Multiple stable reference points in oyster populations: biological relationships for the eastern oyster (Crassostrea virginica) in Delaware Bay

Abstract—In the first of two companion papers, a 54-yr time series for the oyster population in the New Jersey waters of Delaware Bay was analyzed to develop biological relationships necessary to evaluate maximum sustainable yield (MSY) reference points and to consider how multiple stable points affect reference point-based management. The time series encompassed two regime shifts, one circa 1970 that ushered in a 15-yr period of high abundance, and a second in 1985 that ushered in a 20-yr period of low abundance. The intervening and succeeding periods have the attributes of alternate stable states. The biological relationships between abundance, recruitment, and mortality were unusual in four ways. First, the broodstock–recruitment relationship at low abundance may have been driven more by the provision of settlement sites for larvae by the adults than by fecundity. Second, the natural mortality rate was temporally unstable and bore a nonlinear relationship to abundance. Third, combined high abundance and low mortality, though likely requiring favorable environmental conditions, seemed also to be a self-reinforcing phenomenon. As a consequence, the abundance –mortality relationship exhibited both compensatory and depensatory components. Fourth, the geographic distribution of the stock was intertwined with abundance and mortality, such that interrelationships were functions both of spatial organization and inherent populatio

Multiple stable reference points in oyster populations: implications for reference point-based management

In the second of two companion articles, a 54-year time series for the oyster population in the New Jersey waters of Delaware Bay is analyzed to examine how the presence of multiple stable states affects reference-point–based management. Multiple stable states are described by four types of reference points. Type I is the carrying capacity for the stable state: each has associated with it a type-II reference point wherein surplus production reaches a local maximum. Type-II reference points are separated by an intermediate surplus production low (type III). Two stable states establish a type-IV reference point, a point-of-no-return that impedes recovery to the higher stable state. The type-II to type-III differential in surplus production is a measure of the difficulty of rebuilding the population and the sensitivity of the population to collapse at high abundance. Surplus production projections show that the abundances defining the four types of reference points are relatively stable over a wide range of uncertainties in recruitment and mortality rates. The surplus production values associated with type-II and type-III reference points are much more uncertain. Thus, biomass goals are more easily established than fishing mortality rates for oyster population

Do confronto à conciliação : debates presidenciais na TV como eventos persuasivos

Este estudo faz uma análise dos debates presidenciais na televisão como eventos persuasivos de campanha. O objetivo foi contribuir para a compreensão não só do papel dessa fonte de informação política no contexto brasileiro, mas discutir também de maneira sistemática os seus possíveis efeitos. Os debates na TV são uma variável comunicacional de curto prazo dos processos eleitorais. Eles oferecem estímulos comunicacionais que são disseminados no ambiente da campanha, seja por quem o assiste diretamente, seja por quem fica sabendo desses eventos e dos desempenhos dos candidatos através de outros dispositivos, como a imprensa e o Horário da Propaganda Gratuita Eleitoral (HPGE). Como apenas informação não basta para explicar mudanças de opinião, focamos o estudo em dois eixos principais. O primeiro deles na identificação e no mapeamento das estratégias persuasivas adotadas pelos candidatos, porque eles são instados a confrontar seus adversários, num evento ao vivo, e por meio do qual os eleitores podem avaliar não só o seu posicionamento político, como a maneira que se apresentam. Está presente, neste caso, um impacto sobre a atitude dos eleitores com relação aos competidores. Os principais resultados indicam haver um padrão no objetivo das mensagens, prevalecendo, no agregado, o ataque entre os candidatos da oposição, e a aclamação entre os candidatos da situação. O posicionamento do candidato, bem como o conteúdo político das mensagens apresentaram resultados significativos para um possível efeito sobre a atitude dos eleitores. No estudo, propomos ainda a análise dos enquadramentos adotados pelos competidores, cuja função é estabelecer um quadro de referência para a audiência. Esta variável, que procura levar em conta aspectos da comunicação verbal e nãoverbal, também apresentou resultados significativos. No segundo eixo analítico, tratamos dos efeitos agregados desses acontecimentos de campanha. Foram analisados os debates de 2002, quando prevalecia um clima de opinião favorável à oposição, e 2010, quando o clima é favorável à situação. Com relação ao impacto dos debates no ambiente informacional, os dados sugerem que, em 2002, a atuação de Luiz Inácio Lula da Silva (PT), candidato da oposição, levou a uma ampliação da cobertura jornalística positiva sobre o candidato; enquanto houve um declínio dessa cobertura para José Serra (PSDB), candidato da situação. Em 2010, na cobertura da imprensa após os debates, tanto a candidata da situação, Dilma Rousseff (PT), quanto o da oposição, José Serra, apresentaram equilíbrio. O impacto no ambiente informacional da campanha foi acompanhado de um aumento da intenção de voto agregada para os candidatos que lideravam as pesquisas e que representavam a mudança em 2002, no caso Lula, ou a continuidade em 2010, no caso Dilma. Nas duas eleições, portanto, os debates na TV no Brasil indicaram ser eventos persuasivos importantes, apesar de terem um papel menos central como dispositivo de informação eleitoral e de não levarem à troca de posição entre os competidores nas pesquisas opinião. Mas eles contribuem, ao menos indiretamente, para consolidar e ampliar intenções de voto dos primeiros colocados a partir de uma percepção positiva disseminada sobre os seus desempenhos.

Benthic invertebrates that form habitat on deep banks off southern California, with special reference to deep sea coral

There is increasing interest in the potential impacts that fishing activities have on megafaunal benthic invertebrates occurring in continental shelf and slope ecosystems. We examined how the structure, size, and high-density aggregations of invertebrates provided structural relief for fishes in continental shelf and slope ecosystems off southern California. We made 112 dives in a submersible at 32−320 m water depth, surveying a variety of habitats from high-relief rock to flat sand and mud. Using quantitative video transect methods, we made 12,360 observations of 15 structure-form-ing invertebrate taxa and 521,898 individuals. We estimated size and incidence of epizoic animals on 9105 sponges, black corals, and gorgonians. Size variation among structure-form-ing invertebrates was significant and 90% of the individuals were <0.5 m high. Less than 1% of the observations of organisms actually sheltering in or located on invertebrates involved fishes. From the analysis of spatial associations between fishes and large invertebrates, six of 108 fish species were found more often adjacent to invertebrate colonies than the number of fish predicted by the fish-density data from transects. This finding indicates that there may be spatial associations that do not necessarily include physical contact with the sponges and corals. However, the median distances between these six fish species and the invertebrates were not particularly small (1.0−5.5 m). Thus, it is likely that these fishes and invertebrates are present together in the same habitats but that there is not necessarily a functional relationship between these groups of organisms. Regardless of their associations with fishes, these invertebrates provide structure and diversity for continental shelf ecosystems off southern California and certainly deserve the attention of scientists undertaking future conservation efforts.

Reference area as a factor affecting potential yield estimates of coral reef fishes

A compilation of 48 estimates of Caribbean and Pacific coral reef fish catches, ranging from 0.1 to 23.7 t km super(-2) year super(-1), obtained from coral reef areas ranging from 0.1 to nearly 4-10 super(5) km super(2), are used to show that observed catches, and hence potential yield estimates, depend strongly on the reference area. The implications for coral reef fisheries assessments are discussed.

The introduction of exotic fish in Sri Lanka with special reference to tilapia

Introductions of exotic finfish between 1948 and 1953 are reported in this paper, with a brief reference to earlier and later introductions. Exotic fish were introduced principally to develop the potential for aquaculture in fresh and brackish waters in order to increase the availability of fish for rural communities through the biological control of aquatic vegetation. The algal feeding tilapia (Sarotherodon mossambicus) has created a new food industry in inland and brackishwaters. It has supplemented marine fishery production in a community where animal protein intake consists mainly of fish. It is also being cultured in flooded rice fields and used in the control of malaria. This excellent table fish has not had any adverse environmental impact.

Spectroscopic study of galaxies in the Herschel Reference Sample

Galaxies are clusters of millions and billions of stars dynamically stable, with gas, dust and dark matter. They are the biggest isolated objects known in the Universe . Even though they are very complex systems, today we have a clear knowledge about their evolution and about their physical phenomena. Aside from the stellar component there is a gaseous component, principally neutral Hydrogen (HI), and dust that, although is not a significant component in terms of the mass, plays an important role on the absorption phenomena. Finally, cinematic and other kind of observations suggest the existence of a spheric dark matter halo, dominant in terms of mass and more extensive than the barionic component.

Long-Term Epidemiology of Streptococcus pneumoniae Serogroup 6 in a Region of Southern Europe with Special Reference to Serotype 6E

Streptococcus pneumoniae serotype 6E has recently been described, but its long-term epidemiology is not well known. From 1981-2013, 704 serogroup 6 clinical isolates were obtained in Gipuzkoa, Basque Country, Spain. All invasive and one in four non-invasive isolates were included. Overall, 75, 97, 51 and 45 serotypes 6A, 6B, 6C and 6E isolates, respectively, were detected. No serotype 6D isolates were identified. The prevalence of serotypes 6E and 6B, but not that of serotypes 6A and 6C, declined after the introduction of pneumococcal conjugate vaccines. Serotype 6E isolates showed the highest resistance rate. Most serotype 6E isolates were ST90.

Comparison of some traits of economic importance in tilapias (Orechromis niloticus and Sarotherodon galilaeus) with particular reference to their culture in Ghana

This study was conducted to determine which of the two major tilapia species in freshwater capture fisheries in Ghana, Oreochromis niloticus or Sarotherodon galilaeus, is more suitable for breed improvement and pond culture. It compares traits of economic importance, including seed output, specific growth rate, survival and sex ratios following androgen sex reversal. The results of the study showed that the aquaculture potential of S. galilaeus compares favorably with that of O. niloticus. However, S. galilaeus may be preferred because the males and females have an equal growth rate, which allows for manual sorting to raise both sexes in monosex culture, an inexpensive appropriate technology that an ordinary smallscale fish farmer can apply.

Biological reference points for managing kingfish, Scomberomorus commerson, in Oman

The 1987-1995 length composition of quarterly catches of Scomberomorus commerson (Lacepede 1800) was analyzed to determine various biological reference points for management purposes. These include: fishing mortality producing maximum yield-per-recruit in weight (F sub(max)), fishing mortality producing 50% relative mean mature biomass (F sub(50)), and fishing mortality producing recruits that would exactly replace their parent stock (F sub(rep)). F sub(max) provided misleading suggestions to increase fishing mortality on the stock which is currently at a low level. On the other hand, both F sub(50) and F sub(rep) provided acceptable results, suggesting reduction on the current fishing mortality by 17-40%.

Background Concepts for a Rotating Harvesting Strategy with Particular Reference to the Mediterranean Red Coral, Corallium rubrum

A simple cohort model was used as the basis for selecting the appropriate periodicity and number of separate unit areas in a rotating harvest scheme for a sedentary species, the red coral, Corallium rubrum, in the General Fisheries Management Council for the Mediterranean area. The rotation period in years, and hence the minimum number of unit areas involved, was determined on the basis of the time to maximum biomass by a simple calculation of the yield-per-recruit type, requiring a knowledge of natural mortality and growth rates. Other criteria may be more important, however, and in general for a long-lived species, will result in shorter rotation periods. These criteria may include economic factors, criteria based on the preferred size or quality of product, or criteria that take into account the cumulative risk of illegal fishing of closed areas with time, hence the growing cost of enforcement as harvestable product accumulates. For red coral, although maximum biomass is predicted to be reached after some 15-44 years, the above considerations suggest that a rotation period ofsome 9-15 years would be close to optimal, taking into account a range ofthe above considerations. This article discusses the relative merits of rotating harvest schemes in contrast to quota management for sedentary and semi-sedentary resources or geographically isolated substocks ofa mobile resource, and concludes that this approach may have considerable potential as an alternative approach to resource management.

Episodic variations in stream water chemistry associated with acid rainfall and run-off and the effect on aquatic ecosystem, with particular reference to fish populations in N.W. England

This is the episodic variations in stream water chemistry associated with acid rainfall and run-off and the effect on aquatic ecosystems, with particular reference to fish populations in North West England produced by the North West Water Authority in 1985. This report looks at the biological, physical and chemical information collected over a five year period from over 100 sites on upland streams in the North West Region of which drained rocks of low buffering capacity. In both Lake District and South Pennine sites striking differences were found between the composition of invertebrate communities inhabiting acid-stressed and less acid-stressed streams. Electric fishing surveys showed that acidic streams (geometric mean pH <5.5) generally had abnormally low densities of salmonids ( < 0 .2m2) and that 0+ fish were very few or absent. The latter indicates recruitment failure. Salmon were more sensitive than trout to low pH.

A report on the strategic stock assessment survey of the Colton Beck catchment 1994 with particular reference to salmonids

This is the report on the strategic stock assessment survey of the Colton Beck catchment in 1994 with particular reference to salmonids in Colton Beck, River Ea, River Gilpin and Rusland Pool. This report forms one part of the third year of a triennial survey programme for the South West Cumbria and South Cumbria catchments. It was produced by the National Rivers Authority in 1994. Colton Beck had excellent densities of sea trout (Salmo trutta) and a small population of salmon (Salmo salar) in its lowest reaches. The total productivity was very good throughout the catchment. Stocking of sea trout fry in 1993 has enhanced the population with survivors through to parr probably adding to the scoring of double class A at two sites in the survey in 1994. Stocking was not undertaken in 1994, but the population appears to be maintaining itself at a very high level.

A report on the strategic fisheries stock assessment survey of the minor catchments in South West Cumbria 1996 with particular reference to salmonids

This is the report on the strategic fisheries stock assessment survey of the minor catchments in South West Cumbria 1996 with particular reference to salmonids, produced by North West Water in 1994. The 1996 Minor Catchment survey indicates variations in salmonid production within these catchments. Survey results indicate that production may be reaching its limit in certain areas whilst others are underachieving and others are unsuitable for salmonid production. Trout production within the catchments is higher and more widespread than that of salmon. Water quality levels vary considerably between catchments and intra-annually within individual catchments. The need for selective habitat surveys, with a view to habitat improvement schemes (H.I.S) is discussed. This report formed a basis for subsequent reports, thus, allowing data comparisons and analysis of production level fluctuations. It was the most extensive assessment of these catchments to date, taking into account comparisons with the new National Database on salmonid production in England and Wales.