Pelagic anglerfishes (Lophiiformes: Ceratioidei) of The Gully Marine Protected Area

ABSTRACT

A listing of the ceratioid anglerfishes occurring in and around The Gully, a submarine canyon and Marine Protected Area (‘MPA’) off the coast of Nova Scotia that has been reserved to protect its biodiversity, is provided. The compilation was based on 138 specimens, including members of at least 24 species, collected during four midwater-trawl surveys at meso- and bathypelagic depths, supplemented by previous records from the surrounding region. The Gully specimens included seven new records for Canadian waters, two representing major extensions of reported ranges for Bufoceratias wedli and Gigantactis herwigi. In all, more than 40 species, a quarter of the global total of ceratioids, have either been confirmed as occurring in the MPA or can be anticipated as being present occasionally. However, most of the species are effectively planktonic and are carried through the MPA by along-slope and up-canyon currents, without receiving effective protection while in the Area. As iconic examples of the deep-sea fauna, they nevertheless remain important to the MPA’s public-outreach functions.

KEYWORDS:

• Ceratioidei
• anglerfishes
• submarine canyon
• Marine Protected Area
• The Gully

Introduction

The suborder Ceratioidei, the deep-sea anglerfishes, is by far the most speciose taxon among bathypelagic vertebrates. Its members are of considerable scientific interest, not least for their extreme sexual dimorphism (Pietsch 2009), but they have also become iconic examples of the deep-pelagic fauna, widely recognized by the general public, and are correspondingly valuable as vehicles for conveying lessons in ocean conservation. They are absent from the Arctic Ocean but are otherwise widespread. However, an understanding of their biogeography is confounded by rarity: of the 160 species recognized in 2009, half were then known from less than eight specimens each and 22 only from their holotypes. Hence, deep-pelagic survey programmes often reveal multiple, major range extensions based on single specimens, while new species continue to be found (Pietsch 2009). Moreover, recent genetic studies have suggested the existence of cryptic distinctions within some relatively abundant ceratioids (Kenchington et al. 2017; Bañón et al. 2019).

Although most members of the suborder are fishes of open ocean, some can be found in large submarine canyons. One prominent example, The Gully, is incised into the continental margin immediately east of Nova Scotia’s Sable Island (Figures 1 and 2). It extends about 50 km from its head to the shelf break, where it is ∼2,000 m deep, while its thalweg can be traced from there down the continental slope. In 2004, much of The Gully was declared a Marine Protected Area (‘MPA’), with objectives that include preservation of the canyon’s diverse biota and increasing public understanding of its ecosystems (Department of Fisheries and Oceans 2008). The anglerfishes have potential for major contributions to the MPA’s outreach and education functions.

Figure 1. Map of part of the north-west Atlantic, showing the location of The Gully and other places named in the text. The Offshore and Slope Stations are marked by stars. (Contours shown at 200 and 2000 m depths; Scale bar in kilometres.)

Figure 2. Map of The Gully, showing its bathymetry, the boundary of the MPA and the locations of the principal trawling stations: 1: Head Station, 2: Main Station, 3: Wall Station, 4: Deep Station (Scale bar in kilometres).

There is a slow (<0.02 ms⁻¹) but substantial (35,500 m³ s⁻¹) up-canyon flow through The Gully, below the depth of the surrounding banks, which takes about a month to transport water from the canyon’s mouth to its head (Greenan et al. 2014). That flow appears to entrain oceanic meso- and bathypelagic nekton from outside the mouth (Kenchington et al. 2020). Within the core depth ranges of ceratioids, two water masses are found over the continental slope, where they supply the in-draught to The Gully. Labrador Sea Water (‘LSW’), formed west of Greenland, can round Grand Bank and flow along the continental slope past the canyon. Alternatively, a portion of the subsurface water of the Sargasso Sea (here termed North Atlantic Central Water, ‘NACW’) appears to pass under the Gulf Stream and northward to the continental slope. The Stream itself flows far south of The Gully but, after passing Cape Hatteras, it sheds eddies, carrying biota from the Florida Strait, into the Warm Slope Water (‘WSW’) – a surface water mass but one that extends to 400 m depth and thus contains some ceratioids. The WSW also usually passes Nova Scotia well to the south of the shelf break, but its northern boundary is highly variable and sometimes reaches the mouth of The Gully (see: Kenchington et al. (2014b) and works cited therein). Based on their morphology and the few observations of live examples, ceratioids are thought to have limited sustained mobility (Pietsch 2009). While able to maintain their preferred depths, they are effectively planktonic in the horizontal plane and hence susceptible to both long-distance transport by ocean currents and entrainment into The Gully’s in-draught. Thus, it is expected that the MPA will see occurrences of all open-ocean ceratioid species normally found anywhere between the Gulf of Mexico, Bermuda and Greenland. Some will only be there at very rare intervals but the rarity of these species is an important aspect of their interest.

When the MPA was established, almost nothing was known of the deep-pelagic nekton within The Gully. During 2007–10, therefore, Kenchington et al. (2009, 2014a) conducted a series of four midwater-trawl surveys of the canyon and adjacent waters with the aim, inter alia, of documenting the meso- and bathypelagic nekton, as a component of the MPA’s biodiversity. While identification of non-ceratioid specimens is continuing, the surveys caught examples of at least 255 fish species. They included 137 metamorphosed female ceratioids, including members of at least 24 species, plus one free-living male and some attached parasitic males. While none were new to science, seven had not previously been recorded from Canadian waters and some had very rarely been encountered anywhere.

We here present the surveys’ catches of these unusual species, as a contribution to ceratioid biogeography but also in support of the MPA’s management programme. The trawling achieved unusually intensive sampling of the anglerfishes’ depth ranges but cannot be assumed to have captured all of the rare species that sometimes occur in the canyon. To provide a comprehensive account of ceratioid diversity in the MPA, we therefore include a supplementary list of nine additional species which have either been recorded in the general vicinity of The Gully (from Bear Seamount to the Tail of Grand Bank) or else have been taken both north and south-west of there. This paper complements previous work on the crustaceans (MacIsaac et al. 2014) and the numerically dominant fish species (Thompson and Kenchington 2017; Kenchington et al. 2018, 2020) taken by the same surveys.

Materials and methods

The field methods of the four surveys have been presented by Kenchington et al. (2009, 2014a). In brief: three surveys were made in late summer (August–September) of 2007–09 and the fourth in March 2010. They followed a fixed-station, depth-stratified design, with replicate sampling in daylight and at night. Six named stations were worked (Figures 1 and 2), three arrayed along The Gully’s thalweg (named ‘Head’, ‘Main’ and ‘Deep’ stations, respectively), plus one each over the canyon wall (‘Wall Station’), at a location south of the canyon (‘Offshore Station’) and over the continental slope, away from the canyon’s influence (‘Slope Station’). Only the Head, Main and Deep stations were fished every year. Standard sets were deployed to either 250, 750, 1250 or 1750 m, though there were minor variations in maximum depths reached and some non-standard sets were made.

The primary gear was the International Young Gadoid Pelagic Trawl (‘IYGPT’), which has a 60 m² mouth area and was usually fitted with a rigid ‘aquarium’ codend. 167 IYGPT sets yielded catch data – 117 of which had fished to maximum depths of >700 m. A much-larger Diamond IX trawl was deployed on six sets (five to >1200 m). Both are open nets and fished from the surface to the maximum depth of the set. With few exceptions, those which went below 300 m followed double-oblique (‘V’) profiles, sampling all depths equally (Kenchington et al. 2009, 2014a).

None of the sets fished only a single water mass, all passing through multiple layers and some also through frontal surfaces. During the 2007, 2009 and 2010 surveys, on all stations except the Head, most of the water sampled by sets that passed 700 m depth had the characteristics of NACW. On the Head Station, however, the subsurface water resembled LSW. The 2008 survey suffered a CTD failure but the limited available data suggest that The Gully, below 400 m depth, may then have contained LSW throughout its length. During the 2009 survey, a tongue of WSW passed across the mouth of The Gully, its boundary lying over the Deep Station (Kenchington et al. 2009, 2014a).

After each set, the net was picked clean, the catch was sorted and identified to species (or the lowest taxon possible), the catch of each taxon (for the ceratioids, often a single specimen) was weighed, each fish was measured (standard length: ‘SL’) and, when workloads permitted, individually weighed. Selected specimens were photographed while still fresh. Rarities and specimens that could not be immediately identified with confidence, which included most ceratioids, were fixed and brought ashore for subsequent examination (Kenchington et al. 2009, 2014b). Tissue samples were collected from examples of most species for DNA ‘barcoding’ (Kenchington et al. 2017).

Specimens with uncertain at-sea identifications were re-examined ashore and, as necessary, were referred for specialist attention. Most of the ceratioids have since been deposited in permanent collections at the Atlantic Reference Centre (ARC), the Los Angeles County Museum (LACM) or the University of Washington (UW).

The species accounts which follow compare the records from The Gully with Pietsch’s (2009) global summaries and with previous reports of specimens taken between the Grand Banks and north-eastern US waters. We have drawn the latter from the compilation of collection catalogues provided by the Global Biodiversity Information Facility (www.gbif.com) and the catalogues of particular collections. Most of those earlier specimens were recorded by one of four survey programmes: sampling of the Deep-Scattering Layer above the 2000 m bathymetric contour around the Grand Banks by Brandal in 1968 (unpublished but see: Bakken 1968; Scott et al. 1970; Zurbrigg and Scott 1972; Scott and Scott 1988), sampling east and south of Grand Bank during 1979–82 (McKelvie 1985; McKelvie and Haedrich 1986), extensive surveys of the waters from the Scotian Slope to the Gulf Stream during the 1980s (Themelis and Halliday 2012) and irregular sampling over Bear Seamount since 2000 (only the earlier results of which have yet been published: Moore et al. 2003a, 2003b, 2004; Hartel et al. 2008). Finally, some information on ceratioids over the High-Seas portion of Grand Bank and Flemish Cap is available from bottom-trawl surveys, the protocols of which have been upgraded in recent years to include identification of pelagics taken as the nets are hauled back (Vázquez et al. 2013; Bañón et al. 2019).

For the many rare ceratioid species, Pietsch (2009) provided information on every known specimen, all of which he had examined. That comprehensive coverage could not be extended to the few relatively common species and his accounts of those were confined to those for which he could confirm identifications. Thus, those accounts underestimate abundances and perhaps known distributions. Nevertheless, Pietsch’s (2009) numbers are quoted here as the only available, comparable indications of relative frequency of the various species. Inevitably, the abundances are always those of recorded captures, which may not reflect the relative frequencies of the species in the ocean, since vulnerability to survey nets will vary.

Species accounts

Details of each of the 137 metamorphosed female ceratioid specimens taken by the Gully surveys are presented in Table S1. They included three specimens that could not be identified beyond the subordinal level. The other 134 are reported here. Selected images of most of the 24 species known to have been taken are provided in Figure S1. The nets used in The Gully were not suited to capture of free-living, dwarf male ceratioids (though one was taken and is included in Table S1). Some attached, parasitic males were noted but, under the conditions of the ships’ laboratories, they were not comprehensively recorded. Thus, the accounts given here are confined to metamorphosed females unless otherwise stated.

Ceratiidae

Ceratias holboelli Krøyer, 1845

Ceratias holboelli is almost cosmopolitan, though absent from the Arctic and Southern oceans (replaced in the latter by Ceratias tentaculatus (Norman, 1930)). It is the fourth most frequently collected ceratioid. Pietsch (2009) examined 161 specimens but that underestimates the species’ abundance: Jónsson and Pálsson (1999) noted 94 records from Icelandic waters alone. Dozens of specimens are known from Canadian Atlantic waters, though none were taken by Themelis and Halliday’s (2012) surveys off Nova Scotia. C. holboelli has been recorded from 120 m depth downwards but most specimens are taken between 400 and 2000 m. Individuals as large as 855 mm SL are known (Pietsch 2009).

The Gully surveys caught six specimens, five of them on the Head, Main and Deep stations, and all taken by sets which fished to below 700 m. C. holboelli is the most frequently collected ceratioid off Greenland and in the Irminger Sea (Møller et al. 2010; Dolgov 2015). Thus, it may be more than chance that three specimens were caught in 2008, when available data suggest that the canyon was filled with LSW.

Ceratias uranoscopus Murray, 1877 – New Canadian record

Ceratias uranoscopus was long confused with C. holboelli, most small specimens being from the former species (though individuals of up to 240 mm SL are known), while most large ones are members of the latter. After resolution of that issue, Pietsch (2009) examined 112 C. uranoscopus. The species is broadly distributed, though not found at the highest latitudes reached by C. holboelli. It has been taken as shallow as 95 m depth, though most have been caught between 500 and 1000 m. Specimens have been recorded off New England (Pietsch 2009), including MCZ 164080, 164739 and 167890, caught near Bear Seamount during 2004–08. MOM-0091-1627 was taken in 1913, by Hirondelle, 300 nautical miles south-east of Sable Island. It was identified as C. uranoscopus by Pietsch (1986).

A single specimen was taken by a set on the Deep Station that reached 1755 m. It was the first of its species reported from Canadian waters.

Cryptopsaras couesii Gill, 1883

Cryptopsaras couesii is the most frequently collected of all ceratioids, with 983 specimens examined by Pietsch (2009). It is broadly distributed, with a range similar to that of C. holboelli (Pietsch 2009), though recent DNA data suggest that there is a cryptic specific difference between the fish in the Atlantic and Pacific basins (Kenchington et al. 2017; Bañón et al. 2019). C. couesii is the only ceratioid routinely encountered in Canadian Atlantic waters (Scott and Scott 1988). It is the most abundant anglerfish taken off Newfoundland (McKelvie and Haedrich 1986), south of Nova Scotia, where Themelis and Halliday (2012) caught 82, and over Bear Seamount (Moore et al. 2003b, 2004). Although known from as shallow as 75 m depth, most have been taken between 500 and 1250 m. C. couesii reaches at least 358 mm SL (Pietsch 2009).

The Gully surveys took 21 specimens, most on the Deep Station, though at least one was taken at each station except the Head. Of the 20 taken by IYGPT, 11 were caught during the spring 2010 survey and only one in 2008, perhaps indicating an affiliation with NACW. The largest individual was 305 mm SL and weighed 903 g.

Two small specimens were found amongst the catch of a night set that only reached 252 m depth. That was immediately preceded by deeper fishing but both specimens were in excellent condition and it is unlikely that they were carried over from the previous set. All other specimens were taken by sets that reached depths >700 m.

Himantolophidae

Himantolophus groenlandicus Reinhardt, 1837

Himantolophus groenlandicus is one of the more frequently collected ceratioids. Pietsch (2009) examined 143 specimens, while Jónsson and Pálsson (1999) noted 91 records from Icelandic waters. The species is widely distributed through the Atlantic Ocean, though encountered especially frequently on the fishing grounds around Iceland and Greenland, where a number of large specimens (up to 465 mm SL) have been taken by bottom trawls at depths of less than 200 m. Smaller specimens taken by midwater nets have typically been caught by sets that reached 200–800 m (Pietsch 2009). H. groenlandicus is one of the very few anglerfishes recorded from the Gulf of Maine (Moore et al. 2003a). Nearer to The Gully, MCZ 33928 was taken by bottom trawl at the shelf break south of Sable Island in 1935 and ARC 8603205 on the Scotian Slope south-west of the Island in 1978. Over deep ocean, Themelis and Halliday (2012) reported five probable specimens, though identified only to genus.

The Gully surveys took five specimens identified to this species, three of them inside the canyon, on the Main and Head stations, and the others on the Offshore Station. One of the latter was caught by a night set which fished to a maximum depth of 204 m. There had been no deeper set during the previous several hours and the good condition of the specimen leaves no doubt that it was freshly caught.

A sixth specimen, taken on the Main Station, could only be identified to Himantolophus sp. Although 24 species are currently recognized in the genus, H. groenlandicus is much the most common in the vicinity of The Gully and thus this last specimen was probably a member of the species, though it cannot be confirmed as such.

Himantolophus albinares Maul, 1961

Only 25 specimens of H. albinares were known to Pietsch (2009). It is primarily a species of the tropical and subtropical Atlantic, known from depths of 300–2000 m (but usually below 500 m), though specimens have been taken in the Denmark Strait. (The species may also exist in the Pacific, though specimens from there have been wrongly assigned to other species: Bañón et al. 2019.) Specimens reach at least 190 mm SL (Pietsch 2009). Several examples have been taken from the US zone and adjacent international waters as far to the north-east as Bear Seamount (Mooreet al. 2003a). Only three have previously been reported from Canadian waters and a fourth nearby: ARC 9914962 and 9914963 were caught over the Scotian Slope, south-west of Sable Island, in 1995, while MNCN_ICTIO 291.460 was taken from the High Seas near the Tail of Grand Bank in 2015 (Bañón et al. 2019). In contrast, ARC 8601683 was found in the Cabot Strait in 1974. There, the Laurentian Channel is about 500 m deep and has a subsurface inflow on its northern side which draws in, alternately, WSW or LSW from beyond the shelf break (Bugden 1991; Gilbert et al. 2005). That current doubtless transports occasional ceratioids.

During the Gully surveys, a fourth Canadian specimen, of 140 mm SL, was taken on the Main Station by a Diamond IX set that reached 1285 m depth.

Diceratiidae

Bufoceratias wedli (Pietschmann, 1926) – New Canadian record

Bufoceratias wedli, a species of the tropical and subtropical Atlantic, is one of the few ceratioids that appears to live near (though not necessarily on) the seabed, a relatively high proportion of the 82 known specimens having been taken in bottom (rather than pelagic) trawls at depths greater than 400 m. In consequence, it is a species of continental margins, not the open ocean. In the western Atlantic, B. wedli has not previously been reported from north of the Gulf of Mexico. The largest known specimen was 196 mm SL (Pietsch 2009).

A single specimen was taken in The Gully by a set that reached 772 m depth on the Head Station. While far from its expected latitude, the location in the canyon head was consistent with a preference for continental-slope habitats.

Melanocetidae

Melanocetus johnsonii Günther, 1864

Melanocetus johnsonii is the second most frequently collected ceratioid worldwide, Pietsch (2009) having examined 852 specimens of up to 154 mm SL. Other than the Arctic Ocean and the most southerly waters, it is almost cosmopolitan. Many of the known specimens were taken above 1000 m depth. In the Atlantic, the species has been found from the Falkland Islands (Malvinas) to Greenland (Pietsch 2009). Twelve specimens have previously been reported from Canadian Atlantic waters and three more from outside the international boundary, five of those 15 having been taken by Themelis and Halliday (2012) south of Nova Scotia.

The Gully surveys added 20 specimens with specific identifications to M. johnsonii, all taken on either the Main or Deep stations and most by sets that fished below 1200 m depth. Six additional specimens could only be identified to the genus, five of them taken by the same set. If all 26 specimens were M. johnsonii, this would have been the most abundant ceratioid in the surveys’ catches. However, the limited number caught by sets which did not fish below 800 m suggests that some of the specimens (potentially including some misidentified at sea) may have been members of the deeper-living M. murrayi Günther, 1887, the only other known Atlantic species (Pietsch 2009).

Melanocetus murrayi Günther, 1887

Melanocetus murrayi is less often encountered than its congener but it is the third most frequently collected ceratioid globally, with 310 specimens examined by Pietsch (2009). It has a similarly wide geographic distribution to that of M. johnsonii but is deeper-living and has rarely been caught above 1000 m (Pietsch 2009). Six specimens were previously known from Canadian waters, all taken by either Themelis and Halliday (2012) or Halliday et al. (2012). ARC 8909809 was caught near Georges Bank in 1985, ARC 9914977 and 26945 on the Scotian Slope, south-west of Sable Island in 1994 and 1995 respectively, while ARC 7822, 21484 and 29654 were taken from open ocean south-west, south and south-east of Sable Island in 1988, 1987 and 1986 respectively.

A single specimen, taken by the same 1765 m set which caught five individuals identified only to Melanocetus sp., was confirmed as M. murrayi.

Oneirodidae

Lophodolos acanthognathus Regan, 1925

Lophodolos acanthognathus is relatively frequently collected, with 149 specimens (of up to 73 mm SL) examined by Pietsch (2009). It is known from all tropical oceans but most records are from the North Atlantic, where the species has been taken from the Gulf of Mexico to the Denmark Strait and eastward, at depths below 650 m depth, with those larger than 30 mm SL usually below 1000 and often below 1500 m (Pietsch 2009). It is among the most abundant of ceratioids on the northern Mid-Atlantic Ridge (Sutton et al. 2008; Cook et al. 2013) and in the Irminger Sea (Dolgov 2015). Nearly 20 Canadian specimens have previously been reported, most taken around the Grand Banks in 1968, though Themelis and Halliday (2012) added four from south of Nova Scotia. More recently, multiple specimens have been taken over Bear Seamount (MCZ 164220—4, 164730—1, USNM 410065, YPM ICH 025524, 025774, 0273279, 027815), the flank of Grand Bank and Flemish Cap (Vázquez et al. 2013; Bañón et al. 2019).

The Gully surveys took 14 specimens of up to 62 mm SL. Hence, L. acanthognathus was the third most abundant ceratioid in the catches. Most were taken on the Deep Station but some on the Head, Main and Offshore stations also. Five were caught by sets which fished to below 1700 m depth and all but three by sets which fished to at least 1250 m. The shallower specimens, all caught by sets which fished to below 700 m, were taken on the Main and Head stations, suggesting an up-canyon elevation of the species’ depth distribution.

Chaenophryne longiceps Regan, 1925

Pietsch (2009) recognized a ‘C. longiceps Group’ within which he placed one species defined by the characteristics of metamorphosed females, C. longiceps (with 84 known specimens of up to 245 mm SL), plus larval and male forms that did not fit within his ‘C. draco Group’, though he stopped short of placing the latter within C. longiceps itself. Recently, DNA ‘barcodes’ have indicated that the nominal species, as defined by its metamorphosed females, may itself be a cryptic complex containing at least two units, each found in both the North Atlantic and North Pacific (Kenchington et al. 2017).

Those complications aside, as currently recognized, C. longiceps is widespread and has been recorded in the Atlantic from the equator to Greenland, from 500 m depth downwards, with most specimens taken deeper than 850 m (Pietsch 2009). It is among the more frequently collected ceratioids off Iceland (Jónsson and Pálsson 1999). Five have been caught off the US coast north of Cape Hatteras, while MCZ 49876 was taken south-east of Grand Bank in 1964 and another specimen was recorded on Flemish Cap in 2006 (Vázquez et al. 2013). The only known eastern Canadian specimen was ARC 704914, caught off Baffin Island in 1986, but three have been taken from Canadian Pacific waters, west of Vancouver Island (Weil et al. 2015).

During the Gully surveys, two specimens were taken on the Main Station by sets which fished to below 700 m depth.

Spiniphryne gladisfenae (Beebe, 1932) – New Canadian record

Spiniphryne gladisfenae is a widespread species but most of the 21 specimens known to Pietsch (2009) were from the North Atlantic. They included five taken near Bear Seamount during 2002–05 (MCZ 161504, 161524, 162993, 164225 and 164732), MCZ 61084 caught in international waters east of there, and two taken off Greenland. Most known specimens were taken by sets that reached 1000 m or deeper but one was caught by a net that reached 800 m. The largest was 131 mm SL (Pietsch 2009).

Two specimens, the first reported from Canadian waters, were taken on the Main Station by sets which fished to 751 and 769 m respectively. Those were the shallowest records of the species yet reported, perhaps reflecting up-canyon elevation of their depth distributions.

Oneirodes eschrichtii Lütken, 1871

Oneirodes eschrichtii is a broadly distributed species, with 115 specimens, of up to 213 mm SL, known to Pietsch (2009). In the western Atlantic, the species has been found from Bermuda to Greenland, usually at depths between 750 and 2500 m (Pietsch 2009). It is especially notable in the far north, being among the most frequently collected ceratioids off Greenland (Møller et al. 2010) and Iceland (Jónsson and Pálsson 1999), as well as in the Irminger Sea (Dolgov 2015). Four have been caught in Canadian waters of the Labrador Sea, while MCZ 51138 was taken in 1969 on the edge of the Canadian zone south of Cape Sable. Recently, a number of specimens have been taken around Grand Bank and Flemish Cap, including MNCN_ICTIO 291.449, 291.450 and 291.452 (Vázquez et al. 2013; Bañón et al. 2019).

The Gully surveys took three fish identified to this species, the largest being 140 mm SL. While one was caught on the Deep Station by a set that reached 1279 m depth, the others were taken on the Wall Station –where only one other ceratioid (a small C. couesii) was recorded– by sets that reached 762 and 738 m depth respectively.

Oneirodes macrosteus Pietsch, 1974

The 28 specimens of O. macrosteus known to Pietsch (2009), which were up to 185 mm SL, were all found in the Atlantic and mostly above 1000 m depth. The species’ range extends from south of the equator to Greenland, though most specimens have been taken from the north-west (Pietsch 2009), including several from US waters (Moore et al. 2003a). The holotype, ROM 27262, was taken near Flemish Cap in 1968. ROM 27259 and ROM 27265 were caught in the same area, while MCZ 58867 and MCZ 61082 were taken in the Canadian zone but far south of, respectively, Halifax and Cape Sable.

The Gully surveys took four specimens, one each on the Head, Main, Deep and Offshore stations. Two of those (ARC 28615 and ARC 28666) were previously misidentified as Oneirodes bradburyae Grey, 1956 and Kenchington et al. (2017) published a DNA ‘barcode’ of one of them under that name (BOLD Process Reference Code SCAFB1172-09). Both specimens have since been definitively identified as O. macrosteus.

Other Oneirodes species

Ten further specimens taken by the Gully surveys were identified to Oneirodes sp. but not to any particular species, while two more were identified only to the Oneirodidae. Amongst the 10, one was caught by the same 204 m set on the Offshore Station which took an H. groenlandicus. Like that specimen, the Oneirodes sp. was in good condition and hence freshly caught. Most of the others were taken by sets which fished below 1200 m.

There are currently 38 recognized species in the genus – three having been added since Pietsch’s (2009) summary of the Ceratioidei. Most are rare, yet broadly distributed, and hence might be represented amongst the incompletely identified specimens. However, aside from O. eschrichtii and O. macrosteus, only two other species in the genus have been confirmed as occurring in the region around The Gully (Moore et al. 2003a; Hartel et al. 2008; Pietsch 2009). Oneirodes epithales was described by Orr (1991) from ARC 8602571, taken by Themelis and Halliday (2012) more than 200 nautical miles south-east of Sable Island in 1986. A second specimen, MCZ 164733, was caught over Bear Seamount in 2005 (Pietsch 2009). Oneirodes posti Bertelsen & Grobecker, 1980 is known from only three specimens, two taken in the vicinity of the Mid-Atlantic Ridge. The third, MCZ 162998, was caught over Bear Seamount in 2003 (Hartel et al. 2008; Pietsch 2009).

Pietsch (2009) placed eight other species in an informal, infrageneric unit which he designated the ‘Oneirodes schmidti Group’. Of the eight, only Oneirodes theodoritissieri Belloc, 1938 has been reported from the Atlantic basin and then only through three specimens taken off West Africa, while the only confirmed specimens of O. schmidti (Regan & Trewavas, 1932) itself are from Indonesia’s Banda Sea (Pietsch 2009). McKelvie and Haedrich (1986) nevertheless gave that name to a specimen taken east of Grand Bank, while ROM 27281, caught east of Sable Island in 1968, has since been identified to the O. schmidti Group. The correct identifications of those specimens remain unclear.

Leptacanthichthys gracilispinis (Regan, 1925)

Microlophichthys microlophus is widespread in both the Atlantic and Pacific oceans, usually between 800 and 2200 m depth. Pietsch (2009) examined 94 specimens, the largest being 112 mm SL. Several have been taken in US waters north of Cape Hatteras, including MCZ 164734, 165987 and 169547, caught near Bear Seamount in 2005, 2006 and 2012 respectively. Four were taken from Canadian waters in 1968: ROM 27256, 27278 and 27326 around Grand Bank and ROM 27286 over the Scotian Slope, 50 nautical miles east of The Gully. Themelis and Halliday (2012) added a fifth Canadian specimen, ARC 9914722, caught 140 nautical miles south of Sable Island. One specimen, ZMUC 66750, is known from off Greenland (Møller et al. 2010).

During the Gully surveys, a single specimen was caught on the Main Station by a set which fished to 1233 m.

Phyllorhinichthys micractis Pietsch, 1969 – New Canadian record

Phyllorhinichthys micractis is broadly distributed in the subtropical gyres, though Pietsch (2009) examined only 11 specimens, the largest being 140 mm SL. The known material includes NMHUK 2001.2.1.75, taken off Bermuda in 1973, ARC 8602570, taken by Themelis and Halliday (2012) from international waters 270 nautical miles south-east of Sable Island, and ZMH 111443, taken over the northern Mid-Atlantic Ridge in 1973.

The Gully surveys added one large specimen, 138 mm SL, taken on the Deep Station by a set which reached 1589 m depth.

Dolopichthys species

Three damaged specimens, taken on the Main and Deep stations, were identified only to Dolopichthys sp. There are seven recognized species in the genus, five of which are known from the western North Atlantic (Pietsch 2009). The Gully specimens may have been members of any of them.

• Dolopichthys pullatus Regan & Trewavas, 1932 is widespread, with at least 45 known specimens (Pietsch 2009). ROM 27279 was taken on the western flank of Grand Bank in 1968, MCZ 51201 was caught in international waters south of Nova Scotia the following year and MCZ 169546 was taken over Bear Seamount in 2012.

• Pietsch (2009) examined only 26 specimens of Dolopichthys longicornis Parr, 1927 but they came from all major ocean basins, including one taken over Bear Seamount (MCZ 162989: Hartel et al. 2008). The species has also been reported from off Greenland (Møller et al. 2010) and Iceland (Jónsson and Pálsson 1999), over the northern Mid-Atlantic Ridge (Sutton et al. 2008) and in the Irminger Sea, where it was among the most frequently collected ceriatioids (Dolgov 2015).

• Dolopichthys danae Regan, 1926 is a North Atlantic species with six known specimens, including one (MCZ 164089) taken over Bear Seamount (Pietsch 2009).

• Pietsch (2009) knew of 15 specimens of Dolopichthys allector Garman, 1899, found in mid-latitudes in the Atlantic or else spread across latitudinal zones in the eastern Pacific (Pietsch 2009). ARC 9914774 was caught in Canadian waters of the Labrador Sea, ROM 27257 on the northern flank of Grand Bank, ARC 89098210 near Flemish Cap and ARC 130614 on the flank of Georges Bank. Vázquez et al. (2013) reported an additional specimen from Flemish Cap.

• The 10 known specimens of Dolopichthys karsteni Leipertz & Pietsch, 1987 have all been recorded from the western North Atlantic, between Cape Hatteras and the Mid-Atlantic Ridge (Pietsch 2009, plus recent records). Among them, MCZ 61090 was taken south of Cape Cod, MCZ 60991, the holotype, south-east of there and MCZ 165969 over Bear Seamount. MNCN_ICTIO 291.465 was taken in 2015 on the eastern flank of Grand Bank, in Canadian waters, and MNCN_ICTIO 291.453 in 2017 on Flemish Cap (Bañón et al. 2019).

Leptacanthichthys gracilispinis (Regan, 1925)

Leptacanthichthys gracilispinis is a species of the subtropical gyres of the North Atlantic and North Pacific. Pietsch (2009) examined 24 specimens of up to 103 mm SL, most caught by gear that fished below 1200 m depth. Half were taken in the western North Atlantic, including examples from Bear Seamount and US waters south-west of there (Moore et al. 2003a). Three have been recorded from Canadian waters and two from outside the international boundary: ROM 27293, caught 50 nautical miles east of Sable Island in 1968, ROM 27284, taken further to the south-east that same year, ARC 9914750 caught by Themelis and Halliday (2012) 200 miles south-west of the Island, MCZ 50705 taken 220 miles south of the Island in 1969 and MNCN_ICTIO 291.466 on Flemish Cap in 2017 (Bañón et al. 2019).

During the Gully surveys, a single specimen was taken on the Main Station by a set which fished to 1242 m depth.

Lasiognathus species

A single, damaged specimen taken on the Deep Station, by a Diamond IX set that reached 1,435 m depth, was identified as Lasiognathus sp. Six species are currently recognized in the genus – which was formerly placed in the Thaumatichthyidae but has been moved to the Oneirodidae by Pietsch and Sutton (2015). The Gully specimen was likely either Lasiognathus beebei Regan & Trewavas, 1932 or Lasiognathus intermedius Bertelsen & Pietsch, 1996, the only members of the genus yet recorded in the region:

• Pietsch (2009) noted only five specimens of L. beebei, three of which were from the western Atlantic south of Cape Hatteras. Three Canadian specimens had previously been assigned to the species: ROM 27273, taken on the northern flank of Grand Bank in 1968, ROM 27288, taken near the mouth of the Laurentian Channel that same year, and ARC 9914733, taken on the Scotian Slope south-west of Sable Island in 1988 – though Moore et al. (2003a) and Pietsch (2009) have re-identified ROM 27288 as L. intermedius.

• Of seven specimens assigned to L. intermedius by Pietsch (2009), five were taken in the western North Atlantic. Apart from ROM 27288, all were found from off Cape Hatteras and southwards. However, YPM ICH 025927 has subsequently been taken over Bear Seamount.

Most of the known specimens of Lasiognathus spp. were taken in nets that fished to 1200 m or below. The largest was 157 mm SL (Pietsch 2009).

Gigantactinidaea

Six specimens of Gigantactis spp. were taken by the Gully surveys, only three of which could be confidently identified to species. Four species in the genus had been recorded in the region around The Gully before the surveys reported here, though three of them only from a single specimen each. The Gully surveys added a fifth species. Since the genus includes several rarely encountered but widespread members, it is fully possible that the incompletely identified Gully specimens belonged to other species, not yet recorded from the north-western Atlantic.

Gigantactis vanhoeffeni Brauer, 1902

Gigantactis vanhoeffeni is the only species of Gigantactis collected modestly frequently, with 90 specimens (the largest 420 mm SL) noted by Pietsch (2009), though recent DNA data suggests that the nominal species may contain three cryptic groups (Bañón et al. 2019). As presently understood, the species is circumglobal, though absent from the Arctic and Southern oceans, and has been recorded in the Atlantic from the Cape of Good Hope to Greenland. Most specimens appear to have been taken between 700 and 1300 m depth but at least one was caught above 300 m (Pietsch 2009). More than a dozen have been caught in the western Atlantic north of Cape Hatteras, including: MCZ 162994 and YPM ICH 027791, taken near Bear Seamount in 2003 and 2014 respectively, MCZ 101608, recorded in 1993 from the northern edge of Georges Bank, MCZ 61048, taken in the Canadian zone, 160 miles off Cape Sable in 1982, ARC 9914964, 27562 and 26944, taken by deep bottom trawling on the Scotian Slope south-west of Halifax in 1994 and 1995 (Halliday et al. 2012), ARC 8704915, caught 180 miles east of Sable Island in 1984, and ARC 25520, taken near the Tail of Grand Bank in 2005. It is notable that six of those nine were taken close to the continental margin and another actually on the shelf.

The Gully surveys took one specimen confirmed as G. vanhoeffeni on the Deep Station, by a set that reached 746 m depth.

Gigantactis gibbsi Bertelsen, Pietsch & Lavenberg, 1981 – New Canadian record

Only four specimens of G. gibbsi were known before the Gully surveys. The holotype was taken in the Gulf of Guinea and the other three from the western Atlantic – one caught near Bermuda and two in US waters. The latter include MCZ 164218, taken over Bear Seamount in 2004 (Hartel et al. 2008). The largest of those specimens was 114 mm SL (Pietsch 2009).

The one fully identified specimen of G. gibbsi taken during the Gully surveys was caught on the Deep Station by a set which reached 1750 m depth. At 131 mm SL and 35 g, it was the largest of its species yet found (Figure 3).

Figure 3. Gigantactis gibbsi (Scale bar: 100 mm) – from a photograph of the fresh specimen (original image included in Figure S1).

Gigantactis herwigi Bertelsen, Pietsch & Lavenberg 1981 – New Canadian record

Only two specimens of G. herwigi were known before the Gully surveys. The holotype, ZMH 138194 (262 mm SL), was taken in mid-Atlantic, north-east of Cabo de Sao Roque, in 1968, while UW 047536 was caught in the Gulf of Mexico in 1999 (Bertelsen et al. 1981; Pietsch 2009).

A single specimen, of 133 mm SL, was caught on the Gully surveys’ Main Station by a set which fished to 1233 m depth (Figure 4).

Figure 4. Gigantactis herwigi (Scale bar: 100 mm) – from a photograph of the fresh specimen (original image included in Figure S1).

Linophrynidae

The Gully surveys took 22 specimens identified to members of the Linophrynidae. The majority were identified to species but three metamorphosed females and one free-living male could only be identified to Linophyryne sp., while only familial identifications were possible for another five females. The family includes five recognized genera but two have only been reported from the Pacific Ocean, while a third is monotypic (comprising only Photocorynus spiniceps Regan, 1925) and, in the Atlantic, has only been found in tropical latitudes. Thus, the five specimens with familial identifications were very likely members of either Linophryne or Haplophryne. The latter is another monotypic genus and well known from off Nova Scotia. In contrast, Linophryne is speciose, with seven of its species previously recorded in the region, two of which were confirmed amongst the catches of the Gully surveys.

Haplophryne mollis (Brauer, 1902)

Haplophryne mollis is circumglobal in tropical and temperate latitudes. Of the 88 specimens noted by Pietsch (2009), the largest was 159 mm SL. At least one was been taken above 550 m depth but most have been caught by sets that fished deeper than 1000 m (Pietsch 2009). Seventeen have previously been reported from the western Atlantic north of Cape Hatteras, including six taken over Bear Seamount, four of them in July 2002 (Moore et al. 2003a, 2003b), MCZ 165991 in 2006 and YPM ICH 025514 in 2012. Themelis and Halliday (2012) took four specimens in Canadian waters south-west of Sable Island in 1988 and three outside the international boundary during 1986–87. McKelvie and Haedrich (1986) had previously taken ROM 50682 east of Grand Bank, while Bañón et al. (2019) have added MNCN_ICTIO 291.464 from Flemish Cap. At least four other specimens were apparently taken on the Cap during 2006–12 (Vázquez et al. 2013).

The Gully surveys recorded a further 11 specimens fully identified as H. mollis –quadrupling the number of Canadian records. Most were taken on the Main and Deep stations, though one came from each of the Head and the Offshore. Each survey saw between two and four specimens caught. All were taken by sets that fished to below 740 m but five of them (including three of five on the Main Station and the one on the Head) were caught by sets that did not go as deep as 800 m, consistent with there being some up-canyon elevation of the depth distribution.

Linophryne brevibarbata Beebe, 1932 – New Canadian record

Linophryne brevibarbata is a species of the subtropical gyre of the North Atlantic, known from only nine specimens, the largest 100 mm SL. Two were taken off Bermuda but the next four were all caught over the Mid-Atlantic Ridge or further east (Pietsch 2009). Two further specimens (MCZ 164211 and 164212) were found over Bear Seamount in 2004 (Hartel et al. 2008), while MNCN_ICTIO 291.462 was taken on Flemish Cap in 2017 (Bañón et al. 2019).

During the Gully surveys, one specimen was caught on the Main Station by a set which reached 746 m depth.

Linophryne coronata Parr, 1927

Linophryne coronata is primarily a North Atlantic species, with records from the tropics to the Denmark Strait, though three specimens have been recorded from the eastern Pacific. Pietsch (2009) noted 22 specimens of up to 225 mm SL, including three caught around Grand Bank and Flemish Cap: ROM 27258, 27276 and 64549, each taken in 1968, the first of them inside Canadian waters. Another was taken on Flemish Cap in 2007 (Vázquez et al. 2013). In addition, Themelis and Halliday (2012) took one 230 miles south-west of Sable Island in 1986, while MCZ 162991 was taken over Bear Seamount in 2003 (Hartel et al. 2008).

One specimen was taken on the Head Station by a set which reached 737 m depth. It was the second known Canadian specimen.

Other Linophryne species

Of the five species known from the region surrounding The Gully but not confirmed amongst the specimens taken there:

• All 31 specimens of Linophryne arborifera Regan, 1925 noted by Pietsch (2009) were taken in the subtropical gyres of the North and South Atlantic. Several have been recorded off Bermuda and the southern USA, while MCZ 164735 and 164736 were taken over Bear Seamount in 2005.

• Linophryne lucifer Collett, 1886 is a northern species, most of the 29 specimens noted by Pietsch (2009) having been taken off Iceland and Greenland, where it is one of the most frequently collected ceratioids (Jónsson and Pálsson 1999; Møller et al. 2010). Three have been caught in the vicinity of Flemish Cap: NHMUK 1965.5.26.3 in 1965, ROM 27267 and 27268 in 1968.

• Pietsch (2009) noted 10 specimens of Linophryne macrodon Regan, 1925, all but one taken in the western Atlantic, from the Gulf of Mexico to Bear Seamount, where MCZ 164217 and 165968 were caught in 2004 and 2006 respectively. In 1986, Themelis and Halliday (2012) took ARC 8602168 and 8602566, respectively 170 and 220 miles south-east of Sable Island. In 1988, they added ARC 9914712, from 150 miles south-east of Cape Sable. Sutton et al. (2008) have since reported catching an additional specimen over the northern Mid-Atlantic Ridge.

• Only seven specimens of Linophryne bicornis Parr, 1927 are known, five of them taken between Bermuda and Greenland. They include MCZ 138063, caught off New Jersey in 1995, MNCN_ICTIO 291.463, taken on Flemish Cap in 2015, and another caught on the continental slope north-east of Newfoundland (Moore et al. 2003a; Pietsch 2009; Møller et al. 2010; Bañón et al. 2019) In addition, McKelvie and Haedrich (1986) reported taking one east of Grand Bank, though no specimen is known.

• Most of the nine specimens of Linophryne algibarbata Waterman, 1939 noted by Pietsch (2009) were taken in the western North Atlantic between Cape Hatteras and the Denmark Strait. They included ROM 27270, taken near Flemish Cap in 1968, and MCZ 162995, caught over Bear Seamount in 2003.

Additional species previously recorded in the region

Himantolophidae

Himantolophus mauli Bertelsen & Krefft, 1988

Himantolophus mauli occurs in the North Atlantic from the subtropics to the Denmark Strait, though there are only 20 known specimens (Pietsch 2009). Two have been taken off Nova Scotia: ROM 26760 south of Cape Sable and ROM 37721 south of Halifax.

Oneirodidae

Pentherichthys atratus (Regan & Trewavas, 1932)

Pentherichthys atratus is widespread in tropical and subtropical latitudes, with 26 known specimens. MCZ 161496 was taken over Bear Seamount in 2002 (Moore et al. 2003a; Pietsch 2009).

Chaenophryne draco Beebe, 1932

Chaenophryne draco is a widespread species, with over 120 known specimens, but is more frequently collected around Greenland and in the eastern North Atlantic (Pietsch 2009; Møller et al. 2010). Recent specimens have been taken on the northern Mid-Atlantic Ridge and in the Irminger Sea (Sutton et al. 2008, 2013; Dolgov 2015) – all of them far north and east of The Gully. However, the holotype was caught off Bermuda (Pietsch 2009).

Danaphryne nigrifilis (Regan & Trewavas, 1932)

Twenty specimens of D. nigrifilis are known. The species is widespread in low latitudes and, in the Atlantic, also northwards to Greenland, with specimens taken off Bermuda and over the northern Mid-Atlantic Ridge (Pietsch 2009). Themelis and Halliday (2012) took ARC 18021 in Canadian waters south of Sable Island in 1988.

Phyllorhinichthys balushkini Pietsch, 2004

Six of the seven known specimens of P. balushkini have been caught in the North Atlantic, including MCZ 164228, taken over Bear Seamount in 2004 (Hartel et al. 2008; Pietsch 2009).

Caulophrynidae

Caulophryne jordani Goode & Bean, 1896

Thirty-eight specimens of C. jordani are known, including ones taken in the North Atlantic from the equator to the Denmark Strait (Pietsch 2009). MCZ 162990 was caught near Bear Seamount in 2003 (Moore et al. 2003a), while ROM 27250 was taken over the continental slope north-east of Newfoundland 1968.

Caulophryne polynema Regan, 1930

Caulophryne polynema Regan, 1930 is widespread, though only 14 specimens are known. Until recently, all North Atlantic records were from subtropical latitudes (Pietsch 2009). However, MBCN_ICTIO 291.461 was taken on Flemish Cap in 2017 (Bañón et al. 2019).

Gigantactinidae

Gigantactis longicirra Waterman, 1939

Most of the 10 known specimens of G. longicirra have been taken in the Atlantic, from off Brazil to the Gulf of St. Lawrence. The holotype, MCZ 35065, was caught east of New Jersey (Pietsch 2009). Little is known of the Gulf of St. Lawrence specimen (MCZ 52570) but a note on its catalogue index card indicates that it was identified by Bertelsen in 1978 (cf. Bertelsen et al. 1981).

Gigantactis ios Bertelsen, Pietsch & Lavenberg, 1981

Gigantactis ios was known to Pietsch (2009) only from four eastern Atlantic specimens but MCZ 163303, taken over Bear Seamount in 2003, has since been identified to this species (Hartel et al. 2008).

Discussion

The catches of the Gully surveys were particularly notable for the high number and broad diversity of ceratioid specimens taken. While the shallower sets were not expected to catch many, the 117 IYGPT sets which fished deeper than 700 m took 119 individuals between them, while the five Diamond IX sets which went below 1200 m took 14. Not surprisingly, the way to record ceratioids is to filter large volumes of water at lower-mesopelagic and upper-bathypelagic depths. Whether the numbers caught reflect a relative richness of anglerfishes in The Gully remains unclear, as few previous programmes have done so much fishing at great depths with large trawls. Themelis and Halliday (2012), for example, took 114 ceratioids off Nova Scotia despite only 38 of their many IYGPT sets going below 700 m.

The Gully catches included multiple examples of five of the six globally most frequently collected species that are known to occur in the north-western Atlantic (Pietsch 2009): Cryptopsaras couesii, Melanocetus johnsonii, Ceratias holboelli, Lophodolos acanthognathus and Himantolophus groenlandicus. Only Melanocetus murrayi, represented in the Gully material by a single confirmed specimen, was seen less frequently than expected. Conversely, Haplophryne mollis was perhaps more abundant in the survey catches than would have been expected. Unsurprisingly, given so many specimens, the collection also included most of the less-common species known from the region, plus a few extreme rarities. Even the exceptional Gigantactis herwigi was consistent with the previous two specimens of that species, in being taken from the western Atlantic.

When Pietsch (2009) compiled existing knowledge of the suborder, the Ceratioidei included 11 families, 35 genera and 160 species, though additional species have been added since. At least seven families, 17 genera and 24 species were recorded in The Gully. The above lists name 22 further species known from the waters surrounding the canyon’s mouth, some of which may be represented amongst the incompletely identified specimens from the four surveys. Even with those additions, the species listed cannot include all ceratioids that pass through the Gully MPA as major extensions of recorded ranges (unlikely to be changes in actual, biological ranges) continue to be revealed when survey programmes are conducted at appropriate depths (Pietsch 2009). The rarest species are particularly liable to show such extensions, as in the case of G. herwigi, but some more-frequently encountered are already known from nearby and may occur off Nova Scotia occasionally. Neoceratias spinifer Pappenheim, 1914 and Gigantactis perlatus Beebe & Crane, 1947, for example, have both been found as far north as off New Jersey (as MCZ 61075 and MCZ 57780, respectively: Moore et al. 2003a; Pietsch 2009). Thus, while no definitive list of the ceratioids of The Gully can yet be prepared, the MPA may see rare visits from about one quarter of all extant species in the suborder and one half of the genera. That is not a function of the importance of the canyon for these fishes but a reflection of the very broad distributions of many of them.

Despite the relatively high numbers of specimens of such rare species taken by the Gully surveys, interpretations of the distributions of ceratioids within the canyon are frustrated by their low absolute numbers. Specimens were taken in both spring and summer (indeed by each of the four surveys), as well as at every station, and both in daylight and at night. However, only 19 specimens were taken in 2008, the year that the canyon may have been flooded with LSW – though half of the recorded individuals of the northern C. holboelli were taken that year. The depth stratification of the surveys did not include sets with intended maximum depths between 250 and 750 m, though some missed those targets by a few tens of metres. With that design, it was not to be expected that many ceratioids would be taken by sets which did not fish below 700 m, though four individuals were taken above 300 m at night. All species represented by more than a single specimen were caught, at least sometimes, by sets which did not fish below 800 m but only five of 20 M. johnsonii and three of 14 L. acanthognathus were taken at such depths. Both of those species are known to be deeper-living than some other ceratioids (Pietsch 2009). Otherwise, all that can be seen in the data was some indication of up-canyon elevation of depth distributions, at least in L. acanthognathus and H. mollis.

Based on the distributions and size compositions of the 20 principal fish species caught by the Gully surveys, Kenchington et al. (2020) hypothesized that oceanic species, lacking behaviours adapted to the peculiar conditions of the canyon, are drawn through its mouth by the known inflow as quasi-passive particles, while maintaining active control of their depths. Those two processes should, together, concentrate fish in the canyon head but catches on the Head Station of most of the 20 species were small – only the seabed-associated Melanostigma atlanticum Koefoed, 1952 being more abundant there than on other survey stations. It appears that the fishes experience intense predation pressure during their month-long passage up The Gully, while diel migrants are additionally lost over the adjacent banks when caught in cross-canyon surface flows (Kenchington et al. 2018, 2020). No equivalent conclusion can be drawn from the limited data on ceratioids, though their catches were not inconsistent with the hypothesis. It is sure that there was no marked concentration of ceratioids in the canyon head, though the sole specimen of Bufoceratias wedli, suspected to be a bottom-associated species (Pietsch 2009), was taken there, much as was M. atlanticum. With that one possible exception, the ceratioids do not appear to be resident within the Gully MPA but are carried through it by the moving waters – carried to their deaths, in the case of those entrained in the up-canyon flow. As such, it is unlikely that the MPA provides them with any significant conservation benefit, though they remain valuable to its outreach and educational roles.

Acknowledgements

We are indebted to the captains, crews and scientific staffs of the four survey cruises, including Bill MacEachern, Andrew Cogswell and Megan Best, who photographed the fresh specimens. Various specimens were identified by Drs Lou Van Guelpen, Rick Feeney and Margaret Neighbors, in addition to the authors. Support in specimen curation was provided by Megan Best, Barry MacDonald and Sarah Thompson, Katherine Maslenikov processed specimen loans to UW from other collections, while Cam Lirette both ensured effective data management and drafted the maps. Drs Ellen Kenchington and Javier Murillo-Perez provided helpful reviews of earlier drafts. Throughout, Dr Ellen Kenchington provided overall direction of the survey programme.

Disclosure statement

No potential conflict of interest was reported by the authors.