!!  Copyright (C)  Stichting Deltares, 2012-2014.
!!
!!  This program is free software: you can redistribute it and/or modify
!!  it under the terms of the GNU General Public License version 3,
!!  as published by the Free Software Foundation.
!!
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!!  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
!!  GNU General Public License for more details.
!!
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!!
!!  contact: delft3d.support@deltares.nl
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!!  P.O. Box 177
!!  2600 MH Delft, The Netherlands
!!
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!!  rights reserved.

C
C  *********************************************************************
C  *         SUBROUTINE TO CALCULATE GRAZING RATE CONSTANTS            *
C  *********************************************************************
C
C    0895 MvdV  dimension for more than one grazer type added to ZOOD
C               and ZOOPR
C               dimension of X changed from MT to MX + 1
C
      SUBROUTINE GRAZIN(X,GRAMOR,ZOOD,ITNUM,LGRAZ)
      IMPLICIT REAL*8 (A-H,O-Z)
      INCLUDE 'blmdim.inc'
      INCLUDE 'size.inc'
      INCLUDE 'phyt2.inc'
      INCLUDE 'graas.inc'
      INCLUDE 'ioblck.inc'
      DIMENSION X(MX+1),GRAMOR(MT)
C
C  SET INITIAL VALUES
C
      LGRAZ=0
      TOTGRA=0.
      BITOT=0.
      KK=0
   10 KK=KK+1
      IF (ZOOPR(KK,0) .LT. 1.0D-6 .AND. KK .LT. NUSPEC) GO TO 10
      GRAMOR(KK)=0.
C
C  CALCULATE TOTAL BIOMASS EATABLE SPECIES
C
      K1 = NUROWS
      DO 20 K=1,NUSPEC
      K1 = K1 + 1
      IF (X(K1) .LT. 1.D-6 .OR. ZOOPR(K,0) .LT. 1.0D-6) GO TO 20
      BITOT=BITOT+X(K1)
   20 CONTINUE
      IF (IDUMP .EQ. 0) GO TO 35
      WRITE (IOU(6),30) BITOT
   30 FORMAT(2X,'Total biomass edible species: ',F8.2)
   35 CONTINUE
      IF (BITOT .LT. 1.D-6) GO TO 45
C
C  CALCULATE GRAZING DEATHRATE CONSTANT
C
      GRACON=ZOOGR*ZOOD*(BITOT-XMIN)/((ZOOK+BITOT-XMIN)*BITOT)
      DO 40 K=1,NUSPEC
      GRAMOR(K)=ZOOPR(K,0)*GRACON
      IF (GRAMOR(K) .LT. 0.) GRAMOR(K)=0.0
      TOTGRA=TOTGRA+GRAMOR(K)
   40 CONTINUE
   45 CONTINUE
      IF (IDUMP .EQ. 0) GO TO 55
      WRITE (IOU(6),50) GRAMOR(KK)
   50 FORMAT(2X,'Grazing deathrate constant: ',F5.2,//)
   55 CONTINUE
      IF (TOTGRA .GT. 1.D-6 ) GO TO 70
      IF (IDUMP .EQ. 0) GO TO 65
      WRITE (IOU(6),60)
   60 FORMAT (3X,'*** No grazing ***',//)
   65 CONTINUE
      RETURN
   70 IF (ITNUM .LT. IPERM ) LGRAZ=1
      RETURN
      END