Problem with move code

function PlayerFish::onLevelLoaded(%this, %scenegraph)
{
   $FishPlayer = %this;

   moveMap.bindCmd(keyboard, "w", "fishPlayerUp();", "fishPlayerUpStop();");
   moveMap.bindCmd(keyboard, "s", "fishPlayerDown();", "fishPlayerDownStop();");
   moveMap.bindCmd(keyboard, "a", "fishPlayerLeft();", "fishPlayerLeftStop();");
   moveMap.bindCmd(keyboard, "d", "fishPlayerRight();", "fishPlayerRightStop();");
}

function fishPlayerUp()
{
   $FishPlayer.setLinearVelocityY( -15 );
}

function fishPlayerDown()
{
   $FishPlayer.setLinearVelocityY( 15 );
}

function fishPlayerLeft()
{
   $FishPlayer.setLinearVelocityX( -30 );
}

function fishPlayerRight()
{
   $FishPlayer.setLinearVelocityX( 30 );
}

function fishPlayerUpStop()
{
   $FishPlayer.setLinearVelocityY( 0 );
}

function fishPlayerDownStop()
{
   $FishPlayer.setLinearVelocityY( 0 );
}

function fishPlayerLeftStop()
{
   $FishPlayer.setLinearVelocityX( 0 );
}

function fishPlayerRightStop()
{
   $FishPlayer.setLinearVelocityX( 0 );
}