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From Farming to Fishing: Marine Resource Conservation

Tue, 01 Jan 2008 00:00:00 GMT

Title: From Farming to Fishing: Marine Resource Conservation Authors: Versleijen, Nicole; Hoorweg, Jan Abstract: This paper examines the arrival of a new group of fishermen on the Kenyan coast and what this has meant for the state of fishery resources. It reviews four subject areas: access and the number of fishermen; the fishermen’s identity; the choice of fishing gear; and the fishing grounds selected. Data were collected from a small number of fishing households in the villages of Uyombo and Takaungu in Kilifi District, using mainly qualitative research methods. Local households on the Kenyan coast face increasing pressure on land as well as on marine resources. The declining economic situation and greater pressure on land have made people turn to fishing as an income-generating activity. This group of fishermen is referred to as the ‘new’ generation of fishermen as they have been involved in fishing for only one or two generations (including the current one) in contrast to the ‘old’ generation from families who have been fishing or in fishingrelated activities for much longer. The old generation of fishermen and their households have also diversified their incomes, with many fishing households turning to farming, for example, with women and grown-up children involved in various activities. The new generation of fishermen, mainly of the Mijikenda population group, has often been blamed for the loss of traditional access regulations and for using harmful fishing gear. This paper discusses the new generation of fishermen and their identity as they perceive it and relates this to employment generation as a policy measure for marine conservation.

Digestive endo-proteases from the midgut glands of the Indian white shrimp, Penaeus Indicus (Decapoda: Penaeidae) from Kenya

Sat, 01 Jan 2005 00:00:00 GMT

Title: Digestive endo-proteases from the midgut glands of the Indian white shrimp, Penaeus Indicus (Decapoda: Penaeidae) from Kenya Authors: Omondi, J.G. Abstract: In order to provide information on the digestive capacity of marine crustacea of mariculture potential in Kenya with a view to aiding the development of suitable feeds to support the industry, a biochemical survey was made of enzymes of extracellular digestion in the Indian White shrimp, Penaeus indicus. Results showed midgut gland endo-proteases in wild adult shrimp from the Kenya coast to have optima between pH 7.2 and 8.5 (Trypsin pH 7.5-8.0, Chymotrypsin pH 7.2-7.8, Elastase pH 6.8-8.5) with maximum specific activities of 101-408, 37-516, 70-90 Units mg protein-1 min-1 for trypsin, chymotrypsin and elastase respectively. There was no pepsin. The North Sea Norway lobster, Nephrops norvegicus, was investigated to a lesser extent and found to have much lower trypsin activity than the shrimp and no chymotrypsin. In addition to the cited serine endo-proteases, significant activity in the shrimp was thought to originate from non-serine proteases. This situation may differ from other shrimps in which serine endo-protease activity, especially trypsin, is dominant. Diphenylcarbamyl chloride (DPCC) and 2-Nitro-4-Carboxyphenyl N,N-Diphenylcarbamate (NCDC) inhibited chymotrypsin but not trypsin, Soybean Trypsin Inhibitor (SBTI), Bowman-Birk Chymotrypsin-Trypsin Inhibitor (BBSTCI), N-Tosyl-L-Phenylalanine Chloromethyl Ketone (TPCK), 4-(2-Aminoethyl)-Benzenesulfonylfluoride Hydrochloride (AEBSF) and N-Tosyl-Llysine Chloromethyl Ketone/1-Chloro-3-Tosylamido-7-Amino-L-2-Heptanone Hydrochloride (TLCK) inhibited both, while Phenyl Methanesulfonyl Fluoride/ Phenylmethyl Sulfonyl Fluoride/ á-Toluenesulfonyl Fluoride (PMSF) and Ovomucoid Trypsin Inhibitor (Ovomucoid/OTI) precipitated shrimp homogenate. The effect of the former was inferred from the action of AEBSF which together with TLCK inhibited shrimp trypsin more than chymotrypsin. In contrast, TPCK inhibited shrimp chymotrypsin more than trypsin. These results indicate that relying on imported commercial feeds, usually developed for other species or strains of farmed shrimp in other parts of the world, may not only be too uneconomical but may not provide adequate nutrition to local animals if not efficiently digested. There is, therefore, greater need and urgency to establish detailed enzymic profiles and digestive capacities of locally cultured fin and shellfish. Such studies should parallel those prospecting for suitable feed ingredients while developing local capacity for feed technology.

Characterisation of chitosan from blowfly larvae and some crustacean species from Kenyan marine waters prepared under different conditions

Sat, 01 Jan 2005 00:00:00 GMT

Title: Characterisation of chitosan from blowfly larvae and some crustacean species from Kenyan marine waters prepared under different conditions Authors: Oduor-Odote, P.M.; Struszczyk, M.H.; Peter, M.G. Abstract: Isolation of chitosan from cuticles of blue bottlefly larvae Calliphora erythrocephala, and shells of crab Sylla cerrata, lobster Panulirus ornatus, prawn Paeneaus indicus was carried out. The yield of chitin was 12.0%, 23.0%, 15.7% and 28.0% respectively. In the same order the yield of chitosan was 66.0%, 74.6% 74.3% and 75.0% from chitin. Ash in the crab and lobster chitosan demineralised with 0.5M HCl was 30.2 and 22.4% respectively. This was reduced to 0.2 % for lobster and 0.4% for crab using 2M HCl for demineralisation and 0.5M HCL was adequate for demineralisation of prawns to bring the ash content to < 1%. The ash content in the blowfly larvae was negligible. The conditions used for chitosan isolation in blowfly larvae were milder requiring no demineralisation step. The time to obtain soluble chitosan in 1% v/v acetic acid was 8 hr for crab and lobster at 100Â°C deacetylation and 4 hr at 120Â°C while for prawns it was 6 hr at 100Â°C and 3 hr at 120Â°C deacetylation temperature. The average molecular weight (Â¯MV) for crabs was 556,000 after 8 hr deacetylation and 148,000 at 140Â°C deacetylation temperature. With 2M HCl used for demineralisation first, it was 439,000 for a 4 hr period. Crabs, first demineralised then deprotenised the Â¯MV was 155,000 for a 3 hr deacetylation at 120Â°C and 417,000 for 1 hr deacetylation. An 8 hr deacetylation at 100Â°C for lobsters gave Â¯MV of 791,000. It was reduced to 560,000 after 4 hr of deacetylation at 120Â°C and to 236,000 at 140Â°C for 3 hr. Prawns had a Â¯MV of 507,000 after 6 hr deacetylation at 100Â°C and reduced to 455,000 after a 3 hr deacetylation. For insect larvae, at 100Â°C deacetylation for 4 hr the Â¯MV was 413,500 while for 1 hr, 2 hr and 2.5 hr deacetylation time at 120Â°C it was 369,000, 308,500 and 263,000 respectively. The degree of deacetylation (DD) increased with temperature and time of deacetylation. For crab, demineralised then deproteinised, it increased from 72.9% in 1 hr then 81.5% in 3 hr. In prawn chitosan it was 60.0% for the 6 hr deacetylation at 100Â°C and 69.2% for 3 hr deacetylation at 120Â°C. The DD of insect larvae was 62.56% after 4 hr of deacetylation at 100Â°C. When deacetylated at 120Â°C it was 64.0% after 1 hr, 79.9% after 2 hr and 80.7% after 2.5 hr. The moisture content showed a slight increase with DD. Temperature increase and time of deacetylation caused a decrease in MV and a more conservative increase in DD.

An antimalarial cembranolide from Tanzania soft corals, Lobophytum crassum (von Marenzeller (1886) and L. rotundum (Tixier-Durivault (1957)

Sat, 01 Jan 2005 00:00:00 GMT

Title: An antimalarial cembranolide from Tanzania soft corals, Lobophytum crassum (von Marenzeller (1886) and L. rotundum (Tixier-Durivault (1957) Authors: Said, S.A. Abstract: Bioscreening guided fractionation of the extracts of soft corals Lobophytum crassum and L. rotundum using brine shrimp larvae cytotoxicity assay led to the isolation of a cembranolide diterpene (E,E,E)-6,10,14-trimethyl-3-methylene- 3a,4,7,8,11,12,15,15aoctahydrocylotetradeca [b]furan-2(3H)-one (1). This diterpene, identified as cembranolide compound 1, was found to be active against the multidrug-resistant and chloroquine-sensitive strains of Plasmodium falciparum malaria parasite in vitro. It also possessed cytotoxic properties.