Screening thirty soybean genotypes under solid and intercropping plantings in Egypt

Journal of Crop Science and Biotechnology - Cropping systems are relatively more important for testing soybean genotypes under Egyptian conditions. A field experiment was carried out at the...     

Water use and carbon exchange of red oak- and eastern hemlock-dominated forests in the northeastern USA: implications for ecosystem-level effects of hemlock woolly adelgid

Water use and carbon exchange of a red oak-dominated (Quercus rubra L.) forest and an eastern hemlock-dominated (Tsuga canadensis L.) forest, each located within the Harvard Forest in north-central Massachusetts, were measured for 2 years by the eddy flux method. Water use by the red oak forest reached 4 mm day(-1), compared to a maximum of 2 mm day(-1) by the eastern hemlock forest. Maximal carbon (C) uptake rate was also higher in the red oak forest than in the eastern hemlock forest (about 25 versus 15 micromol m(-2) s(-1)). Sap flux measurements indicated that transpiration of red oak, and also of black birch (Betula lenta L.), which frequently replaces eastern hemlock killed by hemlock woolly adelgid (Adelges tsugae Annand.), were almost twice that of eastern hemlock. Despite the difference between species in maximum summertime C assimilation rate, annual C storage of the eastern hemlock forest almost equaled that of the red oak forest because of net C uptake by eastern hemlock during unusually warm fall and spring weather, and a near-zero C balance during the winter. Thus, the effect on C storage of replacing eastern hemlock forest with a forest dominated by deciduous species is unclear. Carbon storage by eastern hemlock forests during fall, winter and spring is likely to increase in the event of climate warming, although this may be offset by C loss during hotter summers. Our results indicate that, although forest water use will decrease immediately following eastern hemlock mortality due to the hemlock woolly adelgid, the replacement of eastern hemlock by deciduous species such as red oak will likely increase summertime water use over current rates in areas where hemlock is a major forest species.     

Integration of mapping and socio‐economic status of cage culture: Towards balancing lake‐use and culture fisheries in Lake Victoria,Kenya

Mapping of lacustrine aquaculture and socio‐economic assessment of cage farmers operations can be employed as decision support tools in an integrated fashion for fisheries management. We simultaneously mapped and reported the location of cages and characterized socio‐economic and indicators of cage farming in Lake Victoria, Kenya. Structured questionnaires and interviews from cage farmers generated socio‐economic data and management information. Vital water quality parameters were analyzed in selected sampling sites. Cage culture was found to be a male‐dominated activity with the majority of owners aged <45 years (n = 23; 59%). Siaya County had the highest cage establishments (n = 20) and number (n = 1,343). Proximity to Dominion Farm, pioneers of cage culture, as well as decreased presence of water hyacinth (Eichhornia crassipes) coverage may have contributed to high cage numbers in Siaya County. The only species cultured was Oreochromis niloticus. Most cage establishments (n = 30; 76%) were located within 200 m from the shoreline. Total operational costs for a cycle (8 months) amounted to USD 465,250 worth a total production value of USD 8,827,000, farmers often realizing a mark‐up of >100%, indicative of its robust viability within “The Blue Economy” concept. With the increasing number of cages in the lake, there is the need for policy and regulations to guide its investment, both to protect local economies through improved business practices and to ensure sustainability for the lake ecosystem due to the likelihood of exacerbation in water quality deterioration in cage culture sites.     

Combined effects of photoperiod and temperature on growth and survival of African catfish (Clarias gariepinus,Burchell 1822) larvae under laboratory conditions

ABSTRACT

The effect of photoperiod (24L:00D, 12L:12D, and 00L:24D) and temperature (22 ± 1°C and 28 ± 1°C) on performance of Clarias gariepinus larvae was tested. Larvae weighing 3.2 ± 0.24 mg were cultured in aquaria at a stocking density of 20 fish L^?1 and fed twice a day on catfish starter diet (40% CP) at 10 % BW day^?1. Highest mean weight gain (31.00 mg), SGR (7.56% day^?1), and survival (83%) were achieved at photoperiod and temperature combination of 00L:24D and 28 ± 1°C. Percent survival of larvae differed significantly (p < .05) among treatments with optimal survival of (83%) in treatment combination of 28 ± 1°C and 00L:24D, while lowest survival (40%) in treatment combination of 22 ± 1°C and 24L:00D.     

Exploring the demarcation requirements of fish breeding and nursery sites to balance the exploitation,management and conservation needs of Lake Victoria ecosystem

Fisheries resources in vital freshwater ecosystems have been reported to be under immense threat, resulting in conflicts between conservation, management and exploitation. This study established requirements for identifying and mapping fish breeding and nursery grounds in such ecosystems in the Kenyan part of Lake Victoria. The criteria were characterised by the use of indigenous knowledge, field data, literature on breeding sites, macroinvertebrates distribution, larval and relative fish abundances, digitisation, participatory mapping, and periodic sampling. Data were collected from trawl and seine net surveys. Digitisation and mapping of the proposed conservation sites were carried out using Quantum GIS software. Participatory physical demarcation of sites was done using buoys and markers. Larval and juvenile fishes were diverse and abundant in all seven river mouths and six bays surveyed with little variance; an important aspect of breeding areas. Additionally, a preponderance of macroinvertebrates and high fish diversity compared with offshore sites in the lake strengthened the hypothesis that these are critical habitats for spawning and preferred habitats for nurseries for fish. The approach can be adopted globally to guarantee the long‐term integrity of critical fish habitats for sustainable fisheries management and blue growth.     

Using fish landing sites and markets information towards quantification of the blue economy to enhance fisheries management

Fisheries management uses important fish market information and information from Communication Technology (ICT) to improve fish trade by identifying inefficiencies, inequity and post‐harvest losses. The current study reports fisheries output using ICT at major landing sites and markets in Kenya and Uganda from the Kenya Marine and Fisheries Research Institute (KMFRI) Enhanced Fish Market Information Service (EFMIS) database for 2009 – 2017. Catch assessment survey data validated the use of market data in drawing conclusions. Regional Frame Survey data provided information before EFMIS, enabling comparisons of fish trade costings. The average quantity of fish traded in Kenya depended on seasons of active lake fishing, which occurs in January – March and August – October, while Uganda had an irregular pattern associated with fish trade throughout the year. The quantity of fish traded weekly depended on the average price of fish. Lower sales margins during the EFMIS project showed the merits of information sharing using ICT platforms for efficient and equitable fish trade. Such evaluation of fish market information is useful in fish trade policy formulation and for fisheries management and ecological sustainability in rural and peri‐urban communities.