Gooseberry sawfly

I went over to the Community Orchard to water the currant and blueberry bushes that we are growing in pots in the fruit cage. Although there is quite a lot of fruit in the gooseberries but there seemed to be a shortage of leaves. On closer inspection,  found these wee creepy crawlies and once I got my eye in, they were everywhere! I came home and googled them to find that they are sawfly caterpillars. I’ve heard about these from fellow gardeners but I’ve never encountered them before. They were making short work of the leaves so I suppose this will have an adverse effect on the development of the fruit.