% Starve hungry sharks
  starve = ( sharkeat(  2:d+1, 2:d+1 ) > STARVE );
  shark(2:d+1,2:d+1)    = ( ~starve ) & shark(2:d+1,2:d+1);
  sharkeat(2:d+1,2:d+1) = ( ~starve ) .* sharkeat(2:d+1,2:d+1);
  sharkage(2:d+1,2:d+1) = ( ~starve ) .* sharkage(2:d+1,2:d+1);
  sharkdir(2:d+1,2:d+1) = ( ~starve ) .* sharkdir(2:d+1,2:d+1);
% Age remaining sharks
  sharkage( 2:d+1, 2:d+1 ) = sharkage( 2:d+1, 2:d+1 ) + shark( 2:d+1, 2:d+1 );
  sharkeat( 2:d+1, 2:d+1 ) = sharkeat( 2:d+1, 2:d+1 ) + shark( 2:d+1, 2:d+1 );