Thursday, October 11, 2012

Fisheries/Ecology Cruise - October 2012



We’ve been experiencing remarkably fair weather thus far.  Clear days, cool nights, and wind no higher than a few knots.  Except for the occasional fishing vessel during the first day or so and tankers thereafter, we haven’t seen many other boats out here.  As Will Overholt (Georgia Tech) attested in his blog during the previous leg, the food is quite good and there is something for everyone, from the purest carnivore to the vegan.  The RV WEATHERBIRD II crew is fantastic.  Hats off to you guys!
We worked today between 460 and 865 m on soft mud bottom.   The gear being used is primarily bottom longlines with multiple-sized hooks set along their length.  At the start and end of the set are baited traps intended to catch whatever bottom-associated invertebrates and fish are around.  From the longlines, we get a few bony fishes, but mostly sharks.  So part of the intent, here, is to describe the biological diversity and determine the reproductive strategies of the deep-water sharks, some of which are new to science.
 Among the more notable species we encountered today were a suite of scavengers cum predators -- the giant isopod Bathynomus giganteus (pictured in a pile at the top of the page and top in the lineup below with Emily Marcus) and two species of hagfish-- the Gulf hagfish Eptatretus springeri and the Caribbean hagfish Myxine mcmillanae.  These animals will prey on other animals, but they are best known for eating the carcasses that fall from the open water to the ocean floor, from whales to squid and fish.  Anything caught in the trap with one of them often showed signs of being at least partially devoured and clearly by them, given tell-tale signs on their bodies.
Hagfish tied in nautical knots.
So you may be wondering a bit about that subtitle.  What you need to know first is that hagfish create an enormous amount of snotty slime — about 2 gallons for one hagfish.  The pictures below say it all. The consistency is something like oozy rubber cement mixed with mud, but it isn’t as easy to get off the gear or your hands.  Remarkable.  So why would a blind animal that lives in deep water cover itself in a cocoon of slime?  Several reasons come to mind: (1) as protection against predation (the slime makes it hard for a predator to hold on and so the hagfish can escape); (2) to incapacitate prey by smothering them; and (3) to ease entrance into or exit from a carcass. 
HAGFISH SLIME and happy campers Jim Barley (with cage) and Malinowski (with Coleman)
Another interesting behavior they exhibit is tying themselves in knots.   The purpose here is to get rid of the slime, which actually inhibits their movement as well.  All one has to do (if one is a hagfish) is wrap your body in a knot near your head (the overhand knot works nicely) and slide the knot down the length of your body.    VoilĂ !
Just so you know, and as luck would have it, HAGFISH DAY, a day to celebrate all that is beautiful in nature, will occur on the day we are steaming back to Panama City, Florida.   It’s a real day, folks, proclaimed in 2009- http://www.daysoftheyear.com/days/hagfish-day/.   We’re trying to figure out how to celebrate it now.  I see a hagfish cake in our future, iced with . . .
But enough of that.  Other animals we caught occupy a slightly different spot in the trophic web.  These include the Taiwan gulper shark Centrophorus cf niaukang (photo left:  shark on left, Malinowski on right – I know it’s hard to tell, same teeth, same orange outfit), and the Black belly rosefish Helicolenus dactylopterus (photo below left).  As far as is known, the gulper shark’s diet consists of squid and perhaps other invertebrates.  It is considered by the IUCN to be nearly threatened, due largely to bycatch in eastern Atlantic fisheries (e.g., off Portugal).   Its status in the Gulf of Mexico is unknown, as are most aspects of its biology.  Jose Castro’s book, The Sharks of North America (with illustrations by Diane Peebles), is a great general reference on sharks.    
The blackbelly rosefish (L) is a scorpion fish, and like most other fish in this group, its spines contain venom that can hurt you!  We wear thick gloves all the time while on the back deck working with these animals. The rosefish eats primarily benthic invertebrates, including crabs and other decapods, brittlestars, ascidians, and polychaetes . . . essentially anything that moves slower than it does.
And that’s about enough out of me.  The next post will be a combo post from the grad students so stay tuned.
Over and out from the western shelf of the De Soto Canyon where we are headed to depths between 1000 and 2000 m.
Posted by:
Dr. Felicia Coleman

3 comments:

  1. Pretty interesting love-hate relationship between hagfish and their "slime". A good defensive technique and yet an inhibitor of their own movement.

    Happy hagfish day!

    ReplyDelete
  2. Happy Hagfish Day!

    from
    Jake, the SeaDog
    WhaleTimes

    ReplyDelete
  3. Hi.Dear.
    I am very interested taiwan hagfish.
    If you have any information, please let me know about catch area and depth.

    thank you.

    ReplyDelete