This study was undertaken with a view to: (a)describe the species composition and the community structure of copepods in the Tudor Creek; (b) describe the spatio-temporal distribution of pelagic copepods as well as estimating their abundance, and finally to estimate both primary production, biomass and respiration in Tudor Creek. The first quantitative study of the pelagic zooplankton community of the Tudor Creek, Mombasa, Kenya, was undertaken from December 1984 to December 1987. Using a Bongo plankton net of 335 µm mesh from R.V. Maumba from December to March 1985. From April 1985 to December 1987 a small canoe with an outboard engine was used. A conical plankton net having a mesh aperture size of 335 µm fitted with a flow-meter at the mouth of 45 cm diameter and a length of one meter long was used for sampling. Surface-plankton samples were taken using a small canoe at each of the five permanent stations during day-time and night-time during one neap and one spring of every month from September 1985 to August 1986. Thereafter only day-time neap and spring samples were taken from September 1986 to December 1987 in five stations. 24-hours cycle sampling was occasionally done at stations 1 and 5 simultaneously. The neap tide sampling of the 24-hour cycle started at 0900 h on 23rd September 1985 and the last samples were taken at 0900 h the following day. Sampling during the spring tide started at 0900 h on 1st October 1985 to 0900 h on 2nd October 1985. Every two hours zooplankton was collected by horizontal hauls at 1.3 m depth with a 335 µm mesh net. Simultaneously the following abiotic parameters were measured: for information on salinity, temperature, transparency, oxygen concentration and pH. Fresh zooplankton was sampled from January 1986 to February 1986, in February 1987 and from February 1988 to March 1988 every moming with a plankton net of 335 µm mesh aperture on board of the small canoe at very low speed during about 2 hour. Live sample was put in a bucket with fresh sea water and brought to the laboratory, for respiration experiments, length and weight measurements. Hydrographic parameters, including surface water salinity and temperature, turbidity, dissolved oxygen and pH were also monitored during this study. Photosynthesis of phytoplankton biomass was measured in the field, using light and dark glass bottles and using oxygen methods. Results from the study have shown that zooplankton is rich and abundant and over 51 taxa were recorded. Close to 74% of zooplankton comprised copepods of which the most important were calanoids followed by cyclopoids, poecilostomatoids, harpacticoids and monstrilloids in that order. Calanoids were the dominant group of copepods in all the samples, followed by poecilostomatoids, cyclopoids, harpacticoids and lastly Monstrilloids. The most commonly encountered calanoid species included: Centropages orsinii, Acrocalanus longicornis, Clausocalanus farrani, Temora turbinata, Paracalanus aculeatis, Canthocalanus pauper, Undinula vulgaris, Acartia danae, Paracalanus simplex, Euchaeta marina, and Eucalanus spp. The most common cyclopoid species encountered were Corycaeus specious, Oncaea venusta, Copilia mirabilis Dana and Sapphirina lactens, Oithona plumifera, O.setigera, and O.simplex. Three harpacticoids, Microsetella rosea, Euterpina acutifrons, and Macrosetella gracilis were the commonest. Only occasionally did copepods of the order Monstrilloida show up in the samples. Some 99 copepod species, representing 41 genera and 30 families, have been identified. Amongst these 17 species are dominant but 6 species including Calanus darwini, Labidocera laevidentata, Paracalanus crassirostris, P.indicus, P.tropicus and Sapphirina lactens, have been recorded in Western lndian Ocean off Kenya coast for the first time. Both diel and seasonal changes in the abundance of zooplankton catches occur. While night catch numbers are hi |
