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Plectropomus

bruising on beach mulloway -- any theories??

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Hi there brains trust.

For years I have wondered why pictures of big mulloway often show a pink area of bruising on the flanks. In contrast, I have never seen this on underwater footage of NSW/Qld mulloway taken by divers and spearos. I am really curious to see if anyone knows more. I even began to collect images to see if the bruising was limited to one side, or the other, and if it occurred only on largest fish. 

Early indications are it is mainly surf-caught, bigger fish, and often down the side toward the vent. See examples below, and the one with a yellow circle.

The only things I have shortlisted from a range of possibilities are (a) a parasitic infection of some sort on the skin under the scales, (b) sand rubbing the fish when it is being landed, (c) some sort of contact with the line during the  typical way mulloway fight, and (c) "spawning behaviour" where males might nudge females.

As a semi-retired fish biologist, this is one of those questions that buzzes around in my head begging for an answer!! I don't think it is anything sinister.

Apologies if the photos below are yours! I just Googled them off various FaceBook forums and the net.

Any ideas or observations??

Thanks

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good pick up Plecro' 

It is spawining season when the large mullys are targeted most on the west coast of SA so fair bet it may have something to do with this. It is possible that is bruising from the fight though, as they say the bigger you are the harder you fall and fish that size could cause some damage to themselves quite easily under their own weight, with line wrap or even the sinker banging against them, but the wounds look like they may be older than a few minutes so my bet is on spawning aggression or behaviours.

 

https://www.pir.sa.gov.au/__data/assets/pdf_file/0004/232393/Yalata_Mulloway_Recreational_Fishery_-_FINAL.pdf

image.png.8c7545ed9b9a47986915d2b9ff38a96b.png

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1 hour ago, mrfish said:

good pick up Plecro' 

It is spawining season when the large mullys are targeted most on the west coast of SA so fair bet it may have something to do with this. It is possible that is bruising from the fight though, as they say the bigger you are the harder you fall and fish that size could cause some damage to themselves quite easily under their own weight, with line wrap or even the sinker banging against them, but the wounds look like they may be older than a few minutes so my bet is on spawning aggression or behaviours.

 

https://www.pir.sa.gov.au/__data/assets/pdf_file/0004/232393/Yalata_Mulloway_Recreational_Fishery_-_FINAL.pdf

image.png.8c7545ed9b9a47986915d2b9ff38a96b.png

Thanks Mr Fish. That report will make interesting reading! I have not done a proper survey of photos (presence/absence of bruising "rash" +location+ month) and it is sometimes hard to know if the picture in an internet post (say, "tackletactics.com") is a reliable indicator of location, but it certainly seems most common in SA West Coast Fish. Not just there, though, the ones below are Salt Creek, Murray Mouth and (allegedly) Victoria (the smaller one with white fishing rod). I have not seen any (yet) in pics from WA, NSW/SEQ, or South Africa (where they call them "kob"). I have located the contact of a parasitologist in New Zealand (ex-SA) who I will email pics too for an opinion, too. 

Maybe.Victoria.jpg

MurrayMouth.jpg

SaltCreek.jpg

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Ive watched carp spawn and they are super aggressive

bashing into rocks,  even beaching themselves for the chance to be the guy that gets his sperm on the eggs

the males also relentlessly head butt the females in the guts to get her to release her eggs

im not saying that’s what these bruises are as I have seen similar bloody bruised areas  on bream  around spawn time and carp for that matter  - but I’ve heard them also described as fungal in fections

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Another theory ties back to the Mulloway emitting a scent to attract beach worms - they might be rubbing their slime coat on the sand to leave a stink spot - then going back to suck up the worms.

That area is open to infection?

Again - I'm not saying thats whats happening - just throwing some possibilities out there that match the location of your photos

 

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27 minutes ago, yellow door 1 said:

Another theory ties back to the Mulloway emitting a scent to attract beach worms - they might be rubbing their slime coat on the sand to leave a stink spot - then going back to suck up the worms.

That area is open to infection?

Again - I'm not saying thats whats happening - just throwing some possibilities out there that match the location of your photos

 

have you seen the rash/bruising in Victoria???

 

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I've got a couple of special dates that I class as my opening days for certain spots - I've already missed April 14th

And my May the 5th, looks like its not going to happen either

What dates are your season openers.

(p.s. circular saw is viewed as and "essential travel" accessory😉)

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Just now, ChuckTseeker said:

All the creek mulloway we catch have them too...

wow....and they would not be the monster/adult sizes either, would they? Gulf systems or Glenelg River?  I emailed a fish parasitologist and attached the pictures for a professional opinion.

 

 

 

 

 

 

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I've had a look - and a chat to a fella thats caught more Jewies than me -  and our river fish, landed in nets, dont seem to have sores or bruises - But they arent suppossed to spawn in our rivers either.

I'm still waiting on a bloke who has 100's of Melbourne river Mulloway photos, to get back to me. But so far, all we can remember, are clean skins😉

(The Bream - which do spawn in our rivers -  get beat up and exhibit sores during spawning time - not so much bruises - but their tails get bloody and they will have bloody sores on their bodies aswell )

117.jpg

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6 minutes ago, ChuckTseeker said:

I think its because they school up so close and are rubbing against each other?? Thats what we have always thought anyway as we have seen them in schools of a 100 and more fish.. if you look at this photo you can see the mark behind the rod..

 

101_0074 adj.jpg

Beautiful photo, and another explanation.!!

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If you cant find any info on sores or bruises on Mulloway - search google for sores and bruises on other fish - "Red spot" seems to crop up a bit on a variety of different species around the world - Any bruising on Species like carp or bass will have been thoroughly discussed and may offer clues to why it happens in Mulloway

 

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Just now, yellow door 1 said:

If you cant find any info on sores or bruises on Mulloway - search google for sores and bruises on other fish - "Red spot" seems to crop up a bit on a variety of different species around the world - Any bruising on Species like carp or bass will have been thoroughly discussed

 

Yes, there is plenty on EUS {epizootic ulcerative syndrome - or "Red Spot"} but those ulcers are caused by a fungus (Aphanomyces) that is not a problem until the fish get stressed by sudden changes in temperature, salinity, or acidity (in the case of northern NSW flooding of acid sulphate soils}. Common on mullet and bream in NSW estuaries, and very nasty. The fish get stressed, the fungus blooms in minor abrasions, and bacteria move in too to form a horrible ulcer.

These surf mulloway with rashes/bruises are coming from pristine, remote, surf beaches. Hard to imagine better water quality. Might be stress induced by spawning and some secondary infection, as you say.....

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Parasitologist Dr Kate Hutson replied to my email and sent some interesting papers and a photo. Here is her reply:

"....

.  About two years ago some fishers were seeing this quite a bit in SA on mulloway and some photos were sent to me (among others). It was confirmed as the skin fluke, Benedenia sciaenae by some folks based in SA who got to sample some fish.  See attached paper by my PhD supervisor Ian Whittington (now deceased). This is a monogenean ectoparasite that feeds on skin cells and mucous. Fish tend to get irritated and (presumably in an attempt to dislodge them) will rub (‘flash’) against surfaces. This can lead to secondary infections – bacteria usually. I’ve found B. sciaenae in wild fish in SA and it is not uncommon.  I have not seen the clinical signs of disease progression on wild fish in person, just photos.  To diagnose, immerse the fish skin in fresh water and the parasites (transparent when alive) will die and turn opaque/white (see photo attached; the big sucker to the right is the posterior end).  Of course, it could be something else entirely, but this is the most likely diagnosis.

 As to the reasons for not seeing it on fish from other states… well I’ve seen it in farmed A. japonicus (mulloway) in NSW, so it can occur there.  It could be seasonal.  It could be infection intensity.  It is not unusual for capsalid monogeneans to be site specific. We found adults might congregate for mating and new recruits seem to bury under the scales in some species (see my student’s paper attached)........"

So, the parasite is definitely in SA fish and the "rub it off" reaction would cause the rash/brusing and associated inflammation/secondary bacterial infection.  It is interesting to see a related species lives under barramundi scales. So, I have scratched my itch on this one!!!

 

 

Benedenia sciaenae on mulloway in NSW_KSH.jpg

Trujillo-Gonzalez et al. 2015_Tracking transparent monogenea.pdf

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