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Published journal articles by MLML faculty, staff and students. Full text is included when copyright allows.


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Adrenal function in wild and rehabilitated pacific harbor seals (Phoca vitulina richardii) and in seals with phocine herpesvirus-associated adrenal necrosis
Adrenal function in wild and rehabilitated pacific harbor seals (Phoca vitulina richardii) and in seals with phocine herpesvirus-associated adrenal necrosis
Adrenal function in harbor seals (Phoca vitulina richardii) was evaluated using adrenocorticotrophic hormone (ACTH) stimulation tests and fecal cortisol levels. The effect of ACTH administration on plasma cortisol and aldosterone levels in five free-living and 14 rehabilitated harbor seal pups was determined using enzyme immunoassay and radioimmunoassay, respectively. In free-living seals, injection of ACTH caused a significant increase in mean plasma cortisol but not of mean aldosterone levels 60 min postinjection. In these seals, mean initial plasma aldosterone was significantly higher than initial levels in rehabilitated seals, while initial cortisol levels were similar. Of the rehabilitated seals, eight died with adrenal cortical necrosis associated with herpesvirus inclusions, while six lived to be released. In the seals that were released, both mean initial cortisol levels and response to ACTH decreased through rehabilitation. In the seals that died, mean initial cortisol and response to ACTH increased through rehabilitation. The differences between initial cortisol levels in seals that lived and those that died were significant at weeks two and four of rehabilitation but not at the week of admission. There was considerable individual variation in initial plasma aldosterone levels and responses to ACTH, although initial aldosterone levels were significantly higher in rehabilitated seals that died than in seals that lived. Seals with adrenal necrosis associated with herpesvirus infection did not have decreased adrenal hormone responses to ACTH. Differences between initial hormone levels and responses to ACTH in different groups of seals may be associated with differing stress levels. Fecal cortisol assays were not a useful method of assessing adrenal function in these seals, as measured levels did not correlate with plasma cortisol levels., Cited By (since 1996):13, CODEN: MMSCE, Marine Mammals, Birds & Turtles
Advances in Shark Research
Advances in Shark Research
Export Date: 4 September 2015
Age and Growth of Elasmobranchs and Applications to Fisheries Management and Conservation in the Northeast Pacific Ocean
Age and Growth of Elasmobranchs and Applications to Fisheries Management and Conservation in the Northeast Pacific Ocean
In addition to being an academic endeavour, the practical purpose of conducting age and growth studies on fishes is to provide biological data to stock assessment scientists and fisheries managers so they may better understand population demographics and manage exploitation rates. Age and size data are used to build growth models, which are a critical component of stock assessments. Though age determination of elasmobranchs in the northeast Pacific Ocean (NEP) began in the 1930s, the field has evolved substantially in recent years, allowing scientists to incorporate age data into assessments for more species than ever before. Owing to the highly diverse biology of this group of fishes, each species has its own set of challenges with regard to age determination. Age determination methods typically rely on semicalcified hard structures that form regular growth patterns; however, the structure selected and preparation method used is often species specific. New staining techniques have improved the ability to assess age and improve ageing precision for some species, and advances in microchemical methods have allowed for independent means of estimating age and validating age determination accuracy. Here we describe current age determination methods for NEP elasmobranchs. While the library of available techniques is increasing, there are still some NEP species for which reliable ageing methods have yet to be defined; we discuss these challenges and potential avenues of future research. Finally, we conclude by describing how age estimates are used in growth models and subsequently in stock assessments of selected NEP elasmobranchs.
Age and growth characteristics of the Starry Skate, Raja stellulata, with a description of life history and habitat trends of the central California, U.S.A., skate assemblage
Age and growth characteristics of the Starry Skate, Raja stellulata, with a description of life history and habitat trends of the central California, U.S.A., skate assemblage
Skates are prevalent in fisheries worldwide, but rarely are they identified to species. This is of conservation and management concern since skates exhibit a broad range of life history characteristics. The present study investigated the age and growth of the Starry Skate, Raja stellulata, and compared it to other regional skates inhabiting the U.S. West Coast. Age and growth parameters were determined using two vertebral preparation techniques: gross sectioning and histological sectioning. Gross section age estimates ranged from zero to 11 years and growth was described by the two parameter von Bertalanffy growth function (2 VBGF; L ∞ = 915 mm total length (TL) and k = 0.13 year-1; n = 189). Histological section age estimates ranged from zero to 15 years and growth was also described by the 2 VBGF (L ∞ = 1092 mm TL, k = 0.06 year-1; n = 68). Histological section results reflect a more conservative life history, specifically a lower von Bertalanffy growth coefficient, but had slightly biased results and a smaller sample size than the gross section results. An age and depth trend was found within the central California skate assemblage, in which habitat depth and maximum age were positively correlated. © 2013 Springer Science+Business Media Dordrecht., Fish and Fisheries
Age and growth of Lithothamnion muelleri (Corallinales, Rhodophyta) in the southwestern Gulf of California, Mexico
Age and growth of Lithothamnion muelleri (Corallinales, Rhodophyta) in the southwestern Gulf of California, Mexico
The nongeniculate coralline alga Lithothamnion muelleri Lenormand ex Rosanoff is commonly found as a free-living rhodolith in the wave-exposed shallow waters of the southwestern Gulf of California. This species has bands along the main branch axes suggesting that growth is periodic and that may be used to determine age and growth. As part of our ongoing research related to rhodoliths and their ecology, we have made observations on the nature of these bands based on their structure in entire plants and on field and laboratory growth experiments. Individual plants from different size classes were tagged, stained with alizarin and returned to the field, while another set was tested in the laboratory. Half of the plants were sampled after 6 months and the rest after 12 months. The data indicate that this species grew at a rate of 0.60 mm yr-1 in the field and 0.87 mm yr-1 in the laboratory. There were no significant differences among branches within a plant, or among plants of different size. Growth was seasonal, with high rates in winter and spring, and low rates in summer and fall. This may explain the observed alternating light-dark bands (up to 4) along branch axes. The growth rates suggest that larger plants (ca 15 cm diameter) may be over 100 years old.
Age and growth of the pacific grenadier (Coryphaenoides acrolepis) with age estimate validation using an improved radiometric ageing technique
Age and growth of the pacific grenadier (Coryphaenoides acrolepis) with age estimate validation using an improved radiometric ageing technique
Current and historic longevity estimates for the Pacific grenadier (Coryphaenoides acrolepis) range from 6 to greater than 60 years. Age estimates in this study using growth increment counts in thin otolith sections indicate the Pacific grenadier is a long-lived fish. To validate this growth information, age was determined using the radioactive disequilibria of 210Pb and 226Ra in otolith cores from adult Pacific grenadier. Radiometric ages closely agreed with age estimates from counting growth increments, which confirms their annual periodicity. Radiometric results indicate the Pacific grenadier can live at least 55.8 years (-7.4, +10.1 years). Growth increment counts from large fish indicate longevity may approach 73 years. Because the Pacific grenadier is long-lived and matures late in life, it may be vulnerable to heavy fishing pressure. Therefore, conservation measures need to be taken to sustain this rapidly developing fishery., Cited By (since 1996):39, Fish and Fisheries, CODEN: CJFSD
Age and growth of the roughtail skate Bathyraja trachura (Gilbert 1892) from the eastern North Pacific
Age and growth of the roughtail skate Bathyraja trachura (Gilbert 1892) from the eastern North Pacific
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. © 2007 Springer Science+Business Media, Inc., Cited By (since 1996):9, Fish and Fisheries, CODEN: EBFID
Age and growth of the sandpaper skate, Bathyraja kincaidii, using vertebral centra, with an investigation of caudal thorns
Age and growth of the sandpaper skate, Bathyraja kincaidii, using vertebral centra, with an investigation of caudal thorns
The sandpaper skate, Bathyraja kincaidii, is one of four skate species commonly taken in trawl fisheries off central California although very little is known about its life history. In this study, age and growth were evaluated from 187 vertebrae using a common growth band counting method. An attempt to use marginal increment analysis and centrum edge analysis failed to validate the annual periodicity of growth band formation; however, it is a valid assumption based on structural similarity from other studies. Assuming annual band formation, von Bertalanffy growth parameters were determined for females (L ∞ = 537.3 mm; k = 0.237; t o = -1.629; N = 99) and males (L ∞ = 580.2 mm; k = 0.185; to = -2.530; N = 88). Maximum likelihood ratios indicated no significant difference (P > 0.05) between male and female von Bertalanffy growth parameters, thus data were combined (L ∞ = 557.8 mm; k = 0.207; t o = -2.147; N = 187). Age estimates from band counts in vertebral centra indicated a minimum longevity of 17 and 18 years for female and male B. kincaidii, respectively. Caudal thorns were also assessed for age analyses, but were deemed unreliable and could not be used to verify age estimates from vertebral centra. © Copyright Marine Biological Association of the United Kingdom 2010., Cited By (since 1996):1, Fish and Fisheries, CODEN: JMBAA
Age and growth of two genera of deep-sea bamboo corals (Family Isididae) in New Zealand waters
Age and growth of two genera of deep-sea bamboo corals (Family Isididae) in New Zealand waters
We provide a detailed description of growth zone counts at two locations in the skeletal structure of four bamboo coral colonies (Family Isididae, sub-family Keratoisidinae, genera Lepidisis spp. and Keratoisis sp. from New Zealand). Zone counts were made microscopically on skeletal cross-sections of calcareous internodes producing counts of up to 90 for Lepidisis spp. and 160 for Keratoisis sp. Scanning Electron Microscope (SEM) images taken of cross-sections at the junction of the calcareous internode and gorgonin node revealed clear zone resolution and produced counts that were substantially higher (a maximum 490 zones). Lead-210 dating was applied to the skeletal structure of one specimen of Lepidisis sp. to develop an independent estimate of age and growth. Radial micro-sampling of the skeletal carbonate indicated the age of the colony at the largest section (7.4 mm average radius) was 43 yrs old (26-61 yrs 95% CI), with an average radial growth rate of 0.18 mm yr -1 (0.13-0.29 mm yr-1 95% CI). Comparisons between the three age estimates for Lepidisis sp. were made and it was hypothesized that zones observed by light microscope have a bi-annual periodicity and that SEM-observed zones at the nodal juncture may represent an environmental event, such as lunar periodicity. © 2007 Rosenstiel School of Marine and Atmospheric Science of the University of Miami., Cited By (since 1996):25, Invertebrates, CODEN: BMRSA
Age and growth studies of chondrichthyan fishes
Age and growth studies of chondrichthyan fishes
Validated age and growth estimates are important for constructing age-structured population dynamic models of chondrichthyan fishes, especially those which are exploited. We review age and growth studies of chondrichthyan fishes, using 28 recent studies to identify areas where improvements can be made in describing the characteristics of ageing structures (both traditional and novel) utilized to estimate ages of sharks, rays, and chimaeras. The topics identified that need consistency include the: (1) terminology used to describe growth features; (2) methods used to both verify and validate age estimates from chondrichthyan calcified structures, especially edge and marginal increment analyses; and (3) the functions used to produce and describe growth parameters, stressing the incorporation of size at birth (L0) and multiple functions to characterize growth characteristics, age at maturity and longevity. © 2006 Springer Science+Business Media, Inc., Cited By (since 1996):76, Fish and Fisheries, CODEN: EBFID
Age and sex of Common Murres Uria aalge recovered during the 1997-98 Point Reyes Tarball Incidents in central California
Age and sex of Common Murres Uria aalge recovered during the 1997-98 Point Reyes Tarball Incidents in central California
We examined 1,138 Common Murre Uria aalge carcasses recovered along the central California coast from November 1997 through March 1998 during the Point Reyes Tarball Incidents, a prolonged oiling event traced to the sunken vessel S. S. Jacob Luckenbach. We used head plumage, supraorbital ridge, and bursa of Fabricius, to classify age among carcasses as hatch-year (HY), or after-hatch year (AHY). We then separated AHY birds into two maturity categories based on gonad development: subadult and adult. The observed age class composition (14.6% HY, 37.6% subadult, and 47.8% adult) was not different from expected values generated with a stage-based matrix model that assumed a year-round resident population. The sex ratio for HY birds was equal (1.2:1 ), indicating little difference in at-sea distribution among male and female HY birds during winter. We found male-biased sex ratios in subadult (1.6:1) and adult (1.5:1) age classes. Sex-based differences in winter dispersal or colony attendance may have caused different risks to oiling among AHY birds. Mortality of mostly AHY murres during the Point Reyes Tarball Incidents and other oil spills has contributed to slow recovery of the central California population following historic and recent declines., Cited By (since 1996):11, Marine Mammals, Birds & Turtles
Age determination and validation studies of marine fishes
Age determination and validation studies of marine fishes
Age determination and validation studies on deep-water marine fishes indicate they are difficult to age and often long-lived. Techniques for the determination of age in individual fish includes growth-zone analysis of vertebral centra, fin rays and spines, other skeletal structures, and otoliths (there are three sets of otoliths in most bony fish semicircular canals, each of which is made of calcium carbonate). Most have regular increments deposited as the fish (and its semicircular canals) grows. The most commonly used otolith for age determination is the largest one called the sagitta. Age validation techniques include: (1) tag-recapture, often combined with oxytetracycline injection and analysis in growth-zones of bone upon recapture; (2) analysis of growth-zones over time; and (3) radiometric approaches utilizing a known radioactive decay series as an independent chronometer in otoliths from bony fishes. We briefly summarize previous studies using these three validation approaches and present results from several of our radiometric studies on deep-water, bony fishes recently subjected to expanding fisheries. Radiometric age validation results are presented for four species of scorpaenid fishes (the bank, Sebastes rufus, and bocaccio, S. paucispinis, rockfishes, and two thornyhead species, Sebastolobus altivelis and S. alascanus). In addition, our analysis of scorpaenids indicates that longevity increases exponentially with maximum depth of occurrence. The reason that the deep-water forms of scorpaenid fishes are long-lived is uncertain. Their longevity, however, may be related to altered physiological processes relative to environmental parameters like low temperature, high pressures, low light levels, low oxygen, and poor food resources. Copyright © 2001 Elsevier Science Inc., Cited By (since 1996):102, Fish and Fisheries, CODEN: EXGEA
Age estimation and lead-radium dating of Antarctic toothfish (Dissostichus mawsoni) in the Ross Sea
Age estimation and lead-radium dating of Antarctic toothfish (Dissostichus mawsoni) in the Ross Sea
Antarctic toothfish (Dissostichus mawsoni) are the target of an important commercial fishery in the Southern Ocean, yet age data used for management have not been comprehensively tested for accuracy. In this study, Antarctic toothfish were aged using counts of otolith growth zones based on criteria established for Patagonian toothfish, D. eleginoides, a closely related species. To validate these ages, the radioactive disequilibrium of lead-210 and radium-226 in otolith cores was measured and used as an independent chronometer to accurately determine age across the range of fish caught in large numbers by the fishery. Growth-zone counts indicated Antarctic toothfish live to at least 39 years of age, and were in close agreement with the chronometer, validating the age estimation criteria and the accuracy of age estimates. Von Bertalanffy growth function parameters indicated Antarctic toothfish were relatively slow-growing (k = 0.111), especially in relation to their maximum size (L ∞ = 158.9 cm). © 2010 Springer-Verlag., Cited By (since 1996):4, Fish and Fisheries, CODEN: POBID
Age of black coral (Antipathes dendrochristos) colonies, with notes on associated invertebrate species
Age of black coral (Antipathes dendrochristos) colonies, with notes on associated invertebrate species
In 2005, a dead 2.1-m high colony of the Christmas tree black coral, Antipathes dendrochristos Opresko, 2005, was collected from 106 m of water off southern California. Based on growth increment counts, a radiocarbon ( 14C) analysis, and an indirect corroboration by lead-210 dating from a second, live colony, the colony was about 140 yrs old when it died. The dead skeleton was heavily colonized by invertebrates with 2554 individuals living on the colony. Corophioid amphipods, sea anemones, brittle stars, and crinoids dominated this assemblage. Thus, along with living colonies, it is arguable that the destruction of dead antipatharian colonies may have as yet unknown effects on a range of deep-water organisms. © 2007 Rosenstiel School of Marine and Atmospheric Science of the University of Miami., Cited By (since 1996):13, Invertebrates, CODEN: BMRSA
Age ratios as estimators of productivity
Age ratios as estimators of productivity
The ratio of hatch-year (HY) to after-hatch-year (AHY) individuals (HY:AHY ratio) can be a valuable metric for estimating avian productivity because it does not require monitoring individual breeding sites and can often be estimated across large geographic and temporal scales. However, rigorous estimation of age ratios requires that both young and adult age classes are sampled in an unbiased manner, an assumption that is rarely tested. We estimated HY:AHY ratios for Marbled Murrelets (Brachyramphus marmoratus), a threatened seabird, using at-sea surveys and captures to assess whether age-specific differences in behavior and distribution result in biased productivity estimates in central California. AHY and HY Marbled Murrelets were distributed similarly at sea, and HY individuals did not congregate in nursery areas. Moreover, dispersal by radiomarked AHY Marbled Murrelets out of our survey area occurred at a low rate, and AHY densities were constant over the survey period, which suggests that AHY immigration and emigration did not significantly bias productivity estimates. HY density increased linearly over the survey period as expected if little dispersal occurred, which suggests that productivity estimates were not significantly biased by HY dispersal. Finally, simulation analyses indicated that annual variation in the timing of breeding resulted in only small biases in HY:AHY ratios. HY:AHY ratios were corrected for the proportion of AHY Marbled Murrelets that were incubating and the proportion of HY individuals that had not fledged at the time of sampling. Mean corrected HY:AHY ratios were low on the basis of both at-sea surveys conducted from 1996 to 2003 (0.032; SE = 0.011) and captures conducted from 1999 to 2003 (0.037; SE = 0.028), implying that productivity was poor in central California. Estimating age ratios may be an effective way of monitoring changes in reproductive success and identifying environmental factors that affect Marbled Murrelet populations, though tests of assumptions are needed in other regions. © The American Ornithologists' Union, 2007., Cited By (since 1996):15, Marine Mammals, Birds & Turtles, CODEN: AUKJA
Age validation of canary rockfish (Sebastes pinniger) using two independent otolith techniques
Age validation of canary rockfish (Sebastes pinniger) using two independent otolith techniques
Canary rockfish (Sebastes pinniger) have long been an important part of recreational and commercial rockfish fishing from south-east Alaska to southern California, but localised stock abundances have declined considerably. Based on age estimates from otoliths and other structures, lifespan estimates vary from ∼20 years to over 80 years. For the purpose of monitoring stocks, age composition is routinely estimated by counting growth zones in otoliths; however, age estimation procedures and lifespan estimates remain largely unvalidated. Typical age validation techniques have limited application for canary rockfish because they are deep-dwelling and may be long-lived. In this study, the unaged otolith of the pair from fish aged at the Department of Fisheries and Oceans Canada was used in one of two age validation techniques: (1) lead-radium dating and (2) bomb radiocarbon (14C) dating. Age estimate accuracy and the validity of age estimation procedures were validated based on the results from each technique. Lead-radium dating proved successful in determining that a minimum estimate of lifespan was 53 years and provided support for age estimation procedures up to ∼50-60 years. These findings were further supported by Δ14C data, which indicated that a minimum estimate of lifespan was 44 ± 3 years. Both techniques validate, to differing degrees, age estimation procedures and provide support for inferring that canary rockfish can live more than 80 years. © CSIRO 2007., Cited By (since 1996):12, Fish and Fisheries, CODEN: AJMFA
Age validation of quillback rockfish (Sebastes maliger) using bomb radiocarbon
Age validation of quillback rockfish (Sebastes maliger) using bomb radiocarbon
Rockfishes (Sebastes spp.) support one of the most economically important fisheries of the Pacific Northwest and it is essential for sustainable management that age estimation procedures be validated for these species. Atmospheric testing of thermonuclear devices during the 1950s and 1960s created a global radiocarbon (14C) signal in the ocean environment that scientists have identified as a useful tracer and chronological marker in natural systems. In this study, we first demonstrated that fewer samples are necessary for age validation using the bomb-generated 14C signal by emphasizing the utility of the time-specific marker created by the initial rise of bomb-14C. Second, the bomb-generated 14C signal retained in fish otoliths was used to validate the age and age estimation method of the quillback rockfish (Sebastes maliger) in the waters of southeast Alaska. Radiocarbon values from the first year's growth of quillback rockfish otoliths were plotted against estimated birth year to produce a 14C time series spanning 1950 to 1985. The initial rise in bomb-14C from prebomb levels (∼ -90‰) occurred in 1959 [±1 year] and 14C levels rose relatively rapidly to peak Δ14C values in 1967 (+105.4‰) and subsequently declined through the end of the time series in 1985 (+15.4‰). The agreement between the year of initial rise of 14C levels from the quillback rockfish time series and the chronology determined for the waters of southeast Alaska from yelloweye rockfish (S. ruberrimus) otoliths validated the aging method for the quillback rockfish. The concordance of the entire quillback rockfish 14C time series with the yelloweye rockfish time series demonstrated the effectiveness of this age validation technique, confirmed the longevity of the quillback rockfish up to a minimum of 43 years, and strongly confirms higher age estimates of up to 90 years., Cited By (since 1996):22, Fish and Fisheries, CODEN: FSYBA
Age, growth and radiometric age validation of a deep-sea, habitat-forming gorgonian (Primnoa resedaeformis) from the Gulf of Alaska
Age, growth and radiometric age validation of a deep-sea, habitat-forming gorgonian (Primnoa resedaeformis) from the Gulf of Alaska
Sustainable fisheries require (1) viable stock populations with appropriate harvest limits and (2) appropriate habitat for fish to survive, forage, seek refuge, grow and reproduce. Some deep-water habitats, such as those formed by deep-water stands of coral, may be vulnerable to fishing disturbance. The rate at which habitat can be restored is a critical aspect of fishery management. The purpose of this study was to characterize growth rates for a habitat-forming deep-sea coral. Two nearly complete colonies of red tree coral (Primnoa resedaeformis) collected from waters off southeast Alaska were used for an analysis of age and growth characteristics. CAT scans revealed that colonies consisted of multiple settlement events, where older basal structures provided for settlement of new colonies. The decay of 210Pb over the length of the colony was used to validate age estimates from growth ring counts. Age estimates were over 100 yr for sections near the heavily calcified base. Based on validated growth ring counts, growth of red tree coral ranged from 1.60 to 2.32 cm per year in height and was approximately 0.36 mm per year in diameter. These growth rates suggest that the fishery habitat created by red tree coral is extremely vulnerable to bottom fishing activities and may take over 100 years to recover., Cited By (since 1996):69, Fish and Fisheries, CODEN: HYDRB

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