The Worm Pipefish (Nerophis lumbriciformis) is a small (up to 15 cm in total length) pipefish that occurs in the Northeast Atlantic from Norway, the North Sea, and southern coast of the Scandinavian Peninsula to the Iberian Peninsula, and the northwestern Mediterranean at depths of 0–30 m. This pipefish inhabits rocky inter- and subtidal habitats among macrophytes or under loose stones, and estuaries. It is not known to be traded or exploited commercially. The main potential threats are primarily from macrophyte habitat degradation due to climate change and coastal development. There is little known about the population size or trend for this pipefish, but it is projected to undergo an increase in available habitat due to climate change. There are no conservation actions in place, but its distribution overlaps with multiple marine protected areas. Overall, due to the wide range, diversity of habitats used, projected habitat availability increase, and overlap with marine protected areas, it is suspected that this pipefish has a stable population. Therefore, the Worm Pipefish is assessed as Least Concern.

The Worm Pipefish inhabits the Northeast Atlantic from Norway and southern coast of the Scandinavian Peninsula to the Iberian Peninsula (GBIF 2024, N. Monteiro unpub. data 2024). There is also an apparently disjunct portion of the population off the Mediterranean coast of France (GBIF 2024). This species is suspected to be expanding its northern boundary up the coast of Norway (Monteiro et al. 2017, GBIF 2024).

There have been no dedicated population estimates for this species. DNA studies have shown a lack of population structure (Mendes et al. 2020). It is predicted that suitable ocean conditions will be maintained or possibly increase in the next 20 to 70 years (Monteiro et al. 2023). There is no evidence of a decline for this species, therefore population size is suspected to be stable.

The Worm Pipefish inhabits rocky inter- and subtidal areas among macrophytes such as kelp, or under loose stones (Monteiro et al. 2003, 2005, Salland and Smale 2021). It can also be found in estuaries, and ranges in depth from 0–30 m (Monteiro et al. 2005). They have pelagic larvae (Monteiro et al. 2005). Site fidelity and homing behavior have been documented in this pipefish (Monteiro et al. 2005, 2006). It is small, with a recorded maximum total length of 15 cm (Monteiro et al. 2005). 
This pipefish feeds on harpacticoid and cyclopoid copepods as well as other epiphytic crustacean meiofauna, with increased feeding in reproductively active individuals. They prey on these organisms near the substrate, often under macrophyte canopy (Lyons and Dunne 2004).

The Worm Pipefish is sexually dimorphic, with females being larger, more active and more colourful than males (Monteiro et al. 2017). Breeding is correlated with seawater temperatures below 15.5°C. Gestation lasts 25–30 days depending on water temperature. Males release free-swimming juveniles that swim up into the water column and drift where they feed on zooplankton near the surface. Juveniles settle at one to four months, depending on the location, and 4 cm total length (Monteiro et al. 2003). They become sexually mature at two years (Muus and Nielsen 1999). This pipefish often displays a female-biased sex ratio and thus male abundance is the reproductively-limiting factor (Lyons and Dunne 2005).

Threats to this species include kelp degradation due to coastal development and climate change. Kelp forests are declining globally and in some parts of Europe (Waycott et al. 2009, Wernberg et al. 2019, Dunic et al. 2021). As with any macroalgal-associated species, the Worm Pipefish is and will continue to suffer habitat loss and degradation through direct and indirect anthropogenic disturbances such as pollution and climate change (Wernberg& et al. 2019, Garcia-Soto et al. 2021). In addition, throughout its range, rocky inter- and sub-tidal areas are under threat directly from coastal development and indirectly through changes in water clarity that are detrimental to kelp and other canopy-forming macroalgae that this species depends upon (Airoldi and Beck 2007).In southern Europe, such as the Northwestern Iberian Peninsula and the Bay of Biscay, kelp forests are in decline (Araújo et al. 2016). However, other European kelp forests display differing trends based on kelp species present, such as those in Norway, Germany, and France (Araújo et al. 2016). Further research is required concerning the kelp species preference of the Worm Pipefish to better understand changes in habitat quality.

The Worm Pipefish is likely to be especially susceptible to anthropogenically-induced climatic warming, as migration and breeding are correlated with cooler water temperatures (<15.5°C). Subsequent oceanographic changes associated with upwelling could potentially reduce larval dispersal and recruitment (Monteiro et al. 2005).However, species distribution modeling projections by Monteiro et al. (2023) found that under various climate scenarios, suitable ocean conditions for the Worm Pipefish will increase, ranging from 100.7–103.4% retained by 2040–2050 and 101.9–111.4% retained by 2090–2100 (Monteiro et al. 2023).

The Worm Pipefish is not known to be traded or exploited commercially. Although it is not clear whether the Worm Pipefish is of interest for the aquarium trade, it has been observed to be held in aquarium environments (Denk et al. 2020).

Currently, there are no known conservation actions in place for the Worm Pipefish and it does not appear in any international legislation, but its distribution overlaps with multiple Marine Protected Areas such as the Pertuis Charentais, France and Espacio Marino de las Rias Baixas de Galicia, Spain (UNEP-WCMC and IUCN 2022).

Further research and monitoring are needed to establish population size, trends in abundance, and understand how kelp loss affects this species, especially in light of climate change.