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Searun Cutt Copepods

2K views 18 replies 9 participants last post by  SeaRun Fanatic 
#1 ·
Fished the South Sound Sunday and caught a good mix of searuns and resident coho. At some point, I had an interesting realization that for some reason hadn't occurred to me before: the cutts all had the familiar large dark parasitic copepods (Argulus? http://www.tidelineaquatics.net/nla/newsletters/09_11_2007.pdf), mostly along their dorsal surface, but the coho had none. After briefly researching old WFF threads about these parasites, I didn't see this difference addressed. So....

  1. Has anyone ever seen the variety of "sea lice" found on searuns on resident coho?
  2. Any theory as to the nature of the species specificity?
  3. Any positive ID?
 
#4 ·
My best guess would be that this has something with a preference to cutthroat due to physiological differences between the species. It may be that they prefer to feed on the slim coating of cutthroat or that something about the scales on salmon repels them better.

It may also have something to do with habitat use, sea run cutthroat are not known spend much time in deep/ open water and tend to hug the shoreline. While resident coho may come in close to shore to feed, they also spend much of their time in deeper water. However if this were the main factor, than you would still expect to see some coho with these parasites. It is odd how both fish seem to have the normal sea lice, but only the cutthroat seem to get the large blob like copepods.
 
#6 ·
As pointed out we have discussed this topic several times.

While I have seen this critter on other fish it has been extremely rare - I think I have seen few on other fish in total than what we typically see on a single cutthroat.

I think that Gigharborflyfisher may be on the right track in that the cutthroat's behavior and habitat use makes it more likely to become infected with this critter. Since the last discussion I have thought some more about this issue and now have to wonder if whether the critter in question is a true fish parasite.

We know from some radio tracking studies (and obseravtion) that at times that sea-runs while hold for extend periods in eel grass beds with very little movement. I wonder if this "sea-louse" is some sort of critter that lives on the blades of eel grass and during those periods of the cutthroats inactivity in those grass beds that the critter is able to transfer from the eel grass to the cuttrhoat.

It doesn't seem that the other anadromous salmonids engage in this behavior which may account for why we see it on the cutts and not the resident coho or other salmonids (anyone see them on anadromous bull trout?). Anyway just a theory but for now it fits what we seem to know - need more information.

tight lines
curt
 
#7 ·
Hmmm... habitat differences...

Could it be that this is something the adult cutts pick up on their return to salt from freshwater? This is one key difference between the species. Problem is, I'm not sure how to ID a 1st year cutt to look for infestation. Smaller, obviously, but otherwise...?

Also, no, Curt, I've never seen one on any of the many dolly/bulls I've caught in the salt. Maybe that shoots down the outmigrating adult theory, eh?

Seriously, though... nobody has a solid ID on these guys? They've been discussed here for years. Obviously we don't know a life cycle or their impact on the host. I haven't been able to dredge up anything solid after a myriad of Google searches either. This is starting to sound like a killer fisheries grad thesis to me. Maybe when I get laid of in the economic downturn, I'll go back to school just for this! Can you say grant $$$ to fish for cutties? :clown:
 
#12 ·
I like the intermediate host as prey item theory a lot. Would seem to allow the observed species specificity.

Freedon: did the coho in question seem unduly stressed or in an unusual environment?

C'mon saltwater anglers... anyone else with reports of coho with these guys?
 
#9 ·
All I can offer is more confusion. I have seen those hitch hikers on both species in the far south sound. A couple of years ago, I caught a batch of coho in sight of the capitol building that were grotesquely crusted with the things, as in more than 20 per fish. so, it does happen to salmon as well, but not as much. I've attached a rather poor picture that I took last week of cutthroat infested with what we are calling copepods.

I apologize for the glare on the water, but on the larger SRC, once you get past the glare, you can see all the grayish ovals along the dorsal area, thicker toward the tail, The same organism looks darker on the small (13") brown fish. The fall I was finding them on the coho, they were so slimy green, that I first thought it was sea weed globs.

By the way, before I get mobbed for keeping SRC's,we were collecting them for WDFW for a transponder tagging study. Jaw Automotive lighting Gas Automotive exterior Bumper
There is an aerator tube in the water,and all fish survived.
 

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#10 ·
A general question: How does one distinguish between the North Sound and South Sound? Is there some generally accepted real or imaginary line that seperates the two? I continually see references in print, both on this forum and other mediums, that make that distinction without any clear definition of where one ends and the other begins! Am guessing that it has something to do with "Marine Areas" but not sure....?:confused:

Would appreciate any clarifications, subjective or otherwise.:beathead:

Thanks.

Jc
 
#13 ·
The coho appeared to be in good health aside from the layer of parasites. As far as unusual locations, they were in fact in the boat basin at the extreme end of the inlet, where the flow is a little stagnant, and the bottom shallow and muddy. However, with that said, these are net pen fish, which are nothing if not highly mobile. We generally find them out in the faster flowing passages, off points and the like. I was only in Budd inlet because I'd received a phone call that "salmon were jumping all over, right by the houses".

I assume that the school had simply migrated into the basin, whether randomly, or not is speculative. I doubt they'd been in the bay long enough for that to be a factor. They were feeding aggressively, were fat and healthy, and ate well.
 
#15 ·
I hear so far (and from my own experience) that an association with shallow muddy bottom, slow moving brackish water, and possibly a cutthroat-specific prey preferece may have something to do with the specificity of this parasite of cutthroat. So I started looking at the literature, and found a citation that mentions Sticklebacks as a possible intermediate host for sea lice. Starting to make sense then - Sea run cutthroat tend to overlap with high dernsities of sticklebacks in those kinds of habitats, perhaps more so that other salmonids. Cutthroat eat Sticklebacks and/or are often in close proximity with them. Total speculation on my part that this may be "the" explanation but I'm going to do a little more rearch on this and pull the publication they cite in the piece I pasted below the link:

http://www.oag-bvg.gc.ca/internet/English/pet_160_e_28894.html

We suspect that the dynamics of sea lice production in the winter in the Broughton area may be key to understanding how both farmed and wild salmon become infected. It is possible that there may be a link with the relatively large number of sea lice on adult returning salmon (Beamish et al. 2005) and the onset of sea lice productivity that appears to start in the winter. We are examining several possible mechanisms involved in the sea lice infection of juvenile salmon. The infection may be more related to sea lice dynamics and sticklebacks than with salmonids as over-wintering hosts for sea lice. For further information please refer to:

Beamish, R.J., C.M. Neville, R.M. Sweeting and N. Ambers. 2005. Sea lice on adult Pacific salmon in the coastal waters of Central British Columbia, Canada. Fish. Res. 76:198-208.

In response to the second bullet of your question, Salmon species are the primary hosts of the marine ecoto-parasite Lepeophtheirus salmonis (a species of sea lice). The "primary host" is the host on which the parasite achieves sexual maturity. However, there are numerous examples in parasitology of intermediate and transport (paratenic) hosts on which the parasite survives but does not achieve sexual maturity. These hosts often serve to bridge an ecological gap such as may occur in parasites that are transmitted through different trophic levels (e.g., from snails to fish to birds-in which the fish "bridges" the gap). We believe sticklebacks may serve as temporary hosts and have stated this in a paper recently accepted for publication in the Journal of Parasitology (see below). In support of this we have observed that the abundance of L. salmonis on sticklebacks was consistently higher than on sympatric juvenile pink and chum salmon in 2003, 2004 and 2005 in the Broughton. Some of the highest sea lice infection levels on sticklebacks have in fact been observed in locations 20-40 miles from the salmon farms in the Broughton, and "upstream" of the farms relative to the general water current patterns. While we have observed L. salmonis on sticklebacks in the Broughton, we have seen virtually no evidence that L. salmonis matures sexually on the stickleback. We have also observed Caligus clemensi (a generalist sea lice species) on sticklebacks. There is a need for more work to understand exactly how the stickleback serves the ecological needs of L. salmonis. For example there is evidence in the literature that motile L. salmonis will "jump" from non-salmonid to salmonid hosts. We will be exploring this hypothesis with laboratory studies this spring and summer.

Regarding other areas in BC with no salmon farms and other areas with salmon farms-we have some sea lice data but mainly from juvenile salmon. Very little information is available regarding the abundance or distribution of stickleback or their infection levels by sea lice in these other areas. Sampling by other groups outside of the Skeena River and in Nootka Sound have reported small numbers of sticklebacks in their samples but none have reported the incidence of lice on the sticklebacks retained in 2003 or 2004. A summary of 2005 sampling in Nootka Sound provided January 29, 2006, reports 45 sticklebacks sampled with an infection rate of 24 percent with 23 chalimus-stage lice counted but not identified to species. Since the data outside of the Broughton are limited, we have not attempted to compare lice levels on sticklebacks in the Broughton with those that may occur in other areas. The juvenile salmon data from these other areas (with or without salmon farms) all show lower levels of lice than we have observed in the Broughton Archipelago.
 
#17 ·
There are also behavioral mechanisms that separate juvenile fish from adults that carry the breeding sea lice parasites. Perhaps cutthroat adult and juvenile life history overlap plays a role in infection of cutthroat juveniles?

Here's an example of how fish farming breaks down the natural segragation of adult salmon and juvenile salmon, leading to increased sea lice infection:

"The epizootics arise
through a mechanism that is new to our understanding of emerging
infectious diseases: fish farms undermine a functional role of
host migration in protecting juvenile hosts from parasites associated
with adult hosts. Although the migratory life cycles of Pacific
salmon naturally separate adults from juveniles, fish farms provide
L. salmonis novel access to juvenile hosts, in this case raising
infection rates for at least the first !2.5 months of the salmon’s
marine life (!80 km of the migration route). Spatial segregation
between juveniles and adults is common among temperate marine
fishes, and as aquaculture continues its rapid growth, this disease
mechanism may challenge the sustainability of coastal ecosystems
and economies."
 
#18 ·
Personally I have not seen lice on anything other than Searuns here in the North Sound (North of Everett). My first observation of lice on Searuns was in the South Hood Canal area at about the early 80’s; prior to this time (60’s & 70’s) I don’t recall seeing any at all.

In the North Sound my first observation was in the early late 80's to early 90’s.
Over the years I have definitely seen a huge increase of the number of parasites on specific Searuns. I have observed some with there backs so completely covered with parasites you had to wonder about the health of the fish and its ability to function normally but they don’t seem to show any signs of stress. I have to believe that it does have some affect but to what extent is anybody’s guess.

Fortunately Cutthroat are anadromous and these buggers fall off once they leave the salt.
Here are a couple photos I took last year.
 

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#19 ·
Double-D's suggestion of increasing parasite burden over the decades is exactly what I was afraid of. Could these wonderful anadromous fish many of us so love be telling us something abouth the health of Puget Sound? As though we didn't already know the answer to that question! bawling: Like the now extinct grayling in watersheds across America, could searun cutthroat be an indicator species - the canary in the coal mine? Seems quite possible to me.

Any observations of these parasites on searuns outside Puget Sound? How about Grays Harbor? The Olympic Peninsula?

I can say that I haven't seen them on the cutts I've caught in saltwater in AK and don't remember them on Straight of Juan de Fuca fish (but Uncle Jimmy or Bob Triggs would be better folks to answer for out there).
 
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