Defining Forage Species to Prevent a Management Dilemma

ESSAY

Defining Forage Species to Prevent a Management Dilemma Konstantine J. Rountos Department of Biology, St. Joseph's College, 155 Roe Blvd., Patchogue, NY 11772. E-mail: [email protected]

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MOTIVATION )RUDJHVSHFLHVDUHRIWHQGH¿QHGLQVFLHQWL¿FDQGSRSXODU literature  using  terms  such  as  “small,”  “schooling,”  “short-­ OLYHG´SHODJLF¿VKIRXQGDWLQWHUPHGLDWHWURSKLFOHYHOVRI marine  food  chains.  However,  not  all  stakeholders  use  the  same   FRPELQDWLRQRIWHUPVDQGWKHLUGH¿QLWLRQVLQFOXGHDQDUUD\RI ¿VKDQGLQYHUWHEUDWHVWKDWUDQJHLQVL]HOLIHVSDQDQGKDELWDW preferences.  Because  forage  species  are  ecologically  important   (e.g.,  Pikitch  et  al.  2012),  often  economically  important  (e.g.,   Pikitch  et  al.  2014),  and  increasingly  promoted  for  direct  human   nutrition  (e.g.,  Tacon  and  Metian  2013),  it  is  both  surprising   DQGDFRQFHUQWKDWWKHUHLVVXFKDQDUUD\RIGH¿QLWLRQVEHLQJ used.  This  diversity  may  cause  undue  confusion  that  will  further   complicate  the  sustainable  management  of  these  species.   The  International  Symposium  on  the  Role  of  Forage  Fishes   in  Marine  Ecosystems  held  in  Alaska  determined  that  “forage   ¿VKLVDFRQFHSWWKDWPDQ\SHRSOHKDYHFRPHWRXQGHUVWDQG because  of  the  context  it  is  used  in,  but  for  which  we  lack  a   FRQFUHWHGH¿QLWLRQ7KHWHUPHPERGLHVDSHFXOLDUFRPELQDWLRQ of  ambiguity  and  precision”  (Springer  and  Speckman  1997:773).   Nearly  20  years  later,  we  still  lack  a  common  operational   GH¿QLWLRQXVHGDPRQJVFLHQWLVWVLQGXVWU\SROLF\PDNHUVDQG WKHSXEOLF)LQGLQJDEHWWHUGH¿QLWLRQLVLPSRUWDQWEHFDXVHWKHUH is  not  only  a  global  interest  in  understanding  the  trade-­offs  and   approaches  needed  to  sustainably  manage  these  species  (e.g.,   Peck  et  al.  2014;;  Essington  et  al.  2015;;  Rountos  et  al.  2015),   EXWDOVRDQHHGIRULGHQWLI\LQJWKHPIRUHFRODEHOFHUWL¿FDWLRQV (e.g.,  Agnew  et  al.  2014).  It  is  time  that  we  created  a  consistent   GH¿QLWLRQRIIRUDJHVSHFLHVZKDWWKH\DUH²DQGDUHQRW²WR prevent  a  future  dilemma. APPROACH This  micro-­analysis  aimed  to  examine  and  analyze  how   GLIIHUHQWVWDNHKROGHUVKDYHGH¿QHGIRUDJHVSHFLHVLQWKHSDVW LQRUGHUWRKHOSLGHQWLI\DQGGH¿QHWKRVHVSHFLHVLQWKHIXWXUH Two  approaches  were  used  to  compile  and  evaluate  the  various   GH¿QLWLRQVRIIRUDJHVSHFLHVEHLQJXVHG)LUVWDOLWHUDWXUHVHDUFK was  conducted  to  explore  the  diversity  of  forage  terminology   DQGVFLHQWL¿FFULWHULD1H[WDVHDUFKRIWKHDWWULEXWHVLH maximum  total  length,  life  expectancy,  trophic  level,  habitat)  of   those  species  included  in  the  literature  search  was  carried  out   using  FishBase  (Froese  and  Pauly  2015)  and  other  sources.  The   GLYHUVLW\RIGH¿QLWLRQVLQWKHUHVXOWVVXJJHVWVWKDWDVWDQGDUGL]HG GH¿QLWLRQRIIRUDJHVSHFLHVVKRXOG EHPRUHVSHFL¿FLQ life  history  attributes  and  (2)  focus  more  on  whether  or  not  a   species  is  providing  a  critical  role  as  prey  in  marine  ecosystems.   The  latter  may  be  accomplished  by  establishing  criteria  based   on  dietary  contributions  of  the  forage  species  or  using  other   trophodynamic  indicators. THE NAME GAME There  are  many  terms  currently  used  to  identify  forage   VSHFLHVLQFOXGLQJ³IRUDJH¿VK´³IRUDJHVSHFLHV´³VPDOO pelagics,”  and  “lower-­trophic-­level  species.”  Scientists  who  

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Fisheries  |  Vol.  41  •  No.  1  •  January  2016

XVHWKHVHWHUPVRIWHQLQFOXGHDYDULHW\RI¿VKDQGLQYHUWHEUDWHV (e.g.,  euphausiids,  cephalopods,  shrimp);;  thus,  the  term  forage   ¿VKVKRXOGLPPHGLDWHO\EHSKDVHGRXW7KHWHUPWKDWLVPRVW appropriate  from  a  technical  standpoint  is  forage  species,   EHFDXVHLWLVQRWH[FOXVLYHWR¿Q¿VKVL]HKDELWDWRUWURSKLF level. TO INCLUDE OR NOT TO INCLUDE, THAT IS THE QUESTION Scientists  do  not  always  agree  on  whether  to  include  juvenile   ¿VKP\FWRSKLGVHXSKDXVLLGVLHNULOO FHSKDORSRGVRU VKULPSLQWKHLUGH¿QLWLRQVRIIRUDJHVSHFLHV0RVWFRQVLGHUDWLRQV have  included  krill,  but  there  is  not  a  clear  consensus  on  other   invertebrates  such  as  cephalopods  or  shrimp.  Some  studies  and   management  documents  argue  that  cephalopods  should  not  be   included,  because  they  can  be  quite  piscivorous,  whereas  other   studies  show  that  certain  species  of  cephalopods  provide  an   important  dietary  component  to  upper-­trophic-­level  predators   (e.g.,  Szoboszlai  et  al.  2015)  and  thus  should  be  categorized  as   forage  species.  Ultimately,  this  may  depend  on  the  species  of   cephalopod,  because  they  represent  a  range  of  trophic  levels   &ROOHWDO ,QFOXVLRQRIMXYHQLOH¿VKLVDOVRGHEDWDEOH EHFDXVHWKH\GRQRWIXO¿OODUROHDVSUH\WKURXJKRXWWKHLUHQWLUH life  history.  Juvenile  Alaska  Pollock  Theragra  chalcogramma,   URFN¿VKSebastes  spp.,  and  salmon  Oncorhynchus  spp.  are   VLJQDWXUHH[DPSOHVRI¿VKWKDWDUHLPSRUWDQWIRUDJHZKHQ MXYHQLOHVEXWGRQRW¿WWKLVFULWHULRQDVDGXOWV0\FWRSKLGVDQG SRVVLEO\RWKHUVPDOOPLGZDWHU¿VKHVDUHDQRWKHUJURXSWKDWDUH UDUHO\LQFOXGHGLQIRUDJHVSHFLHVGH¿QLWLRQVHYHQWKRXJKWKH\ are  ecologically  important  as  prey  (e.g.,  Catul  et  al.  2011).   IS IT A “SMALL PELAGIC” WORLD AFTER ALL? Categorization  of  species  as  forage  has  often  depended  on   physical,  ecological,  and  behavioral  attributes.  In  particular,   forage  species  are  often  considered  small  (