not from a picture at this age. I'd say the easiest way to tell is the females will have a loud quack and the males is very soft and whispery..like a mumble. you can vent sex them at this age, but if you don't know what you're doing you could hurt them. when they get a few months old and have adult feathers the males will have the drake feather ( a feather on the tail that curls up)
From the picture, they look 4-5 weeks old. At this age females will have just started to quack. They still peep, bet every now and then they make this hoarse little quack. Male vocal cords take longer to develope.