We received a very specific question from a reader a few days ago about cultivating the “marine bloodworm Glycera dibranchiata.” Glycera dibranchiata are commonly used for fish bait, so the reader’s motivation for rearing or breeding bloodworms – essentially, setting up a bloodworm farm – is presumably tied to fishing. The reader was first of all wondering if bloodworms can be cultivated “successfully,” and if so, he was wondering how he might go about doing so. He also wanted to know if there are any publications that are available to assist with the rearing task.
We have been asked about cultivating worms on a few different occasions before. We’ve written about rearing marine worms and rearing polychaete worms, and in fact we’ve even touched on the topic of rearing bloodworms in particular. This last article points out that “bloodworm” is an ambiguous term that can refer to a few different creatures – the polychaetes that make up the genus Glycera (not just Glycera dibranchiata) and the larval form of some species of non-biting midges. The reader makes it clear what he is looking for, so we won’t dwell on this topic, but thought it worth noting lest anyone is confused by our use of the term “bloodworm,” which is eminently possible since both Glycera dibranchiata and midge larvae “bloodworms” can be used for fish bait. (Midge larvae appear to be more commonly used simply as a fish food for those with aquariums, and they are bred to this end, but evidently it is possible to use them for fishing purposes as well.)
One common theme that has run throughout our articles on rearing worms is that it probably technically possible, with unlimited resources, to rear almost any worm, but that practical considerations might make it unrealistic. This appears to be the case with Glycera dibranchiata, which requires a fairly precise marine habitat, and can only survive in a narrow temperature range. They are also carnivorous, which might present certain difficulties for feeding a population. Even if these factors could be easily overcome, however, it is telling that people do not appear to rear them. Indeed, there is a multi-million dollar industry centered on “worm picking” – people have to go out and collect bloodworms, digging through mud in shallow marine waters to find them. So, the only way we can see someone rearing bloodworms in some sort of organized capacity is if they happen to own land, or rather a strip of shoreline, where bloodworms naturally live. The worms could be harvested in a systematic and careful way, allowing the population to sustain itself despite one’s occasional picking.
Given that this is the case, we don’t have any specific publications we can point to that will help with cultivating bloodworms. As far as we can tell, they appear in nature and are picked, with their numbers expanding and contracting not only because of harvesting, but also because of the natural rhythm of population cycles. So, our reader can perhaps pick bloodworms if he is so inclined, but we don’t think he’ll be able to rear them.