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Chimaera carophila (Chondrichthyes: Chimaeriformes: Chimaeridae), a new species of chimaera from New Zealand
Chimaera carophila (Chondrichthyes: Chimaeriformes: Chimaeridae), a new species of chimaera from New Zealand
A new species of chimaeroid, Chimaera carophila sp. nov., is described from 37 specimens collected from deepwater slopes and seamounts around New Zealand. The new species is distinguished from its closest congeners, Chimaera fulva Didier et al. 2008, Chimaera macrospina Didier et al. 2008, and Chimaera obscura Didier et al. 2008, by its uniform pale-brown coloration, geographic distribution, and a combination of morphological characters, including longer dorsal and ventral caudal fin bases, a shorter first dorsal fin height, a shorter dorsal fin spine, and shorter claspers that are divided distally for one-third of their length. Chimaera carophila sp. nov. also can be distinguished from closely related species in New Zealand and Australian waters based on DNA sequence divergence of the NADH2 gene. Comparisons of body size in a large sample of specimens show considerable overlap in character ranges among congeners making species distinctions difficult. New combinations of morphometrics are suggested including ratios of head length to eye length and dorsal spine length to head length, to better distinguish among species of chimaeroids that are similar in overall appearance and size. Also, a key to New Zealand and Australian Chimaera species is provided. © 2015 Rosenstiel School of Marine & Atmospheric Science of the University of Miami., Export Date: 31 July 2015
Chimaera notafricana sp. nov. (Chondrichthyes: Chimaeriformes: Chimaeridae), a new species of chimaera from southern Africa
Chimaera notafricana sp. nov. (Chondrichthyes: Chimaeriformes: Chimaeridae), a new species of chimaera from southern Africa
A new species of chimaera, Chimaera notafricana sp. nov., is described from specimens collected off the west and south coasts of southern Africa. The new species is distinguished from its closest congener, the eastern North Atlantic Chimaera monstrosa, by a combination of morphometric characters and coloration: pectoral fin when depressed reaches to origin of pelvic fin base; caudal fin ventral margin terminating slightly posterior to caudal fin dorsal margin insertion; distance from anterior base of dorsal-fin spine to center of supratemporal canal short (6.5-14.8% HDL); pelvic claspers externally trifid and short (12.1-12.3% BDL), divided for distal one-third of length, not extending past distal tip of pelvic fins; uniform blackish brown with dark bluish streaking, precaudal tail with longitudinal light and dark stripes. This new species has a restricted distribution from Lüderitz, Namibia to south of Algoa Bay, Eastern Cape Province, South Africa. Copyright © 2010 Magnolia Press., Fish and Fisheries
Chitin in Diatoms and Its Association with the Cell Wall
Chitin in Diatoms and Its Association with the Cell Wall
Chitin is a globally abundant polymer widely distributed throughout eukaryotes that has been well characterized in only a few lineages. Diatoms are members of the eukaryotic lineage of stramenopiles. Of the hundreds of diatom genera, two produce long fibers of chitin that extrude through their cell walls of silica. We identify and describe here genes encoding putative chitin synthases in a variety of additional diatom genera, indicating that the ability to produce chitin is more widespread and likely plays a more central role in diatom biology than previously considered. Diatom chitin synthases fall into four phylogenetic clades. Protein domain predictions and differential gene expression patterns provide evidence that chitin synthases have multiple functions within a diatom cell. Thalassiosira pseudonana possesses six genes encoding three types of chitin synthases. Transcript abundance of the gene encoding one of these chitin synthase types increases when cells resume division after short-term silicic acid starvation and during short-term limitation by silicic acid or iron, two nutrient conditions connected in the environment and known to affect the cell wall. During long-term silicic acid starvation transcript abundance of this gene and one additional chitin synthase gene increased at the same time a chitin-binding lectin localized to the girdle band region of the cell wall. Together, these results suggest that the ability to produce chitin is more widespread in diatoms than previously thought and that a subset of the chitin produced by diatoms is associated with the cell wall., published
Chlamydoselachus africana, a new species of frilled shark from southern Africa (Chondrichthyes, Hexanchiformes, Chlamydoselachidae)
Chlamydoselachus africana, a new species of frilled shark from southern Africa (Chondrichthyes, Hexanchiformes, Chlamydoselachidae)
Frilled sharks (Chondrichthyes, Hexanchiformes, Chlamydoselachidae), long believed to be a monotypic family and genus, consisting of a single wide ranging species, Chlamydoselachus anguineus (Garman, 1884), is now known to contain at least two species. A new species of frilled shark, Chlamydoselachus africana, sp. nov., is described from five specimens collected from southern Africa. The new species, although difficult to distinguish externally from the well known C. anguineus, differ internally by the structural differences in the chondrocranium, lower total vertebral and spiral valve counts, and pectoral-fin radial counts. The new species, Chlamydoselachus africana, is known from off southern Angola, Namibia, and South Africa. © 2009 · Magnolia Press., Cited By (since 1996):3, Fish and Fisheries
Chronic oiling of marine birds in California by natural petroleum seeps, shipwrecks, and other sources
Chronic oiling of marine birds in California by natural petroleum seeps, shipwrecks, and other sources
We assessed temporal and spatial patterns of chronic oiling of seabirds in California during 2005-2010, using data on: (1) live oiled birds reported to the Oiled Wildlife Care Network (OWCN) from throughout the state, and (2) dead oiled birds found during systematic monthly beached-bird surveys in central California. A mean of 245 (±141 SD) live miscellaneous oiled birds (not associated with known oil spills) were reported to the OWCN per year, and 0.1 oiled dead birds km-1 per month were found on beach surveys in central California. Chemical fingerprinting of oiled feathers from a subset of these birds (n = 101) indicated that 89% of samples tested were likely from natural petroleum seeps off southern and central California. There was a pronounced peak during late winter in the number of oiled birds reported in southern California, which we theorize may be related to large storm waves disturbing underwater seeps. © 2013., Marine Mammals, Birds & Turtles, Article in Press
Clathromorphum nereostratum (Corallinales, Rhodophyta): The oldest alga?
Clathromorphum nereostratum (Corallinales, Rhodophyta): The oldest alga?
The longevity of organisms is intrinsically interesting and can provide useful information on their population structure and dynamics and the dynamics of associated communities. With the exception of perennial Laminariales that have rings in the stipe, the life spans of most perennial macroalgae are unknown or based on anecdotal observations. Using morphological analyses combined with the location and time of the rise in 14C from atmospheric nuclear testing within the thallus, we determined that the growth rate of a specimen of Clathromorphum nereostratum Lebednik from Adak Island was 0.30 mm·yr -1, the 30 bands within the thallus were annual, and the specimen sampled was 61-75 years old. Living crusts of this species from the same geographic region are reported to be up to 20 cm thick. Assuming our growth rate is typical, C. nereostratum can be approximately 700 years old, the oldest known living alga. This longevity and consistent banding within the thallus suggest that smaller scale sampling and additional chemical analyses of this alga could provide a detailed long-term record of environmental variation at high latitudes in the North Pacific. © 2005 Phycological Society of America., Cited By (since 1996):25, Seaweeds, CODEN: JPYLA
Climate variability and spatiotemporal dynamics of five Southern Ocean krill species
Climate variability and spatiotemporal dynamics of five Southern Ocean krill species
Understanding the ecological response of marine organisms to future climate change will benefit from quantifying spatiotemporal aspects of their distribution and abundance as well as the influence of ocean-atmospheric climate modes on their population cycles. Our study provides a synthesis of 18. years of data (1992-2009) for 5 krill (euphausiid) species monitored near the North Antarctic Peninsula (NAP) during austral summer. Distribution and abundance data are presented for postlarval stages of Euphausia crystallorophias, E. frigida, E. superba, E. triacantha and Thysanoessa macrura and larval E. superba and T. macrura. Intraseasonal, interannual and longer-term distribution and abundance patterns are quantified relative to climate modes driving ecosystem variability off the Antarctic Peninsula: El Niño-Southern Oscillation (ENSO), Southern Annual Mode (SAM) and associated zonal and meridional winds. Interannual abundance variations of all 5 species are significantly correlated with seasonally averaged ENSO indices and, with the exception of E. triacantha, elevated population sizes are associated with the higher productivity La Niña phase. Time-lagged responses of each species to ENSO indices approximate their generation times and suggest evolution of their life histories and reproductive efforts in accordance with the ENSO cycle. Postlarval E. crystallorophias and E. frigida and larval T. macrura demonstrate significant abundance increases after 1998 associated with a shift from an El Niño dominated period to predominantly La Niña and "Nino-neutral" conditions. Seasonal changes in species distributions and co-occurrence indicate portions of the southernmost E. frigida, E. triacantha and T. macrura populations move poleward with E. superba during late-summer, suggesting that environmental conditions associated with sea ice development (e.g., food, retention) may be more favorable than within the Antarctic Circumpolar Current during low productivity seasons. Spatial distributions of larval and postlarval T. macrura suggest 2 separate spawning populations within oceanic and coastal waters. Lastly, mean euphausiid species concentrations and abundance relationships encountered during 1992-2009 are remarkably similar to those reported for the Antarctic Peninsula during the 1928-1935 Discovery Investigations. Circumpolar observations of E. superba "superswarms" associated with a major climatically related ecosystem change in the late 1970s may have represented an episodic period of anomalous peak abundance. 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Climate variability and spatiotemporal dynamics of five Southern Ocean krill species
Climate variability and spatiotemporal dynamics of five Southern Ocean krill species
Understanding the ecological response of marine organisms to future climate change will benefit from quantifying spatiotemporal aspects of their distribution and abundance as well as the influence of ocean-atmospheric climate modes on their population cycles. Our study provides a synthesis of 18. years of data (1992-2009) for 5 krill (euphausiid) species monitored near the North Antarctic Peninsula (NAP) during austral summer. Distribution and abundance data are presented for postlarval stages of Euphausia crystallorophias, E. frigida, E. superba, E. triacantha and Thysanoessa macrura and larval E. superba and T. macrura. Intraseasonal, interannual and longer-term distribution and abundance patterns are quantified relative to climate modes driving ecosystem variability off the Antarctic Peninsula: El Niño-Southern Oscillation (ENSO), Southern Annual Mode (SAM) and associated zonal and meridional winds. Interannual abundance variations of all 5 species are significantly correlated with seasonally averaged ENSO indices and, with the exception of E. triacantha, elevated population sizes are associated with the higher productivity La Niña phase. Time-lagged responses of each species to ENSO indices approximate their generation times and suggest evolution of their life histories and reproductive efforts in accordance with the ENSO cycle. Postlarval E. crystallorophias and E. frigida and larval T. macrura demonstrate significant abundance increases after 1998 associated with a shift from an El Niño dominated period to predominantly La Niña and "Nino-neutral" conditions. Seasonal changes in species distributions and co-occurrence indicate portions of the southernmost E. frigida, E. triacantha and T. macrura populations move poleward with E. superba during late-summer, suggesting that environmental conditions associated with sea ice development (e.g., food, retention) may be more favorable than within the Antarctic Circumpolar Current during low productivity seasons. Spatial distributions of larval and postlarval T. macrura suggest 2 separate spawning populations within oceanic and coastal waters. Lastly, mean euphausiid species concentrations and abundance relationships encountered during 1992-2009 are remarkably similar to those reported for the Antarctic Peninsula during the 1928-1935 Discovery Investigations. Circumpolar observations of E. superba "superswarms" associated with a major climatically related ecosystem change in the late 1970s may have represented an episodic period of anomalous peak abundance. Subsequent abundance estimates compared to these anomalies would indicate a significant decrease, but should not be taken to reflect the impact of climate warming.
Clonal diversity in introduced populations of an Asian sea anemone in North America
Clonal diversity in introduced populations of an Asian sea anemone in North America
Previous reports hypothesized that introduced populations of the Asian sea anemone Diadumene lineata (Verill, 1870) which reproduces by fission, are often monoclonal or to be composed of few clones. To test this hypothesis, sea anemones were collected from thirteen sites in three non-native regions and one native region: Chesapeake Bay, New England, central California, and Japan. The internal transcribed spacer (ITS) region separating nuclear ribosomal RNA genes was amplified from each individual using PCR and surveyed for DNA sequence variation using single strand conformational polymorphism analysis (SSCP). Fifty-six distinct electrophoretic banding patterns were found in 268 anemones, and each pattern was considered a different genotype. The number of genotypes in a population ranged from one to thirteen. Only one sample (York River, Chesapeake Bay, n = 10) was monoclonal, although six populations were dominated (>50%) by single genotype. Only four genotypes were found in more than one population, and these were confined to single regions. Walker Creek, California was sampled in 1995 and 1997 and no genotypes were found in both years, suggesting rapid shifts in genotype frequency. We conclude that multiple genotypes of D. lineata have invaded North America and that the primary importance of clonal growth for introduced populations is the production of colonizing propagules., Cited By (since 1996):8, Invertebrates, CODEN: BLINF
Coastal Ocean Mammal and Bird Education and Research Surveys (BeachCOMBERS), 1997-2007
Coastal Ocean Mammal and Bird Education and Research Surveys (BeachCOMBERS), 1997-2007
U.S. Departement of Commerce; National Oceanic and Atmostpheric Administration; National Ocean Service; Office of Ocean and Coastal Resource Management; Office of National Marine Sanctuaries. Downloaded from: http://sanctuaries.noaa.gov/science/conservation/beachcomber.html (18 July 2014). 72 pp.
Cobalt and copper distributions in the waters of Santa Monica Basin, California
Cobalt and copper distributions in the waters of Santa Monica Basin, California
The trace metals cobalt and copper are removed from the oceans interior by scavenging on to particle surfaces, but the mechanisms for removal of these two metals are probably quite different. Cobalt appears to be scavenged by manganese oxide particles, whereas organic compounds are the main carrier phase for copper. Remobilization of these metals in marine sediments therefore proceeds by different pathways. The differences in the pathways of remobilization are accentuated in oxygen-deficient environments: manganese oxide reduction is accelerated at low oxygen levels and organic carbon is preserved. Cobalt fluxes from sediments underlying oxygen-deficient waters should be enhanced and copper fluxes reduced. We report here measurements of the cobalt and copper distributions in the waters of an oxygen-deficient marine basin in the Southern California Bight. Cobalt concentrations near the bottom are raised four times above the background level, whereas copper concentrations show no increase. These measurements confirm features of existing models for the oceanic cycles of these metals., Cited By (since 1996):18, Oceanography, CODEN: NATUA
Cobalt in north-east Pacific waters
Cobalt in north-east Pacific waters
Significant understanding has been gained recently about the biogeochemical cycling of trace metals in the ocean. This knowledge has mostly resulted from the accurate measurement of dissolved species in oceanic water columns. We report here that cobalt's vertical distribution is similar to that exhibited 1-3 by Mn; that is, its surface enrichment/deep depletion (Fig. 1). However, amounts of Co (1-7 ng 1 -1) are ∼10-20 times less than those for Mn (Table 1), as might be expected from crustal abundance estimates 4 for these elements (Mn=950; Co=25 μg per g). The similarity between Mn and Co profiles implies the same biogeochemical pathways. The Co excess in nearshore surface waters probably results from continental weathering input processes, as suggested by the remarkable Co-salinity mirror-image relationship shown in Fig. 1, and the Co-salinity scatter diagram in Fig. 2a. The steady decrease in Co concentrations also indicates that Co is usually scavenged rather than regenerated at depth, as is the case with Mn (Fig. 1; Table 1). © 1982 Nature Publishing Group., Cited By (since 1996):47 Oceanography
Cognitive control of heart rate in diving harbor porpoises
Cognitive control of heart rate in diving harbor porpoises
Summary Marine mammals have adapted to forage while holding their breath in a suite of aquatic habitats from shallow rivers to deep oceans. The key to tolerate such extensive apnea is the dive response, which comprises bradycardia and peripheral vasoconstriction. Although initially considered an all-or-nothing reflex [1], numerous studies on freely diving marine mammals have revealed substantial dynamics of the dive response to meet the impending dive demands of depth, duration and exercise [2]. Such adjustments are not only autonomic responses, but are under acute cognitive control in pinnipeds [3] living amphibiously on land and in water. The fully aquatic cetaceans would similarly benefit from cognitive cardiovascular control; however, even though they have exercise-modulated diving bradycardia [2] and full voluntary control of their respiratory system to such extent that even mild anesthesia often leads to asphyxiation [4], cognitive cardiovascular control has never been demonstrated for this large group of marine mammals. To address this, we tested the hypothesis that porpoises modulate bradycardia according to anticipated dive duration. Two harbor porpoises, instrumented with ECG recording tags, were trained to perform 20- and 80-second stationary dives, during which they adjusted bradycardia to the anticipated duration, demonstrating cognitive control of their dive response.
Collaborative research: An effective way to collect data for stock assessments and evaluate marine protected areas in California
Collaborative research: An effective way to collect data for stock assessments and evaluate marine protected areas in California
Collaborative fisheries research (in contrast to cooperative research) is based on the intellectual partnership between scientists and fishermen and is an effective way to collect data for stock assessments and to evaluate marine protected areas. Collaborative fisheries research is discussed in the context of comanagement of marine resources and how it contributes to a more democratic form of fisheries management. Many benefits result from working together, including (1) the incorporation of fishers' knowledge and expertise into the management process and (2) the development of shared perspectives derived through science-based investigations on the status of marine resources. The California Collaborative Fisheries Research Program was formed in 2006 to participate in the monitoring of marine reserves established through California's Marine Life Protection Act. This program has shown that it can serve as a model for other areas that are trying to implement collaborative research and that collaborative research can greatly contribute to the realization of community-based co-management of marine resources. © Copyright by the American Fisheries Society 2009., Cited By (since 1996):5 Fish and Fisheries
Color aberrations in Chondrichthyan fishes
Color aberrations in Chondrichthyan fishes
Two softnose skate specimens with abnormal coloration, one complete albino and one partial albino (leucistic), were captured during fishery-independent trawl surveys. The complete albino specimen was collected in 2007 in Prince William Sound, Alaska, and the leucistic specimen was collected in 2011 off northern California. Based upon meristic and morphometric measurements, the albino skate specimen was identified as the Aleutian Skate, Bathyraja aleutica, and the leucistic skate specimen was identified as the Roughtail Skate, Bathyraja trachura. These are the first documented cases of any type of albinism in the genus Bathyraja. A comprehensive review encompassing reported cases of any type of albinism in Chondrichthyans from peer-reviewed literature to-date is provided.
Combining demographic and count-based approaches to identify source-sink dynamics of a threatened seabird
Combining demographic and count-based approaches to identify source-sink dynamics of a threatened seabird
Identifying source-sink dynamics is of fundamental importance for conservation but is often limited by an inability to determine how immigration and emigration influence population processes. We demonstrate two ways to assess the role of immigration on population processes without directly observing individuals dispersing from one population to another and apply these methods to a population of Marbled Murrelets (Brachyramphus marmoratus) in California (USA). In the first method, the rate of immigration (i) is estimated by subtracting local recruitment (recruitment from within the population due to reproduction) estimated with demographic data from total recruitment (f; recruitment from within the population plus recruitment from other populations) estimated using temporal symmetry mark-recapture models developed by R. Pradel. The second method compares population growth rates estimated with temporal symmetry models (λ TS) and/or population growth rates estimated from counts of individuals over multiple sampling periods (λ C) with growth estimates from a stage-structured projection matrix model (λ M). Both λ TS and λ C incorporate all demographic processes affecting population change (birth, death, immigration, and emigration), whereas matrix models are usually constructed without incorporating immigration. Thus, if λ TS and λ C are ≥1 and λ M < 1, the population is sustained by immigration and is considered to be a sink. Using the first method, recruitment estimated with temporal symmetry models was high (f̂ = 0.182, SE = 0.058), the mean adult birth rate, as estimated using the ratio of juveniles to ≥1 year old individuals (observed during ship-based surveys) was low (b̄ A = 0.039, SE = 0.014), and immigration was 0.160 (SE = 0.057). Using the second method, murrelet numbers in central California were stable (λ C = 1.058, SE = 0.047; λ TS = 1.064, SE = 0.033), but were projected to decline 9.5% annually in the absence of immigration (λ M = 0.905, SE = 0.053). Our results suggest that Marbled Murrelets in central California represent a sink population that is stable but would decline in the absence of immigration from larger populations to the north. However, the extent to which modeled immigration is due to permanent recruitment or temporarily dispersing individuals that simply mask population declines is uncertain. © 2006 by the Ecological Society of America., Cited By (since 1996):36 Marine Mammals, Birds & Turtles, CODEN: ECAPE
Community structure of temperate reef fishes in kelp-dominated subtidal habitats of northern Chile
Community structure of temperate reef fishes in kelp-dominated subtidal habitats of northern Chile
An important aim of fish ecology is to understand and predict patterns of distribution and abundance in marine communities. Such patterns were examined at four kelp-dominated sites along the northern coast of Chile (19° through 30°S) over 1 year. Fish species richness, diversity and abundance estimates obtained via observational and destructive sampling methods were compared among sites as were habitat and environmental variables that characterised the sites; including sea water temperature below the surface, nutrients, productivity, visibility, density of macroalgae stands, and percentage cover of observed microhabitats (including understorey algae and faunal assemblages). In total, 19 fish species belonging to 14 families were observed from all sites. Species richness and diversity were highest in sites where kelp canopy was composed of two species and where kelp was densest, although only species diversity was significantly different among sites. The sites with high kelp density, in turn, sustained abundant habitat-forming species in the kelp understorey. Principal coordinate analysis indicated that the composition and structure of the fish assemblages varied significantly with depth at all study sites. The depth distribution of fishes was correlated with the arrangement of site-specific biological microhabitats, defined by the algae or invertebrate species that form the microhabitat. Temperature, productivity, and nutrients did not vary consistently across study sites, but did vary within individual sites. We suggest that kelp cover and composition strongly affects the diversity and distribution of fishes at shallow coastal habitats in northern Chile through the availability of microhabitats. © CSIRO 2007., Cited By (since 1996):8 Fish and Fisheries Seaweeds, CODEN: AJMFA
Comparative Demography of Skates: Life-History Correlates of Productivity and Implications for Management
Comparative Demography of Skates: Life-History Correlates of Productivity and Implications for Management
Age-structured demographic models were constructed based on empirical estimates of longevity and maturity for five deepwater Bering Sea skates to investigate how observed differences in life history parameters affect population growth rates. Monte Carlo simulations were used to incorporate parameter uncertainty. Estimated population growth rates ranged from 1.045 to 1.129 yr-1 and were lower than those reported for other Alaskan skates and most chondrichthyans. Population growth rates of these and other high-latitude skates increased with relative reproductive lifespan, but displayed no significant relationship with body size or depth distribution, suggesting that assemblage shifts may be difficult to predict for data-poor taxa. Elasticity analyses indicated that juvenile and adult survival had greater per-unit effects on population growth rates than did egg-case survival or fecundity. Population growth rate was affected more by uncertainty in age at maturity than maximum age. The results of this study indicate that if skates are deemed to be a management concern, gear modifications or depth-specific effort controls may be effective. © 2013 Barnett et al., Fish and Fisheries, Art. No.: e65000
Comparative age and growth of the Aleutian skate, Bathyraja aleutica, from the eastern Bering Sea and Gulf of Alaska
Comparative age and growth of the Aleutian skate, Bathyraja aleutica, from the eastern Bering Sea and Gulf of Alaska
The Aleutian skate (Bathyraja aleutica) is a large deep-water species that commonly occurs in bycatch of Alaskan trawl and longline fisheries. Although prominent in the skate biomass of the eastern Bering Sea (EBS) and Gulf of Alaska (GOA) ecosystems, minimal biological information exists. To increase our understanding of this potentially vulnerable species, and address the possibility of two separate populations in Alaskan waters, the age and growth of B. aleutica was studied. Vertebral centra were examined for age determination, and multiple growth models were evaluated to determine growth characteristics. Skates from the EBS attained maximum ages of 17 and 16 years for females and males, respectively, and the two-parameter von Bertalanffy growth functions generated estimates of k = 0.13 yr.-1 and L∞ = 162.1 cm for females, with similar results for males. Skates from the GOA reached 19 years in females and 18 years in males. Growth parameters of female skates from the GOA were estimated as k = 0.11 yr.-1 and L∞ = 160.0 cm, whereas males grew faster, with estimates of k = 0.15 yr.-1 and L∞ = 138.2 cm. The results of this study may indicate the presence of distinct populations of B. aleutica in the eastern North Pacific.
Comparative age and growth of the Aleutian skate, Bathyraja aleutica, from the eastern Bering Sea and Gulf of Alaska
Comparative age and growth of the Aleutian skate, Bathyraja aleutica, from the eastern Bering Sea and Gulf of Alaska
The Aleutian skate (Bathyraja aleutica) is a large deep-water species that commonly occurs in bycatch of Alaskan trawl and longline fisheries. Although prominent in the skate biomass of the eastern Bering Sea (EBS) and Gulf of Alaska (GOA) ecosystems, minimal biological information exists. To increase our understanding of this potentially vulnerable species, and address the possibility of two separate populations in Alaskan waters, the age and growth of B. aleutica was studied. Vertebral centra were examined for age determination, and multiple growth models were evaluated to determine growth characteristics. Skates from the EBS attained maximum ages of 17 and 16 years for females and males, respectively, and the two-parameter von Bertalanffy growth functions generated estimates of k = 0.13 yr.-1 and L∞ = 162.1 cm for females, with similar results for males. Skates from the GOA reached 19 years in females and 18 years in males. Growth parameters of female skates from the GOA were estimated as k = 0.11 yr.-1 and L∞ = 160.0 cm, whereas males grew faster, with estimates of k = 0.15 yr.-1 and L∞ = 138.2 cm. The results of this study may indicate the presence of distinct populations of B. aleutica in the eastern North Pacific.
Comparative age‑determination techniques for white sturgeon in California
Comparative age‑determination techniques for white sturgeon in California
We compared growth patterns of clavicles, cleithra, opercles, medial nuchals, dorsal scutes, and pectoral fin ray sections from white sturgeon Acipenser transmontanus in California. The legibility and interpretability of growth patterns, ease of collection and processing, and relative precision of age estimates were evaluated for each structure with data collected on skeletal structures and morphometric measurements of 147 individuals ranging in size from 31 to 224 cm total length. Various methods were used to elucidate growth zones (thin-sectioning, oil and water clearing, staining, and X-ray radiography) to determine the most useful ageing technique for each structure. All calcified structures contained concentric growth zones that increased in number with the size of the fish and were interpreted as annual events. There was a direct linear relationship between size of the structures and size of the fish. Pectoral fin sections were the most practical ageing structure in terms of ease of collection, processing, legibility, and precision of interpretation. Age estimates from other structures resulted in poor precision between readers but relatively good intrareader precision. This suggests possible corroborative use with the development of better interpretive criteria and elucidation techniques. The von Bertalanffy, growth curve calculated from age estimates based on pectoral fin sections for all samples produced a growth model for white sturgeon that compared favorably with those from previous studies.

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