Potential for farmed European spiny lobster juveniles to support fisheries restoration
European lobster has traditionally been the main target of fisheries off Ireland, UK, France, Portugal, Spain, Italy, Greece, Tunisia and Morocco , as well as adjacent Mediterranean waters (Goñi & Latrouite, 2005). Poor biological knowledge and excessive fishing pressure, combined with poor management, caused this valuable fishery to suffer a catastrophic population collapse in the Atlantic.
Once one of the most important fisheries in the UK coastal sector, it has long since ceased to contribute to commercial fishing landings in certain areas. There are signs of a slight recovery in parts of the UK, but in other former strongholds the species has been commercially extinct since the late 1970s. As of 2021, fewer than 10 animals have been captured in the Llŷn Peninsula, North Wales.
Despite the weakened status of the UK p. elephant fishery, the species is still targeted due to very high prices in the UK and international seafood markets, by destructive fishing techniques such as entangling nets (Cosgrove et al.2016). p. elephant seems very sensitive to fishing pressure, with some overfished populations taking several decades to show signs of recovery. Even in parts of Europe where fisheries are better managed, some populations are still in steady decline. Despite its economic and ecological importance, little information is available to conduct stock assessments and make sound management decisions. There is also an overall lack of knowledge of basic life history and population parameters, such as age, growth and maturity, compared to other commercial lobster species (Santos et al, 2022). As the lobster fishery declines, anglers may be encouraged to fish longer and travel farther to catch these valuable crustaceans. This directly contributes to lobster being considered one of the least sustainable seafood species caught due to associated emission levels (Gephart et al., 2021).
UK p. elephant research has been limited to field surveys to monitor the species’ continued decline, while attempts to confer greater protection have been thwarted by arguments that show poor understanding of the species’ biology . Attempts to improve knowledge of the larval phases of p. elephant biology is virtually non-existent since Kittaka’s early work et al. (2001). Meanwhile, decades of major funding have focused on the clawed lobster (Homarus gammarus) – a species with exceptionally few characteristics to support the economic production of large-scale juveniles for breeding or restoration initiatives.
After several years of research, RAS Aquaculture Research Ltd (RASAR) has generated some understanding of p. elephant phyllosoma biology, which resulted in the production of the first juveniles in Europe in 2019 and again in 2021. Juveniles were secured within a 2-3 month culture period, as opposed to the 7-9 month larval cycle in nature. Subsequent data from the ongoing growth studies, which took place in Anglesey, with p. elephant juveniles indicate that aquaculture could offer an additional management tool to help restore depleted fisheries in Europe. These trials were carried out under community conditions and some interesting data are summarized below:
- p. elephant juveniles show no serious aggression or cannibalism under communal culture conditions. This remains the situation even when newly settled pueruli are mixed with older juveniles and, subsequently, when juveniles varying in size, age, or molting state are reared together.
- Only very brief skirmishes at preferred shelter sites were observed, with juveniles occupying suitable nearby shelters while maintaining occasional antennal contact.
- Juveniles will modify a suitable refuge by removing sand and gravel to enlarge a shelter.
- Juveniles identify a range of natural prey and quickly develop skills in capturing polychaete worms and opening bivalve shells.
- Pellet feeds with appropriate attractants are acceptable.
- Juveniles are strongly nocturnal for the first 9 months after settlement, becoming more active at dusk.
- Intermolt periods average 26 days, to a total body length of 5.5–7.5 cm, at 9 months post-puerulus.
- No mortalities in juvenile lobsters have been recorded at the research scale, but this observation may not be true at commercial production levels.
UK, p. elephant is considered a key component of biodiversity on Annex I reef habitats, essential for favorable conservation and good environmental status (GES) of these habitats. Recovery of p. elephant was considered vitally important for obtaining GES under the EU Marine Strategy Framework Directive (Leslie & Shelmerdine, 2012). In 2014, concern over the lack of accurate assessments of his status led to the classification of p. elephant by the International Union for Conservation of Nature (IUCN) as “vulnerable”.
Contrary to H. gammarus culture, the larval cycle of p. elephant is more complex and settlement to the benthic phase takes longer. However, techniques for overcoming the main obstacles to large-scale juvenile production are advancing. During the 2022 season, special attention was paid to automating the cleaning of larval tanks and reducing feed and labor costs. The main advantage of p. elephant
finished H. gammarus culture is observed during the juvenile growth phase. The aggressive behavior of H. gammarus requires the growth of juveniles in isolation, which greatly increases labor, maintenance and production costs. In contrast, growing juvenile p. elephant is undertaken in communal reservoirs where the main requirement is well controlled water quality supplying a reservoir system designed to maximize production. Depending on the optimum size required for restoration programs, growth to a size suitable for tagging can be achieved within 4-6 months of egg hatch.
Besides its ecological importance, the restoration of this high-value seafood species is important for the benefit of small-scale coastal fisheries (SSF). Since 2000, the relative role that SSFs play in European regional economies has fallen by 20-30% and 30-50% respectively in terms of employment and income (Lloret et al., 2016). Where domestic capture fisheries can be properly managed, hatchery production of p. elephant juveniles for restocking Marine Protected Areas (MPAs) or suitable offshore energy structures may be of interest. Using culture techniques as a tool to support fishery restoration or improve management options for a lobster fishery will always require financial support. However, the very high market value and post-establishment characteristics of the species present a number of possible options. Potential commercial projects have been identified and will be further explored with EU partners. These may include growth p. elephant lobsters directly for the seafood market, where their very high market value can simultaneously support a production of juveniles for restoration initiatives.
The involvement of regional fisheries cooperatives in such programs would be essential to ensure the protection of recovering fisheries. Integration with RAS fish farms, MPAs or cooperation with tourism and renewable energy projects could also help finance hatchery operations for restoration activities. Such an approach could support the concept of integrating mariculture into marine conservation, i.e. supporting ecosystem services (Le Gouvello et al2022) and may even reduce the significant CO2 emissions specifically associated with this capture fishery (Parker et al., 2018).
A key area for further research relates to the need for enhanced foods during the planktonic phyllosome phase. High mortality (30 to 100 percent) can be observed after the final stage of the phyllosome which molts into puerulus. Poor phyllosome nutrition can result in weak pueruli with insufficient reserves to survive starvation until the juvenile stage. The puerulus is a resting phase before turning into a juvenile lobster in 2-3 weeks. A characteristic common to all lobster species such as p. elephant is that the puerulus stage does not feed. Further development at this stage requires adequate nutrient reserves stored during the earlier feeding period of the phyllosomas. These reserves can also be large for significant periods even after the transition to the first juvenile lobster if food supplies are inadequate or environmental conditions are unfavorable (Limbourn et al., 2008; Espinosa-Magaña et al., 2017).
Current work also highlights the potential for manipulating juvenile growth rates, developing juvenile pelleted diets, and maximizing the production of 10-15 g juveniles in multi-level tank systems. RASAR plans to expand current juvenile growth trials to determine the performance of this species at larger sizes that may be acceptable for the seafood market.