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A catshark nursery in a deep gorgonian field in the Mississippi Canyon, Gulf of Mexico


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The habitat functions of Gulf of Mexico gorgonians are still poorly known and understood. Benthic transects were conducted at three deep-water (> 200 m) sites in the northwestern Gulf of Mexico in September 2003: Viosca Knoll (Lease Block 826–340 m), Green Canyon (Lease Block 354–538 m), and Mississippi Canyon (Lease Block 885–533 m) using the Sonsub Innovator ROV aboard the R/V Ronald H. Brown. Octocorals were present at all three sites and were the dominant benthic megafauna at one of the three dive sites. Colony heights were estimated to be 25–50 cm tall, with a mean height of ~35 cm. In total, 296 catshark egg cases were attached to 117 colonies (11% of the total). All egg cases observed appeared to be the same size and shape, suggesting that a single scyliorhinid species was responsible for depositing the eggs.
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BULLETIN OF MARINE SCIENC E, 81(3): 553–559, 2007
Bulletin of Marine Science
© 2007 Rosenstiel School of Marine and Atmospheric Science
of the University of Miami
Peter Etnoyer and Jon Warrenchuk
Gorgonian corals (Anthozoa: Alcyonaria: Gorgonacea) are a conspicuous compo-
nent of the deep-water benthic megafauna in the Gulf of Mexico (Alcyonaria: Deich-
mann, 1936; Bayer, 1954; Giammona, 1978; MacDonald et al., 1996; Cairns and Bayer,
2002). Callogorgia spp. primnoid colonies in particular are widespread throughout the
Gulf, with one endemic species in the Mississippi delta region, Callogorgia americana
delta Cairns and Bayer, 2002. Primnoid octocorals in the North Pacific are considered
habitat-forming because they grow large enough to provide substrate and shelter for
associated species of fish and invertebrates (Krieger and Wing, 2002; Etnoyer and Mor-
gan, 2003, 2005). e habitat functions of Gulf of Mexico gorgonians are still poorly
known and understood.
e nature of the relationship between deep-water corals and fish in general is
unclear. Deep scleractinian reefs [Lophelia pertusa (Linnaeus, 1758) and Oculina
varicosa (Lesueur, 1821)] may provide nursery habitat for deep-water redfish Sebastes
viviparous (Kroyer, 1885) (Fossa et al., 2002), gag grouper [Mycteroperca microlepsis
(Goode and Bean, 1879)], and scamp Mycteroperca phenax Jordan and Swain, 1884
(Gilmore and Jones, 1992), but evidence of fish using gorgonian corals as nursery
habitat is limited. Krieger and Wing (2002) noted that most large rockfish occur near
boulders and corals on the continental shelf of the Gulf of Alaska. e question re-
mains whether gorgonian habitat for fishes is obligate or facultative (Auster, 2005).
An early woodcut print of a single egg case attached to a seafan from Lydekker’s
Royal Natural History (1896) shows a shallow gorgonian serving as nursery habitat
for a skate, ray, or oviparous shark, but physical specimens and in situ reports of this
habitat function are rare. One Paragorgia sp. colony with tendrils from a single egg
case attached to a branch resides at the Santa Barbara Museum of Natural History
(Id. no. 24471 CH, location unknown) (B. Horvath, Westmont College, pers. comm.).
Another Paragorgia sp. colony from the North Atlantic hosts a dozen catshark egg
cases at the Canadian Shark Research Laboratory (S. E. Campana, Bedford Institute
of Oceanography, pers. comm.). Submersible observations documented egg cases of
the chain catshark Scyliorhinus retifer (Garman , 1881) attached to soft corals, hy-
droids, and derelict fishing gear in the Mid-Atlantic Bight (Able and Flescher, 1991).
To date, catsharks using deep gorgonians as nursery habitat has not been document-
ed in the deep Gulf of Mexico.
Egg cases of an unknown species of scyliorhinid catshark were found in abundance
on a low-relief mound at 533 m depth in a large field of C. a. delta (family Primnoidae)
in the Mississippi Canyon, Gulf of Mexico during exploratory surveys in September
2003. A smaller field of Acanella sp. Gray, 1870 octocorals (Gorgonacea: Isididae)
without egg cases was also encountered at 340 m depth on Viosca Knoll (Fig. 1). Two
species of Acanella are known from the Gulf of Mexico. Acanella eburnea (Pourtalès,
1868) is common in the northern Gulf of Mexico between 283 and 1829 m, whereas
Acanella arbuscula (Johnson, 1862) was described from only one preserved speci-
men (Giammona, 1978). Areal coverage and density for both species are unknown
(Gulf of Mexico and South Atlantic Fishery Management Council, 1982).
Video transects were conducted at three deep-water (> 200 m) sites in the northwestern
Gulf of Mexico in September 2003: Viosca Knoll (Lease Block 826–340 m), Green Canyon
(Lease Block 354–538 m), and Mississippi Canyon (Lease Block 885–533 m) using the Son-
sub Innovator ROV aboard the R/V R H. B. A 2.5-km round trip linear video
transect was conducted on September 31, 2003 in the southwest saddle of the Mississippi
Canyon (28°3.9´N, 89°43.1´W) on a low-relief knoll at 533 m depth. e linear transect mea-
sured 1.25 km, but the ROV deviated from this path several times. e ROV was positioned
approximately 1 m off the bottom and stopped intermittently to collect samples and conduct
close-up video taping with a Sony TRV900 3-chip camera recording to Mini-DV tape. e
total survey time was 7 hrs 3 min. e dominant macrofauna along the entire transect was
the primnoid octocoral C. a. delta. Colony heights were approximated by comparison with
the known measures of the ROV and its tools, e.g., the manipulator claws and arms. Colony
density was estimated based upon the number of colonies in the field of view. Nearly 51% of
the dive was spent motionless, making observations and collections, and waiting for visibility
to improve.
e dive site on Viosca Knoll (29°06´N, 88°23´W) was surveyed on September 23, 2003. is
site is also a low-relief knoll, 200 km to the northeast of Mississippi Canyon, slightly shallower
than the previous site. e total elevation of the feature was ~70 m height. e ROV survey was
conducted at depths of 300–350 m in a series of eight east-west parallel belt video transects
Figure 1. Map of Callogorgia spp. occurrences in the Gulf of Mexico, illustrating the range and
distribution of primnoid habitat. Callogorgia americana delta is endemic to the Mississippi
Delta region, but Callogorgia spp. primnoid corals are widespread. Octocoral occurrence data
from Smithsonian NMNH, Texas Cooperative Wildlife Collection (TCWC), and Harbor Branch
Oceanographic Institution. Bathymetry data from Smith and Sandwell, 1997.
~200 m in length across a northeast trending spur of the knoll with two rises. e area surveyed
at Viosca Knoll was 50,000 m2 in a 1.85-km linear distance over an 8 hr period.
Octocoral samples and attached epibionts were collected. Branched segments of octocoral
colonies were preserved in 90% ethanol; duplicate collections were deposited at the California
Academy of Sciences and the Smithsonian Institution National Museum of Natural History
(USNM 1085704 and 1085705). Acanella sp. was not collected. Four egg case specimens were
collected with the ROV’s suction device and preserved in 70% ethanol for identification. ese
could not be identified because eggs had hatched, and no embryos were present. e video
transect was analyzed by quantifying the numbers of octocoral colonies with and without egg
cases and the number of egg cases per colony.
Octocorals were present at all three sites and were the dominant benthic megafau-
na at one of the three dive sites. Callogorgia americana delta was the most conspicu-
ous benthic megafauna in Mississippi Canyon, while C. a. delta, Acanella sp. bamboo
corals, and Leiopathes spp. black corals were all observed in surveys of Viosca Knoll.
e scleractinian L. pertusa dominated some crests and mounds at Viosca Knoll
(Schroeder, 2006). Only two species of zoantharian black corals, Stichopathes sp.
Brook, 1889, and Leiopathes sp. were collected from third deep site at Green Canyon.
ese occurred as isolated or scattered individuals.
e epibenthos at the Mississippi Canyon site was heavily silted. No hard bottom
substrate was evident, though the presence of C. a. delta implied buried hard attach-
ment surfaces. A total of 1010 individual colonies of C. a. delta were counted along
the 2.5 km round trip transect. Colonies were sparsely spaced, between 1 and 2 m
apart on average, with several colonies visible at any given time. e greatest number
of visible colonies at any one time along the transect was 18. Colony heights were
estimated to be 25–50 cm tall, with a mean height of ~35 cm. In total, 296 egg cases
were attached to 117 colonies (11% of the total). A maximum of 17 cases were ob-
served on a single colony and the mode was 1 egg case per colony (Figs. 2, 3). Octoc-
orals with egg cases appeared to be somewhat clustered, that is, corals with egg cases
tended to be located near other corals with egg cases. No egg cases were observed in
the field of Acanella sp. at Viosca Knoll.
All egg cases observed appeared to be the same size and shape, suggesting that a
single scyliorhinid species was responsible for depositing the eggs. All four egg cases
collected were hatched and did not contain embryos. e cases ranged from 48–57
mm in length and 18–22 mm in width, consistent with the description of the chain
catshark S. retifer (Castro et al., 1988). However, egg cases of many other scyliorhinid
species have yet to be described, no sharks were definitively identified in situ, and no
living embryos were obtained, so the species identification remains inconclusive.
Scyliorhinid catsharks are a specious group of small benthic sharks that range
throughout the deep-sea (Compagno, 1988). eir egg cases are distinctive, with
long tendrils, and a bulging fusiform shape. Scyliorhinids reported from the Gulf
of Mexico (Kiraly et al., 2003; Froese and Pauly, 2006) include: smallfin catshark
Apristurus parvipinnis Springer and Heemstra, 1979; broadgill catshark Apristurus
riveri Bigelow and Schroeder, 1944; the marbled (aka roughtail) catshark Galeus arae
(Nichols, 1927); chain catshark S. retifer (Garman , 1881); the Iceland catshark Apris-
turus laurussonii (Saemundsson, 1922); and the Campeche catshark Parmaturus
campechiensis Springer, 1979. Of these, the egg cases of only S. retifer and A. riveri
have been described (Castro et al., 1988; Compagno, 1988).
Elasmobranch egg cases have been found attached to several types of substrates,
including octocorals, but to our knowledge, this is the first in situ documentation of
a shark nursery in a deep gorgonian field. Unfortunately, embryos were not collected
but the characteristics of the egg case fit the known description of S. retifer. Scyliorhi-
nus retifer is a small, slender oviparous benthic catshark (Nichols, 1931) with a strik-
ing charismatic pattern and fluorescent coloration (Matz, 2005) found commonly
along North Atlantic continental shelf and slope at depths of 50–750 m (Sminkey
and Tabit, 1992). In captivity, mature S. retifer females lay eggs every 14–17 d. e
observed egg-laying behavior shows that egg case tendrils extending from the cloaca
must snag on a structure as the shark passes close, then the shark circles the struc-
ture until the egg case is pulled from the cloaca and the egg case is attached (Castro
et al., 1988).
Callogorgia americana delta colonies on average are elevated above the sediment
by nearly 35 cm, with likely benefits of increased survivorship for the shark embryos
due to increased water circulation and perhaps reduced predation. e branches of
C. a. delta are strong and flexible. Colonies are plumose, with broadly spaced pinnate
branches. ey have a uniform proteinaceous axis with heavily-armored retractile
polyps arranged in whorls. e polyps are protected by on all sides by large roughly
textured calcitic scales (Cairns and Bayer, 2002). ese factors may contribute to the
shark’s choice of C. a. delta nursery substrate.
Callogorgia spp. primnoid corals differ greatly from Acanella spp. bamboo coral
colonies in form and character. Acanella spp. colonies have a bushy appearance, with
an alternating axis of calcitic internodes and gorgonaceous nodes. Colonies branch
from the nodes. In contrast to the primnoids, isidid polyps are fleshy and non-re-
Figure 2. Callogorgia americana delta colonies with catshark egg cases attached. Depth 533 m.
ROV suction hose on the left is 15.25 cm (6 in) in diameter.
tractile, protected only by eight small spines projecting from the mesenteries (Ver-
rill, 1883; Kukenthal, 1924; Bayer, 1990). erefore, the texture of Callogorgia spp.
branches is rough, while the texture of bamboo coral branches is fleshy and smooth.
e rough texture of Callogorgia spp. primnoid corals may enhance egg case adhe-
is occurrence demonstrates that large (> 1 km) monotypic fields of gorgonian
octocorals on low relief mounds can provide nursery habitat to fish species in the
Gulf of Mexico. Yet, this one occurrence is insufficient to determine whether cat-
shark nursery habitat is substrate-specific, taxon-specific, or site-specific. Callogor-
gia spp. primnoids are widespread throughout the Gulf of Mexico (Cairns and Bayer,
2002) (see Fig. 1). Catshark nursery habitat may or may not be widespread. Egg cases
have not been reported on other commonly occurring benthic megafauna in the Gulf
of Mexico such as antipatharian black corals. Deep scleractinian thickets are rare in
the Gulf, therefore, gorgonians may provide essential fish habitat for catsharks sim-
ply due to a lack of alternatives. Future research and management of catshark popu-
lations should consider the status and distribution of deep-water gorgonian fields, as
they may have an important role in the life history of sharks. Widespread and local
anthropogenic impacts to gorgonian communities, such as bottom trawling, longlin-
ing, and ocean dumping may inadvertently impact deep-water nursery habitat for
catshark populations.
e authors thank the scientists and crew of the 2003 Gulf of Mexico Deep Habitat Expe-
dition. We thank M. Wicksten, J. MacEachran, and R. A. Martin for sharing their expertise
on scyliorhinid sharks. We also thank F. M. Bayer, S. D. Cairns, and T. Coffer of Smithso-
nian NMNH for identifying and curating octocoral specimens and D. Opresko for identifying
black corals specimens. Special thanks to J. Reed of Harbor Branch Oceanographic Institu-
tion and M. Wicksten of the Texas Cooperative Wildlife Collection at Texas A&M University
for octocoral data. Finally, we express our gratitude to the editors and three anonymous re-
Figure 3. Frequency of Callogorgia americana delta colonies in Mississippi Canyon with cat-
shark egg cases attached.
viewers. NOAA Office of Ocean Exploration provided funding for the research through grant
number NA03OAR4600118.
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A: (P.E.) Harte Research Institute, Texas A&M University-Corpus Christi, 6300
Ocean Dr., Unit 5869, Corpus Christi, Texas 78421. (J.W.) Oceana, 175 South Franklin Street,
Suite 418, Juneau, Alaska 99801. C A: (P.E.) E-mail: <peter.etnoyer@>.
... Water temperature has been shown to affect the incubation time of elasmobranch eggs (Hume, 2019) and it is possible that females deposit their egg cases in shallower water to benefit from warmer summer water temperatures, which may decrease the overall incubation period (Benjamins et al., 2021). (Hitz, 1964;Etnoyer & Warrenchuk, 2007;Hoff, 2008;Love et al., 2008;Quattrini, Partyka & Ross, 2009;Hoff, 2010;Hunt, Dhugal & Raushan, 2011;Treude et al., 2011;Serra-Pereira et al., 2014;Henry et al., 2016;Hoff, 2016), which are located on seamounts and shelf breaks close to deeper water. It has been suggested that these characteristics provide favourable conditions of egg case ventilation for successful incubation (Treude et al., 2011). ...
... m in length' on the sea bed in the Red Rocks and Longay pMPA and egg case density was observed to be highest on the tops and flanks of these structures in ROV flights. These localized elevated areas may be selected to help deliver optimal current conditions for ventilation of egg cases for successful incubation in a similar way to oviparous deep-water sharks which are reported to preferentially deposit their egg cases on elevated colonies of octocorals and gorgonians (Etnoyer & Warrenchuk, 2007). ...
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... Despite this reduced sampling effort in those areas, a multitude of unique benthic ecosystems dwelling on continental shelves and margins around the world have been discovered in recent years (e.g., Bo et al., 2012;Cau et al., 2015;Grinyó et al., 2018). In these deep environments, hydrodynamic processes offer a high and relatively stable food supply that allows for dense aggregations of benthic suspension feeders to develop, ranging from crinoid beds (Fonseca et al., 2014) to sponge grounds and reefs (e.g., Enrichetti et al., 2020;Maldonado et al., 2015), gorgonian forests (e.g., Etnoyer & Warrenchuk, 2007), or impressive cold-water coral reef formations (Corbera et al., 2019;Orejas et al., 2009), among many others. ...
... Among echinoderms, the star sh Odontaster penicillatus was also found (Fig. 7b) predominantly inside gorgonian habitats. According to Mutschke and Mah (2009), the species features preference predation on sponges, and this feeding habit is also reported for other close species (Lawrence 2013 (Fig. 7d), similarly to reported in close species (Scyliorhinus canicula or Scyliorhinus rotifer) using coral reefs as nursery habitats (Etnoyer and Warrenchuk 2007;Bo et al. 2015). This hypothesis is further supported by observations of catshark eggs attached to colony branches during our samplings. ...
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We present the outcomes of the first deep-sea remotely operated vehicle study of previously unexplored submarine canyon systems along the southwest Australian continental margin. This was conducted around: (1) the Bremer Marine Park; (2) the Mount Gabi seamount and nearby slope-shelf margin at the interface of the Southern and Indian oceans; with new information from (3) the Perth Canyon Marine Park located in the SE Indian Ocean. These canyons differ from many explored around the world in having no connectivity to continental river systems, thus little detrital input, with the Bremer systems and Mount Gabi facing the Southern Ocean which plays a key role in the global ocean circulation and climate systems. Such studies in the vast deep waters around the Australian continent are rare given the lack of local ROV capability available for research, thus little is known about these environments. Using the resources of the Schmidt Ocean Institute, we characterised the submarine topography from high-resolution bathymetric mapping, geology, physical and chemical oceanography, and provide an overview of these environments and fauna observed and collected. We show that these Southern Ocean-influenced environments incorporate South Indian Central Water, Subantarctic Mode Water, Antarctic Intermediate Water, and Upper and Lower Circumpolar Deep Water, with Antarctic Bottom Water present in deep water just south of the Bremer canyon systems. The richness in megabenthos, especially along the steep, rocky substrates of the canyon heads and walls around the Bremer canyon systems, contrasts to the comparatively depauperate fauna of the more northerly Perth Canyon. Various corals serve as important substrates for a range of other species and often exhibit particular faunal associations. Especially notable are distinct ecological zones including a bryozoan and sponge-dominated (animal) forest on the shelf edge, spectacular coral gardens along canyon margins, and the occurrence of solitary scleractinians well below the aragonite saturation horizon. Subfossil coral deposits were discovered across all three study areas, reflecting periodic waxing and waning of deep-water Scleractinia throughout this southwest region. Extensive pre-modern assemblages at Mount Gabi contrast markedly with the sparse populations of living species and suggest that it might have once been a major coral ‘hotspot’, or whether they reflect long-term coral aggregations is yet to be determined. Nevertheless, stark differences in both living and past coral distribution patterns across our study sites point to at least localised fluctuations in Southern Ocean-derived nutrient and/or oxygen supplies to these deep-sea communities.
... Kyne and Simpfendorfer (2010) noted ambiguity over what qualifies as nursery habitat for sharks, some studies identifying vast coastal areas or extensive shallow slope waters that overlap with older stages rather than a specific separate location for young fish, i.e. a dedicated nursery. For example, in terms of deepwater species, Etnoyer and Warrenchuk (2007) observed catshark egg cases to be associated with deepwater corals, but it was unclear whether the coral areas constituted a separate nursery or part of a general distribution of the species with all stages present. As well, Treudel et al. (2011) and Salinas-de-León (2018) suggested that given the presence of abundant catshark and skate egg cases, cold-seep ecosystems and hydrothermal vents may serve as nurseries for deepwater elasmobranchs but were also unable to verify that those locations comprise dedicated nurseries. ...
Context Shark pupping and nursery grounds are essential habitats, yet these areas are undocumented for deepwater species. Young juveniles of black dogfish (Centroscyllium fabricii) were found to be dominant in the Laurentian Channel, prompting an analysis of their distribution in Canadian waters of the Northwest Atlantic. Aims This study documents patterns of distribution by sex and life stage for black dogfish in shelf and slope waters of Canada. Methods Over 40 years of trawl survey data from the Canadian Department of Fisheries and Oceans (DFO) Newfoundland and Labrador Region was analysed to document patterns of distribution of black dogfish by sex and life stage. Key results Free-swimming neonates were found in the Laurentian Channel, along with adult females, including some with pups, indicating that the Laurentian Channel is the pupping grounds for this species. Small black dogfish, highly abundant in the Channel, is largely absent in slope waters, indicating that the Channel is the nursery ground for black dogfish in Canada. Conclusions As they grows, black dogfish individuals undergo a multi-year distributional shift extending over ∼4000 km, originating in the Laurentian Channel out to slope waters, with the largest fish being found furthest from the Channel. No other deep demersal chondrichthyans are known to undergo a progressive migration as they grow, more akin to pelagic sharks where separate pupping–nursery grounds and long-distance migrations are commonly documented. Implications The segregation by life stages shown in the present study differs from previously reported distribution patterns of black dogfish in Greenland and Iceland. Given warm and stable ambient temperatures in the Channel, similar to slope waters, black dogfish is stenothermal, maintaining a narrow thermal profile throughout its life. Identifying the essential habitats of pupping and nursery grounds is crucial to the management and conservation of this species.
... The genus Callogorgia Gray, 1858 (Alcyonacea: Primnoidae) is considered a habitat-forming coral due to its abundance and morphology, which create habitats for a diverse array of fauna in the Gulf of Mexico and the northeast Pacific Ocean (Etnoyer and Morgan, 2003;Etnoyer and Warrenchuk, 2007;Quattrini et al., 2013). Several records of the associations of Callogorgia spp. ...
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The habitat formed by the Callogorgia species, with their abundance and colony sizes, provides an important refuge for a variety of brittle stars which are recognized as the epibionts of octocorals in both shallow and deep environments. In such a relationship, ophiurans benefit directly from being elevated because they facilitate their feeding by suspension, while octocorals do not seem to benefit or be harmed. During three different expeditions developed in the Colombian Pacific from 2012 to 2013 and in the Caribbean Sea during 1998 and 2012 by the INVEMAR - Marine and Coastal Research institute, different samplings were carried out on soft bottoms through trawls with an epibenthic net. For the Pacific Ocean, 33 fragments of the octocoral Callogorgia cf. galapagensis Cairns, 2018 with 178 specimens of the ophiuroid Astrodia cf. excavata (Lütken and Mortensen, 1899) were found in two stations at depths 530 and 668 m. Considering the abundance of A. cf excavata, other biological characters such as size, presence of mature gonads, and evidence of arm regeneration were also detailed. In contrast, in the Caribbean Sea, Callogorgia gracilis (Milne Edwards and Haime, 1857) was found with ophiuroids belonging to the genera Asteroschema and Ophiomitra. The octocoral Callogorgia americana (Cairns and Bayer, 2002) was also found, but without associated brittle stars. These findings constituted the first specific association reported in the Eastern Tropical Pacific, and new relationships for the Caribbean Sea. This further reflected a possible specific association between the Callogorgia and Astrodia species that needed to be further explored. Thus, the Callogorgia species and the brittle star A. cf. excavata represented new records for the Colombian Pacific Ocean and the southern Caribbean Sea.
... Photo credit: Bree Yednock oil from the corals, although some of the brittle stars died as a result of their efforts (Girard et al., 2016; Figure 5). Octocoral colonies serve as nursery grounds for some fish species, including the chain catshark (Etnoyer and Warrenchuk, 2007) and Sebastes spp. (Baillon et al., 2012), as well as octopus species (Shea et al., 2018). ...
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Gulf of Mexico (GOM) ecosystems are interconnected by numerous physical and biological processes. After the Deepwater Horizon (DWH) disaster, these ecological processes facilitated dispersal of oil-spill toxicants or were damaged and broken. A considerable portion of post-DWH research focused on higher levels of biological organization (i.e., populations, communities, and ecosystems) spanning at least four environments (onshore, coastal, open ocean, and deep benthos). Damage wrought by the oil spill and mitigation efforts varied considerably across ecosystems. Whereas all systems show prolonged impacts because of cascading effects that impacted functional connections within and between communities, deep-sea and mesopelagic environments were particularly hard hit and have shown less resilience than shallow environments. In some environments, such as marshes or the deep-sea benthos, products from the spill are still biologically accessible. Some shallow ecosystems show signs of recovery, and populations of some species show resilience; however, a return to a “pre-spill” state is questionable. Importantly, habitats in which large amounts of energy flow through the ecosystem (marshes, coastal regions) recovered more quickly than low energy habitats (deep-sea benthos). Functional interactions between Gulf of Mexico systems are more complex and widespread than generally recognized. Moreover, ecosystems in the Gulf are subject to multiple stressors that can combine to impart greater, and less predictable, impacts. To help mitigate the effects of future insults, we identified four salient areas of research that should be addressed for each of the major environments within the GOM: establishing monitoring systems; quantifying coupling between GOM ecosystems; developing criteria for assessing the “vulnerability” and “resilience” of species, communities, and ecosystems; and developing holistic predictive modeling.
... The exploration of slopes and canyons accelerates the ongoing discovery of new functions and services, such as the emerging role of demersal and deepwater fish on continental slopes in transferring carbon from the deep scattering layer to greater depths in the ocean (Trueman and others, 2014;Gallo, 2018;Vieira and others, 2019). Nursery support functions have been found on slopes off the coast of Costa Rica for octopus at 3,000 m and fish eggs attached within xenophyophores (giant protozoans) (Levin and Rouse, 2019), for elasmobranch egg cases associated with methane seeps on slopes off Chile and the Mediterranean (Treude and others, 2011) and in gorgonian coral fields (Etnoyer and Warrenchuk, 2007). Physical processes within canyons contribute to the upwelling of nutrients to the shelf and the offshore transport of shelf productivity to deeper waters (Fernandez-Arcaya and others, 2017). ...
... Oviparous elasmobranchs produce large collagen egg cases containing yolk and a developing embryo. Literature suggests oviparous elasmobranchs spawn in localised nursery grounds (Hitz 1964;Etnoyer and Warrenchuk 2007;Hoff 2008Hoff , 2010Love et al. 2008;Treude et al. 2011;Sabata and Clò 2013). Egg cases are deposited on the seafloor, sometimes attached to benthic flora and fauna, and the embryos develop without parental care (Hamlett and Koob 1999;Love et al. 2008). ...
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Since 2014 elasmobranch egg cases that are washed up on the Dutch North Sea beaches can be registered by beachcombers using the Great Eggcase Hunt database. For this study, individuals often registering multiple egg cases were asked to send these to the authors for a predation study. After disposing of heavily damaged (over 50% gone) egg cases, a total of 736 egg cases of six different elasmobranch species (Raja microocellata, Raja brachyura, Raja montagui, Raja undulata, Raja clavata, Scyliorhinus canicula) were examined. All egg cases were scored for number of predation marks, the condition of the egg case and status of the hatching slit. The shape of the predation marks was classified into five types: parabolic, circular, elongated, scratched and irregular shaped and it was noted whether or not the boreholes were complete. Predation rate across species was 14.4%. Results show no discernible difference in proportion of egg cases with any kind of predation mark between species, which is beneficial for future analysis and conservation strategies, as the same approach can be used for all species. The presence of multiple incomplete predation marks on 38% of predated egg cases shows evidence of site selection by the predator. This site selection, as well as borehole shape and diameter found points to gastropods and octopus as potential predators.
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Deep-sea corals are important benthic inhabitants that support the biodiversity and function of the wider faunal community; however, their taxonomy is underdeveloped and their accurate identification is often difficult. In our study, we investigated the utility of a superextended (>3000 bp) barcode and explored the effectiveness of various molecular species delimitation techniques with an aim to put upper and lower bounds on the estimated number of calcaxonian species in Irish waters. We collected 112 calcaxonians (70 Keratoisididae, 22 Primnoidae, 20 Chrysogorgiidae) and one chelidonisid from the Irish continental slope and sequenced a 3390 bp DNA barcode comprising four mitochondrial regions (mtMutS, COI + igr1, 16S rRNA-ND2, and igr4), recovering 38 haplotypes. Individuals that shared a haplotype were often morphologically distinct, and we thus undertook detailed morphological work, including SEM of sclerites, on one representative of each morphotype within each haplotype. GMYC, bGMYC, and mPTP returned incongruent estimates of species numbers. In total, there are between 25 and 40 species, although no definitive number could be assigned, primarily due to poorly defined keratoisidid species boundaries. As expected, the superextended barcode provided greater discrimination power than single markers; bGMYC appeared to be the most effective delimiter. Among the identified species were Chelidonisis aurantiaca, collected deeper than previously known at 1507 m, and Calyptrophora clinata, recorded for the second time from the Northeast Atlantic. A full understanding of the diversity and distribution of calcaxonians requires substantial taxonomic work, but we highlight the Irish continental slope as harbouring significant diversity.
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Reproduction, embryonic development, and general biology are described from more than 100 chain dogfish, Scyliorhinus retifer, a common catshark found on the continental slopes of the western North Atlantic. Females and males reached sexual maturity at about 520 mm TL and 500 mm TL, respectively. Follicles are ovulated in pairs when they reach 18 mm diameter. In the laboratory, females lay one egg pair at approx. 15.3 d intervals, attaching the eggs to bottom structures. Development at 11.7-12.8 C in artificial seawater averaged 256 d (±SD 8 d, n = 62) to hatching. Embryos averaged 106 mm (±SD 5 mm, n = 63) at hatching. In the wild, juveniles are often found in large numbers over smooth bottoms. Adults congregate in areas with upright structures which females use for egg attachment. Chain dogfish feed on squid, small bony fishes, polychaete worms, and crustaceans.
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Abstract Mid-nineteenth century naturalists once considered the abyssal seafloor a barren, lifeless plain akin to terrestrial deserts. However, in 1872, the H.M.S. Challenger began a four year expedition of the oceans, collecting specimens and revealing for the first time the extensive marine life found below 200 meters. Subsequent deep-sea exploration has discovered that life extends to the hadal depths of the oceans (greater than 10,000m), and that these profound waters are home to a diverse assemblage uniquely adapted to their extreme environment. Few people know,of the vast extent of dep sea corals in temperate waters of the US when, in fact, these corals extend over a much,greater area of the US exclusive economic,zone than the much,more familiar tropical coral reefs. Habitat-forming deep-sea corals, octocorals, hexacorals, and hydrocorals in the Phylum Cnidaria,
Of the three species of Callogorgia now recognized in the western Atlantic, one that had been misidentified as Callogorgia verticillata, an eastern Atlantic and Mediterranean species, is now established as a new species in its own right, comprised of two subspecies. A second, C. gracilis, originally reported from Guadeloupe, is redescribed on the basis of type material and additional specimens. A third species, C. linguimaris, is described as new. Records of all three species preserved in the collection of the National Museum of Natural History, Washington, D.C., are reported, and the species are illustrated by scanning electron micrography.
Few in situ observations have been made of deepwater corals and, therefore, little is known about their biology or ecological significance. Deepwater corals (Primnoa spp.) were observed from a manned submersible at 11 sites in the Gulf of Alaska from 1989 to 1997 at depths of 161–365 m. We identified 10 megafaunal groups that associate with Primnoa to feed on the coral, use the coral branches for suspension feeding, or for protection. Predators on Primnoa polyps included sea stars, nudibranchs, and snails. Sea stars were the main predators, consuming 45% and 34% of the polyps at two sites. Suspension-feeders included crinoids, basket stars, anemones, and sponges. Most suspension-feeders observed at depths >300 m were associated with Primnoa. Protection seekers included rockfish, crab, and shrimp. Six rockfish species were either beneath, among, or above Primnoa. Shrimp were among the polyps, and a pair of mating king crabs were beneath Primnoa. These observations indicate Primnoa are important components of the deepwater ecosystem and removal of these slow-growing corals could cause long-term changes in associated megafauna.