Lamprey are a jawless parasitic fish which have a tubular funnel mouth which is packed with teeth. It's with these teeth that the fish latches onto its prey and sucks its blood ! Lamprey are a great bait to use due to their amazing scent, they ooze fishy flavours into the water as a result of their diet.
Herring are a very oily fish and it's this oil which helps to create a fantastic fishy scent trail for predators to home in on, their attraction can be increased by piercing the flanks prior to casting to release more oil. Unfortunately they aren't as tough as mackerel and it can be difficult to cast them any great distance.
Sardines are another great sea fish packed with predator attracting oil and are best used at short range due to their fragility. They can however be used for medium to long distance casts if they are hooked whilst frozen. Hooking when frozen gives a far stronger hook hold, the disadvantage of this is the bait will rarely stay on the hook when retrieved from any great distance.
Smelt are a costal dwelling fish which travel up rivers in order to spawn. They are pale in colour & have a smell very much like cucumber.
Sprats are a very small sea fish, they can be quite difficult to cast any real distance due to their fragile nature, although they can be used effectively as chopped loose feed or when pre baiting.