Wednesday, November 19, 2014

Disturbing Catch Explored

This past weekend I blogged about our most recent outing where my betweeen my friend John Cail and I, we landed an impressive 21 shortnose (may have been a young Atlantic in there) sturgeon out on the Kennebacasis River.   For the most part if was a fantastic, if not cold, outing with the exception of one sturgeon that had a number of, what appeared to be, fresh lesions across several parts of its body.  Most of the damage was on the head or upper back, and there was a little as well on the belly.   I didn't notice any damage on the tail, and just one spot on on the side.

This past blog article has received a lot of attention.   During the life of this blog, only one post has ever had more than 700 views, and that was from last November, one of my first ever posts!   The post from just a few days ago however has received over 1100 views!  Clearly it's a point of interest to many people!


With this much attention, I needed to take some time to look further into what may have happened to this one fish.   My first premise, based on some quick feedback from friends on Facebook was that the damage may be related to nets.   Also, given how fresh the cuts looked, especially where a scute had been ripped off, I was thinking this must be a relatively recent injury.  


In talking with Dr. Mike Dadswell Ph.D. and researcher Sam Andrews of the Coastal Ecology Lab from Acadia University a few other theories and some great information came to light!  

Sam shared with me several pictures of injured sturgen and in his studies, have seen many fish that with damage and from nets, Typically the damage is easy to define.   Gill nets typically cause the sturgeon fins to be cut shredded and also leave indentations from the net on their body.  Neither was true for the sturgeon here, so while that doesn't eliminate netting as the cause, it does give one doubt.   Here is a picture of one sturgeon that had been damaged by a gill net.  Notice how the fin is all cut up and the scutes are rubbed and red.


The other type of net that could come into play is from trawlers out in the Bay of Fundy.   Now I would not have necessarily thought that shortnose sturgeon from the Kennebacasis River would spend time in the Bay of Fundy but at least a portion of them actually do!  Both Dr. Dadswell and Sam confirmed that at least some shortnose do wander out into the Bay and could be caught up in the nets of fishing vessels.

From the research papers that Dr. Dadswell shared with me, the first photographed and documented shortnose sturgeon caught out in the Minas Basin in June of 2013.    There have been other fishermen reporting shortnose sturgeon in their catch and in some cases university researchers have been able to confirm this.  

Given this information, it is not out of the question that the shortnose which I caught may have been injured by a fishing vessel out in the Bay of Fundy.    Professor Dadswell suspects this may in fact be the case.     Here is a picture of a small atlantic which has been injured severely by a trawler.   The injuries of this particular fish aren't especially consistent with my fish, but the injuries sustained may vary.



Next, Sam told me about the ectoparasites that are common on the sturgeon populations in the Minas Basin and likely here in our river systems.  These parasites are known to hamper the immune systems of sturgeon and could very well cause an old cut to appear new.   It is fairly common to see large Atlantic Sturgeon in the Minas Basis with several injuries very similar to the ones this sturgeon has, and those injuries could be much older than they appear.
Of course, anyone in this area is familiar with Reversing Falls and the wild waters that flow either way through that channel.  Perhaps the sturgeon found itself caught in the rapids of Reversing Falls either on its way out into the Bay of Fundy or on the way back?   That could certianly explain the injuries.

While the net theory shouldn't be completely dismissed, it is only one possibility.  It is certainly disturbing to see a fish with injuries like this, especially in a very rare healthy population of a species that we are fortunate enough to have here.   But one shouldn't immeadiately jump to the worst possible conclusion as I may have let people to do.   For that I apologize.

I hope this post has been informative, even if it isn't especially enlightening for the question at hand.     I know I have learned quite a bit of the past few days, and want to thank Dr. Dadswell and Sam Andrews for their help!   Hopefully I'll be able to return the favor one of these days!

1 comment:

  1. Just some food for thought, but a while back, the ice broke early and lots of debris from shacks and entire shacks sank. I m sure a lot of other debris could have caused this also.

    None the less great article!

    ReplyDelete