Stock assessment of the Atlantic menhaden, Brevoortia tyrannus, fishery

A stock assessment of the Atlantic menhaden, Brevoortia tyrannus, fishery was conducted with purse-seine landings data from 1940 to 1984 and port sampling data from 1955 to 1984. These data were analyzed to determine growth rates, maximum sustainable yield (MSY), spawner-recruit relationships, and yield per recruit. Virtual population analysis was used to estimate stock size, year class size, and fishing mortality rates. Surplus production models produced estimates of MSY from 450 to 490 kmt compared with yields of 416to 436 kmt based roughly on maximum recruitment from a weak spawner-recruit relationship. Recruitment to age-I ranged from 1.2 to 14.8 billion fish for year classes 1955-81. Recent mean recruitment to age-I for the 1975-81 year classes averaged 5.7 billion fish and compared favorably with the mean of 7.7 billion age-I fish recruited during the late 1950's. Mean recruitment from recent years suggests possible coastwide yields of 416 to 481 kmt. Continued dominance of late age-2 spawners among the spawning stock is of concern, since the stock is at greater risk through poor recruitment if recent favorable environmental conditions change. Yield-per-recruit estimates ranged from 46 g to 59 g since 1970. The high dependency of the modern fishery on prespawners has increased concerns about fluctuations in year-to-year availability and catches. To increase yield and enhance the stability of the resource, the number of age classes contributing significantly to the fishery should be increased, creating a butTer against future poor recruitment years and lessening the year-to-year fluctuations in landings. (PDF file contains 24 pages.

Atlantic menhaden, Brevoortia tyrannus, Purse Seine Fishery, 1972-84, with a brief discussion of age and size composition of the Landings

This report summarizes (I) annual purse seine landings of Atlantic menhaden, Brevoortia tyrannus, for 1972-84, (2) estimated numbers of fish caught by fishing area. (3) estimates of nominal fishing effort and catch-per-unit-effort, (4) mean fish length and weight, and (5) major changes in the fishery. During the 1970s stock size and recruitment increased and the age composition broadened. reversing trends witnessed during the fishery's decline in the 1960s. Landings steadily improved and by 1980 the total coast wide landings exceeded 400,000 metric tons. Nevertheless, the character of the fishery changed considerably. Eleven reduction plants processed fish at seven ports in 1972, but in 1984 only eight plants operated at live ports. Beginning in the mid-1960s the center of fishing aclivity shifted from the Middle Atlantic area to the Chesapeake Bay area, which has continued to dominate the fishery in landings and effort through the 1970s and 1980s. During this period the average size and age of fish in the catches declined. (PDF file contains 30 pages.

An extended XMM-Newton observation of the Seyfert galaxy NGC 4051. II. Soft X-ray emission from a limb-brightened shell of post-shock gas

An extended XMM-Newton observation of the Seyfert I galaxy NGC 4051 in 2009 revealed a complex absorption spectrum, with a wide range of outflow velocities and ionisation states.The main velocity and ionisation structure was interpreted in Paper I in terms of a decelerating, recombining flow resulting from the shocking of a still higher velocity wind colliding with the ISM or slower moving ejecta. The high sensitivity of the XMM-Newton observation also revealed a number of broad emission lines, all showing evidence of self-absorption near the line cores. The line profiles are found here to be consistent with emission from a limb-brightened shell of post-shock gas building up ahead of the contact discontinuity. While the broad emission lines remain quasi-constant as the continuum flux changes by an order of magnitude, recombination continua of several H- and He-like ions are found to vary in response to the continuum, providing an important key to scaling the ionised flow.Comment: Accepted for publication in MNRA

Augmentation of cytotoxic drug action and X-irradiation by antibodies.

The effect of an antiserum containing antibodies against cell surface components of PyBHK cells on the action of certain anticancer agents has been studied using a colony formation inhibition assay. The effects of x-rays, chlorambucil, CCNU and possibly ICRF 159 are augmented by the antiserum whereas methotrexate and vinblastine are not

Population characteristics of gulf menhaden, Brevoortia patronus

The status of the Gulf menhaden, Brevoortia patronus, fishery was assessed with purse-seine landings data from 1946 to 1997 and port sampling data from 1964 to 1997. These data were analyzed to determine growth rates, biological reference points for fi shing mortality from yield per recruit and maximum spawning potential analyses, spawner-recruit relationships, and maximum sustainable yield (MSY). The separable virtual population approach was used for the period 1976–97 (augmented by earlier analyses for 1964–75) to obtain point estimates of stock size, recruits to age 1, spawning stock size, and fishing mortality rates. Exploitation rates for age-1 fi sh ranged between 11% and 45%, for age-2 fi sh between 32% and 72%, and for age-3 fi sh between 32% and 76%. Biological reference points from yield per recruit (F0.1: 1.5–2.5/yr) and spawning potential ratio (F20: 1.3–1.9/yr and F30: 0.8–1.2/yr) were obtained for comparison with recent estimates of F (0.6–0.8/yr). Recent spawning stock estimates (as biomass or eggs) are above the long-term average, while recent recruits to age 1 are comparable to the long-term average. Parameters from Ricker-type spawner-recruit relations were estimated, although considerable unexplained variability remained. Recent survival to age-1 recruitment has generally been below that expected based on the Ricker spawner-recruit relation. Estimates of long-term MSY from PRODFIT and ASPIC estimation of production model ranged between 717,000 t and 753,000 t, respectively. Declines in landings between 1988 and 1992 raised concerns about the status of the Gulf menhaden stock. Landings have fl uctuated without trend since 1992, averaging about 571,000 t. However, Gulf menhaden are short lived and highly fecund. Thus, variation in recruitment to age 1, largely mediated by environmental conditions, infl uences fi shing success over the next two years (as age-1 and age-2 fi sh). Comparisons of recent estimates of fi shing mortality to biological reference points do not suggest overfishing. (PDF file contains 22 pages.

Biological Analysis of Two Management Options for the Atlantic Menhaden Fishery

Biological implications of two managment options (the closed corridor and the recommended shortened season (Option 7) options) for the Atlantic menhaden, Brevoortia tyrannus, fishery are reported based on purse-seine landings and port sampling data from 1970 to 1984 and captain's daily fishing reports from 1978 to 1982. Large catches of age-O menhaden raise concern for growth overfishing. Area-specific yield-per-recruit analyses are used to investigate the biological consequences of these management options. The closed corridor option indicates coastwide gains in yield-per-recruit ranging from 0.3 to 7.2% depending on changes in fishing activity with most areas showing gains. The shortened fishing season indicates coastwide gains in yield per recruit ranging from O. 4 to 10.2% depending onf ishing year with most geographic areas showing gains. The shortened fishing season option offers the greatest gains when large numbers ofy oung menhaden would be caught late in the fishing year, while gains from the closed corridor option depend on how the fishing fleet responds to that management plan. The shortened season offers greater potential coastwide gains to the fishery, but also may result in greater losses to the North Carolina fall fishery. The analytical approach is applicable to the management of other coastal migratory fish stocks that fall under the Atlantic States Marine Fisheries Commission or other interstate management groups

Survival of pneumococcus on hands and fomites

<p>Abstract</p> <p>Background</p> <p>Pneumococcal hand contamination in Indigenous children in remote communities is common (37%). It is not clear whether this requires frequent inoculation, or if pneumococci will survive on hands for long periods of time. Thus the aim of this study was to determine the survival time of pneumococci on hands and fomites.</p> <p>Findings</p> <p>The hands of 3 adult volunteers, a glass plate and plastic ball were inoculated with pneumococci suspended in two different media. Survival at specified time intervals was determined by swabbing and re-culture onto horse blood agar. Pneumococci inoculated onto hands of volunteers were recovered after 3 minutes at 4% to 79% of the initial inoculum. Recovery from one individual was consistently higher. By one hour, only a small number of pneumococci were recovered and this was dependent on the suspension medium used. At subsequent intervals and up to 3 hours after inoculation, < 10 colony forming units were recovered from hands. On a glass plate, pneumococcal numbers dropped an average 70% in the two hours after inoculation. Subsequently, < 100 colony forming units were recovered up to 15 hours after inoculation.</p> <p>Conclusion</p> <p>The poor survival of pneumococci on hands suggests that the high prevalence of pneumococcal hand contamination in some populations is related to frequent inoculation rather than long survival. It is plausible that hand contamination plays a (brief) role in transmission directly, and indirectly through contamination via fomites. Regular hand washing and timely cleansing or removal of contaminated fomites may aid control of pneumococcal transmission via these routes.</p

X-ray and optical variability of Seyfert 1 galaxies as observed with XMM-Newton

We have examined simultaneous X-ray and optical light curves of a sample of eight nearby Seyfert 1 galaxies observed using the EPIC X-ray cameras and Optical Monitor on board XMM. The observations span ~1 day and revealed optical variability in four of the eight objects studied. In all cases, the X-ray variability amplitude exceeded that of the optical both in fractional and absolute luminosity terms. No clearly significant correlations were detected between wavebands using cross correlation analysis. We conclude that, in three of the four objects in which optical variability was detected, reprocessing mechanisms between wavebands do not dominate either the optical or X-ray variability on the time-scales probed.Comment: 9 pages, 2 figures, accepted for publication in MNRA