Preacher, it appears to me that the shooters are probably standing in line to take their turn at shooting bats that are attracted to the bugs near the shoreline close to dusk. I'd assume the net is possibly to entangle and catch the dead and wounded bats. Or perhaps some sort of divider line, with bats shot further out garnering a higher score.
I kinda doubt if the purpose of the net is to catch unbroken glass ball targets, as skeetx speculated. Since the net is oriented vertically, the unbroken glass balls would simply fall off due to gravity, and get broken anyway. Of course, such a spectacular design failure would have contributed to the demise of this game. So I'm going with bat shooting from the evidence I see. If the bats caught in the net were collected to be sold in the "Wet Market" in Wuhan, China, this might have been the real origin of the Covid19 virus pandemic.
Despite the fact that this event has drawn a large crowd of spectators, you may be quite concerned that this is an illegal activity as you did here:
https://www.doublegunshop.com/forums/ubbthreads.php?ubb=showflat&Number=56078&page=1So you may wish to report this possible game law violation to the authorities in New Zealand, on the remote chance that the violators are still alive, and the statute of limitations has not expired. No person is above the law, except Hunter Biden!
Other than that, I see no point in playing guessing games and engaging in wild speculations based upon an old photo with no details. We can't even see what sort of guns are being used. Just think... If Dave Weber had Image Hosting here, he could pay to store every gun and shooting image you find during obsessive searches on the internet. Of course, he would need more data storage space than the Summit Supercomputer, or the Servers owned by Google.