Image: Manuel Garci ©
Species description and status: The undulate ray (Raja undulata) is a medium-sized, inshore skate that occurs in waters down to about 200 m depth, although it is more common in coastal shallow waters. It has a patchy distribution in the northeast and eastern central Atlantic (Figure 1), with discrete areas where it may be locally common1. It also occurs in the Mediterranean Sea, though it appears to be uncommon. Its patchy distribution means that populations are widely separated, possibly with little exchange. This species is the target of small scale fisheries2 and taken as bycatch by trawl, trammel net and other demersal fisheries3. In the areas where it is known to be locally common, available data suggest declines have occurred. Though relatively little is know about its life-history characteristics, its slow generation time makes it more vulnerable to exploitation than smaller ray species (three year generation period of ~45 years)4,5. Given this, the species is recognized as Endangered by IUCN globally and Near Threatened in Europe.
Knowledge gaps: Because Raja undulata is retained, marketed for human consumption in areas where it is common, and is considered a large ray, it is more vulnerable to depletion than smaller skate species, and observed declines may reflect changes in the population of the species3. It is also a known bycatch of the Spanish demersal trawl fleet3. Like many other larger rays, this species possesses life history characteristics that may increase its vulnerability to exploitation, low resiliency and increase the risk of extinction, including delayed age at maturity, long generation time (14-15 years), low fecundity, and consequently slow population growth6. An understanding of R. undulata spatial ecology, the potential benefits of MPAs on the conservation of the species, and fisher behaviour are therefore fundamental for effective fisheries management7.
Figure 1. Undulate ray distribution. Range colours indicate degree of habitat suitability which can be interpreted as probabilities of occurrence (Source: FishBase)
Regions of interest: Atlantic continental shelf. At a more local scale (short-movement patterns), understanding spatial ecology and social behaviour of this species is key. At a large-scale (migrations), research is needed to disentangle potential connectivity between meta-populations and stocks.
Telemetry tools: Scientific evidence demonstrates high survival rates of undulate rays following tagging, so telemetry tools can be successfully be used to study this species8. Telemetry studies contribute to a greater understanding of habitat use during different life history stages. Information from the distribution models and feeding behaviour9 could be used for specific spatio-temporal management measures. How ray foraging might influence ecosystem dynamics through bioturbation remain relatively unexplored10. A better understanding of the distribution of species can also help reduce bycatch of protected species such as R. undulata.
Benefits within ETN: Understand spatial ecology of this ray in European waters will provide essential information about the life-history, population dynamics and connectivity between stocks (ETN Key knowledge gap 7) to achieve sustainable management of this highly valuable resource. On the other hand, given the unknown responses to environmental conditions of R. undulata, it is important to address ecological questions closely related with impact of climatic chance (ETN Key knowledge gap 5). Previous projects on Raja undulata include: TAC and DESTAC projects (pleamar program 2018 and 2019 respectively, Fundación Biodiversidad).
Contacts: Alexandre Alonso
1 Figueiredo, I., Maia, C., & Carvalho, L. (2020). Spatial distribution and abundance of the by‐catch coastal elasmobranch Raja undulata: Managing a fishery after moratorium. Fisheries Management and Ecology 27 (5): 454-463.
2 Alonso-Fernández, A., Otero, J., Bañón, R., Campelos, J. M., Quintero, F., Ribó, J. ... & Molares, J. (2019). Inferring abundance trends of key species from a highly developed small-scale fishery off NE Atlantic. Fisheries Research, 209, 101-116.
3 Coelho, R., Erzini, K., Bentes, L., Correia, C., Lino, P.G., Monteiro, P., Ribeiro, J. and Gonálves, J.M.S. 2005. Semi pelagic longline and trammel net elasmobranch catches in the Algarve (southern Portugal): catch composition, catch rates and discards. Journal of Northwest Atlantic Fisheries Science 35: 531–537.
4 Coelho, R. and Erzini, K. 2002. Age and growth of the undulate ray, Raja undulata, in the Algarve (southern Portugal). Journal of the Marine Biological Association of the United Kingdom 82(6): 987-990.
5 Coelho, R. and Erzini, K. 2006. Reproductive aspects of the undulate ray, Raja undulata, from the south coast of Portugal. Fisheries Research 81: 80-85.
6 Dulvy, N.K., Metcalfe, J.D., Glanville, J., Pawson, M.G. and Reynolds, J.D. 2000. Fishery stability, local extinctions and shifts in community structure in skates. Conservation Biology 14: 283-293.
7 Simpson, S. J., Humphries, N. E., & Sims, D. W. (2020). The spatial ecology of Rajidae from mark-recapture tagging and its implications for assessing fishery interactions and efficacy of Marine Protected Areas. Fisheries Research, 228, 105569.
8 Morfin, M., Simon, J., Morandeau, F., Baulier, L., Méhault, S., & Kopp, D. (2019). Using acoustic telemetry to estimate post-release survival of undulate ray Raja undulata (Rajidae) in northeast Altantic. Ocean & Coastal Management, 178, 104848.
9 Moura, T., Figueiredo, I., Farias, I., Serra-Pereira, B., Neves, A., Borges, M.F. and Gordo, L.S. 2008. Ontogenetic dietary shift and feeding strategy of Raja undulata Lacepède, 1802 (Chondrichthyes: Rajidae) on the Portuguese continental shelf. Scientia Marina 72: 311-318.
10 Flowers, K. I., Heithaus, M. R., & Papastamatiou, Y. P. (2020). Buried in the sand: Uncovering the ecological roles and importance of rays. Fish and Fisheries.