Your book may not necessarily be set in the Amazon, but here's what I've recently learned. I will use the Amazon as an example because the situation is similar to what you described.
We used palm weevil larvae as bait in the Amazon. They are easily collected from palm trees. You can check which species is local to your setting. They are found in South America, Africa and Asia. Depending on the location of your setting, if the soil is too dry, you may not be able to find worms. But other natural baits can be substituted. Perhaps a little more details can help us help you. Don't worry, we're not going to take your idea to the publishers
LOL
Splashing on the water surface attracts fish in the Amazon. You can do that simply with a stick. Perhaps that's one tactic that can be explored. However, it doesn't necessarily draw fish to the surface within sight and strike range, but just to the area in general. Many Amazonian rivers and tributaries have poor visibility (less than 12 inches), so spotting fish, even large ones below the surface is extremely difficult. When we were fishing, we couldn't even see 4-5lb fish under the surface when they were just 2 feet below the surface. It is that murky.
However, so fish do strike on the surface often. We will often hear Pacu make loud splashed on the surface as they take insects, seed or fruits that are floating. Sometimes, you hear a big splash like something tossing a brick in the water and it could be a Catfish chasing baitfish up to the surface. In lakes, ponds or swamps, Brycons can be seen in the shallow chasing other smaller fishes against the shore and making commotion. Perhaps you can incorporate these elements in the story as the character move about looking for the fish.
I can imagine tribal people putting the palm weevil on the thin end of a bamboo pole or stick, and suspend the larvae on the surface to draw fish to it. Alternatively, I can imagine the character tying the larvae onto thin fibrous threads or rope to suspend the larvae on the water, by tying the rope to a branch along the shoreline, or maybe holding it with one hand while the other hand holds the spear ready to strike. Lots of species will react to a grub on the water surface in the Amazon, include Pacu species, Piranha species. Brycon species, and Catfish species. To make it authentic, find local names of those fish.
But many primitive tribes knows how to make fish hooks out of bones, and spin natural material to make fishing line. My guide shown us some spider web in the Amazon that was extremely strong that could be spun into fishing lines. So I'm just curious why it is limited to spear? Don't want to mess up your plot, but there are alternatives.
In the Amazon, locals spear Arapaima by watching where they come up to breathe, especially when the Arapaima is trapped in small lakes or ponds during the dry season and the water is depleted in flow and oxygen. These lakes or ponds usually has slightly better visibility. The Arapaima also seems to come up to breathe regularly around the same location, unless the fish is actively moving around and hunting. But when an Arapaima is aware or scared by the presence of people, it can stay submerged much longer (as long as 30min) before surfacing again to breathe in the same spot, or relocating to another part of the lake or pond.
Hope this helps.
