To be honest Brian it varies depending on the water im fishing but if i had to take just one to a new water that i knew nothing about it would be mackerel or smelt purely based on consistent results. If i know a bit about where im fishing and/or its heavily fished i may also use natural fish to the water, in most cases roach, trout or lamprey and avoid the normal deadbaits just in case it makes that difference.
Neil |