170
Tanga Tanzania mainland, Fumba Bay Zanzibar and Fundo Island Pemba Mshigeni 1983, 1987 was able to demonstrate that Eucheuma farming was technically and economically feasible in Tanzania. Lisaran and Twide
1993 conducted Eucheuma planting trials using two species E. cottonii and E. spinosum and found that the latter species performed better in terms of growth measured as daily growth rates and resistance to ice-ice disease. The
authors further reported that the attempted farming trials with E. cottonii failed.
In an investigation on the environmental aspects of open water algal cultivation in Zanzibar Johnstone and Ólafsson 1995 found that the farming has no discernible effects on water-column microbial production, but has
an effect on both benthic microbial processes and meiofauna populations. They speculate that these changes are attributable to the mechanical alteration of the sediment surface and possible enhancement of local benthic fish
grazing. Collén et al. 1995 demonstrated that Eucheuma plants that are stressed e.g. through high density planting, grazing, high light intensities succumbed easily to ice-ice disease, and produced hydrogen peroxide and
volatile halogenated compounds as part of their chemical defence.
6.2.5 Review studies
Review studies that present latest information on various aspects of the resources are a good source of information for researchers as well as students. In fact scientists, from time to time, should be encouraged to write
comprehensive publishable reviews on selected topics because this type of work is has not yet been adequately done. A recent book on East African sea shores Richmond, 1997 does a good job as a review text but also covers
material from field observations in a comprehensive manner.
Several papers have reviewed various aspects of the resources and habitats. Bryceson 1981 published a review of some problems of tropical marine conservation with particular reference to the Tanzanian coast. Issues relevant
to the conservation of marine mammals and turtles in Tanzania Howell, 1988a and waterbirds Howell, 1988b have been reviewed and research priorities recommended. Mgaya et al. 1999c reviewed prawn farming issues
using Bagamoyo as a case study.
6.3 Research methodology
This section covers baseline, observational, experimental and applied studies.
6.3.1 Sampling aspectsparameters
The methodology used for the various studies is scientific and acceptable. However, the methods differ among studies and resources. For example, plankton nets are used in sampling plankton, quadrats and corers for sampling
macrobenthos and meiobenthos. Studies on turtles and waterbirds, were generally based on field observations. The studies done on marine mammals were mainly conducted with the aid of photographs and field observations.
The objectives of these studies vary according to the type of resource being considered.
6.3.2 Instrumentation and techniques of sampling and data collection
Techniques involving
14
C isotope were used to measure both benthic and water column primary production. Analytical methods in chemistry e.g. Infrared spectroscopy were used in studies that analysed the phycocolloids
of some seaweeds e.g. Semesi and Mshigeni, 1977 and Spectrophotometer in the determination of chlorophyll concentration Bryceson, 1977; Ólafsson et al., 1995. Basic laboratory equipment e.g. microscope has been used
in the various studies. Microcosms have also been employed in laboratory studies Ólafsson and Ndaro, 1997. Ecological studies have often been accompanied by measurements of abiotic factors e.g. salinity refractometer,
temperature thermometer, turbidity Secchi disc, and meteorological factors.
171
6.3.3 Sampling frequency and time of collection
Frequency of sampling is very variable for different studies. For example, studies on phycocolloids were based on a single field sampling of seaweeds Mshigeni and Nzalalila, 1977; Semesi and Mshigeni, 1977. In a study by
Newton et al. 1993, on the effects of shell collecting on the abundance of gastropods, field sampling lasted 32, 24, and 37 hours for Dar es Salaam, Zanzibar and Mafia respectively. Ndaro and Ólafsson 1995, in their
investigation on the selection of meiobenthic prey by the fish Gerres oyena, sampled meiobenthos once in November 1993, and sampled fish three times on 12 and 13 November, 1992 and 21 November, 1993. Chande
et al. 1994 investigated marine mammals and fisheries interactions in a study that lasted six months June to November. Khatib 1998 reported results from a one-year turtle nest-recording programme in Zanzibar.
The authors do not give explanations as to why a particular sampling frequency was chosen. However, where the authors should have increased sampling frequency e.g. Newton et al., 1993; Ndaro and Ólafsson, 1995, it
appears that the constraint has been financial and available time. The latter is partcularly relevant where a postgraduate student was involved.
6.3.4 Data analysis methods and procedure
