observer I spent several years in the 1980s and
early 90s calculating species composition, total catch weight, and a
bunch of other stuff on a variety of vessels and fisheries along the
west coast, North Pacific, and Bering Sea. I was basically a sea going
fish accountant.

So to answer your question ya gotta consider a few conditions:

Length of Vessel
Type of gear used (Longline, pot, midwater, drag, gillnet, purse,
trawl, troll, surimi MS etc...
Target species (salmon, pollock, Cod, hake, crab)

So how do you estimate catch size? Depends on a lot of factors. Are you
talking about 100 MT midwater bag of pollock sitting on the trawl deck
of a 360' factory trawler (F/T) bouncing around the Bering Sea on a
typical January day with 50 k wind and 30' seas or a 38 pound king
salmon getting landed on a sweet little 32' double ended salmon
troller built in 1932 and planked with Port Orford Cedar?

Thanks to everyone who has replied so far - the main thing everyone has made
me realise is that it's not as easily as I thought, and actually I didn't
think it would be easy anyway! :-)

For a bit more info, what we are trying to do is to automatically quantify
how much is being caught on the fishing boats, and to transmit that
information back along with position, speed, etc as part of Fisheries
monitoring.

This is in Asia, and there are some problems with vessels selling the fish to
other countries instead of locally, not to mention selling of their
subsidized diesel, so we can't really rely on information from the crew.

The vessels are maybe 30' to 40' wooden trawlers. Not sure what they catch,
but from looking at the sorting areas in port I believe they just take
everything they catch & don't do any sorting on board, nor throw anything
away (unless it's maybe a turtle or something big that they don't really
want). Undersize individual fish don't appear to be a problem either - seems
they are more prized actually!

Weather could be anything from dead calm to typhoon, though I'm guessing they
probably don't fish much in anything more than 2m of seas.

It actually sounds like a tricky task - weight on winch would probably be
highly inaccurate & too dependent on sea state & vessel speed. Hold weight?
Maybe also difficult to instrument? Especially as these are relatively cheap
hand-made wooden fishing boats that just go out with loads of ice to pack the
catch in & have no refrigeration or no standard size or position holds.

And then we have the problems of low bandwidth to transmit the information
back to shore, and the very high potential for sabotage..... :-(

Dave