Size heterogeneity, growth potential and aggression in juvenile yellowtail kingfish (Seriola lalandi Valenciennes)

The ontogenetic development of size heterogeneity and aggression was monitored in commercial culture tanks of yellowtail kingfish (Seriola lalandi Valenciennes). Size heterogeneity increased substantially with the introduction of Artemia as a food source at 12 days post‐hatch (DPH), and was correlated with the appearance of aiming behaviour, a precursor to more direct aggressive interactions. Chasing behaviour started at approximately 19 DPH (10–12 mm total length), with the main aggressors being large‐grade individuals comprising 8% of the population. At any one time, only 10–30% of this grade carried out all of the chases, meaning that a very small proportion of the entire population (1%) was responsible for most of the aggressive interactions. The main recipients of aggression were the small grade, comprising 42% of the population, while the medium grade (50% of the population) were generally not aggressive and received only a low to moderate level of aggression. A grading trial showed that large‐grade juveniles only displayed aggressive behaviour in the presence of size heterogeneity, and that medium‐ or small‐grade juveniles did not establish an agonistic hierarchy in the absence of large individuals. A high level of aggression in the ungraded control treatment was associated with mortality of most of the small individuals. Even in the absence of aggression, the small‐grade juveniles failed to gain weight or show an increase in the RNA/DNA ratio after 12 days. The large‐ and medium‐grade larvae showed an isometric increase in RNA/DNA ratio during development, indicating that faster‐growing individuals are likely the result of better food capture or processing traits rather than better protein synthesis rates. Decreasing size heterogeneity and aggression via grading mostly benefits the medium‐grade individuals, as the majority of small individuals within a batch appear to be on a degenerative developmental trajectory irrespective of an aggressive environment.     

A qPCR MGB probe based eDNA assay for European freshwater pearl mussel (Margaritifera margaritifera L.)

1. Environmental (e)DNA assays are becoming increasingly used to detect rare or invasive aquatic species. 2. The Critically Endangered freshwater pearl mussel Margaritifera margaritifera is undergoing range‐wide reduction in population numbers and distribution. 3. An eDNA assay to detect the presence of M. margaritifera was developed, based on the mitochondrial cytochrome oxidase I gene, utilizing species‐specific primers, a minor groove binding (MGB) probe and quantitative (q)PCR approaches. 4. The results from this pilot study demonstrated high sensitivity both in laboratory and field trials, and provide a valuable non‐invasive tool for detecting M. margaritifera.     

Low stress response exhibited by juvenile yellowtail kingfish (Seriola lalandi Valenciennes) exposed to hypercapnic conditions associated with transportation

Transportation of yellowtail kingfish (Seriola lalandi Valenciennes) juveniles from hatchery to on‐growing operations in New Zealand exposes the fish to significantly elevated carbon dioxide (CO₂) concentrations. Experiments were undertaken to assess metabolic and haematological stress responses after a 5‐h period of hypercapnia, followed by recovery in normocapnia. Mortality was low (0.5%) and secondary stress indices (blood glucose, blood lactate, muscle pH and muscle lactate) remained largely unchanged during a simulated transportation and recovery, despite juveniles being exposed to CO₂ concentrations as high as 75 mg CO₂ L^?1 (38 mm Hg partial pressure). There was some haematological disturbance midway through simulated transports, where water was maintained at fixed CO₂ concentrations of 8 and 50 mg CO₂ L^?1 (4 and 26 mm Hg respectively). Persistent erythrocyte swelling continued during transport at 50 mg CO₂ L^?1, whereas at 8 mg CO₂ L^?1, haematological variables had returned to control levels. There was no mortality recorded for any of the treatments, and haematological variables were restored to pre‐manipulation levels after 31 h. The results indicated that juvenile yellowtail kingfish have a robust physiology and can cope with the stressors imposed by acute exposure to moderate to high levels of CO₂ associated with live transport.     

Comparative thermometric coagulation studies of plasmas from normal outbred Swiss Webster mice and persons.

The functional capabilities of a thermometric clot-timer have been demonstrated in a comparative study of human and mouse plasma coagulation. The influence of some variables on coagulation times of mouse and human plasmas were examined in activated partial thromboplastin time, one-stage prothrombin time, and Russell's viper venom time assays. Mouse plasma coagulation times were generally shorter and more reproducible than those of human plasma. Optimal assay conditions are also described.     

Shea (<Emphasis Type="Italic">Vitellaria paradoxa</Emphasis> C. F. Gaertn.) at the crossroads: current knowledge and research gaps

Shea (Vitellaria paradoxa C. F. Gaertn.) is arguably socio-economically and environmentally the most important plant species in the semi-arid and arid zones of Africa where it is widely distributed. Apart from the economic gains in international export markets where shea butter is valued for use in luxury cosmetic, pharmaceutical and confectionary industries, locally the fat (butter) is the main cooking oil for over 86 million inhabitants. Research during the past decades has acknowledged the chemical and nutritional composition as well as the ethnobotanical uses of shea which has resulted in its butter being used in a wide array of products. This review summarizes the current knowledge of the morphological and genetic diversity; propagation, initial growth, and management; ecology and population structure; chemical and nutritional composition as well as the socioeconomic and livelihood empowerment potential of shea. Little is known about the fruiting behaviour and the responses of shea to the inevitable changes in climate. We suggest ecophysiological and dendrochronological studies as an option to predict how the domestication of this multipurpose tree species can be sustained even under the prospects of global climate change.     

An invertebrate harmfulness scale for research on plant pest diversity and impacts

Traditional methods of quantifying the harmful effects of invertebrates on plants require time-consuming identification of large numbers of individuals at species level. Collected specimens usually are killed; this may be unacceptable for some strictly protected species and may bias the results of subsequent surveys at the same site.

We developed a “harmfulness scale” for quick, non-invasive assessment of invertebrate impacts on plants, and used the scale to test differences in invertebrate attack on species of Balsaminaceae, Polygonaceae and Asteraceae growing in lowland and mountains in Poland. In 2010–2011, we recorded 9190 invertebrates and identified them in situ to family or superfamily level. Among them were 7593 pests, accounting for 82.6% of all recorded organisms. Pests were three times more numerous in the mountains than in the lowland. Balsaminaceae were most heavily attacked by pests (92.9% of all organisms detected on them). Aphidoideae were the most numerous pests.

This method can help reduce the costs and labour required for this type of research, facilitating progress in theoretical biology and in the development of practical phytosanitary measures.     

Relative impacts of native and non‐native crayfish on shelter use by an indigenous benthic fish

• 1. The North American signal crayfish Pacifastacus leniusculus has been widely introduced throughout Europe where it is expanding its range and in many areas replacing the native white‐clawed crayfish Austropotamobius pallipes. There is concern with regards to the impact of this species replacement on benthic fish. Interspecific behavioural interactions and competition for shelter between the benthic fish, bullhead Cottus gobio and A. pallipes and P. leniusculus were measured to assess the comparative impact of native and non‐native crayfish.
• 2. Both white‐clawed crayfish and signal crayfish were dominant over bullhead. Bullheads moved away from approaches of crayfish, left shelters on entry of crayfish and rarely entered an occupied shelter. Signal crayfish made significantly more aggressive approaches towards bullheads than white‐clawed crayfish.
• 3. Alone, bullheads spent most of their time by day under shelter (median 96%), reflecting a highly entrained behavioural response, which was relaxed by night (median 60%). Both crayfish species reduced shelter use by bullheads although the extent of shelter sharing by bullheads was higher in trials with white‐clawed crayfish than with signal crayfish.
• 4. Sampling in the River Wharfe, northern England, where signal and white‐clawed crayfish and bullhead currently exist, demonstrated a negative relationship between the densities of signal crayfish and bullhead, with high bullhead abundance where crayfish were absent or where white‐clawed crayfish were present at low density.
• 5. Assuming that shelter is sometimes limited under natural conditions, crayfish are likely to displace bullheads from shelters, which may increase predation risk for bullheads. Although the effects of signal crayfish on bullhead shelter use were more intense, the pattern was highly evident for the native white‐clawed crayfish. The higher fecundity and densities attained by signal crayfish may be more significant than differences in the behaviour of the two crayfish species in determining the impact of crayfish on bullheads.

Copyright © 2008 John Wiley & Sons, Ltd.     

Cost–benefit analysis of two culture methods that influence pearl production from the black‐lip pearl oyster,Pinctada margaritifera

The black‐lip pearl oyster, Pinctada margaritifera, used for round pearl production in Polynesia, is generally cultured using “ear‐hanging” where they are attached to a rope to form “chaplets.” In other countries, pearl oysters are cultured using panel (pocket) nets that are more expensive than chaplets but afford more protection to cultured oysters. Prior research has shown panel nets produce pearls of higher quality and value, potentially generating higher profits. This study used cost–benefit analysis to compare pearl production using chaplet‐based and panel net‐based culture methods. Whole farm data, including gross revenues and annual production costs, fixed and variable, were analyzed. Average production cost per pearl using panel net‐based culture was USD 22.47 and for chaplet‐based culture was USD 21.55. However, use of panel nets saved around 3,430 hr (USD 6,860) of labor a year, offsetting the greater capital investment. A chaplet‐based pearl farm generated USD 65,738 in annual profits compared to USD 88,774 for a panel net‐based farm. Positive cash flow was achieved 1 year earlier (Year 7) for the panel net‐based farm. This is the first economic analysis of different pearl culture methods for P. margaritifera and evidence of profitability will support further development of the black‐lip pearl industry in the Indo‐Pacific region.     

Farmland bird responses to intersecting replanted areas

Despite increasing revegetation of cleared landscapes around the world, there is limited research on the implications of different types of plantings for birdlife. We examined the “intersection effect”, whereby species richness is higher at the intersection of “corridors” or vegetation strips for birds inhabiting replanted areas. We also examined individual species responses. Replicated sites at the intersections of plantings were compared with “internal controls” (located in the same plantings ∼100 m from intersections), “external controls”(sites in isolated linear plantings), and block plantings. We surveyed the 39 sites in our experimental design repeatedly – on different days by different observers and in different seasons. We found no significant difference in species richness between intersections and block plantings, but intersections had higher species richness than isolated linear strips and the internal controls. Similar results were found for bird assemblage scores derived by correspondence analysis. We found evidence of extra-variation at the farm-level for species richness and derived assemblage scores, suggesting a farm-scale response. This suggests the importance of other (often unmeasured) factors at the farm level (e.g. baiting for feral animals). Our results suggest that replanting programs aimed at maximizing bird species richness may benefit from consideration of planting geometry. In particular, linking strip plantings to create intersections and/or establishing block plantings appear to be superior to isolated strips for aggregate species richness.