Recovery and recruitment of the brown mussel,Perna perna (L.), in Transkei: implications for management

The brown mussel Perna perna, has been an important food resource for indigenous inhabitants of the Transkei coast for centuries. The impoverished state of mussel stocks in this region and major differences in low-shore community structure between exploited and protected areas, have been ascribed to the ever-increasing exploitation of this species. In spite of this there has been no effective management of this resource owing to political and logistical problems related to law-enforcement, and misconceptions concerning the resilience of P. perna and the interspecific interactions which govern its recovery. Our present understanding of the ecological impacts of exploitation, and of the potential for recovery, is based on a series of studies and observations made over the last 15 years. These studies have shown that algae usually replace mussels following disturbance and that recovery may take more than eight years. As mussels tend to recruit preferentially into existing mussel beds, exploitation not only affects reproductive output but also reduces the preferred habitat. Recruitment onto both natural and artificial substrata is extremely low, even in marine reserves where standing stock is considerably higher than in exploited areas. Under these conditions stock enhancement in conjunction with rotational cropping may be the best management strategy.     

Measurement of biological oxygen demand in sandy beaches

Measurements of biological oxygen demand in a sandy beach using conventional in situ techniques are compared with laboratory measurements of interstitial oxygen changes in intact cores. Oxygen uptake as measured in the laboratory was approximately three times that measured in the field despite the fact that the cores were undisturbed. In addition, the effect of disturbance on sediment cores was investigated and it was found that oxygen demand in disturbed cores increased by up to 60%, due mainly to an increase in bacterial activity. This effect was still evident after 24 hours of incubation. The applicability of conventional respirometer techniques to well-drained systems such as open sandy beaches is questioned and an alternative approach suggested.     

Environmental factors on virulence of <Emphasis Type="Italic">Aeromonas hydrophila</Emphasis>

Aeromonas hydrophila are known for being opportunistic pathogens, harboring various virulence factors and triggering lesions and death in fish. The disease caused by bacteria can make fish inappropriate for human consumption, besides representing a risk to public health. The pathogenesis can be influenced by environmental variables, affecting fish productivity and mortality. The present study aimed to determine whether A. hydrophila harbor the virulence genes aerolysin, hydrolipase, elastase, lipase, cytotonic enterotoxin (ast), lateral flagellum (laf), and polar flagellum (fla) and to evaluate the influence of environmental variables on in vitro growth, in vivo virulence and expression of some of these genes. Polymerase chain reaction (PCR)-based screening for the presence of these virulence genes was performed on 35 isolates. Six isolates containing different profiles of virulence genes were tested for in vitro growth under different conditions of pH, temperature, and ammonia and for in vivo virulence under these same environmental conditions. RT-qPCR was used to quantify the expression of aerolysin, lipase, and fla genes. All the tested environmental factors influenced the growth of A. hydrophila, while pH and ammonia concentrations influenced the bacterial virulence. The expression of the fla gene increased when bacteria were grown in higher ammonia concentration. The mortality established by Aeromonas is influenced by several environmental factors pinpointing the importance of its control in fish farming to avoid higher economic loses associated to bacterial disease outbreaks.     

IgG subclass responses in a longitudinal study of canine visceral leishmaniasis

Visceral leishmaniasis (VL), caused by Leishmania infantum, is an important disease of domestic dogs. Here, we present data on the IgG subclass antibody response to crude L. infantum antigen in a cohort of naturally infected Brazilian dogs. Specific IgG1-IgG4 responses could be detected in 98, 58, 70 and 82%, respectively of 57 dogs that were seropositive for specific IgG. Levels of all IgG subclasses were strongly inter-correlated. Levels of all IgG subclasses increased at the time of seroconversion, before reaching a plateau after several months. Levels of all IgG subclasses were higher in sick dogs than healthy dogs, and levels of all except IgG2 were higher in parasite-positive (by PCR) than parasite-negative dogs. However, levels of IgG2 relative to IgG1 were lower in sick or parasite-positive dogs compared to healthy or parasite-negative infected dogs. In contrast to previous studies, the results suggest that canine VL is associated with upregulation of specific antibody of all IgG subclasses, particularly IgG1, IgG3 and IgG4.     

Growth Acceleration of Seawater-Adapted Female Chinook Salmon Oncorhynchus tshawytscha by Constant Infusion of Recombinant Bovine Growth-Hormone Under Ambient Summer Conditions

Seawater-adapted female chinook salmon ( Oncorhynchus tshawytscha ) in their second summer were treated with one of three doses of recombinant bovine growth-hormone (rbGH) administered in a continuous fashion by osmotic pump for approximately five weeks. Untreated fish, sham-treated fish and fish treated with the low dose of hormone (0.003 μg/g bwt/day) did not differ significantly in their growth performance over the 10 week course of the experiment. By the end of the treatment period (week 6) the mean increases in fork length and weight for these groups were 7.6% and 38.9%, respectively. A dose-dependent enhancement of growth was observed for the fish treated with the mid (0.016 μg/g bwt/day) and high (0.078 μg/g bwt/day) doses of hormone. After 6 weeks, the fish given the mid dose of rbGH had gained 9.6% in fork length and 45.3% in weight, while the fish treated with the high dose of rbGH had gained 13.9% in fork length and 52.9% in weight. A significant increase in specific growth rate was observed for these latter two groups during the treatment period while condition factor declined in response to the high dose of rbGH. This experiment indicates that chronic administration of growth-hormone to chinook salmon can result in a dose dependent elevation of growth rate. Results are discussed in relation to previous attempts to accelerate the growth of Pacific salmon with growth-hormone and the potential for using recombinant growth-hormone to improve the production characteristics of salmon being cultured in seawater.     

The detection of a population of submillimeter-bright, strongly lensed galaxies

Gravitational lensing is a powerful astrophysical and cosmological probe and is particularly valuable at submillimeter wavelengths for the study of the statistical and individual properties of dusty star-forming galaxies. However, the identification of gravitational lenses is often time-intensive, involving the sifting of large volumes of imaging or spectroscopic data to find few candidates. We used early data from the Herschel Astrophysical Terahertz Large Area Survey to demonstrate that wide-area submillimeter surveys can simply and easily detect strong gravitational lensing events, with close to 100% efficiency.     

Applying distribution model projections for an uncertain future: the case of the Pacific oyster in UK waters

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Aquatic food security: insights into challenges and solutions from an analysis of interactions between fisheries,aquaculture, food safety,human health,fish and human welfare,economy and environment

Fisheries and aquaculture production, imports, exports and equitability of distribution determine the supply of aquatic food to people. Aquatic food security is achieved when a food supply is sufficient, safe, sustainable, shockproof and sound: sufficient, to meet needs and preferences of people; safe, to provide nutritional benefit while posing minimal health risks; sustainable, to provide food now and for future generations; shock‐proof, to provide resilience to shocks in production systems and supply chains; and sound, to meet legal and ethical standards for welfare of animals, people and environment. Here, we present an integrated assessment of these elements of the aquatic food system in the United Kingdom, a system linked to dynamic global networks of producers, processors and markets. Our assessment addresses sufficiency of supply from aquaculture, fisheries and trade; safety of supply given biological, chemical and radiation hazards; social, economic and environmental sustainability of production systems and supply chains; system resilience to social, economic and environmental shocks; welfare of fish, people and environment; and the authenticity of food. Conventionally, these aspects of the food system are not assessed collectively, so information supporting our assessment is widely dispersed. Our assessment reveals trade‐offs and challenges in the food system that are easily overlooked in sectoral analyses of fisheries, aquaculture, health, medicine, human and fish welfare, safety and environment. We highlight potential benefits of an integrated, systematic and ongoing process to assess security of the aquatic food system and to predict impacts of social, economic and environmental change on food supply and demand.