Systematic changes have affected the taxonomical arrangement of Brachyura by Zariquiey Álvarez (1968) and Manning and Holthuis (1981), which were followed in the Canarian catalogue by González (1995). The main changes in the systematics of brachyuran crabs after those impressive catalogues were recently explained by Marco-Herrero et al. (2015).

So, instead of the 20 crab families and 67 genera considered in González (1995), a total of 39 brachyuran families and 77 genera are presented here. Several currently accepted families were included within other families in González (1995), as follows: Ethusidae within the Dorippidae; Eriphiidae, Oziidae, Pilumnidae, Pseudoziidae, Domeciidae, and Panopeidae within the Xanthidae; Euryplacidae within the Goneplacidae; Progeryonidae within the Geryonidae; Epialtidae and Inachidae within the Majidae; Carcinidae and Polybiidae within the Portunidae; Percnidae, Plagusiidae, and Varunidae as subfamilies within the Grapsidae. The family Cryptochiridae was reported as Hapalocarcinidae in González (1995). Ocypodidae (Castro 2012) and Varunidae (Moro et al. 2014) were reported based on very few findings of few individuals. The western Atlantic family Mathildellidae (Fransen and González in prep.) and the Thiidae (Monterroso and González in prep.) are newly reported from the Canaries here.

The current account of brachyuran crabs of the Canary Islands adds another 22 to the 108 valid species in González (1995). According to d’Udekem d’Acoz (1999), Homologenus rostratus (A. Milne-Edwards, 1880) (Bouvier 1922) is a misidentification with Homologenus boucheti Guinot and Richer de Forges, 1995. Maja crispata Risso, 1827 (Herrera et al. 1993, as M. crisperata) should not be considered here because it is a misidentification with Pisa tetraodon. Macropodia aegyptia (H. Milne-Edwards, 1834) should be considered a synonym of Macropodia deflexa Forest, 1978. Portunus sp. in González (1995) should be assigned to Laleonectes vocans (A. Milne-Edwards, 1878). According to Reuschel and Schubart (2006), Xantho incisus Leach, 1814 is considered here a synonym of X. hydrophilus (Herbst, 1790), and the erroneous citation of the Indo-Pacific crab Lophozozymus incisus (H. Milne-Edwards, 1834) by Moro et al. (2014) is based on a secondary homonym of Xantho incisus, the true record. According to Neumann (1996), records for Maja squinado (Herbst, 1788) from the Canaries, the type locality, should be reassigned to Maja brachydactyla Balss, 1922. Pinnotheres pinnotheres (Linnaeus, 1758) is now considered as a new combination, Nepinnotheres pinnotheres (Linnaeus, 1758), made by Manning (1993) when he described a new genus (Nepinnotheres) with several previously Pinnotheres species.

After González (1995), Chaceon inglei Manning and Holthuis, 1989 was reported from the Canaries by Araújo et al. (2009) as a result of deep sea surveys with selective crab traps. Ebalia tuberculata Miers, 1881 was reported from both littoral (Quiles et al. 2002) and bathyal bottoms (Moro et al. 2014). Ebalia tumefacta (Montagu, 1808) was first recorded from the Canaries by Quiles et al. (2002). Some littoral crab species have recently been found by expert scuba divers and reported by Moro et al. (2014): Xaiva mcleayi (Barnard, 1947), Liocarcinus pusillus (Leach, 1816), and Pinnotheres pisum (Linnaeus, 1767). Other littoral species were reported based on dredging sampling: Macropodia linaresi Forest and Zariquiey Álvarez, 1964, Liocarcinus navigator (Herbst, 1794), and Thia scutellata (Fabricius, 1793) (Monterroso and González in prep.).

Some additional species are now present in Canarian waters, probably due to natural range expansions from nearby eastern Atlantic or Mediterranean areas: Calappa galloides Stimpson, 1859 (González et al. 2000), Ebalia tuberculata Miers, 1881 (Quiles et al. 2002), Merocryptus boletifer A. Milne-Edwards and Bouvier, 1894, and Macropipus tuberculatus (Roux, 1830) (Moro et al. 2014). However, the finding of one specimen of Neopilumnoplax sp. in Canarian waters (Fransen and González in prep.) may represent a recent colonization from the subtropical western Atlantic, or reflect that the deep-water crabs Neopilumnoplax americana (Rathbun, 1898) or Neopilumnoplax gervaini Tavares and Guinot, 1996 are amphi-Atlantic species. Regarding the specimens of Brachynotus sexdentatus (Risso, 1827) found in a brackish littoral pond with mobile sandy substrate (Charca de Maspalomas, S of Gran Canaria), under stones at 1.5 m of depth (Moro et al. 2014), given that this species has been introduced in other zones (for instance, the U.K.) and that even the habitat observed is not the more appropriate for this species, the most plausible reason for that finding is a human-mediated activity (through ballast water, fouling or oil platform, or a release from aquarium or pet trade).

The finding in 2011 of one single male of Uca (Afruca) tangeri (Eydoux, 1835) on a sandstone platform on a crowded urban beach (Las Canteras, Gran Canaria) could be a consequence of larvae drifting transport between the African coast and the Canary archipelago, and the subsequent process of settlement and growing of an isolated individual (Castro 2012). Another plausible explanation is a human-mediated introduction (release from aquarium or pet trade).

Acanthonyx brevifrons A. Milne-Edwards, 1869 is first recorded from the Canary Islands herein, based on one male (ICCM408, 3.8 mm carapace length) collected by hand at the Bay of Melenara, Gran Canaria, 27°59’N 15°12’W, Dec. 1997, on red algae Gelidium, 0-7 m. An eastern Atlantic species, appearing to be endemic from the NE Atlantic archipelagos of Azores (Milne-Edwards and Bouvier 1894), Madeira (Chapman and Santler 1955, as A. lunulatus var. brevifrons) and the Cape Verde Islands (Milne-Edwards 1869, type locality), associated with Cystoseira meadows or rocks with algae, from the intertidal to up more than 110 m of depth (d’Udekem d’Acoz 1999).

Although Forest and Zariquiey Álvarez (1964) reviewed the Mediterranean species of Macropodia Leach, 1814 and their nomenclature, specific identification of the eastern-central Atlantic Macropodia has remained particularly difficult (Manning and Holthuis 1981, d’Udekem d’Acoz 1999). Eight Macropodia species not fully identified at specific level from the Canary-Cape Verde region were included in the Fransen (1991) account. Of them, four species were compiled in the d’Udekem d’Acoz (1999) inventory, with three of them (M. aff. hesperiae, M. aff. longirostris, and Macropodia spec. 2) potentially representing endemic forms from the Macaronesia.

Machaerus atlanticus (Miers, 1881) has only been recorded from the Canary Islands by Barquín-Diez and Carrillo (1988) (as Pilumnoplax atlantica, with no collecting data). In the Eastern Atlantic, it is known from Senegal to Congo-Brazzaville, on mixed bottoms dominated by mud, 10-90 m (d’Udekem d’Acoz 1999).

From the time when Santaella (1973) conducted his research, confusion has long existed over the validity of records for the species of Carcinus from the Canaries. Unfortunately, neither González (1995) nor this work have shed too much light on this issue. Carcinus maenas (Linnaeus, 1758) was first recorded from the Canaries by Heller (1863) (with no location), and then compiled by García Cabrera (1971) (“Canaries”). Santaella (1973) did not give validity to these citations based on the absence of a well-documented finding, and also the fact that the European species of Carcinus had not yet been separated in the 19th century. Although live specimens of this species were recorded as commercialized bait (Núñez et al. 2011), they were imported. The species’ supposed natural range of distribution covered the eastern Atlantic, from SE Iceland to Atlantic Morocco, the Western Sahara and Mauritania, and it is also known from the western Mediterranean. However, it has been introduced in the NE Pacific, South Africa, S of Australia, and perhaps in the NW Atlantic and has been accidentally observed in many locations around the world (d’Udekem d’Acoz 1999). It is found in intertidal and shallow subtidal zones, 0-60 m, mainly at 0-6 m, rarely to 200 m (?), under rocks and algae, tide pools, marshes and seagrass beds, and in low to full salinity areas (d’Udekem d’Acoz 1999, Fransen 2015a in WoRMS). Carcinus aestuarii Nardo, 1847 was probably first recorded from the Canaries by Heller (1863) (as C. maenas) and Almaça (1960), and then compiled by Zariquiey Álvarez (1968) (as C. mediterraneus), García Cabrera (1971) (as C. maenas), and Manning and Holthuis (1981) among others. The presence of this species in waters of the Canaries was corroborated by Barquín-Diez et al. (1982-1983) (one spec., Tenerife, muddy sand, 10 m), and collected again on polluted bottoms of the Port of Santa Cruz de Tenerife (González 1995, based on a pers. comm.). Were both specimens well identified? If correctly identified, were both specimens introduced? It has been recorded in scattered localities worldwide: the West Pacific (Japan, introduced, d’Udekem d’Acoz 1999), the Indo-West Pacific, the Indian Ocean (Suez Canal, ?Red Sea), the western Atlantic (USA). It has been found in the eastern Atlantic, the Mediterranean and Black Seas, in Morocco, Mauritania, and South Africa (Fransen 2015b in WoRMS), on muddy sand, under rocks, and seagrass meadows, at 1-26 m (Abelló et al. 1988, d’Udekem d’Acoz 1999). If C. aestuarii is the right identification for the species occurring in the Canaries, it should be considered as introduced. If C. maenas occurs in the Canaries, this would represents a range extension of this west-African species.

Ethusina alba Filhol, 1884: an eastern Atlantic species, found between France and the Azores, off Azores and off Cape Verde Islands, on mud bottoms often with pumice stone, 2800-4265 m (Manning and Holthuis 1981, Fransen 1991). Ebalia affinis Miers, 1881: an eastern Atlantic species, known from Seine Bank, N of Madeira (Doflein 1904), the Cape Verde Islands (Monod 1956) and from Senegal to Angola, including São Tomé and Principe Islands (Manning and Holthuis, 1981), on calcareous algae and mud with shells, 4-140 m (d’Udekem d’Acoz 1999). Portunus (Portunus) inaequalis (Miers, 1881): an eastern Atlantic species, known from Madeira (Türkay 1976), the Cape Verde Islands and Guinea-Bissau southward to Angola, including the islands of the Gulf of Guinea, on various bottom types, 4-73 m, mainly at 4-40 m (Manning and Holthuis 1981, d’Udekem d’Acoz 1999). To date no records for these three crab species exist from the Canaries. However, as they have been recorded from northern and southern adjacent areas, their presence in the Canary Islands is very probable. Very recently, photographic evidence was provided to me proving the occurrence of large specimens of P. (P.) inaequalis in waters of both Tenerife and Gran Canaria islands.

Monodaeus rouxi (Capart, 1951): an eastern Atlantic species, found in Madeira (Fransen 1991), Senegal, Gambia and southward to Angola (d’Udekem d’Acoz 1999), mainly on mud, also on sand and clay (Forest and Guinot 1966, Fransen 1991), from 11 m (Manning and Holthuis 1981) to 510 m depth (Fransen 1991). No record exists for this species from the Canaries. However, it has been recorded from Madeira and the neighbouring African coast, so its presence in the Canary Islands is very probable.

Cancer pagurus Linnaeus, 1758: an eastern Atlantic species, known from Norway (70°N) to S Portugal, including the Mediterranean (very rare), rocks and sand, from the intertidal to 520 m of depth, rarely down to 100 m (d’Udekem d’Acoz 1999). Some doubtful findings from Canada, USA and the Pacific Ocean have been reported in global databases. Macaronesia: Azores (Borges et al. 2010). Up to three fishermen have reported to us on sporadic catches of ox crab (= ‘buey liso’ in Canarian Spanish), few individuals per trap, off Fuerteventura. Some of these catches were sold in local supermarkets, and a dried carapace used as an ornamental object was examined by us. So the northeastern sector of the Canaries seems to be the southern distribution limit for the species, coinciding with the coldest waters around the archipelago.

Of the 132 brachyuran species occurring around the Canary Islands, 130 are benthic forms (Table 1). Polybius henslowii has been reported as epi- to bathypelagic, with benthic stages (e.g. González-Gurriarán 1987). Planes minutus is epipelagic, living on loggerhead sea turtles and inanimate flotsam (e.g. Dellinger et al. 1997), but also has benthic stages when flotsam reaches the beaches. Dorhynchus thomsoni is known to be benthic with a pelagic initial stage (e.g. Hartnoll et al. 1987). Portunus (Portunus) hastatus has juveniles with pelagic stages, but adults are clearly benthic (Table 1).

Of the 130 brachyuran benthic species occurring in the Canaries, 112 are forms of the shelf and transition area between shelf and slope (ST, 86.2%, mainly inhabiting at a depth interval of 0-300 m), 11 are upper slope species (US, 8.5%, mainly at a depth interval of 301-800 m), 4 are middle-slope species (MS, 3.1%, mainly at a depth interval of 801-2000 m), and 3 are lower slope species (LS, 2.3%, mainly at a depth greater than 2000 m) (Table 1).

Seven brachyuran benthic species seem to occur in waters of the Canary Islands at the shallowest depth ever recorded elsewhere: Homologenus boucheti, Ilia spinosa, Velolambrus expansus, Xaiva mcleayi, Laleonectes vocans, Euryozius bouvieri, and Percnon gibbesi. Seventeen brachyuran benthic species seem to occur in waters of the Canary Islands at the greatest depth ever recorded elsewhere: Dromia marmorea, D. personata, Cryptosoma cristatum, Cancer bellianus, Paragalene longicrura, Ebalia edwardsii, E. tuberculata, E. tumefacta, Ilia nucleus, Pisa carinimana, Inachus aguiarii, Stenorhynchus lanceolatus, Maja goltziana, Liocarcinus corrugatus, L. zariquieyi, Portunus (Portunus) hastatus and Thalamita poissonii.

Zoogeographic considerations

To describe for the first time the different components of the brachyuran fauna, all the Canarian brachyuran crabs listed herein (132 species) are grouped by biogeographic pattern in Table 2. A first preliminary description showed three main groups: 39 ATLM species (29.5%), 28 TSEA species (21.2%), and 27 EACT species (20.5%). The remaining eight biogeographic groups varied from six EAWD species (4.5%) to one AAWD species (0.8%) (Table 2).

The presence of one MAC endemic species, Macropodia aff. hesperiae Manning and Holthuis, 1981, is noteworthy. The only record for this middle-slope species from the Canary Islands was by González (1995), based on one specimen caught off Playa de Santiago, S of La Gomera, 821 m, which was identified by C.H.J.M. Fransen, and then validated by d’Udekem d’Acoz (1999). Since all Macropodia species known to date were discarded during the identification, the Canarian specimen may represent a new species, even being an endemism from the Canary Islands or the Macaronesia. The true Macropodia hesperiae Manning and Holthuis, 1981 inhabits littoral waters at depths between 46 and 97 m from Senegal to Nigeria (Manning and Holthuis 1981).

The Canarian brachyuran crabs inhabiting the shelf and transition area between shelf and slope (123 species), i.e. those living shallower than the upper slope, at 0-300 m, are grouped by biogeographic pattern in Table 2. This description of the benthic littoral and/or upper-bathyal species showed the same three main groups: 39 ATLM species (31.7%), 28 TSEA species (22.8%), and 21 EACT species (17.1%). The remaining eight biogeographic groups varied from ten EAWT species (8.1%) to one AAWD species (0.8%) (Table 2).

The presence of four ECAI species is noteworthy. 1. Cryptosoma cristatum Brullé, 1837: known from the Azores (Wirtz and Martins 1993), Porto Santo, Madeira, Desertas Islands (Türkay 1976, as Crytosoma cristatum, erroneous spelling), the Canaries (Brullé 1837-1839, as C. cristata, type locality), the Cape Verde Islands (Monod 1956), and St. Helena Island; as an introduced species, found in the southwestern Mediterranean, with one record from the Alboran Sea (García-Raso 1993). 2. Acanthonyx brevifrons A. Milne-Edwards, 1869: from the Azores (Milne-Edwards and Bouvier 1894), Madeira (Chapman and Santler 1955, as A. lunulatus var. brevifrons), the Canaries (present work) and the Cape Verde Islands (Milne-Edwards 1869, type locality). 3. Euryozius bouvieri (A. Milne-Edwards, 1869): from the Azores (Barrois 1888, as Ozius Edwardsi), Madeira (Türkay 1976), the Canaries (Santaella 1973) and the Cape Verde Islands (Milne-Edwards and Bouvier 1900). 4. Glyptoxanthus cavernosus (A. Milne-Edwards, 1878): from the Canaries (Fransen 1991) and the Cape Verde Islands (Bouvier 1922).

The occurrence of three MAC endemics is also noteworthy. 1. Ebalia fragifera Miers, 1881: from Madeira and the Canaries (Miers 1881, type locality). To date it is only known from the type material and, according to Monod (1956), its status needs to be reviewed. 2. Macropodia aff. longirostris (Fabricius, 1775): from the British Isles, Belgian North Sea, France, and the Mediterranean and Black Seas (d’Udekem d’Acoz 1999), detrital bottoms, sand, rocks covered by algae, and seagrass meadows, 4-130 m, mainly at 18-36 m (d’Udekem d’Acoz 1999). First recorded from the Canaries by Milne-Edwards and Bouvier (1900) (as Stenorhynchus aegyptius) based on “Talisman 1883” material (one spec., 28°49’N 13°53’W, sand and rocks, 30 m). This record was compiled by Bouvier (1940) but the collection was placed at a depth of 40 m. Forest (1964) reassigned this specimen to the genus Macropodia. Forest (1978) demonstrated that H. Milne-Edwards had based the species’ description on material of M. longirostris (Fabricius, 1775). 3. Macropodia spec. 2 Fransen, 1991: only known from the Savage Islands (Fransen 1991, one spec., Selvagem Pequena, 30°01’N 16°00’W, 140-170 m) and the Canary Islands (Fransen 1991, La Palma, one spec., 28°38’N 17°59’W, 200 m; one spec., 28°38’N 17°58’W, mud with oysters, 86-110 m). This material may represent a new species, even being an endemism from the Canary-Savage Islands or more extended in Macaronesia.

Twenty-seven brachyuran benthic species occurring in the Canary Islands currently have their southern limit of distribution in this archipelago: Cancer bellianus, Cancer pagurus, Ethusa mascarone, Paragalene longicrura, Ebalia edwardsii, Ebalia fragifera, Ebalia tuberosa (with certainty in the Canaries and the Western Sahara, Manning and Holthuis 1981), Ebalia tumefacta, Merocryptus boletifer, Anamathia rissoana, Inachus thoracicus (probably), Macropodia deflexa, Macropodia linaresi, Macropodia longirostris, Macropodia sp., Pilumnus villosissimus, Portumnus latipes, Chaceon inglei, Geryon trispinosus, Bathynectes longipes, Liocarcinus navigator, Liocarcinus holsatus, Liocarcinus zariquieyi, Macropipus tuberculatus, Xantho poressa, Pachygrapsus marmoratus and Brachynotus sexdentatus. This southern group of 27 species represents 20.8% of the 130 benthic crabs listed herein.

Another 23 brachyuran benthic species occurring in the Canary Islands currently have their northern limit of distribution in this archipelago: Calappa galloides, Ethusa rosacea, Machaerus atlanticus, Goneplax barnardi, Ebalia tuberculata, Ilia spinosa, Herbstia rubra, Micropisa ovata, Inachus grallator, Inachus nanus, Macropodia aff. parva, Stenorhynchus lanceolatus, Palicus caronii, Velolambrus expansus, Chaceon maritae, Thalamita poissonii, Domecia acanthophora africana, Glyptoxanthus cavernosus, Coralliope parvula, Microcassiope minor, Nanocassiope melanodactyla, Xantho sexdentatus (one single record from the Gulf of Cadiz, Marco-Herrero et al. 2015) and Detocarcinus balssi. This northern group of 23 species represents 17.7% of the 130 benthic crabs listed herein.

Seventy-eight brachyuran benthic species occur in both the Canary and Madeira archipelagos (including 16 species very probably present at Madeira) (Table 1); this represents 60.0% of species shared with Madeira. Sixty-three brachyuran benthic species occur in both the Canary and Cape Verde archipelagos (including two species very probably present at the Cape Verde Islands) (Table 1); this represents 48.5% of species shared with the Cape Verde Islands. Like the Canaries, Madeira belongs to the Macaronesian ecoregion within the Lusitanian province of the Temperate Northern Atlantic realm, whereas the Cape Verde Islands belongs to its own ecoregion within the West African Transition province of the Tropical Atlantic realm (Spalding et al. 2007). The above-mentioned information could be relevant in the context of faunal movements derived from the eastern Atlantic warming.

The ongoing phylogenetic studies together with the use of larval morphology are expected to bring further changes in the systematics of brachyuran decapods; these will have an impact at several taxonomic levels, from species to superfamilies. The main changes will affect new synonymizations, the split of some taxa into new species, and the erection of new genera (e.g. Marco-Herrero et al. 2015). Therefore, significant changes in the Canarian carcinofauna are expected to come in the near future.

Some taxa occurring in waters of the Canary Islands need an in-depth revision. As mentioned, confusion exists over the status of the Carcinus records. The Leucosiidae Samouelle, 1819, in particular the genus Ebalia Leach, 1817, with the necessity to review the status of Ebalia fragifera Miers, 1881, only known from the type material, needs to be revised. The Epialtidae MacLeay, 1838, in particular the genus Pisa Leach, 1814, shows much confusion among species. The Inachidae MacLeay, 1838, in particular the genera Inachus Weber, 1795 and Macropodia Leach, 1814, need to be revised. Within the Inachus species, some geographic distribution remains uncertain due to the morphological similarity and confusion among males of these species and their respective close relatives. The Macropodia species have been traditionally assigned and reassigned to different species, but there remain some doubtful synonyms and several species affinis, i.e. with specimens apparently related to, or resembling, a known species. The Parthenopidae MacLeay, 1838 is a taxonomically problematic group. Fransen (1991) reported on intermediate forms between Parthenope miersii (A. Milne-Edwards and Bouvier, 1898) (a synonym of Spinolambrus macrochelos (Herbst, 1790)) and Parthenope notialis Manning and Holthuis, 1981 from Mauritania and the Cape Verde Islands. In the Geryonidae Colosi, 1923, morphological differences between the Atlantic Geryon trispinosus (Herbst, 1803) and the Mediterranean Geryon longipes A. Milne-Edwards, 1882 are not clear (d’Udekem d’Acoz 1999). The Polybiidae Ortmann, 1893, in particular the genus Liocarcinus Stimpson, 1871, is probably one of the most taxonomically complicate. Within the Domeciidae Ortmann, 1893, the status of Domecia acanthophora africana Guinot, 1964 and its parent Domecia acanthophora (Desbonne, in Desbonne and Schramm, 1867) needs to be clarified, as well as the geographic range of each taxon.

Finally, within the Xanthidae MacLeay, 1838, morphology differences and distribution of the species of genus Paractaea Guinot, 1969 should be better explained. In this regard, records from the Canaries were Brullé (1837-1839) (as Xantho rufo-punctatus), Milne-Edwards and Bouvier (1900) (as Actaea rufopunctata) and Holthuis and Gottlieb (1958) for P. rufopunctata (H. Milne-Edwards, 1834); and Guinot (1969), Santaella (1974), Fransen (1991) and González (1995) for P. monodi Guinot, 1969.

Although description of new brachyuran species is not expected to occur at a significant rate, an increase in the number of species from the Canary Islands is expected to result from trawling and dredging samplings, as well as from human-mediated introduction of non-native species, mainly via the following main vectors: through ballast waters, fouling, oil platforms, and release of aquarium or pet trade. Triay-Portella et al. (2015) pointed out that a process driving massive introduction to the Canaries of non-indigenous tropical and subtropical fish species has been taking place in the last five years through oil platforms. Concerning the natural expansion of species from adjacent areas, northwestern African and Cape-Verdean warm crab species are likely candidates to expand the Canarian checklist. A tropicalization process of fish assemblages in temperate biogeographic transition zones, including the Macaronesian region and some parts of the Mediterranean Sea, has been postulated by many authors (Brito et al. 2005, Wirtz et al. 2008, Afonso et al. 2013, Horta Costa et al. 2014). This process is associated with global warming in many cases (Brito et al. 2005, Perry et al. 2005, Occhipinti-Ambrogi 2007). In temperate marine ecosystems, climate-driven change in biotic interactions can profoundly alter ecological communities, particularly when they impact foundation species (Vergés et al. 2014). In particular, the tropicalization process associated with global warming may mainly affect the presence of the 33 brachyuran benthic species occurring in the Canaries which currently have their southern limit of distribution in this archipelago. These anthropogenic vectors of introduction of warm-affinity exotic species are synergic with the natural range extensions (Triay-Portella et al. 2015), and therefore all causes together are significantly reinforcing the tropical and subtropical component of their littoral and upper-bathyal brachyuran assemblages. The ecological impact of these non-indigenous crabs on the native community remains unknown.

The Brachyura may be claimed to contain the highest degree of diversity among decapod crustaceans and include both crab species with an important role in trophic webs and others of commercial interest (Marco-Herrero et al. 2015).

Several deep-water crab species, such as Cancer bellianus, C. pagurus, Maja goltziana, Chaceon affinis and Paromola cuvieri, are targeted by local small-scale fisheries operating with non-selective bottom traps at some island localities, but their catches are moderate (e.g Santaella 1973, González 1995, Triay-Portella et al. 2014, Biscoito et al. 2015). Maja brachydactyla is seasonally fished with traps and sometimes with gillnets at a few localities (e.g Santaella 1973, González 1995). A dozen intertidal crab species, such as Plagusia depressa, Eriphia verrucosa, Xantho spp., Grapsus adscensionis, Pachygrapsus spp. and Percnon gibbesi, are being intensively harvested, mainly by hand by both recreational and professional fishermen, to be used for human consumption and/or as bait in the small-scale fisheries. P. gibbesi and Platypodiella picta are also collected by hand and used for both aquarium and pet trade.

The Canarian population of P. picta has been considered as potentially menaced by habitat losses and uncontrolled harvesting (aquarium, dry specimens), and its collecting is currently forbidden by the regional government. Similar situations have been observed by the author regarding P. depressa, E. verrucosa, Xantho spp., G. adscensionis, Pachygrapsus spp. and P. gibbesi, with different degrees of harvesting pressure dependent mainly on human demography and resource accessibility at each island and insular sector. On some islands the population status of some of these threatened shallow-water species is critical, even close to local extinction. Basic biological parameters of these crabs should be determined, their island populations evaluated, and some conservation measures urgently implemented in order for them to be recovered in the near future.

A panel of experts in marine organism reproduction proposed the implementation of a minimum landing size (MLS, in cm carapace length) for the following harvested or fished crab species: P. depressa and G. adscensionis (6 cm), C. affinis (13 cm) and C. bellianus (19 cm) (González et al. 2012b). Considering the newness of some of these local fisheries, the absence of reliable landing statistics, and a lack of knowledge pertaining to population biomasses, initial precautionary MLS have been recently proposed for P. cuvieri (9.2 cm) (Triay-Portella et al. 2014) and C. affinis (12.5-13.0 cm) (Biscoito et al. 2015), together with specific additional management measures. However, no conservation measures have been implemented to date by national or regional regulatory bodies for the sustainable use of these 18 exploited species, except an MLS for P. depressa (5 cm) and G. adscensionis (6 cm).