Extinction risk and conservation of the world\u27s sharks and rays

The rapid expansion of human activities threatens ocean-wide biodiversity. Numerous marine animal populations have declined, yet it remains unclear whether these trends are symptomatic of a chronic accumulation of global marine extinction risk. We present the first systematic analysis of threat for a globally distributed lineage of 1,041 chondrichthyan fishes-sharks, rays, and chimaeras. We estimate that one-quarter are threatened according to IUCN Red List criteria due to overfishing (targeted and incidental). Large-bodied, shallow-water species are at greatest risk and five out of the seven most threatened families are rays. Overall chondrichthyan extinction risk is substantially higher than for most other vertebrates, and only one-third of species are considered safe. Population depletion has occurred throughout the world\u27s ice-free waters, but is particularly prevalent in the Indo-Pacific Biodiversity Triangle and Mediterranean Sea. Improved management of fisheries and trade is urgently needed to avoid extinctions and promote population recovery

Constraints on Sustainable Marine Fisheries in the United States: A Look at the Record

The factors that may either constrain or contribute to sustainable marine fisheries were examined by reviewing and analyzing the history and current status of several U.S. fisheries. Among major factors under consideration are inherent vulnerability (vulnerability in some species is high because of low intrinsic rates of increase and/or naturally infrequent recruitment); environmental degradation (fisheries may collapse because of anthropogenic habitat destruction); availability of data (information necessary co conduce accurate stock assessments may be inadequate for some species); quality of the scientific advice (inappropriate models or scientifically inaccurate assessments may be used); and effectiveness of management decisions (managers may disregard recommendations from scientific committees, and/or implement management measures chat are risk-prone). Fisheries that are examined include the Atlantic Coast striped bass Morone saxatilis fishery, the New England groundfish fishery, the Atlantic shark fishery, the Atlantic and Gulf reef fish fisheries, and the Pacific rockfish fishery. Although many of the factors listed above contributed co declines in these fisheries, the root cause in all cases was harvesting at rates that were much higher than could be sustained by recruitment. Management was largely ineffective because management decisions were risk-prone and motivated by short-term economic considerations rather than long-term sustainability. Only after passage of legislation not only authorizing but specifying mandatory stock rebuilding, has most management been sufficiently precautionary to allow sustainability.https://scholarworks.wm.edu/vimsbooks/1011/thumbnail.jp

Constraints On Sustainable Marine Fisheries In The United States: A Look At The Record

The factors that may constrain or contribute to sustainable marine fisheries were examined by reviewing and analyzing the current state and history of several U.S. fisheries. Among major factors under consideration are: inherent vulnerability, (vulnerability in some species is high because of low intrinsic rates of increase and/or naturally infrequent recruitment); environmental degradation (fisheries may collapse because of anthropogenic habitat destruction); availability of data, (information necessary to conduct accurate stock assessments may not be adequate for some species); quality of the scientific advice, (inappropriate models or scientifically inaccurate assessments may be used); effectiveness of management decisions, (managers may disregard recommendations from scientific committees, and/or implement management measures that are 1 risk prone). Fisheries that are examined include the Atlantic coast striped bass fishery, the New England groundfish fishery, the Atlantic shark fishery, the Atlantic and Gulf reef fish fisheries, and the Pacific rockfish fishery. Although many of the factors listed above contributed to declines in these fisheries, the root cause in all cases was harvesting at rates that were much higher than could be sustained by recruitment. Management was largely ineffective because management decisions were risk prone and motivated by short-term economic considerations rather than long-term sustainability. Only after passage of legislation not only authorizing but specifying mandatory stock rebuilding has most management been sufficiently precautionary to allow sustainability

A study to explore the use of orbital remote sensing to determine native arid plant distribution

The author has identified the following significant results. It is possible to determine, from ERTS imagery, native arid plant distribution. Using techniques of multispectral masking and extensive fieldwork, three native vegetation communities were defined and mapped in the Avra Valley study area. A map was made of the Yuma area with the aid of ground truth correlations between areas of desert pavement visible on ERTS images and unique vegetation types. With the exception of the Yuma soil-vegetation correlation phenomena, only very gross differentiations of desert vegetation communities can be made from ERTS data. Vegetation communities with obvious vegetation density differences such as saguaro-paloverde, creosote bush, and riparian vegetation can be separated on the Avra Valley imagery while more similar communities such as creosote bush and saltbush could not be differentiated. It is suggested that large differences in vegetation density are needed before the signatures of two different vegetation types can be differentiated on ERTS imagery. This is due to the relatively insignificant contribution of vegetation to the total radiometric signature of a given desert scene. Where more detailed information concerning the vegetation of arid regions is required, large scale imagery is appropriate

A method of encoding generalized link diagrams

We describe a method of encoding various types of link diagrams, including those with classical, flat, rigid, welded, and virtual crossings. We show that this method may be used to encode link diagrams, up to equivalence, in a notation whose length is a cubic function of the number of 'riser marks'. For classical knots, the minimal number of such marks is twice the bridge index, and a classical knot diagram in minimal bridge form with bridge index $b$ may be encoded in space $\mathcal{O}(b^2)$. A set of moves on the notation is defined. As a demonstration of the utility of the notation we give another proof that the Kishino virtual knot is non-classical.Comment: 17 pages, 13 figures; to appear in the Journal of Knot Theory & Its Ramification

Visual Acuity of Juvenile Loggerhead Sea Turtles (Caretta caretta): A Behavioral Approach

Studies focusing on the visual cues sea turtles use to orient between the nesting site and the sea indicate that sea turtles use diffuse images for orientation and are highly myopic on land. The visual environment encountered by sea turtles, however, is very different in water than on land. In this study, operant conditioning techniques were used to explore the visual acuity of juvenile loggerhead sea turtles (Caretta caretta) in the marine environment. Turtles were trained, in a tank setting, to distinguish between a 45 mm striped panel and 50% gray panel by using squid as a food reward. Though the pace of training was limited by our guidelines for holding these animals in captivity and the amount of food we could give each animal in a week, all turtles were trained in under a month. Once training was achieved, the stripes were reduced in size (stripe width ranging from 45.0 – 0.035 mm) until the turtle chose the striped panel over the 50% gray panel based on chance; this level of choice was designated as threshold. Mean acuity threshold level for all turtles tested was found to be 0.078 (visual angle of 12.89 minutes of arc). These results are similar to those of other marine species and indicate that loggerhead sea turtles use distinct visual cues in the aquatic environment

Reduced renal function is associated with progression to AIDS but not with overall mortality in HIV-infected kenyan adults not initially requiring combination antiretroviral therapy

<p>Abstract</p> <p>Background</p> <p>The World Health Organization (WHO) has recently recommended that antiretrovirals be initiated in all individuals with CD4 counts of less than 350 cells/mm³. For countries with resources too limited to expand care to all such patients, it would be of value to able to identify and target populations at highest risk of HIV progression. Renal disease has been identified as a risk factor for disease progression or death in some populations.</p> <p>Methods</p> <p>Times to meeting combination antiretroviral therapy (cART) initiation criteria (developing either a CD4 count < 200 cells/mm³or WHO stage 3 or 4 disease) and overall mortality were evaluated in cART-naïve, HIV-infected Kenyan adults with CD4 cell counts ≥200/mm³and with WHO stage 1 or 2 disease. Cox proportional hazard regression models were used to evaluate the associations between renal function and these endpoints.</p> <p>Results</p> <p>We analyzed data of 7383 subjects with a median follow-up time of 59 (interquartile range, 27-97) weeks. In Cox regression analyses adjusted for age, sex, WHO disease stage, CD4 cell count and haemoglobin, estimated creatinine clearance (CrCl) < 60 mL/min was significantly associated with shorter times to meeting cART initiation criteria (HR 1.34; 95% CI, 1.23-1.52) and overall mortality (HR 1.73; 95% CI, 1.19-2.51) compared with CrCl ≥60 mL/min. Estimated glomerular filtration rate (eGFR) < 60 mL/min/1.73 m²was associated with shorter times to meeting cART initiation criteria (HR 1.39; 95% CI, 1.22-1.58), but not with overall mortality. CrCl and eGFR remained associated with shorter times to cART initiation criteria, but neither was associated with mortality, in weight-adjusted analyses.</p> <p>Conclusions</p> <p>In this large natural history study, reduced renal function was strongly associated with faster HIV disease progression in adult Kenyans not initially meeting cART initiation criteria. As such, renal function measurement in resource-limited settings may be an inexpensive method to identify those most in need of cART to prevent progression to AIDS. The initial association between reduced CrCl, but not reduced eGFR, and greater mortality was explained by the low weights in this population.</p

CD4 trajectory adjusting for dropout among HIV-positive patients receiving combination antiretroviral therapy in an East African HIV care centre

Objective: Estimates of CD4 response to antiretroviral therapy (ART) obtained by averaging data from patients in care, overestimate population CD4 response and treatment program effectiveness because they do not consider data from patients who are deceased or not in care. We use mathematical methods to assess and adjust for this bias based on patient characteristics. Design: We examined data from 25,261 HIV-positive patients from the East Africa IeDEA Consortium. Methods: We used inverse probability of censoring weighting (IPCW) to represent patients not in care by patients in care with similar characteristics. We address two questions: What would the median CD4 be “had everyone starting ART remained on observation?” and “were everyone starting ART maintained on treatment?” Results: Routine CD4 count estimates were higher than adjusted estimates even under the best-case scenario of maintaining all patients on treatment. Two years after starting ART, differences between estimates diverged from 30 cells/µL, assuming similar mortality and treatment access among dropouts as patients in care, to over 100 cells/µL assuming 20% lower survival and 50% lower treatment access among dropouts. When considering only patients in care, the proportion of patients with CD4 above 350 cells/µL was 50% adjusted to below 30% when accounting for patients not in care. One-year mortality diverged 6–14% from the naïve estimates depending on assumptions about access to care among lost patients. Conclusions: Ignoring mortality and loss to care results in over-estimation of ART response for patients starting treatment and exaggerates the efficacy of treatment programs administering it

Evaluating the Impact of a HIV Low-Risk Express Care Task-Shifting Program: A Case Study of the Targeted Learning Roadmap

In conducting studies on an exposure of interest, a systematic roadmap should be applied for translating causal questions into statistical analyses and interpreting the results. In this paper we describe an application of one such roadmap applied to estimating the joint effect of both time to availability of a nurse-based triage system (low risk express care (LREC)) and individual enrollment in the program among HIV patients in East Africa. Our study population is comprised of 16;513 subjects found eligible for this task-shifting program within 15 clinics in Kenya between 2006 and 2009, with each clinic starting the LREC program between 2007 and 2008. After discretizing followup into 90-day time intervals, we targeted the population mean counterfactual outcome (i.e. counterfactual probability of either dying or being lost to follow up) at up to 450 days after initial LREC eligibility under three fixed treatment interventions. These were (i) under no program availability during the entire follow-up, (ii) under immediate program availability at initial eligibility, but non-enrollment during the entire follow-up, and (iii) under immediate program availability and enrollment at initial eligibility. We further estimated the controlled direct effect of immediate program availability compared to no program availability, under a hypothetical intervention to prevent individualenrollment in the program. Targeted minimum loss-based estimation was used to estimate the mean outcome, while Super Learning was implemented to estimate the required nuisance parameters. Analyses were conducted with the ltmle R package; analysis code is available at an online repository as an R package. Results showed that at 450 days, the probability of in-care survival for subjects with immediate availability and enrollment was 0:93 (95% CI: 0.91, 0.95) and 0:87 (95% CI: 0.86, 0.87) for subjects with immediate availability never enrolling. For subjects without LREC availability, it was 0:91 (95% CI: 0.90, 0.92). Immediate program availability without individualenrollment, compared to no program availability, was estimated to slightly albeit significantly decrease survival by 4% (95% CI 0.03,0.06, p\u3c 0:01). Immediately availability and enrollment resulted in a 7% higher in-care survival compared to immediate availability with non-enrollment after 450 days (95% CI -0.08,-0.05, p\u3c 0:01). The results are consistent with a fairly small impact of both availability and enrollment in the LREC program on in-care survival

Critical assessment and ramifications of a purported marine trophic cascade

When identifying potential trophic cascades, it is important to clearly establish the trophic linkages between predators and prey with respect to temporal abundance, demographics, distribution, and diet. In the northwest Atlantic Ocean, the depletion of large coastal sharks was thought to trigger a trophic cascade whereby predation release resulted in increased cownose ray abundance, which then caused increased predation on and subsequent collapse of commercial bivalve stocks. These claims were used to justify the development of a predator-control fishery for cownose rays, the “Save the Bay, Eat a Ray” fishery, to reduce predation on commercial bivalves. A reexamination of data suggests declines in large coastal sharks did not coincide with purported rapid increases in cownose ray abundance. Likewise, the increase in cownose ray abundance did not coincide with declines in commercial bivalves. The lack of temporal correlations coupled with published diet data suggest the purported trophic cascade is lacking the empirical linkages required of a trophic cascade. Furthermore, the life history parameters of cownose rays suggest they have low reproductive potential and their populations are incapable of rapid increases. Hypothesized trophic cascades should be closely scrutinized as spurious conclusions may negatively influence conservation and management decision