1. This study is valuable as one of the first attempts to apply the methodology of species area curves (developed originally for terrestrial species management) to the marine environment, an approach that might be able to determine how many species may be protected at different depths and over a range of substrate environments as a function of varying protected area sizes.
2. This paper usefully concludes that across-the-board protection targets (e.g. 10%, while helpful to focus political action) are insufficient to protect many marine species in the Northeast Atlantic, especially the rarer ones. Furthermore, for the deeper regions of this study, where species are more scantily distributed (often in patches), even larger targets (e.g. 40%) would very likely not be adequate to protect many species. Given that most regions have not yet attained the CBD’s 10% target, it seems likely that achieving 30-40% is still some years away.
3. The authors do not discuss the policy implications of these findings, however it can be inferred that marine protected areas (MPAs), while most certainly a necessary management measure, will not be sufficient to protect the full range of biodiversity unless supported by other related measures. For environments within depths accessible to bottom contact fisheries, for example, such measures should include comprehensive gear restrictions in order to augment protection, especially for those species that lie outside of MPAs.
4. Data were not provided in the supplemental information regarding the substrate(s) each species was found to be associated with. Judging from the data in Table 1, it is likely that the more common species were found on many or most of the substrate types. Associations of species with particular substrate types could inform spatial management decisions, at least for some of the species encountered.
5. This study deals only with emergent epifauna easily identifiable from video. It is likely that the mud, for example, which had only 10 species visible in the video, would have many more species living in the sediment and thus not easily visible (see Rex and Etter, 2010, Deep-sea Biodiversity: Pattern and Scale, Harvard University Press). And we know that certain groups, such as cumaceans, are represented by several quite rare species that have been described from the area of the Porcupine Sea Bight (e.g., Calman 1905, The marine fauna of the west coast of Ireland, pt. IV, Cumacea. Fisheries, Ireland, Scientific Investigations).
6. A large fraction of the species recorded in the videos are not very numerous (Supplemental Tables S1 and S2). The rarest 35% are not very common at all, at most seven individuals of these rare species were seen in the 61,798 m2 surveyed in the depth layer of 200-1100 m. That is a density of one individual every 8,828 m2 at the most. In the deeper, 1100-1800 m layer, the rarest 35% includes species with maximum abundance of three individuals observed in the 20,883 m2 surveyed, or one individual every 6,961 m2. These levels of rarity suggest that on average a rare species might have population densities of 100 individuals per km2. Such low densities are slightly lower than what Rice et al. (1982, Oceanologica Acta 5: 63-72) recorded from the Porcupine Sea Bight, using a bottom camera sled.
7. In this study, what species are the most rare? In the 200-1100 m layer (Table S1), they are mostly crinoids, sponges, miscellaneous cnidarians (mostly octocorals and actinarians), and a few mobile species. If we extend the rare species to include 35% of the least abundant species, then a few species of gorgonians and more sponges are added. The situation is quite similar in the deeper (1100 to 1800 m) layer (Table S2). For the most part the species making up both the rarest 25 and 35 % of the species were sponges and cnidarians, with a few echinoderms, and the occasional mobile crustacean. For the most part, these are also known to be long-lived and slow-growing species. While we do not know the ages of sponges and actinarians, we do know that gorgonians and antipatharians can live to be several hundred to more than 4000 years.
8. This paper follows the proposition of Desmet and Cowling (2004) who suggested that conservation targets should be established in order to determine how much area should be set aside to assure that 75 % of the species known to occur in an area would be protected. Proposing to protect 75% or so of the species would mean that rare species would be left unprotected. As the authors of this paper show in Table S5, protection of the rarest 25% of the species would require closing at least 80% of the bottom, often around 90%. Of course, it is ultimately a policy decision about how much area will be closed to protect species, but in the deep sea, especially below 400 m depth, closing all or almost all of the area will inconvenience only a small number of people in the fishing industry, and those are generally associated with large and well financed corporate entities.
9. Desmet and Cowling (2004) note: “these targets do not tell us anything about requirements for ecological processes. It is important to remember that the SAR target does not replace other approaches to setting targets that focus, for example, on minimum viable populations, meta-population dynamics, or ecological processes.” In the deep-sea where so many species are “rare” and thus individuals are widely separated from each other, the possibility of reducing densities to the point of creating a depensatory, or Allee, effect on the population needs to be carefully guarded against. In fact, to be precautionary, one can argue that individuals of long-lived rare species that most likely have very low or intermittent recruitment, such as gorgonian octocorals, black corals, and glass sponges, should not be removed until something is known of the ability of larvae to traverse bottom areas that are subject to trawling.
10. In sum, this paper nicely points out that setting aside 10% of the bottom in the upper bathyal waters of the NE Atlantic will protect only about half of the species present. On the other hand, their suggestion of increasing the reserved area of the bottom to 30-40% increases the proportion of species protected to about 75%. But that leaves a number of long-lived and slow growing species unprotected. Since these species are very rare, being found on average once in every 10,000 m2, much more of the bottom needs to be set aside, in fact as much as 90% of the area according to their Tables S4 and S5. However, the idea that 90% of the Northeast Atlantic should be no-take MPAs is unlikely to be embraced. The current European Union proposal to phase out what is the most harmful method of fishing for deep sea species in the NE Atlantic--bottom trawling-- is an important step justified by Morato’s conclusion that one trawl had the impact on the coral community of 116 to 369 longline sets(Morato presentation at DeepFishMan conference, Galway, 2012).


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Les Watling, University of Hawaii at Mānoa, Honolulu, USA
Peter Auster, University of Connecticut and Sea Research Foundation, Mystic Aquarium, Connecticut, USA
Jeff Ardron, Institute of Advanced Studies in Sustainability, Potsdam, Germany
John Guinotte, Marine Conservation Institute, Seattle, USA