Skates are a diverse group within the chondrichthyans and comprise a large component of the bycat... more Skates are a diverse group within the chondrichthyans and comprise a large component of the bycatch in many demersal fisheries. The distribution of the Deepsea Skate, Bathyraja abyssicola, is presently known to be limited to the northern temperate Pacific Ocean. We filmed B. abyssicola from a remote operated vehicle during surveys undertaken on a seamount located north of Darwin Island within the Galapagos Marine Reserve in 2015. This sighting represents the first record of B. abyssicola in the Galapagos Marine Reserve and the first record of the species from anywhere in the tropical eastern Pacific Ocean. The large range extension of this species to tropical low-latitude waters of the Pacific Ocean is a critical contribution to conservation biology of this poorly known species, especially since deepwater skates and rays are generally over-exploited. This new record also highlights our limited knowledge of unique deepwater ecosystems in general and those of the Galapagos Islands in particular.
The discovery of deep-sea hydrothermal vents in 1977 challenged our views of ecosystem functionin... more The discovery of deep-sea hydrothermal vents in 1977 challenged our views of ecosystem functioning and yet, the research conducted at these extreme and logistically challenging environments still continues to reveal unique biological processes. Here, we report for the first time, a unique behavior where the deep-sea skate, Bathyraja spinosissima, appears to be actively using the elevated temperature of a hydrothermal vent environment to naturally "incubate" developing egg-cases. We hypothesize that this behavior is directly targeted to accelerate embryo development time given that deep-sea skates have some of the longest egg incubation times reported for the animal kingdom. Similar egg incubating behavior, where eggs are incubated in volcanically heated nesting grounds, have been recorded in Cretaceous sauropod dinosaurs and the rare avian megapode. To our knowledge, this is the first time incubating behavior using a volcanic source is recorded for the marine environment.
⎯The blurred smooth lanternshark, Etmopterus bigelowi Shirai and Tachikawa, 1993 was recorded for... more ⎯The blurred smooth lanternshark, Etmopterus bigelowi Shirai and Tachikawa, 1993 was recorded for the first time from Indonesian waters based on two specimens collected from a deepwater shark fishery operated in the Flores Sea, eastern Indonesia. This is also the second confirmed record of Etmopterus species from this country.
The discovery of deep-sea hydrothermal vents in 1977 challenged our views of ecosystem functionin... more The discovery of deep-sea hydrothermal vents in 1977 challenged our views of ecosystem functioning and yet, the research conducted at these extreme and logistically challenging environments still continues to reveal unique biological processes. Here, we report for the first time, a unique behavior where the deep-sea skate, Bathyraja spinosissima, appears to be actively using the elevated temperature of a hydrothermal vent environment to naturally " incubate " developing egg-cases. We hypothesize that this behavior is directly targeted to accelerate embryo development time given that deep-sea skates have some of the longest egg incubation times reported for the animal kingdom. Similar egg incubating behavior, where eggs are incubated in volcanically heated nesting grounds, have been recorded in Cretaceous sauropod dinosaurs and the rare avian megapode. To our knowledge, this is the first time incubating behavior using a volcanic source is recorded for the marine environment. Despite being the largest biome, the deep sea remains the least explored ecosystem on earth 1,2. In 1977, the discovery of the first deep-sea ecosystems supported by hydrothermal vent fluid emissions at the Galapagos Rift, challenged our views of ecosystem functioning and fueled new hypotheses about how life on earth could have originated around these chemically reactive environments 3–5. Forty years later, we now know that hydrothermal vent ecosystems exist in every ocean basin, supporting rich communities and unique biological processes 6–9. Initially considered isolated patches of life within a barren deep-sea floor, we are beginning to appreciate that these ecosystems interact with the surrounding environment and influence global geochemical cycles 7,8. Most hydrothermal vent sites remain unexplored, and our understanding of the ecology of these ecosystems in most parts of the world remains limited. Furthermore, some of these chemosynthesis based ecosystems are now under threat from human activities and are targeted for exploitation of their mineral resources 10,11. Here, we report for the first time a unique behavior where the Pacific white skate Bathyraja spinosissima, one of the deepest living of all known skate species 12 , uses active hydrothermal vent fields as a natural incubator for their external egg-capsules. To the best of our knowledge and understanding, this is the first time this incubating behavior at an active hydrothermal vent field has been recorded for a species within the marine environment. The Galapagos Platform in the eastern tropical Pacific consists of 13 major volcanic islands and numerous seamounts that straddle the equator 13. To the north of the archipelago and parallel to the equator, the Galapagos Spreading Center (GSC) extends for over 1000 km west to east, crossing the Galapagos Marine Reserve north of Darwin Island (Fig. 1). Previous exploration of the area revealed the presence of active hydrothermal vents,
A new species of chimaeroid, Hyd rolagus mccosker i sp. nov., is described from the Galápag os Is... more A new species of chimaeroid, Hyd rolagus mccosker i sp. nov., is described from the Galápag os Islands. This species represents the second member of the family Chimaeridae known from the eastern equatorial Pacific. It can b e distinguis hed from its congeners by a combination of the following characters: small head with short, blunt snout; preopercu lar and oral lateral line canals branching from the same node off the infraorbital canal and sharing a short common b ranch; dorsum medium brown with numerous narrow, shar ply delineated circular and elongate white blotches; ventrum white to tan with extremely fine brown mottl ing. The species is compared to Hyd rolagus n ovaezealandiae and Hyd rolagus colliei , the most similar congeners in color pattern and morphology.
Size at maturity, fecundity, and reproductive periodicity were estimated for the spotted ratWsh, ... more Size at maturity, fecundity, and reproductive periodicity were estimated for the spotted ratWsh, Hydrolagus colliei (Lay and Bennett, 1839), oV the coast of California, Oregon, and Washington. Maximum body size and size at median maturity were greater for females than males. Skeletal muscle concentrations of the steroid hormones testosterone (T) and estradiol (E 2 ) predicted similar, but slightly smaller sizes at maturity than the morphological criterion. Stage of maturity for males was estimated identically using internal organs or external secondary sexual characters, thus allowing non-lethal maturity assessments. Size at median maturity was greater north of Point Conception for females, and north of Cape Mendocino for males. Peak parturition occurred from May to October, with increased concentrations of E 2 in skeletal muscle of females correlating with ovarian recrudescence during November to February. No signiWcant seasonal trends in female T were apparent, but mean female 11-ketotestosterone (11KT) was 300% greater in April than any other month during the parturition season. There was a marginal evidence for increased number and size of ova with maternal size. Extrapolation of the hypothesized 6 to 8-month egg-laying season to observed mean parturition rates of captive specimens yielded an estimated annual fecundity of 19.5-28.9 egg cases. DiVerences in fecundity among higher taxonomic classiWcations of chondrichthyans were detected with chimaeriform Wshes more fecund than lamniform, myliobatiform, squaliform, and rhinobatiform Wshes, and less fecund than rajiform Wshes. Communicated by J.P. Grassle.
Marine protected areas (MPAs) can potentially alter food web dynamics by increasing the density o... more Marine protected areas (MPAs) can potentially alter food web dynamics by increasing the density of fishes within their borders. Such increases in the density of potential competitors can cause generalist predators to contract the scope of their diets. This study investigated the effects of increased conspecific fish density on the diets of gopher rockfish Sebastes carnatus at a 35 yr old MPA in Point Lobos, California, and at 4 newly established MPAs in Año Nuevo, Point Lobos, Piedras Blancas, and Point Buchon in central California. Analyses were conducted for 707 stomachs collected from 2007 to 2009. Diets did not differ inside versus outside the old Point Lobos MPA in terms of prey richness, evenness, composition, or gopher rockfish trophic level. However, fish outside the MPA had greater levels of individual specialization. No consistent differences in these metrics were observed inside versus outside the 4 new MPAs, although prey composition and evenness did differ significantly among geographic locations. Diets at Año Nuevo, the most northern and shallow location, consisted predominantly of Cancer spp. and porcelain crabs (Porcellanidae), while diets from southern, deeper locations were dominated by brittle stars (Ophiuroidea). The case study of the old Point Lobos MPA indicates that fish feeding ecology may not change in an MPA after several decades. Differences in prey observed among geographic locations suggest variation in the community composition among central California’s new MPAs, which may influence the effect of each MPA on food web dynamics over time.
A new species of chimaera, Hydrolagus melanophasma sp. nov. (Chimaeridae), is described from the ... more A new species of chimaera, Hydrolagus melanophasma sp. nov. (Chimaeridae), is described from the eastern North Pacific. It is distinct from other eastern Pacific chimaeroids by the following characteristics: a large slightly curved dorsal fin spine extending beyond dorsal fin apex, a long second dorsal fin of uniform height throughout, large pectoral fins extending beyond the pelvic fin insertion when laid flat, trifid claspers forked for approximately one-quarter the total clasper length and a uniform black coloration throughout. The new species is compared to other eastern Pacific members of the genus Hydrolagus including H. alphus, H. colliei, H. macrophthalmus, and H. mccoskeri. Remote Operated Vehicle (ROV) video footage has identified and documented Hydrolagus melanophasma from the Gulf of California. ROV observations suggest that individuals typically occur over soft-bottom habitats or cobble patches with minimal vertical relief. This is in contrast to other eastern Pacific Hydrolagus species that tend to occur in areas of high rocky relief. The known distribution of this new species at present extends from southern California, U.S.A., along the Pacific coast of Baja California, Mexico, and into the Gulf of California.
Hydrolagus africanus (Gilchrist, 1922) is a little-known chimaeroid species, originally described... more Hydrolagus africanus (Gilchrist, 1922) is a little-known chimaeroid species, originally described from the KwaZulu-
Natal coast of South Africa, with a range spanning the western Indian Ocean from Kenya, south to Mozambique and South Africa, and extending into the south-eastern Atlantic to Namibia. This species is characterised by a lateral
patch of denticles on the male prepelvic tenacula, a second dorsal fin slightly indented in the centre, a long, curved
dorsal spine equal to or sometimes exceeding the height of the first dorsal fin, and a uniform light brown body with
no distinctive markings or patterns and slightly darker brown fins. To clarify the taxonomic status of H. africanus,
we examined and compared specimens from throughout its range in southern Africa. Because the syntypes of H. africanus are lost, we designate a neotype and redescribe the species based on the neotype and additional southern African specimens. In addition,
A new species of chimaera, Hydrolagus melanophasma sp. nov. (Chimaeridae), is described from the ... more A new species of chimaera, Hydrolagus melanophasma sp. nov. (Chimaeridae), is described from the eastern North Pacific. It is distinct from other eastern Pacific chimaeroids by the following characteristics: a large slightly curved dorsal fin spine extending beyond dorsal fin apex, a long second dorsal fin of uniform height throughout, large pectoral fins extending beyond the pelvic fin insertion when laid flat, trifid claspers forked for approximately one-quarter the total clasper length and a uniform black coloration throughout. The new species is compared to other eastern Pacific members of the genus Hydrolagus including H. alphus, H. colliei, H. macrophthalmus, and H. mccoskeri. Remote Operated Vehicle (ROV) video footage has identified and documented Hydrolagus melanophasma from the Gulf of California. ROV observations suggest that individuals typically occur over soft-bottom habitats or cobble patches with minimal vertical relief. This is in contrast to other eastern Pacific Hydrolagus species that tend to occur in areas of high rocky relief. The known distribution of this new species at present extends from southern California, U.S.A., along the Pacific coast of Baja California, Mexico, and into the Gulf of California.
A new arhynchobatid skate, Notoraja martinezi, sp. nov., is described from four specimens collect... more A new arhynchobatid skate, Notoraja martinezi, sp. nov., is described from four specimens collected from the eastern Central Pacific from Costa Rica to Ecuador and between depths of 1256–1472 m. The new species is placed in the genus Notoraja based on the long and flexible rostrum and its proportionally long tail with respect to total length. This species is distinct from its congeners in the Western Pacific by the straight margins of its rostrum, long anterior lobes of pelvic fins, and its abundant and very well developed caudal thorns.
A new species of torpedo ray, Torpedo formosa, sp. nov., is described from specimens collected fr... more A new species of torpedo ray, Torpedo formosa, sp. nov., is described from specimens collected from northeastern Taiwan. The new species is placed in the subgenus Tetronarce based on a uniform purplish dorsal coloration and the absence of papillae around the spiracles. It is distinct from the sympatric T. tokionis, the only other known Torpedo (Tetronarce) species from the western North Pacific, by a disc that is wider than long, a shorter tail, a greater number of spiral valve turns, and its dorsal coloration. It has been misidentified as T. nobiliana, but is distinguished from it by having longer snout and spiracle lengths, a lower vertebral count, and a caudal fin height that is greater than the distance from the first dorsal origin to the caudal fin origin. This new species, at present, is known only from the northeast coast of Taiwan between Keelung and Suao primarily at depths of less than 300m.
The genus Cephaloscyllium Gill 1862 (Chondrichthyes, Carcharhiniformes, Scyliorhinidae), arguably... more The genus Cephaloscyllium Gill 1862 (Chondrichthyes, Carcharhiniformes, Scyliorhinidae), arguably has one representative species in the eastern Pacific, C. ventriosum (Garman 1880). While the C. ventriosum holotype was collected from central Chile, a dubious species, C. uter, (Jordan & Gilbert 1896) was described from California. Garman (1913) classified C. uter as a junior synonym of C. ventriosum. This study marks the first morphometric and meristic analysis comparing the holotype of C. ventriosum from Chile with California Cephaloscyllium specimens and presents a revision of the genus for the eastern Pacific. Based on a comparison of morphometric and meristic data from specimens collected from and Valparaiso, Chile, it is concluded that the California and Chilean Cephaloscyllium species represent a single, wide-ranging species, C. ventriosum.
A new species of chimaerid belonging to the genus Hydrolagus Gill, 1862 is described from two spe... more A new species of chimaerid belonging to the genus Hydrolagus Gill, 1862 is described from two specimens collected from the Galapagos Islands. This species was taken from depths ranging from 600 -900 m. Hydrolagus alphus sp. nov. is distinguished from other members of the genus by having proportionately large eyes, dark brown coloration with a noticeable white spot on lateral side, paired fins with a bluish hue and white distal margins, and second dorsal fin with dark anterior and posterior sections separated by a middle portion indented and completely white. This new species is compared to Hydrolagus macrophthalmus, the most similar congener and Hydrolagus mccoskerii the only other known species within this genus to occur in the eastern South Pacific.
The broadnose sevengill shark, Notorynchus cepedianus, a common coastal species in the eastern No... more The broadnose sevengill shark, Notorynchus cepedianus, a common coastal species in the eastern North Pacific, was sampled during routine capture and tagging operations conducted from 2005-2012. One hundred and thirty three biopsy samples were taken during these research operations in Willapa Bay, Washington and in San Francisco Bay, California. Genotypic data from seven polymorphic microsatellites (derived from the related sixgill shark, Hexanchus griseus) were used to describe N. cepedianus genetic diversity, population structure and relatedness. Diversity within N. cepedianus was found to be low to moderate with an average observed heterozygosity of 0.41, expected heterozygosity of 0.53, and an average of 5.1 alleles per microsatellite locus. There was no evidence of a recent population bottleneck based on genetic data. Analyses of genetic differences between the two sampled estuaries suggest two distinct populations with some genetic mixing of sharks sampled during 2005-2006. Relatedness within sampled populations was high, with percent relatedness among sharks caught in the same area indicating 42.30% first-order relative relationships (full or half siblings). Estuary-specific familial relationships suggest that management of N. cepedianus on the U.S. West Coast should incorporate stock-specific management goals to conserve this ecologically important predator. history traits but also because much remains unknown about their biology and ecology to develop informed conservation and fisheries management policy.
California Sea Grant College Program, May 29, 2007
Like sharks, skates are vulnerable to overexploitation because they reproduce relatively late in ... more Like sharks, skates are vulnerable to overexploitation because they reproduce relatively late in life and have relatively low reproductive output. Beyond this, not much is known about the basic biology of many native skate species. The goal of this project was to fill the gap by collecting skate age, growth, diet and reproductive data.
Egg cases for 10 of 11 valid skate species known to occur in the eastern North Pacific (ENP) were... more Egg cases for 10 of 11 valid skate species known to occur in the eastern North Pacific (ENP) were identified and are here described. In addition, egg cases of two unidentified skate species were collected from very deep water off central and southern California, USA. Examples of egg cases for all species, except for two, were removed in utero in order to confirm their species specific identification. The egg cases of seven skate species, including egg cases from the two unidentified species, have not previously been described or illustrated from this region. Previous attempts to identify skate egg cases with their associated species have been inadequate. The ENP skate egg cases can broadly be classified into two main groups: those with broad lateral keels (> 10% maximum egg case width) and those with narrow lateral keels (< 10% maximum egg case width). Egg cases in the former group (with broad lateral keels) generally have a finely striated surface texture that is smooth to the touch. Those in the latter group (with narrow lateral keels), with one exception, tend to have a coarse surface texture, often with prickles, and are rough to the touch. A revised key to the skate egg cases from the ENP is provided.
This study provides the first published age estimates for the roughtail skate, Bathyraja trachura... more This study provides the first published age estimates for the roughtail skate, Bathyraja trachura. Age and growth characteristics of B. trachura, a poorly-known deepwater species, were determined from samples collected along the continental slope of the contiguous western United States. A new maximum size was established at 91.0 cm TL. Age was determined using a traditional structure (vertebral thin sections) with widespread application on multiple skate species and a non-lethal structure (caudal thorns) recently used for age analysis on skate species. Caudal thorns were determined not to be a useful ageing structure for this species based on poor precision and significantly lower age estimates when compared to age estimates from vertebral thin sections. The best model for describing growth of B. trachura was the two parameter VBGF, assuming annual vertebral band deposition and using length-at-age data. Although females grew slower and reached a larger maximum size than males, their growth was not statistically different (ARSS; P = 0.90); therefore, data were pooled (L ¥ = 99.38, k = 0.09). Annual band deposition was found to be a reasonable assumption for this species, but has yet to be validated. The maximum age estimated for B. trachura was 20 years for males and 17 years for females using vertebral thin sections.
Skates are a diverse group within the chondrichthyans and comprise a large component of the bycat... more Skates are a diverse group within the chondrichthyans and comprise a large component of the bycatch in many demersal fisheries. The distribution of the Deepsea Skate, Bathyraja abyssicola, is presently known to be limited to the northern temperate Pacific Ocean. We filmed B. abyssicola from a remote operated vehicle during surveys undertaken on a seamount located north of Darwin Island within the Galapagos Marine Reserve in 2015. This sighting represents the first record of B. abyssicola in the Galapagos Marine Reserve and the first record of the species from anywhere in the tropical eastern Pacific Ocean. The large range extension of this species to tropical low-latitude waters of the Pacific Ocean is a critical contribution to conservation biology of this poorly known species, especially since deepwater skates and rays are generally over-exploited. This new record also highlights our limited knowledge of unique deepwater ecosystems in general and those of the Galapagos Islands in particular.
The discovery of deep-sea hydrothermal vents in 1977 challenged our views of ecosystem functionin... more The discovery of deep-sea hydrothermal vents in 1977 challenged our views of ecosystem functioning and yet, the research conducted at these extreme and logistically challenging environments still continues to reveal unique biological processes. Here, we report for the first time, a unique behavior where the deep-sea skate, Bathyraja spinosissima, appears to be actively using the elevated temperature of a hydrothermal vent environment to naturally "incubate" developing egg-cases. We hypothesize that this behavior is directly targeted to accelerate embryo development time given that deep-sea skates have some of the longest egg incubation times reported for the animal kingdom. Similar egg incubating behavior, where eggs are incubated in volcanically heated nesting grounds, have been recorded in Cretaceous sauropod dinosaurs and the rare avian megapode. To our knowledge, this is the first time incubating behavior using a volcanic source is recorded for the marine environment.
⎯The blurred smooth lanternshark, Etmopterus bigelowi Shirai and Tachikawa, 1993 was recorded for... more ⎯The blurred smooth lanternshark, Etmopterus bigelowi Shirai and Tachikawa, 1993 was recorded for the first time from Indonesian waters based on two specimens collected from a deepwater shark fishery operated in the Flores Sea, eastern Indonesia. This is also the second confirmed record of Etmopterus species from this country.
The discovery of deep-sea hydrothermal vents in 1977 challenged our views of ecosystem functionin... more The discovery of deep-sea hydrothermal vents in 1977 challenged our views of ecosystem functioning and yet, the research conducted at these extreme and logistically challenging environments still continues to reveal unique biological processes. Here, we report for the first time, a unique behavior where the deep-sea skate, Bathyraja spinosissima, appears to be actively using the elevated temperature of a hydrothermal vent environment to naturally " incubate " developing egg-cases. We hypothesize that this behavior is directly targeted to accelerate embryo development time given that deep-sea skates have some of the longest egg incubation times reported for the animal kingdom. Similar egg incubating behavior, where eggs are incubated in volcanically heated nesting grounds, have been recorded in Cretaceous sauropod dinosaurs and the rare avian megapode. To our knowledge, this is the first time incubating behavior using a volcanic source is recorded for the marine environment. Despite being the largest biome, the deep sea remains the least explored ecosystem on earth 1,2. In 1977, the discovery of the first deep-sea ecosystems supported by hydrothermal vent fluid emissions at the Galapagos Rift, challenged our views of ecosystem functioning and fueled new hypotheses about how life on earth could have originated around these chemically reactive environments 3–5. Forty years later, we now know that hydrothermal vent ecosystems exist in every ocean basin, supporting rich communities and unique biological processes 6–9. Initially considered isolated patches of life within a barren deep-sea floor, we are beginning to appreciate that these ecosystems interact with the surrounding environment and influence global geochemical cycles 7,8. Most hydrothermal vent sites remain unexplored, and our understanding of the ecology of these ecosystems in most parts of the world remains limited. Furthermore, some of these chemosynthesis based ecosystems are now under threat from human activities and are targeted for exploitation of their mineral resources 10,11. Here, we report for the first time a unique behavior where the Pacific white skate Bathyraja spinosissima, one of the deepest living of all known skate species 12 , uses active hydrothermal vent fields as a natural incubator for their external egg-capsules. To the best of our knowledge and understanding, this is the first time this incubating behavior at an active hydrothermal vent field has been recorded for a species within the marine environment. The Galapagos Platform in the eastern tropical Pacific consists of 13 major volcanic islands and numerous seamounts that straddle the equator 13. To the north of the archipelago and parallel to the equator, the Galapagos Spreading Center (GSC) extends for over 1000 km west to east, crossing the Galapagos Marine Reserve north of Darwin Island (Fig. 1). Previous exploration of the area revealed the presence of active hydrothermal vents,
A new species of chimaeroid, Hyd rolagus mccosker i sp. nov., is described from the Galápag os Is... more A new species of chimaeroid, Hyd rolagus mccosker i sp. nov., is described from the Galápag os Islands. This species represents the second member of the family Chimaeridae known from the eastern equatorial Pacific. It can b e distinguis hed from its congeners by a combination of the following characters: small head with short, blunt snout; preopercu lar and oral lateral line canals branching from the same node off the infraorbital canal and sharing a short common b ranch; dorsum medium brown with numerous narrow, shar ply delineated circular and elongate white blotches; ventrum white to tan with extremely fine brown mottl ing. The species is compared to Hyd rolagus n ovaezealandiae and Hyd rolagus colliei , the most similar congeners in color pattern and morphology.
Size at maturity, fecundity, and reproductive periodicity were estimated for the spotted ratWsh, ... more Size at maturity, fecundity, and reproductive periodicity were estimated for the spotted ratWsh, Hydrolagus colliei (Lay and Bennett, 1839), oV the coast of California, Oregon, and Washington. Maximum body size and size at median maturity were greater for females than males. Skeletal muscle concentrations of the steroid hormones testosterone (T) and estradiol (E 2 ) predicted similar, but slightly smaller sizes at maturity than the morphological criterion. Stage of maturity for males was estimated identically using internal organs or external secondary sexual characters, thus allowing non-lethal maturity assessments. Size at median maturity was greater north of Point Conception for females, and north of Cape Mendocino for males. Peak parturition occurred from May to October, with increased concentrations of E 2 in skeletal muscle of females correlating with ovarian recrudescence during November to February. No signiWcant seasonal trends in female T were apparent, but mean female 11-ketotestosterone (11KT) was 300% greater in April than any other month during the parturition season. There was a marginal evidence for increased number and size of ova with maternal size. Extrapolation of the hypothesized 6 to 8-month egg-laying season to observed mean parturition rates of captive specimens yielded an estimated annual fecundity of 19.5-28.9 egg cases. DiVerences in fecundity among higher taxonomic classiWcations of chondrichthyans were detected with chimaeriform Wshes more fecund than lamniform, myliobatiform, squaliform, and rhinobatiform Wshes, and less fecund than rajiform Wshes. Communicated by J.P. Grassle.
Marine protected areas (MPAs) can potentially alter food web dynamics by increasing the density o... more Marine protected areas (MPAs) can potentially alter food web dynamics by increasing the density of fishes within their borders. Such increases in the density of potential competitors can cause generalist predators to contract the scope of their diets. This study investigated the effects of increased conspecific fish density on the diets of gopher rockfish Sebastes carnatus at a 35 yr old MPA in Point Lobos, California, and at 4 newly established MPAs in Año Nuevo, Point Lobos, Piedras Blancas, and Point Buchon in central California. Analyses were conducted for 707 stomachs collected from 2007 to 2009. Diets did not differ inside versus outside the old Point Lobos MPA in terms of prey richness, evenness, composition, or gopher rockfish trophic level. However, fish outside the MPA had greater levels of individual specialization. No consistent differences in these metrics were observed inside versus outside the 4 new MPAs, although prey composition and evenness did differ significantly among geographic locations. Diets at Año Nuevo, the most northern and shallow location, consisted predominantly of Cancer spp. and porcelain crabs (Porcellanidae), while diets from southern, deeper locations were dominated by brittle stars (Ophiuroidea). The case study of the old Point Lobos MPA indicates that fish feeding ecology may not change in an MPA after several decades. Differences in prey observed among geographic locations suggest variation in the community composition among central California’s new MPAs, which may influence the effect of each MPA on food web dynamics over time.
A new species of chimaera, Hydrolagus melanophasma sp. nov. (Chimaeridae), is described from the ... more A new species of chimaera, Hydrolagus melanophasma sp. nov. (Chimaeridae), is described from the eastern North Pacific. It is distinct from other eastern Pacific chimaeroids by the following characteristics: a large slightly curved dorsal fin spine extending beyond dorsal fin apex, a long second dorsal fin of uniform height throughout, large pectoral fins extending beyond the pelvic fin insertion when laid flat, trifid claspers forked for approximately one-quarter the total clasper length and a uniform black coloration throughout. The new species is compared to other eastern Pacific members of the genus Hydrolagus including H. alphus, H. colliei, H. macrophthalmus, and H. mccoskeri. Remote Operated Vehicle (ROV) video footage has identified and documented Hydrolagus melanophasma from the Gulf of California. ROV observations suggest that individuals typically occur over soft-bottom habitats or cobble patches with minimal vertical relief. This is in contrast to other eastern Pacific Hydrolagus species that tend to occur in areas of high rocky relief. The known distribution of this new species at present extends from southern California, U.S.A., along the Pacific coast of Baja California, Mexico, and into the Gulf of California.
Hydrolagus africanus (Gilchrist, 1922) is a little-known chimaeroid species, originally described... more Hydrolagus africanus (Gilchrist, 1922) is a little-known chimaeroid species, originally described from the KwaZulu-
Natal coast of South Africa, with a range spanning the western Indian Ocean from Kenya, south to Mozambique and South Africa, and extending into the south-eastern Atlantic to Namibia. This species is characterised by a lateral
patch of denticles on the male prepelvic tenacula, a second dorsal fin slightly indented in the centre, a long, curved
dorsal spine equal to or sometimes exceeding the height of the first dorsal fin, and a uniform light brown body with
no distinctive markings or patterns and slightly darker brown fins. To clarify the taxonomic status of H. africanus,
we examined and compared specimens from throughout its range in southern Africa. Because the syntypes of H. africanus are lost, we designate a neotype and redescribe the species based on the neotype and additional southern African specimens. In addition,
A new species of chimaera, Hydrolagus melanophasma sp. nov. (Chimaeridae), is described from the ... more A new species of chimaera, Hydrolagus melanophasma sp. nov. (Chimaeridae), is described from the eastern North Pacific. It is distinct from other eastern Pacific chimaeroids by the following characteristics: a large slightly curved dorsal fin spine extending beyond dorsal fin apex, a long second dorsal fin of uniform height throughout, large pectoral fins extending beyond the pelvic fin insertion when laid flat, trifid claspers forked for approximately one-quarter the total clasper length and a uniform black coloration throughout. The new species is compared to other eastern Pacific members of the genus Hydrolagus including H. alphus, H. colliei, H. macrophthalmus, and H. mccoskeri. Remote Operated Vehicle (ROV) video footage has identified and documented Hydrolagus melanophasma from the Gulf of California. ROV observations suggest that individuals typically occur over soft-bottom habitats or cobble patches with minimal vertical relief. This is in contrast to other eastern Pacific Hydrolagus species that tend to occur in areas of high rocky relief. The known distribution of this new species at present extends from southern California, U.S.A., along the Pacific coast of Baja California, Mexico, and into the Gulf of California.
A new arhynchobatid skate, Notoraja martinezi, sp. nov., is described from four specimens collect... more A new arhynchobatid skate, Notoraja martinezi, sp. nov., is described from four specimens collected from the eastern Central Pacific from Costa Rica to Ecuador and between depths of 1256–1472 m. The new species is placed in the genus Notoraja based on the long and flexible rostrum and its proportionally long tail with respect to total length. This species is distinct from its congeners in the Western Pacific by the straight margins of its rostrum, long anterior lobes of pelvic fins, and its abundant and very well developed caudal thorns.
A new species of torpedo ray, Torpedo formosa, sp. nov., is described from specimens collected fr... more A new species of torpedo ray, Torpedo formosa, sp. nov., is described from specimens collected from northeastern Taiwan. The new species is placed in the subgenus Tetronarce based on a uniform purplish dorsal coloration and the absence of papillae around the spiracles. It is distinct from the sympatric T. tokionis, the only other known Torpedo (Tetronarce) species from the western North Pacific, by a disc that is wider than long, a shorter tail, a greater number of spiral valve turns, and its dorsal coloration. It has been misidentified as T. nobiliana, but is distinguished from it by having longer snout and spiracle lengths, a lower vertebral count, and a caudal fin height that is greater than the distance from the first dorsal origin to the caudal fin origin. This new species, at present, is known only from the northeast coast of Taiwan between Keelung and Suao primarily at depths of less than 300m.
The genus Cephaloscyllium Gill 1862 (Chondrichthyes, Carcharhiniformes, Scyliorhinidae), arguably... more The genus Cephaloscyllium Gill 1862 (Chondrichthyes, Carcharhiniformes, Scyliorhinidae), arguably has one representative species in the eastern Pacific, C. ventriosum (Garman 1880). While the C. ventriosum holotype was collected from central Chile, a dubious species, C. uter, (Jordan & Gilbert 1896) was described from California. Garman (1913) classified C. uter as a junior synonym of C. ventriosum. This study marks the first morphometric and meristic analysis comparing the holotype of C. ventriosum from Chile with California Cephaloscyllium specimens and presents a revision of the genus for the eastern Pacific. Based on a comparison of morphometric and meristic data from specimens collected from and Valparaiso, Chile, it is concluded that the California and Chilean Cephaloscyllium species represent a single, wide-ranging species, C. ventriosum.
A new species of chimaerid belonging to the genus Hydrolagus Gill, 1862 is described from two spe... more A new species of chimaerid belonging to the genus Hydrolagus Gill, 1862 is described from two specimens collected from the Galapagos Islands. This species was taken from depths ranging from 600 -900 m. Hydrolagus alphus sp. nov. is distinguished from other members of the genus by having proportionately large eyes, dark brown coloration with a noticeable white spot on lateral side, paired fins with a bluish hue and white distal margins, and second dorsal fin with dark anterior and posterior sections separated by a middle portion indented and completely white. This new species is compared to Hydrolagus macrophthalmus, the most similar congener and Hydrolagus mccoskerii the only other known species within this genus to occur in the eastern South Pacific.
The broadnose sevengill shark, Notorynchus cepedianus, a common coastal species in the eastern No... more The broadnose sevengill shark, Notorynchus cepedianus, a common coastal species in the eastern North Pacific, was sampled during routine capture and tagging operations conducted from 2005-2012. One hundred and thirty three biopsy samples were taken during these research operations in Willapa Bay, Washington and in San Francisco Bay, California. Genotypic data from seven polymorphic microsatellites (derived from the related sixgill shark, Hexanchus griseus) were used to describe N. cepedianus genetic diversity, population structure and relatedness. Diversity within N. cepedianus was found to be low to moderate with an average observed heterozygosity of 0.41, expected heterozygosity of 0.53, and an average of 5.1 alleles per microsatellite locus. There was no evidence of a recent population bottleneck based on genetic data. Analyses of genetic differences between the two sampled estuaries suggest two distinct populations with some genetic mixing of sharks sampled during 2005-2006. Relatedness within sampled populations was high, with percent relatedness among sharks caught in the same area indicating 42.30% first-order relative relationships (full or half siblings). Estuary-specific familial relationships suggest that management of N. cepedianus on the U.S. West Coast should incorporate stock-specific management goals to conserve this ecologically important predator. history traits but also because much remains unknown about their biology and ecology to develop informed conservation and fisheries management policy.
California Sea Grant College Program, May 29, 2007
Like sharks, skates are vulnerable to overexploitation because they reproduce relatively late in ... more Like sharks, skates are vulnerable to overexploitation because they reproduce relatively late in life and have relatively low reproductive output. Beyond this, not much is known about the basic biology of many native skate species. The goal of this project was to fill the gap by collecting skate age, growth, diet and reproductive data.
Egg cases for 10 of 11 valid skate species known to occur in the eastern North Pacific (ENP) were... more Egg cases for 10 of 11 valid skate species known to occur in the eastern North Pacific (ENP) were identified and are here described. In addition, egg cases of two unidentified skate species were collected from very deep water off central and southern California, USA. Examples of egg cases for all species, except for two, were removed in utero in order to confirm their species specific identification. The egg cases of seven skate species, including egg cases from the two unidentified species, have not previously been described or illustrated from this region. Previous attempts to identify skate egg cases with their associated species have been inadequate. The ENP skate egg cases can broadly be classified into two main groups: those with broad lateral keels (> 10% maximum egg case width) and those with narrow lateral keels (< 10% maximum egg case width). Egg cases in the former group (with broad lateral keels) generally have a finely striated surface texture that is smooth to the touch. Those in the latter group (with narrow lateral keels), with one exception, tend to have a coarse surface texture, often with prickles, and are rough to the touch. A revised key to the skate egg cases from the ENP is provided.
This study provides the first published age estimates for the roughtail skate, Bathyraja trachura... more This study provides the first published age estimates for the roughtail skate, Bathyraja trachura. Age and growth characteristics of B. trachura, a poorly-known deepwater species, were determined from samples collected along the continental slope of the contiguous western United States. A new maximum size was established at 91.0 cm TL. Age was determined using a traditional structure (vertebral thin sections) with widespread application on multiple skate species and a non-lethal structure (caudal thorns) recently used for age analysis on skate species. Caudal thorns were determined not to be a useful ageing structure for this species based on poor precision and significantly lower age estimates when compared to age estimates from vertebral thin sections. The best model for describing growth of B. trachura was the two parameter VBGF, assuming annual vertebral band deposition and using length-at-age data. Although females grew slower and reached a larger maximum size than males, their growth was not statistically different (ARSS; P = 0.90); therefore, data were pooled (L ¥ = 99.38, k = 0.09). Annual band deposition was found to be a reasonable assumption for this species, but has yet to be validated. The maximum age estimated for B. trachura was 20 years for males and 17 years for females using vertebral thin sections.
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Papers by David Ebert
can cause generalist predators to contract the scope of their diets. This study investigated the effects of increased conspecific fish density on the diets of gopher rockfish Sebastes carnatus at a 35 yr old MPA in Point Lobos, California, and at 4 newly established MPAs in Año Nuevo, Point
Lobos, Piedras Blancas, and Point Buchon in central California. Analyses were conducted for 707 stomachs collected from 2007 to 2009. Diets did not differ inside versus outside the old Point Lobos MPA in terms of prey richness, evenness, composition, or gopher rockfish trophic level. However, fish outside the MPA had greater levels of individual specialization. No consistent differences in these metrics were observed inside versus outside the 4 new MPAs, although prey composition
and evenness did differ significantly among geographic locations. Diets at Año Nuevo, the most northern and shallow location, consisted predominantly of Cancer spp. and porcelain crabs (Porcellanidae), while diets from southern, deeper locations were dominated by brittle stars (Ophiuroidea).
The case study of the old Point Lobos MPA indicates that fish feeding ecology may not change in an MPA after several decades. Differences in prey observed among geographic locations suggest variation in the community composition among central California’s new MPAs, which may influence the effect of each MPA on food web dynamics over time.
Natal coast of South Africa, with a range spanning the western Indian Ocean from Kenya, south to Mozambique and South Africa, and extending into the south-eastern Atlantic to Namibia. This species is characterised by a lateral
patch of denticles on the male prepelvic tenacula, a second dorsal fin slightly indented in the centre, a long, curved
dorsal spine equal to or sometimes exceeding the height of the first dorsal fin, and a uniform light brown body with
no distinctive markings or patterns and slightly darker brown fins. To clarify the taxonomic status of H. africanus,
we examined and compared specimens from throughout its range in southern Africa. Because the syntypes of H. africanus are lost, we designate a neotype and redescribe the species based on the neotype and additional southern African specimens. In addition,
Central Pacific from Costa Rica to Ecuador and between depths of 1256–1472 m. The new species is placed in the genus
Notoraja based on the long and flexible rostrum and its proportionally long tail with respect to total length. This species
is distinct from its congeners in the Western Pacific by the straight margins of its rostrum, long anterior lobes of pelvic
fins, and its abundant and very well developed caudal thorns.
can cause generalist predators to contract the scope of their diets. This study investigated the effects of increased conspecific fish density on the diets of gopher rockfish Sebastes carnatus at a 35 yr old MPA in Point Lobos, California, and at 4 newly established MPAs in Año Nuevo, Point
Lobos, Piedras Blancas, and Point Buchon in central California. Analyses were conducted for 707 stomachs collected from 2007 to 2009. Diets did not differ inside versus outside the old Point Lobos MPA in terms of prey richness, evenness, composition, or gopher rockfish trophic level. However, fish outside the MPA had greater levels of individual specialization. No consistent differences in these metrics were observed inside versus outside the 4 new MPAs, although prey composition
and evenness did differ significantly among geographic locations. Diets at Año Nuevo, the most northern and shallow location, consisted predominantly of Cancer spp. and porcelain crabs (Porcellanidae), while diets from southern, deeper locations were dominated by brittle stars (Ophiuroidea).
The case study of the old Point Lobos MPA indicates that fish feeding ecology may not change in an MPA after several decades. Differences in prey observed among geographic locations suggest variation in the community composition among central California’s new MPAs, which may influence the effect of each MPA on food web dynamics over time.
Natal coast of South Africa, with a range spanning the western Indian Ocean from Kenya, south to Mozambique and South Africa, and extending into the south-eastern Atlantic to Namibia. This species is characterised by a lateral
patch of denticles on the male prepelvic tenacula, a second dorsal fin slightly indented in the centre, a long, curved
dorsal spine equal to or sometimes exceeding the height of the first dorsal fin, and a uniform light brown body with
no distinctive markings or patterns and slightly darker brown fins. To clarify the taxonomic status of H. africanus,
we examined and compared specimens from throughout its range in southern Africa. Because the syntypes of H. africanus are lost, we designate a neotype and redescribe the species based on the neotype and additional southern African specimens. In addition,
Central Pacific from Costa Rica to Ecuador and between depths of 1256–1472 m. The new species is placed in the genus
Notoraja based on the long and flexible rostrum and its proportionally long tail with respect to total length. This species
is distinct from its congeners in the Western Pacific by the straight margins of its rostrum, long anterior lobes of pelvic
fins, and its abundant and very well developed caudal thorns.