My guess is (a guess because of my unprofessional background) there has been
little evidence of a health danger to anadramous fish, in our waters, over
history. It is a fact they acquire them in salt and freshwater rids the
fish of these parasites. What is the organism that hangs from the upper,
inner mouth of summer-run steelhead? My guess, the same organism, or
similar organism. I have been told, by biologists, that a way to ID
summer-run, from winter fish (and that is often a difficulty) is to look
inside the mouth and on summer-run, there will be organisms, like the lice,
hanging from the upper mouth area. Jere
----- Original Message -----
From: "Nicholas Lowry" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Tuesday, July 17, 2001 5:03 PM
Subject: Re: sea lice
> I decided to do some reading to fill in some of the gaps in my knowledge
> of sea lice, prompted by Tom Wolf's post. What I found out was that all
> the "sea lice" are in the same family, and there are a lot of them. The
> two main species which affect sea trout are Lepeophtheirus salmonis and
> Caligus elongatus. Both of these are limpet like copepods, as Tom
> describes them. I'm not sure which species is infesting sea run cutts, but
> I suspect it is L. salmonis, it is bigger, more or les the size of the
> ones I saw. As soon as I catch another fish I will preserve the lice and
> ID them. Nothing I read mentioned cutthroat as a potential host for sea
> lice.
>
> Being crustaceans, the lice have planktonic larvae, which metamorphose
> into an infective stage (a copepodid). These are the ones which can attach
> to the gills, and are presumably too small to be noticed when they are
> there. They also can attach to the fins and eyes. The adults can move
> around on the body of the fish once they have developed.
>
> The lice feed by scraping away at the mucus and skin of the fish. The
> seriousness of this depends on the number of parasites, but can be severe
> skin erosion which causes osmoregulatory failure, or opening avenues for
> secondary bacterial infection. There is also a high instance of fungal
> infection in fish which return to fresh water.
>
> 5 L. salmonis or 12-15 C. elongatus were enough to kill salmon smolts. It
> took 40-50 C. elongatus to kill adult salmon. The lice also act as vectors
> of other diseases, such as Aeromonas salmonicida or infectious salmon
> anaemia. (Other parasites can do this too, and many diseases are directly
> transmitted in water. The fish in the cages are vaccinated and treated
> for disease if it occurs in the pen, wild fish are not so lucky.)
>
> There doesn't seem to be any great seasonality in their occurrance, they
> are present all the time. The greatest numbers in most of the studies were
> in late summer or autumn. It seems to depend on temperature and salinity
> affecting the survival rate.
>
> Fresh water affects different species to different extents. L. salmonis
> can live for up to 25 days in fresh water, but C. elongatus dies sooner.
>
> Most of this information came from "Fish diseases and disorders" Edited by
> P.T.K. Woo, published by CAB International, ISBN 0 85198 823 7.
>
> With regard to the Irish sea trout problem and gill nets, I don't give any
> credence to the theory that the decline was caused by poaching. The
> relationship between the pattern of decline and the siting of cages is too
> consistent, and the first thing that was noticed was the loss of the
> larger sea trout. These were the same size as the wild salmon, but the
> salmon didn't decline at the same time, as they would have if there had
> been poaching on the scale needed to catch all the sea trout.
>
> There has been a lot of focus on sea lice with little conclusion. Lice are
> the most visble disease of course, and others may be more prevalent. I
> wasn't aware that lice could transmit ISA. I believe that ISA is what
> caused the crash of New Brunswick salmon, and that they have now banned
> net pens. More stuff to read up on!.
>
> Anyway, if you got this far, thanks for listening.
>
> N.
>
>
> On Fri, 13 Jul 2001, Jere Crosby wrote:
>
> > Enjoyed your post and your knowledge on the subjects you wrote about is
far
> > above mine. I have done a 360 on the subject of net pens. A recent
> > article, I believe in Flyfisherman Mag., quoted a Scandinavian source as
> > stating, "Any river entering the salt, within 3 miles of net pens, WILL
NOT
> > have native fish."...the pens are that destructive. They applauded the
> > Eastcoast decision to reject net pens. I have learned, as you have
stated,
> > to take, what fly fisherman suggest as fact, with a grain of salt, until
all
> > the evidence is in.....to much emotion involved. Jere
> >
> >
> >
> >
> > ----- Original Message -----
> > From: "Tom Wolf" <[EMAIL PROTECTED]>
> > To: <[EMAIL PROTECTED]>
> > Sent: Friday, July 13, 2001 1:36 AM
> > Subject: Re: sea lice
> >
> >
> > > Nicholas,
> > >
> > > Its been my experience that cutthroat loaded with sea lice mix in with
> > those
> > > that don't. I see this all over the deep south sound and even up into
the
> > more
> > > open main basin areas. I Believe the sea lice that were supposedly
> > responsible
> > > for the Irish trout problems (even though the stronger evidence was
major
> > > poaching with tight mesh nets), attached to the gills of the fish. The
sea
> > lice
> > > in the sound are the limpet like copepods that attach themselves to
the
> > back of
> > > the fish and are found no where near the gills. I have never been able
to
> > tell
> > > while playing a cutt if it was infected with copepods or not until I
could
> > > clearly see his back. I have not been able to find any good science
on
> > the
> > > subject and do not know what the relationship between host and
parasite
> > is. I
> > > use the copepods as a way of gathering information on the run timing
of
> > the fish
> > > i catch. The diversity of the runs of cutthroat put them spawning up
> > rivers as
> > > early as november maybe even october all the way through April and
May.
> > The
> > > copepods attach themselves to the cutts once they spend a certain
amount
> > of time
> > > in the salt water so one can conclude that a cutt in Feb. or March
covered
> > with
> > > copepods is either a fish that has wintered over in the salt or an
early
> > run
> > > fish. In any case a cutt need only a bit of fresh water to shake the
> > critters.
> > > Another gap in the science is that we have no data on the amount of
> > copepods
> > > before the net pens or after. Then we have to look at the life cycle
of
> > the
> > > copepods and determine when the populations are at their greatest
during
> > the
> > > year and what fish are present at these times. I have followed certain
> > pods of
> > > cutts over the years and have observed no loss of populations with
fish
> > that
> > > are more prone to infestation than others. A few years back when the
> > atlantic
> > > salmon escaped from the pens near Bremerton, we had a fishing
emergency
> > and had
> > > to get to the scene right away to test our various patterns on the run
> > away
> > > fish. I do not recall seeing any limpet like copepods on the
atlantics.
> > Did
> > > anybody else? I can most definitely say there is no correlation
between
> > the
> > > infestation of the sea runs and the proximity of the net pens. There
is a
> > more
> > > dangerous threat to our cutts and salmon in the sound in the form of
gill
> > nets.
> > > The state record sea run is around 6 lbs. How many cutts have you seen
> > over 22
> > > -24 inches? A four inch mesh will take these beauties out in a hurry.
Just
> > think
> > > what it could be..............
> > >
> > > The net pens could be a great help to our dwindling salmon runs in the
> > Puget
> > > Sound. They have the potential to take the load off our remaining wild
> > stock (I
> > > use the term wild loosely), while still keeping us active and
interested
> > in our
> > > sport. Before we run the salmon farmers out of town, make sure we have
> > the best
> > > science available to make our case.
> > >
> > > T Wolf
>
>
>
