Interim Report of the Working Group on Multispecies Assessment Methods (WGSAM)

The pan-regional Working Group on Multispecies Assessment Methods (WGSAM) met in San Sebastian, Spain, 16–20 October 2017. In this eleventh report of the group, work focused on three of the multi-annual ToRs (B, C, D).

Based on their knowledge, participants provided an updated inventory of progress of multispecies  models  in  ICES  Ecoregions  (ToR  A),  noting  those  regions  where  no  in-formation was available.

A  Key  Run  (ToR  B)  of  the  North  Sea  Stochastic  Multispecies  Model  (SMS)  was  presented  and  reviewed  in  detail  by  4  WGSAM  experts,  and  approved  by  the  group following  implementation  of  changes  agreed  in  plenary  at  the  meeting  and  verified  by  a  subset  of  experts  post-meeting.  The  Key  Run  is  documented  in  detail  in  Annex  for ToR B, with key outputs summarised in Section 5 and data files made available on the  WGSAM  webpage  and  the  ICES  expert  group  Github  (https://github.com/ices-eg/wg_WGSAM).  Since  the  M2  values  are  used  for  the  assessment  of  important  North  Sea  stocks,  it  is  recommended  to  publish  the  annex  also  on  the  official  stock  annex  website.  In  addition,  WGSAM  does  not  recommend  updating  existing  data  series  of  natural  mortality  by  simply  adding  the  latest  three  new  years.  The  time-series as a whole shows patterns which are not retained by this procedure.

Multispecies  model  skill  assessment  (ToR  C)  and  multi-model  ensemble  methods  (ToR  D)  were  emphasized  this  year.  Considerable  progress  has  been  made  towards  advancing  both  aspects  of  multispecies  modelling.  Investigation  of  skill  assessment  and  ensemble  methods  and  case  studies  is  critical  to  ensure  that  outputs  of  multi-species  assessment  models  are  reliable  for  use  in  operational  assessment  and  to  inform management decisions.

Progress  was  also  made  on  investigations  of  top  predator  impacts  on  managed  fish  across  several  regions  (ToR  F),  including  the  North  Sea  where  new  information  was  included  in  the  SMS  key  run.  Further  progress  was  also  made  on  multispecies  and  ecosystem level reference points and harvest control rules in mixed fisheries (ToR G).