Recovered File NEW

Spiny  Dogfish,  Squalus  acanthias,  Dismemberment  and  Consump7on    of  Large  Prey  

Kailyn  Corriher,  Chuck  Bangley,  Roger  Rulifson  Department  of  Biology,  East  Carolina  University  

Spiny  dogfish  (Squalus  acanthias)  is  a  small,  highly  migratory  coastal  shark  that  inhabits  all  waters  of  the  world  except  in  the  tropics.  Spiny  dogfish  have  long  been  suspected  of  being  a  top-­‐level  predator,  dismembering  and  consuming  fishes  up  to  their  own  size  (Bangley  and  Rulifson  2014).  Data  on  rela7ve  prey  size  are  lacking,  mostly  due  to  the  high  propor7on  of  dismembered  and  uniden7fied  prey  in  most  dogfish  diet  studies.  Using  stomach  contents  collected  from  dogfish  captured  by  trawl  off  of  North  Carolina  and  Virginia,  we  have  aRempted  to  back-­‐calculate  the  total  length  of  dismembered  Atlan7c  Menhaden  (Brevoor2a  tyrannus)  and  other  species  found  in  the  dogfish  diet.  

M  E  T  H  O  D  S     R  E  S  U  L  T  S  

I  N  T  R  O  D  U  C  T  I  O  N    

•  19%  of  Spiny  dogfish  had  dismembered  contents    •  Menhaden  up  to  45%  of  the  dogfish  length  were  found  in  the  stomach  contents    

•  The  par7al  remains  of  other  species  suggest  that  dogfish  may  be  consuming  prey  of  even  larger  rela7ve  sizes    

•  Results  suggest  there  is  low  significance  to  the  prey  size  in  rela7on  to  dogfish  size  

•  Dogfish  are  not  limited  by  gape  size  when  preying  on  Menhaden  

•  Nearly  significant  preference  for  par7cular  Menhaden  size  

R  E  F  E  R  E  N  C  E  S  

•  Samples  of  mature  Spiny  dogfish  collected  by  trawl  from  Chesapeake  Bay  to  Cape  HaReras  

•  Gut  contents  collected  using  gastric  lavage  (Bangley  et  al.  2013)  

•  Measured  lengths  of  predator  and  prey  •  Iden7fied  each  species  in  gut  •  Back-­‐calculated  dismembered  lengths  to  determine  size  ra7os  (head:total  length)    

There  is  no  sta7s7cal  significance  among  Menhaden  sizes  in  the  probability  of  dismemberment  by  Spiny  

dogfish.    

DF   Chi2   Chi2  Probability  

1   0.2277553   0.6332   Using  back-­‐calculated  Menhaden  lengths,  the  graph  suggests  that  dogfish  between  the  sizes  of  

875-­‐975mm  can  dismember  Menhaden  up  to  45%  of  dogfish  total  length.  

DF   Chi2   Chi2  Probability  

1   0.1398549   0.0514  

There  is  no  sta7s7cal  significance  between  the  prey  and  predator  total  length  ra7o  as  predator  total  

length  increases.    

Back-­‐Calculated  Menhaden  Lengths  versus  Dogfish  Total  Length  

Prey/Predator  RaEo  versus  Dogfish  Total  Length    Chance  of  Dismemberment  of  Menhaden  by  Spiny  Dogfish    

DISMEMBERED SPECIES LIST Squid (Teuthida)

Sand Lance (Bammodytes americanus) Octopus (Octopoda)

Unidentified Fish (Teliosti) Peneaid Shrimp (Penaeidae)

Common Octopus (Octopus vulgaris) Bay Anchovy (Anchoa mitchilli) Striped Bass (Morone saxatilis)

Smallmouth Flounder (Etropus microstomus) Atlantic Menhaden (Brevoortia tyrannus)

Mantis Shrimp (Stomatopoda) Weakfish (Cynoscion regalis)

Unidentified Herring (Clupeidae) Goby spp (Gobiidae)

Summer Flounder (Paralichthys dentatus) Unidentified Flatfish (Pleuronectiformes)

American Eel (Anguilla rostrata) Unidentified Shrimp (Caridea)

Bangley,  C.  W.,  and  R.  A.  Rulifson.2014.  Feeding  Habits,  Daily  Ra7on,  and  Poten7al  Predatory  Impact  of  Mature  Female  Spiny  Dogfish  in  North  Carolina  Coastal  Water.  668-­‐670. Bangley,  C.  W.,  R.  A.  Rulifson,  and  A.  S.  Overton.  2013.  Evalua7ng  the  Efficiency  of  Flushed  Stomch-­‐tube  Lavage  for  Collec7ng  Stomach  Contents  from  Dogfish  Sharks.  12(3):523-­‐533.    

Top:  Dismembered  Octopus    BoRom:  Dismembered  Menhaden