Digestive enzymes present in Pacific threadfin Polydactylus sexfilis (Bloch & Schneider 1801) and bluefin trevally Caranx melampygus (Cuvier 1833)

Pacific threadfin Polydactylus sexfilis (Bloch & Schneider 1801) and bluefin trevally Caranx melampygus (Cuvier 1833) are warmwater marine finfish currently under development for aquaculture in the Pacific. Differences in specific activities of digestive enzymes extracted from the stomach and mid-gut were compared to gain insight into their feeding habits in the wild and to understand their nutritional needs. Adult fish were maintained in captivity and fed a commercial pelleted feed. Serine protease measured in all tissues was at least 20 times higher in threadfin than in trevally. Aspartic proteases were the major digestive enzymes found in trevally. There was a 34-fold increase in collagenase activity in the intestine of threadfin from the prefed to the fed state. Chitinase activity was found in the stomach, pylorus and intestine of both species. However, specific activity in pylorus and intestine of threadfin increased 2.75 and 4 times, respectively, but showed little change in trevally. Amlyases were found only in trevally. Increase in lipase specific activity in the gut of trevally was higher than that for threadfin. The results indicated that the two species have diverse digestive capabilities. This appears to be consistent with their feeding habits in nature. Threadfin are more adapted to a wider range of food protein sources than trevally, but appear to be less well adapted than trevally to using complex carbohydrates. These observations may provide a basis for practical diet formulations for these two species.     

Effects of rindite on breaking dormancy of potato microtubers

Potato microtubers were treated with rindite to investigate the effect on dormancy breaking. Postharvest application of rindite by fumigation with 2 ml rindite for 48 hr or 4ml for 24 hr significantly reduced the dormancy period of potato microtubers using a 32 x 15 x 17 cm tightly sealed plastic box. Approximately 2 weeks after the treatments microtubers of all cultivars, Atlantic, Superior, Lemhi Russet, Red Dale and Kennebec started to sprout. The efficiency of the treatments were the greatest for the cv. Lemhi Russet, intermediate for cv. Superior and least for cv. Red Dale. In all cultivars of potato microtubers, more decay was observed the earlier rindite treatment occurred after harvesting, therefore potato microtubers should be treated with rindite at least 2 weeks after harvest when the skin of microtubers is mature. The data indicates that the dormancy of potato microtubers with well-matured skin can be effectively broken with an optimum treatment of rindite.     

Plant invasion and management in turf‐dominated waste landfills in South Korea

A floristic survey was conducted in turf‐dominated fields on some waste landfills in South Korea, to quantify the degree of plant invasion in those degraded lands. The dominant species, except turf (Zoysia japonica), were Conyza canadensis, Setaria viridis, Digitaria sanguinalis and Aster tripolium. Mean species number declined linearly with distance from the edge of the turf stands. Biomass of each species ranged between 0.1 g and 122.6 g, decreasing linearly with distance from the edge of the stand and declining exponentially with turf coverage. Mean soil moisture storage and organic matter content were 12.59 per cent and 5.81 per cent, respectively. Sum of relative cover, frequency and biomass of all species with environmental variables (distance from the stand edge, turf cover, soil moisture storage, soil organic matter content and the ratio of species number of exotic plants to that of native plants) were ordinated by DCA (detrended correspondence analysis). The first axis of the DCA was positively correlated with distance from the stand edge and turf cover and the second axis of the DCA was negatively correlated with soil organic matter content. Highly and lowly invasive species were indicated from DCA results. From analysis of dispersal type, barochore and anemochore were the most widespread of other dispersal types but it was suggested that anthropochore played an important role in plant invasion in these degraded wastelands. Establishment of an edge transition zone, enhancement of turf cover and reduction in traffic is recommended as management options for turf fields. Copyright © 2002 John Wiley & Sons, Ltd.     

Examining talent attraction and retention in small and medium-sized cities: Where do universities fit in?

As universities have become more integrated into their communities and regions, their host cities have become locations of choice for the highly educated facilitating increased innovation and productivity rates in several locales. Recent transitions toward knowledge-driven economies have also intensified growing geographic divides along the lines of education and raised concerns about the possibility of brain drain in a growing number of cities/regions. This study examines the changing geography of highly educated individuals (2000–2017) with a focus on small and medium-sized U.S. metropolitan areas with and without research universities. Results indicate the continuing trend of divergence among regions, but research universities are found to complement (the lack of) talent agglomeration and generate spatial spillovers beyond the county boundaries.     

Development of a low-energy midwater trawl with different combinations of trawl nets and trawl doors through model experiments

Greenhouse gas (GHG) emissions from fisheries are of primary concern because of their effects on the environment. GHG emissions from fisheries are mainly related to their fuel consumption. Furthermore, the fuel consumption of fisheries also influences their economics. Therefore, many studies have been conducted to find ways of reducing fuel consumption in fishing operations that use fishing gear. The fuel consumption of fishing gear is generally related to its hydrodynamic resistance and the distance traveled. It mostly depends on the drag created, which is affected by towing speed. Based on model experiments, this study proposes new designs of trawl net and trawl doors to reduce fuel consumption in fisheries. The low-energy midwater trawl developed here can reduce the resistance force on the gear by 37.5%. It can also save 17% of the fuel consumption per voyage. Furthermore, this study investigates the efficiency of a low-energy trawl from an economic point of view. The findings of this study will be useful in reducing GHG emissions in fishing operations and thus contribute to a reduction in fishing costs through fuel savings.     

Development of a polymerase chain reaction (PCR) procedure for the detection of baculovirus associated with white spot syndrome (WSBV) in penaeid shrimp

The causative viral agent was purified from diseased shrimp Penaeus japonicus with white spot syndrome (WSBV). Several hundred clones were obtained from libraries of the purified viral genomic DNA. According to the results of nucleotide sequence analysis, none of the WSBV clones showed considerable sequence homology with those of other known viruses, indicating that WSBV is a new virus causing a serious disease in shrimp. Based on the sequence data of WSBV genomic DNA, a pair of polymerase chain reaction (PCR) primers was designed. After 30 cycles of PCR amplification of viral genomic DNA extracted from WSBV, a single product of the expected size was detected. Southern blot hybridization confirmed that the amplified product was specific to the DNA of WSBV. The PCR system was able to detect 1 pg of WSBV DNA after 30 cycles, and efficiently amplify the target region of WSBV gene in the total nucleic acids extracted either from the diseased shrimp or hatchery shrimp with no signs of viral infection.     

Use of live and dead probiotic cells in tilapia Oreochromis niloticus

ABSTRACT:   To investigate the effect of live and dead probiotic cells on the non-specific immune system of tilapia Oreochromis niloticus , probiotics were introduced by feeding either in the form of live or dead cells, or supplying live cells to the rearing water in a closed recirculating system. The probiotics treatment enhanced non-specific immune parameters such as lysozyme activity, migration of neutrophils and plasma bactericidal activity, resulting in improvement of resistance to Edwardsiella tarda infection. Especially, oral administration of live cells seemed to be more effective compared with other probiotic treatments such as oral administration of dead probiotic cells and supply of live probiotic cells to the rearing water. These results indicate that probiotics treatment is promising as an alternative method to antibiotics for disease prevention in aquaculture, and the viability of probiotic bacteria is a key factor to induce more potential effect of probiotics used for fish production.     

Integrating physiology and life history to improve fisheries management and conservation

Knowledge of life‐history traits is increasingly recognized as an important criterion for effective management and conservation. Understanding the link between physiology and life history is an important component of this knowledge and in our view is particularly relevant to understanding marine and freshwater fishes. Such linkages (i.e. the life‐history/physiology nexus) have been recently advocated for avian systems and here we explore this concept for fish. This paper highlights the gap in fisheries literature with regard to understanding the relationship between physiology and life history, and proposes ways in which this integration could improve fisheries management and conservation. We use three case studies on different fishes (i.e. the Pacific salmon, the grouper complex and tuna) to explore these issues. The physiological structure and function of fish plays a central role in determining stock response to exploitation and changes in the environment. Physiological measures can provide simple indicators necessary for cost‐effective monitoring in the evaluation of fisheries sustainability. The declining state of world fisheries and the need to develop and implement restoration strategies, such as hatchery production or protected areas, provides strong incentive to better understand the influence of physiology on population and reproductive dynamics and early life history. Physiology influences key population‐level processes, particularly those dealing with reproduction, which must be incorporated into the design and successful implementation of specific and broadscale initiatives (e.g. aquatic protected areas and bycatch reduction). Suggestions are made for how to encourage wider application of the physiology/life‐history link, in fisheries management and conservation, as well as more broadly in education and research.